PRACTICE QUESTIONS WITH ANSWERS

TOPIC: INTRODUCTION TO BIOCHEMISTRY

SET 1.

1. Which of the following best describes biochemistry?

a) The study of chemical processes in rocks
b) The study of the structure and function of biomolecules
c) The study of chemical elements in the air
d) The study of chemical reactions in non-living systems
Answer: b)

2. What are the main classes of bioorganic substances?

a) Carbohydrates, lipids, proteins, nucleic acids
b) Water and inorganic salts
c) Enzymes and hormones
d) Vitamins and minerals
Answer: a)

3. Which of the following is NOT a function of lipids?

a) Forming cell membranes
b) Catalyzing biochemical reactions
c) Serving as an energy source
d) Acting as chemical messengers
Answer: b)

4. What is the primary function of enzymes in biochemical reactions?

a) To store genetic information
b) To catalyze and accelerate chemical reactions
c) To serve as structural components
d) To provide energy for cells
Answer: b)

5. Which molecule is considered the powerhouse of the cell?

a) Nucleus
b) Ribosome
c) Mitochondria
d) Chloroplast
Answer: c)

6. In which organelle does protein synthesis primarily occur?

a) Nucleus
b) Mitochondria
c) Ribosome
d) Lysosome
Answer: c)

7. What is the role of nucleic acids in the cell?

a) Providing energy
b) Storing genetic information and directing protein synthesis
c) Structuring cell walls
d) Catalyzing enzymatic reactions
Answer: b)

8. What is the primary purpose of the cell membrane?

a) To synthesize proteins
b) To separate the internal environment from the external environment
c) To generate energy
d) To transport DNA
Answer: b)

9. Which of the following best defines metabolism?

a) The process of cell division
b) The synthesis of nucleic acids
c) The set of life-sustaining chemical reactions in organisms
d) The formation of organelles
Answer: c)

10. Which organelle is involved in packaging and distributing proteins?

a) Ribosome
b) Nucleus
c) Golgi apparatus
d) Lysosome
Answer: c)

11. Which type of biomolecule is primarily responsible for catalyzing chemical reactions in cells?

a) Proteins
b) Lipids
c) Carbohydrates
d) Nucleic acids
Answer: a)

12. Where does photosynthesis occur in plant cells?

a) Mitochondria
b) Ribosomes
c) Chloroplasts
d) Lysosomes
Answer: c)

13. What is the function of lysosomes?

a) To produce ATP
b) To digest unwanted materials in the cell
c) To synthesize lipids
d) To store genetic material
Answer: b)

14. What is the main function of the endoplasmic reticulum?

a) Protein and lipid synthesis
b) Energy production
c) Digestion of macromolecules
d) Transport of genetic material
Answer: a)

15. What does the nucleus of a cell contain?

a) Lipids and proteins
b) Enzymes and ribosomes
c) Genetic material (DNA)
d) Carbohydrates and RNA
Answer: c)

16. Which of the following describes the structure of the cell membrane?

a) A rigid carbohydrate layer
b) A bilayer of phospholipids
c) A protein-only membrane
d) A single layer of nucleic acids
Answer: b)

17. What is the function of peroxisomes in the cell?

a) Energy production
b) Protein synthesis
c) Breakdown of hydrogen peroxide
d) Genetic information storage
Answer: c)

18. Which element is NOT one of the most common in living organisms?

a) Carbon
b) Oxygen
c) Nitrogen
d) Calcium
Answer: d)

19. What happens in oxidation-reduction reactions in metabolism?

a) Energy is stored in ATP
b) Electrons are transferred between molecules
c) Water is broken down into hydrogen and oxygen
d) Proteins are synthesized from amino acids
Answer: b)

20. Which cellular organelle is known as the "information center"?

a) Endoplasmic reticulum
b) Nucleus
c) Golgi apparatus
d) Lysosome
Answer: b)

SET 2.

1. Which of the following molecules is most abundant in living cells?

a) Lipids
b) Carbohydrates
c) Proteins
d) Water
Answer: d)

2. Which type of bond connects the nucleotides in a DNA strand?

a) Hydrogen bonds
b) Peptide bonds
c) Glycosidic bonds
d) Phosphodiester bonds
Answer: d)

3. What is the primary role of carbohydrates in cells?

a) To store genetic information
b) To provide energy
c) To catalyze reactions
d) To synthesize proteins
Answer: b)

4. Which of the following macromolecules acts as the main structural component of cell membranes?

a) Proteins
b) Carbohydrates
c) Lipids
d) Nucleic acids
Answer: c)

5. What is the primary storage form of glucose in animals?

a) Starch
b) Glycogen
c) Cellulose
d) Sucrose
Answer: b)

6. Which of the following is NOT a property of enzymes?

a) They are reusable
b) They lower the activation energy of a reaction
c) They are consumed during the reaction
d) They are specific to their substrates
Answer: c)

7. What type of molecule is ATP?

a) Carbohydrate
b) Lipid
c) Nucleotide
d) Protein
Answer: c)

8. Which process involves the breakdown of glucose to produce energy?

a) Photosynthesis
b) Glycolysis
c) Protein synthesis
d) DNA replication
Answer: b)

9. In which cellular organelle does oxidative phosphorylation occur?

a) Nucleus
b) Ribosome
c) Mitochondria
d) Chloroplast
Answer: c)

10. Which of the following best describes an amino acid?

a) A component of DNA
b) A building block of proteins
c) A storage form of glucose
d) A type of lipid
Answer: b)

11. What is the role of RNA in protein synthesis?

a) To store genetic information
b) To transport amino acids to ribosomes
c) To catalyze biochemical reactions
d) To provide energy
Answer: b)

12. Which of the following structures is found in plant cells but not in animal cells?

a) Cell membrane
b) Nucleus
c) Mitochondria
d) Cell wall
Answer: d)

13. Which part of the enzyme binds to the substrate?

a) Active site
b) Inhibitor
c) Coenzyme
d) Allosteric site
Answer: a)

14. What is the main function of chloroplasts?

a) ATP production
b) Protein synthesis
c) Photosynthesis
d) DNA replication
Answer: c)

15. Which molecule carries the genetic code from the nucleus to the ribosome for protein synthesis?

a) DNA
b) mRNA
c) tRNA
d) rRNA
Answer: b)

16. What is the backbone of a protein molecule composed of?

a) Sugar-phosphate
b) Amino acids
c) Fatty acids
d) Nucleotides
Answer: b)

17. Which of the following molecules is primarily involved in long-term energy storage in animals?

a) Glucose
b) Fatty acids
c) Amino acids
d) Ribose
Answer: b)

18. What is the function of the Golgi apparatus in the cell?

a) Synthesizing proteins
b) Modifying and packaging proteins
c) Producing ATP
d) Storing genetic information
Answer: b)

19. Which of the following is NOT a function of nucleic acids?

a) Storing genetic information
b) Providing cellular energy
c) Directing protein synthesis
d) Transmitting genetic information
Answer: b)

20. What is the role of cholesterol in cell membranes?

a) To catalyze reactions
b) To maintain membrane fluidity
c) To transport molecules across the membrane
d) To store energy
Answer: b)

TOPIC: CARBOHYDRATES

1. What are carbohydrates chemically classified as?

a) Hydrocarbons
b) Polyhydroxyaldehydes or polyhydroxyketones
c) Amino acids
d) Proteins
Answer: b)

2. Which of the following is NOT a function of carbohydrates?

a) Providing energy
b) Structural components of DNA and RNA
c) Storing genetic information
d) Forming part of cell membranes
Answer: c)

3. What is the empirical formula of carbohydrates?

a) CnH2nOn
b) CnHnOn
c) CnH2n+1On
d) CnH2n-2On
Answer: a)

4. Which of the following is the simplest form of carbohydrates?

a) Disaccharides
b) Polysaccharides
c) Monosaccharides
d) Oligosaccharides
Answer: c)

5. Glucose is classified as a(n):

a) Ketose
b) Aldohexose
c) Pentose
d) Disaccharide
Answer: b)

6. Which disaccharide is found in milk?

a) Maltose
b) Sucrose
c) Lactose
d) Fructose
Answer: c)

7. What is the linkage type found in cellulose?

a) α-1,4-glycosidic
b) β-1,4-glycosidic
c) α-1,6-glycosidic
d) β-1,6-glycosidic
Answer: b)

8. Which of the following is the sweetest sugar?

a) Glucose
b) Galactose
c) Fructose
d) Sucrose
Answer: c)

9. What is the function of glycogen in animals?

a) Immediate energy source
b) Long-term energy storage
c) Structural component
d) Genetic material
Answer: b)

10. The primary structural polysaccharide in plants is:

a) Glycogen
b) Starch
c) Cellulose
d) Chitin
Answer: c)

11. Which sugar is a component of RNA?

a) Glucose
b) Ribose
c) Fructose
d) Galactose
Answer: b)

12. Which molecule is known as blood sugar?

a) Sucrose
b) Glucose
c) Fructose
d) Galactose
Answer: b)

13. Which reaction forms a glycosidic bond between two monosaccharides?

a) Hydrolysis
b) Oxidation
c) Condensation
d) Phosphorylation
Answer: c)

14. What is the reducing disaccharide found in beer and germinating grains?

a) Lactose
b) Sucrose
c) Maltose
d) Cellobiose
Answer: c)

15. Which of the following is NOT a reducing sugar?

a) Maltose
b) Lactose
c) Sucrose
d) Glucose
Answer: c)

16. What polysaccharide gives a blue color when treated with iodine?

a) Glycogen
b) Starch (amylose)
c) Cellulose
d) Chitin
Answer: b)

17. In what form is glucose stored in the liver and muscle of animals?

a) Amylopectin
b) Glycogen
c) Starch
d) Cellulose
Answer: b)

18. What type of glycosidic bond is found in sucrose?

a) α-1,4-glycosidic
b) β-1,4-glycosidic
c) α-1,2-glycosidic
d) β-1,6-glycosidic
Answer: c)

19. Which of the following is a homopolysaccharide?

a) Hyaluronic acid
b) Starch
c) Heparin
d) Chondroitin sulfate
Answer: b)

20. What is the repeating unit in cellulose?

a) D-glucose
b) D-fructose
c) D-galactose
d) Ribose
Answer: a)

21. Which of the following is NOT true about amylopectin?

a) It is a branched polysaccharide
b) It has α-1,4-glycosidic bonds
c) It contains β-1,4-glycosidic bonds
d) It has α-1,6-glycosidic bonds
Answer: c)

22. What enzyme is responsible for the digestion of starch in humans?

a) Lactase
b) Amylase
c) Maltase
d) Sucrase
Answer: b)

23. Which polysaccharide is found in the exoskeleton of arthropods?

a) Starch
b) Chitin
c) Glycogen
d) Cellulose
Answer: b)

24. What is the name of the sugar derivative that results from the reduction of glucose?

a) Glucitol (Sorbitol)
b) Gluconic acid
c) Glucose-6-phosphate
d) Glucuronate
Answer: a)

25. Which polysaccharide serves as a lubricant in joints?

a) Cellulose
b) Hyaluronic acid
c) Chitin
d) Amylopectin
Answer: b)

26. In the structure of D-glucose, what is the name of the anomer where the OH group on the anomeric carbon is below the plane of the ring?

a) β-D-glucose
b) α-D-glucose
c) L-glucose
d) β-D-fructose
Answer: b)

27. Which of the following is a trisaccharide?

a) Raffinose
b) Sucrose
c) Lactose
d) Maltose
Answer: a)

28. Which polysaccharide contains a mixture of α-1,3 and β-1,4-glycosidic linkages?

a) Starch
b) Amylose
c) Carageenan
d) Glycogen
Answer: c)

29. Which sugar is involved in cell recognition processes?

a) Fructose
b) Glucose
c) Galactose
d) Mannose
Answer: d)

30. What is the common term for invert sugar?

a) Glucose
b) Maltose
c) Hydrolyzed sucrose
d) Amylose
Answer: c)

31. Which enzyme is deficient in individuals with lactose intolerance?

a) Amylase
b) Sucrase
c) Lactase
d) Maltase
Answer: c)

32. Which disaccharide contains a β-1,4-glycosidic bond between glucose and galactose?

a) Maltose
b) Lactose
c) Sucrose
d) Cellobiose
Answer: b)

33. Which polysaccharide can humans not digest?

a) Glycogen
b) Amylose
c) Cellulose
d) Amylopectin
Answer: c)

34. Which sugar alcohol is commonly used as a sweetener in chewing gum?

a) Sorbitol
b) Fructose
c) Galactose
d) Ribose
Answer: a)

35. Which polysaccharide plays a structural role in cartilage?

a) Starch
b) Glycogen
c) Chondroitin sulfate
d) Amylopectin
Answer: c)

36. Which enzyme breaks down sucrose into glucose and fructose?

a) Sucrase
b) Lactase
c) Amylase
d) Maltase
Answer: a)

37. What is the general role of glycoproteins?

a) Energy storage
b) Catalyzing metabolic reactions
c) Cell-cell recognition and communication
d) Serving as structural components
Answer: c)

38. What is the source of dietary fiber in food?

a) Digestible carbohydrates
b) Starch
c) Indigestible carbohydrates
d) Protein
Answer: c)

39. What is the consequence of a lack of dietary fiber?

a) Soft stools
b) Increased plaque formation
c) Decreased cholesterol levels
d) Weight loss
Answer: b)

40. What glycosaminoglycan is used as an anticoagulant?

a) Hyaluronic acid
b) Heparin
c) Chondroitin sulfate
d) Glycogen
Answer: b)

TOPIC: LIPIDS

1. What defines a lipid?

a) A molecule that contains nitrogen
b) A water-soluble organic compound
c) An organic compound insoluble in water but soluble in non-polar solvents
d) A compound made up of amino acids
Answer: c)

2. Which of the following is NOT a classification of lipids based on their biochemical function?

a) Energy storage lipids
b) Membrane lipids
c) Vitamins
d) Emulsification lipids
Answer: c)

3. What is the primary function of triacylglycerols?

a) Membrane formation
b) Energy storage
c) Hormone production
d) Cell signaling
Answer: b)

4. Which of the following lipids is involved in membrane structure?

a) Triacylglycerols
b) Phospholipids
c) Eicosanoids
d) Steroid hormones
Answer: b)

5. Which of the following is a saturated fatty acid?

a) Oleic acid
b) Linoleic acid
c) Stearic acid
d) Arachidonic acid
Answer: c)

6. What does the term "polyunsaturated" mean in relation to fatty acids?

a) The fatty acid has no double bonds
b) The fatty acid has one double bond
c) The fatty acid has two or more double bonds
d) The fatty acid is fully hydrogenated
Answer: c)

7. What are omega-3 fatty acids known for?

a) Their ability to synthesize proteins
b) Their role in heart health and inflammation reduction
c) Their high saturation level
d) Their function as enzymes
Answer: b)

8. Which type of lipid is the main component of biological membranes?

a) Steroid hormones
b) Triacylglycerols
c) Phospholipids
d) Waxes
Answer: c)

9. What is the key structural feature of a phospholipid?

a) One fatty acid attached to glycerol
b) Two fatty acids and a phosphate group attached to glycerol
c) A single long-chain alcohol and a fatty acid
d) Four fused carbon rings
Answer: b)

10. Which lipid is classified as a steroid?

a) Cholesterol
b) Stearic acid
c) Lecithin
d) Triglyceride
Answer: a)

11. What is the function of bile acids in lipid digestion?

a) Breaking down proteins into amino acids
b) Emulsifying dietary fats
c) Synthesizing fatty acids
d) Storing energy in adipocytes
Answer: b)

12. Which of the following is an essential fatty acid?

a) Palmitic acid
b) Linoleic acid
c) Stearic acid
d) Oleic acid
Answer: b)

13. What is the primary role of cholesterol in cell membranes?

a) Catalyzing biochemical reactions
b) Providing energy
c) Stabilizing membrane fluidity
d) Serving as a precursor for vitamins
Answer: c)

14. Which molecule is known as a "bad cholesterol" because of its association with cardiovascular disease?

a) LDL (Low-Density Lipoprotein)
b) HDL (High-Density Lipoprotein)
c) VLDL (Very-Low-Density Lipoprotein)
d) Chylomicrons
Answer: a)

15. What are eicosanoids derived from?

a) Triacylglycerols
b) Cholesterol
c) Arachidonic acid
d) Phospholipids
Answer: c)

16. Which of the following is NOT a function of eicosanoids?

a) Regulating blood pressure
b) Inducing labor
c) Producing ATP
d) Mediating inflammatory responses
Answer: c)

17. What is a major function of steroid hormones?

a) Energy storage
b) Regulating reproduction and secondary sex characteristics
c) Forming cell walls
d) Enzyme activity regulation
Answer: b)

18. Which type of fat is considered beneficial and is recommended for consumption in a balanced diet?

a) Saturated fats
b) Monounsaturated fats
c) Trans fats
d) Hydrogenated fats
Answer: b)

19. Which of the following is an artificial fat substitute used in foods?

a) Lecithin
b) Olestra
c) Stearic acid
d) Cholesterol
Answer: b)

20. What lipid-soluble vitamin is involved in blood clotting?

a) Vitamin A
b) Vitamin D
c) Vitamin E
d) Vitamin K
Answer: d)

21. Which lipid is primarily responsible for transporting cholesterol from the liver to cells?

a) HDL
b) LDL
c) VLDL
d) Chylomicrons
Answer: b)

22. What lipid class does wax belong to?

a) Triacylglycerols
b) Steroids
c) Biological waxes
d) Eicosanoids
Answer: c)

23. Which process converts oils into solid fats by adding hydrogen?

a) Hydrolysis
b) Saponification
c) Hydrogenation
d) Esterification
Answer: c)

24. What is the primary difference between fats and oils?

a) Fats are unsaturated, while oils are saturated
b) Fats are solid at room temperature, while oils are liquid
c) Fats contain cholesterol, while oils do not
d) Fats are found in plants, while oils are found in animals
Answer: b)

25. What is the function of lipoproteins?

a) Catalyzing lipid digestion
b) Transporting lipids in the blood
c) Storing lipids in adipose tissue
d) Synthesizing lipids from carbohydrates
Answer: b)

26. Which lipid is a precursor for all steroid hormones?

a) Cholesterol
b) Palmitic acid
c) Lecithin
d) Oleic acid
Answer: a)

27. What type of lipid forms a protective coating on the leaves and fruits of plants?

a) Phospholipids
b) Waxes
c) Triacylglycerols
d) Cholesterol
Answer: b)

28. Which vitamin is known as the "antioxidant vitamin" and protects lipids from oxidation?

a) Vitamin A
b) Vitamin D
c) Vitamin E
d) Vitamin K
Answer: c)

29. What is the primary cause of lipid rancidity?

a) Hydrolysis of lipids
b) Oxidation of unsaturated fatty acids
c) Hydrogenation of fats
d) Saponification of fatty acids
Answer: b)

30. Which class of lipids is involved in cellular signaling and immune responses?

a) Eicosanoids
b) Phospholipids
c) Steroids
d) Triacylglycerols
Answer: a)

31. What lipid is essential for the production of vitamin D in the skin?

a) Cholesterol
b) Sphingomyelin
c) Stearic acid
d) Triacylglycerol
Answer: a)

32. Which lipid is involved in the emulsification of fats during digestion?

a) Phospholipids
b) Cholesterol
c) Bile acids
d) Triacylglycerols
Answer: c)

33. What lipid disorder is characterized by high levels of LDL in the blood?

a) Hypolipidemia
b) Hypercholesterolemia
c) Fatty liver disease
d) Lipid peroxidation
Answer: b)

34. Which lipid is important for the formation of the myelin sheath in neurons?

a) Sphingomyelin
b) Cholesterol
c) Triacylglycerol
d) Lecithin
Answer: a)

35. Which of the following lipids is known to promote inflammation and allergic responses?

a) Thromboxanes
b) Prostaglandins
c) Leukotrienes
d) Cholesterol
Answer: c)

36. What is the product of the saponification of triacylglycerols?

a) Cholesterol
b) Glycerol and fatty acid salts
c) Glycerophospholipids
d) Sphingolipids
Answer: b)

37. Which lipoprotein is known as "good cholesterol"?

a) LDL
b) HDL
c) VLDL
d) Chylomicrons
Answer: b)

38. What lipid forms the backbone of triglycerides?

a) Glycerol
b) Fatty acids
c) Cholesterol
d) Phospholipids
Answer: a)

39. What is the major role of biological waxes in plants and animals?

a) Storing energy
b) Acting as emulsifiers
c) Providing protection and waterproofing
d) Regulating body temperature
Answer: c)

40. Which type of transport requires energy to move lipids across cell membranes?

a) Passive transport
b) Active transport
c) Facilitated transport
d) Diffusion
Answer: b)

TOPIC: PROTEINS

1. What are proteins made up of?

   • A) Nucleotides

   • B) Amino acids

   • C) Lipids

   • D) Sugars
     Answer: B

2. What percentage of a cell's mass do proteins account for after water?

   • A) 10%

   • B) 50%

   • C) 15%

   • D) 5%
     Answer: C

3. Which element is not commonly found in proteins?

   • A) Carbon

   • B) Hydrogen

   • C) Nitrogen

   • D) Silicon
     Answer: D

4. What type of protein contains only amino acid residues?

   • A) Conjugated protein

   • B) Simple protein

   • C) Fibrous protein

   • D) Globular protein
     Answer: B

5. Albumin belongs to which class of proteins?

   • A) Structural proteins

   • B) Transport proteins

   • C) Simple proteins

   • D) Conjugated proteins
     Answer: C

6. Which of the following is a fibrous protein?

   • A) Hemoglobin

   • B) Albumin

   • C) Collagen

   • D) Immunoglobulins
     Answer: C

7. What is the function of myoglobin?

   • A) Transport oxygen in blood

   • B) Store oxygen in muscles

   • C) Breakdown fats

   • D) Fight infections
     Answer: B

8. What kind of protein is insulin?

   • A) Catalytic protein

   • B) Transport protein

   • C) Messenger protein

   • D) Structural protein
     Answer: C

9. Which amino acid is essential and must be obtained from the diet?

   • A) Glycine

   • B) Lysine

   • C) Alanine

   • D) Proline
     Answer: B

10. Which protein is responsible for oxygen transport in the blood?

    • A) Myoglobin

    • B) Collagen

    • C) Hemoglobin

    • D) Albumin
      Answer: C

11. Which protein stores iron in the body?

    • A) Myoglobin

    • B) Ferritin

    • C) Insulin

    • D) Albumin
      Answer: B

12. Which of the following proteins assists in movement?

    • A) Myosin

    • B) Hemoglobin

    • C) Insulin

    • D) Casein
      Answer: A

13. What kind of bond links amino acids in a protein?

    • A) Ionic bond

    • B) Hydrogen bond

    • C) Peptide bond

    • D) Disulfide bond
      Answer: C

14. Which of the following is not a type of secondary protein structure?

    • A) Alpha-helix

    • B) Beta-pleated sheet

    • C) Tertiary coil

    • D) Random coil
      Answer: C

15. What type of bond holds the alpha-helix structure together?

    • A) Covalent bonds

    • B) Hydrogen bonds

    • C) Ionic bonds

    • D) Disulfide bonds
      Answer: B

16. Which of the following proteins contains a prosthetic group?

    • A) Simple protein

    • B) Conjugated protein

    • C) Fibrous protein

    • D) Globular protein
      Answer: B

17. Which amino acid is achiral?

    • A) Glycine

    • B) Alanine

    • C) Phenylalanine

    • D) Serine
      Answer: A

18. Which structure represents the sequence of amino acids in a protein?

    • A) Primary structure

    • B) Secondary structure

    • C) Tertiary structure

    • D) Quaternary structure
      Answer: A

19. What percentage of collagen makes up the body’s total protein?

    • A) 10%

    • B) 50%

    • C) 30%

    • D) 5%
      Answer: C

20. What is the main type of bond involved in the tertiary structure of proteins?

    • A) Peptide bonds

    • B) Disulfide bonds

    • C) Hydrogen bonds

    • D) Covalent bonds
      Answer: B

21. Which amino acid is most commonly found in collagen?

    • A) Glycine

    • B) Proline

    • C) Lysine

    • D) Histidine
      Answer: B

22. The isoelectric point is the pH at which the amino acid:

    • A) Has a net negative charge

    • B) Has a net positive charge

    • C) Has no net charge

    • D) Denatures
      Answer: C

23. Which of the following is an example of a conjugated protein?

    • A) Collagen

    • B) Myoglobin

    • C) Hemoglobin

    • D) Albumin
      Answer: C

24. Which amino acid is a precursor for serotonin?

    • A) Tyrosine

    • B) Tryptophan

    • C) Glycine

    • D) Cysteine
      Answer: B

25. Which protein structure involves multiple polypeptide chains?

    • A) Primary structure

    • B) Secondary structure

    • C) Tertiary structure

    • D) Quaternary structure
      Answer: D

26. What is the primary structural difference between a fibrous and a globular protein?

    • A) Shape

    • B) Size

    • C) Composition

    • D) Charge
      Answer: A

27. Which protein structure is most important in determining function?

    • A) Primary structure

    • B) Secondary structure

    • C) Tertiary structure

    • D) Quaternary structure
      Answer: C

28. In proteins, which bond is responsible for stabilizing secondary structures?

    • A) Peptide bond

    • B) Hydrogen bond

    • C) Ionic bond

    • D) Disulfide bond
      Answer: B

29. Which amino acid forms disulfide bonds?

    • A) Methionine

    • B) Cysteine

    • C) Proline

    • D) Histidine
      Answer: B

30. What is the main role of lipoproteins?

    • A) Transport lipids

    • B) Store oxygen

    • C) Break down proteins

    • D) Fight infections
      Answer: A

31. Which protein is important in forming blood clots?

    • A) Albumin

    • B) Prothrombin

    • C) Myoglobin

    • D) Hemoglobin
      Answer: B

32. Which of the following amino acids is polar?

    • A) Valine

    • B) Serine

    • C) Leucine

    • D) Glycine
      Answer: B

33. What is the main role of structural proteins?

    • A) Store energy

    • B) Regulate metabolism

    • C) Provide mechanical support

    • D) Catalyze reactions
      Answer: C

34. Which amino acid is involved in protein synthesis but not used in standard proteins?

    • A) Selenocysteine

    • B) Proline

    • C) Tyrosine

    • D) Histidine
      Answer: A

35. What kind of molecule is an enzyme?

    • A) Lipid

    • B) Carbohydrate

    • C) Protein

    • D) Nucleic acid
      Answer: C

36. Which protein forms the hard protective covering of nails and hair?

    • A) Myosin

    • B) Keratin

    • C) Albumin

    • D) Globulin
      Answer: B

37. What is the storage form of glucose in animals?

    • A) Glucagon

    • B) Glycogen

    • C) Starch

    • D) Cellulose
      Answer: B

38. Which type of protein transports molecules like oxygen in the blood?

    • A) Structural protein

    • B) Transport protein

    • C) Regulatory protein

    • D) Enzymatic protein
      Answer: B

39. What is the primary structure of a protein determined by?

    • A) Sequence of amino acids

    • B) 3D shape

    • C) Number of peptide bonds

    • D) Polarity
      Answer: A

40. Which amino acid contains sulfur?

    • A) Glycine

    • B) Cysteine

    • C) Tyrosine

    • D) Alanine
      Answer: B

TOPIC: ENZYMES

Set 1.

Multiple Choice Questions (20)

1. What are enzymes primarily composed of?

   • a) Lipids

   • b) Carbohydrates

   • c) Proteins

   • d) Nucleic acids

     Answer: c) Proteins

     Explanation: Enzymes are mostly large, globular proteins.

2. What is the role of a cofactor in enzyme activity?

   • a) It destroys enzymes

   • b) It is a substrate

   • c) It is necessary for activity

   • d) It is the enzyme product

     Answer: c) It is necessary for activity

     Explanation: Cofactors are nonprotein components necessary for enzyme function.

3. Which of the following suffixes do most enzymes have?

   • a) -ase

   • b) -in

   • c) -ose

   • d) -peptide

     Answer: a) -ase

     Explanation: Most enzymes are named with the suffix "-ase."

4. Which enzyme class catalyzes hydrolysis reactions?

   • a) Transferases

   • b) Hydrolyases

   • c) Ligases

   • d) Isomerases

     Answer: b) Hydrolyases

     Explanation: Hydrolyases catalyze reactions that add water to break bonds.

5. What model describes how the enzyme active site is complementary to the substrate shape?

   • a) Induced Fit Model

   • b) Lock-and-Key Model

   • c) Catalytic Model

   • d) Substrate-Affinity Model

     Answer: b) Lock-and-Key Model

     Explanation: This model states that the active site is a rigid shape that fits the substrate.

6. Which of the following is NOT a type of enzyme regulation?

   • a) Allosteric regulation

   • b) Feedback inhibition

   • c) Competitive inhibition

   • d) Passive regulation

     Answer: d) Passive regulation

     Explanation: There is no such regulation termed "passive."

7. What is the active site of an enzyme?

   • a) The site where products are formed

   • b) The part where the substrate binds

   • c) The area where cofactors bind

   • d) The location of enzyme denaturation

     Answer: b) The part where the substrate binds

     Explanation: The active site is where the substrate binds and catalysis occurs.

8. Competitive inhibitors act by:

   • a) Altering the enzyme shape

   • b) Binding to the active site

   • c) Binding to the cofactor

   • d) Increasing substrate concentration

     Answer: b) Binding to the active site

     Explanation: Competitive inhibitors compete with the substrate for the active site.

9. Which reaction type do ligases catalyze?

   • a) Hydrolysis

   • b) Bond formation

   • c) Isomerization

   • d) Electron transfer

     Answer: b) Bond formation

     Explanation: Ligases catalyze the joining of two molecules, often using ATP.

10. What effect does temperature have on enzyme activity?

    • a) Always increases activity

    • b) Optimal at ~37°C but can denature above

    • c) Has no effect

    • d) Decreases activity at all times

      Answer: b) Optimal at ~37°C but can denature above

      Explanation: Enzymes have an optimal temperature, after which they can denature.

11. Which class of enzymes would catalyze the following reaction: AB + C → A + BC?

    • a) Ligases

    • b) Isomerases

    • c) Lyases

    • d) Oxidoreductases

      Answer: c) Lyases

      Explanation: Lyases add or remove groups to form or break double bonds.

12. Which enzyme subclass transfers phosphate groups?

    • a) Kinases

    • b) Peroxidases

    • c) Hydrolases

    • d) Decarboxylases

      Answer: a) Kinases

      Explanation: Kinases transfer phosphate groups often from ATP.

13. What term describes enzymes that are inhibited by their own products?

    • a) Allosteric enzymes

    • b) Feedback inhibitors

    • c) Competitive inhibitors

    • d) Irreversible inhibitors

      Answer: b) Feedback inhibitors

      Explanation: Feedback inhibition occurs when the end product inhibits an earlier enzyme in the pathway.

14. Which type of enzyme acts specifically on the bond between two amino acids?

    • a) Glycosidases

    • b) Esterases

    • c) Proteases

    • d) Kinases

      Answer: c) Proteases

      Explanation: Proteases break peptide bonds between amino acids.

15. Which of the following is an example of a coenzyme?

    • a) Zn²⁺

    • b) NAD⁺

    • c) H₂O

    • d) ATP

      Answer: b) NAD⁺

      Explanation: NAD⁺ is an organic cofactor that assists in enzyme function.

16. Which enzyme class includes those that transfer hydrogen atoms?

    • a) Ligases

    • b) Oxidoreductases

    • c) Transferases

    • d) Lyases

      Answer: b) Oxidoreductases

      Explanation: Oxidoreductases facilitate oxidation-reduction reactions.

17. Which of the following statements about enzyme specificity is true?

    • a) All enzymes have absolute specificity

    • b) Enzymes can only act on one substrate

    • c) Enzymes can have varying specificities

    • d) All enzymes can work on any substrate

      Answer: c) Enzymes can have varying specificities

      Explanation: Enzymes can either have absolute specificity or a broader specificity depending on their type.

18. What happens to an enzyme at very high pH levels?

    • a) It becomes more active

    • b) It is unaffected

    • c) It denatures

    • d) It converts into a coenzyme

      Answer: c) It denatures

      Explanation: High pH can lead to denaturation of proteins, including enzymes.

19. Which of the following processes does NOT involve enzymes?

    • a) DNA replication

    • b) Metabolism

    • c) Passive diffusion

    • d) Protein synthesis

      Answer: c) Passive diffusion

      Explanation: Passive diffusion does not require enzymes.

20. Which model allows for flexibility of the active site to better fit the substrate upon binding?

    • a) Lock-and-Key Model

    • b) Induced Fit Model

    • c) Enzyme-Substrate Complex Model

    • d) Rigid Structure Model

      Answer: b) Induced Fit Model

      Explanation: The induced fit model suggests the active site molds to fit the substrate more effectively after initial contact.

      ---

Identification Questions (10)

1. Apoenzyme: The protein part of an enzyme that is inactive on its own.

2. Cofactor: A nonprotein component that is necessary for enzyme activity (e.g., metal ions like Zn²⁺).

3. Coenzyme: An organic cofactor, often a vitamin, that assists in enzyme function.

4. Active Site: The specific part of an enzyme where the substrate binds and catalysis occurs.

5. Catalytic Site: The location within an enzyme where the actual chemical reaction takes place.

6. Feedback Control: A regulatory mechanism where the end product of a pathway inhibits an enzyme in an earlier step, preventing overproduction.

7. Isoenzymes: Different forms of the same enzyme that catalyze the same reaction but are found in different tissues and may have different kinetics.

8. Allosteric Regulation: A form of regulation where molecules bind to sites other than the active site to enhance or inhibit enzyme activity.

9. Saturated Solution: A point where increasing substrate concentration no longer increases reaction rate because all active sites are occupied.

10. Competitive Inhibition: A type of inhibition where the inhibitor competes with the substrate for binding to the active site.

Set 2.

Multiple Choice Questions

General Characteristics of Enzymes

1. What are enzymes primarily composed of?
   a) Lipids
   b) Proteins
   c) Carbohydrates
   d) Nucleic acids
   Answer: b) Proteins

2. Which of the following is NOT true about enzymes?
   a) They increase the reaction rate.
   b) They are consumed in the reaction.
   c) They lower the activation energy.
   d) They can be reused.
   Answer: b) They are consumed in the reaction.

3. Enzymes that consist only of amino acid chains are classified as:
   a) Conjugated enzymes
   b) Simple enzymes
   c) Holoenzymes
   d) Apoenzymes
   Answer: b) Simple enzymes

4. Which term describes the non-protein part of a conjugated enzyme?
   a) Apoenzyme
   b) Cofactor
   c) Holoenzyme
   d) Catalyst
   Answer: b) Cofactor

5. What is the term for the specific location where the substrate binds to the enzyme?
   a) Active site
   b) Binding site
   c) Catalytic site
   d) Transition site
   Answer: a) Active site

Classification of Enzymes

6. Which enzyme class catalyzes oxidation-reduction reactions?
   a) Hydrolases
   b) Transferases
   c) Oxidoreductases
   d) Lyases
   Answer: c) Oxidoreductases

7. What type of enzyme transfers a functional group between molecules?
   a) Ligases
   b) Transferases
   c) Lyases
   d) Isomerases
   Answer: b) Transferases

8. Which enzyme class catalyzes the rearrangement of atoms within a molecule?
   a) Isomerases
   b) Lyases
   c) Hydrolases
   d) Ligases
   Answer: a) Isomerases

9. Which enzyme catalyzes the removal of a carboxyl group?
   a) Decarboxylase
   b) Dehydratase
   c) Hydratase
   d) Aminotransferase
   Answer: a) Decarboxylase

10. What type of reaction is catalyzed by ligases?
    a) Bond cleavage with water
    b) Bond formation using ATP
    c) Rearrangement of atoms
    d) Oxidation-reduction
    Answer: b) Bond formation using ATP

Enzyme Specificity

11. Which specificity allows enzymes to act only on a single substrate?
    a) Stereochemical specificity
    b) Absolute specificity
    c) Group specificity
    d) Linkage specificity
    Answer: b) Absolute specificity

12. Which enzyme is specific to the stereoisomer L-amino acids?
    a) Trypsin
    b) L-amino acid oxidase
    c) Carboxypeptidase
    d) Phosphatase
    Answer: b) L-amino acid oxidase

13. Phosphatases are an example of enzymes with:
    a) Absolute specificity
    b) Group specificity
    c) Linkage specificity
    d) Stereochemical specificity
    Answer: c) Linkage specificity

Enzyme Kinetics

14. At a constant enzyme concentration, increasing substrate concentration will:
    a) Always decrease enzyme activity
    b) Eventually saturate the enzyme
    c) Have no effect on enzyme activity
    d) Decrease the activation energy indefinitely
    Answer: b) Eventually saturate the enzyme

15. What is the optimum temperature for most human enzymes?
    a) 25°C
    b) 37°C
    c) 50°C
    d) 100°C
    Answer: b) 37°C

16. Pepsin, an enzyme in the stomach, has an optimal pH of:
    a) 7.0
    b) 8.0
    c) 2.0
    d) 5.5
    Answer: c) 2.0

Mechanism of Action

17. The lock-and-key model suggests that:
    a) The active site is flexible and changes shape.
    b) The active site has a fixed shape.
    c) Substrates bind randomly to the enzyme.
    d) Enzymes work without specific binding.
    Answer: b) The active site has a fixed shape.

18. Which model accounts for the flexibility of the active site?
    a) Lock-and-key model
    b) Induced fit model
    c) Enzyme-substrate model
    d) Transition state model
    Answer: b) Induced fit model

Enzyme Inhibition

19. A competitive inhibitor:
    a) Binds to a site other than the active site.
    b) Forms irreversible bonds with the enzyme.
    c) Resembles the substrate.
    d) Increases enzyme activity.
    Answer: c) Resembles the substrate.

20. Noncompetitive inhibitors:
    a) Compete with the substrate for the active site.
    b) Change the enzyme's shape.
    c) Have the same structure as the substrate.
    d) Bind irreversibly to the enzyme.
    Answer: b) Change the enzyme's shape.

Factors Affecting Enzyme Activity

21. Increasing enzyme concentration while keeping substrate concentration constant will:
    a) Decrease enzyme activity
    b) Have no effect on enzyme activity
    c) Increase enzyme activity
    d) Decrease reaction rate
    Answer: c) Increase enzyme activity

22. At which point does the enzyme reach maximum activity due to substrate saturation?
    a) Turnover number
    b) Enzyme saturation
    c) Activation energy
    d) Optimum pH
    Answer: b) Enzyme saturation

23. Which factor can denature an enzyme by disrupting hydrogen bonds and ionic bonds?
    a) Temperature
    b) pH
    c) Substrate concentration
    d) Enzyme concentration
    Answer: a) Temperature

24. If an enzyme's optimum pH is 7.0, what happens at pH 2.0?
    a) Enzyme activity increases
    b) Enzyme activity decreases
    c) Enzyme activity remains constant
    d) Enzyme becomes more stable
    Answer: b) Enzyme activity decreases

25. Enzymes exhibit maximum activity at a specific temperature and pH. This condition is known as:
    a) Turnover state
    b) Optimum state
    c) Transition state
    d) Enzyme saturation
    Answer: b) Optimum state

Extremozymes

26. Which extremophile thrives in highly acidic conditions?
    a) Halophile
    b) Acidophile
    c) Cryophile
    d) Piezophile
    Answer: b) Acidophile

27. Extremozymes are particularly valuable in industrial applications because:
    a) They operate in extreme conditions
    b) They are more stable than other enzymes
    c) They can be used in cold wash cycles
    d) All of the above
    Answer: d) All of the above

28. An extremophile that grows in temperatures below 15°C is called a:
    a) Thermophile
    b) Halophile
    c) Cryophile
    d) Alkaliphile
    Answer: c) Cryophile

29. Which extremophile would you find thriving in environments with high salinity?
    a) Hydrothermophile
    b) Alkaliphile
    c) Halophile
    d) Acidophile
    Answer: c) Halophile

30. What is an extremophile enzyme that can resist extreme pH, temperature, and pressure called?
    a) Cofactor
    b) Extremolyte
    c) Extremozyme
    d) Isozyme
    Answer: c) Extremozyme

Enzyme Regulation

31. Which type of enzyme regulation involves feedback inhibition?
    a) Allosteric regulation
    b) Proenzyme activation
    c) Feedback control
    d) Isoenzymes
    Answer: c) Feedback control

32. In feedback control, the product of the reaction pathway:
    a) Activates allosteric enzymes
    b) Inhibits an earlier step in the pathway
    c) Speeds up the enzyme reaction
    d) Irreversibly binds to the enzyme
    Answer: b) Inhibits an earlier step in the pathway

33. Zymogens are enzymes that are:
    a) Inactive precursors requiring activation
    b) Allosterically regulated
    c) Active without modification
    d) Isoenzymes of one another
    Answer: a) Inactive precursors requiring activation

34. The removal of a fragment from trypsinogen to form trypsin is an example of:
    a) Allosteric activation
    b) Proenzyme activation
    c) Feedback inhibition
    d) Competitive inhibition
    Answer: b) Proenzyme activation

35. Allosteric enzymes are regulated by:
    a) The substrate binding to the active site
    b) The presence of cofactors only
    c) Molecules binding at sites other than the active site
    d) Changing the pH of the enzyme environment
    Answer: c) Molecules binding at sites other than the active site

Clinical and Industrial Applications

36. Which enzyme is used as a diagnostic marker for heart attacks?
    a) Lactate dehydrogenase (LDH)
    b) Amylase
    c) Sucrase
    d) Trypsin
    Answer: a) Lactate dehydrogenase (LDH)

37. What enzyme is used in cold wash detergents for stain removal?
    a) Amylase
    b) Lipase
    c) Protease
    d) Extremozymes
    Answer: d) Extremozymes

38. Elevated levels of alkaline phosphatase (ALP) in the blood may indicate:
    a) Heart attack
    b) Bone disease
    c) Pancreatic disease
    d) Hepatitis
    Answer: b) Bone disease

39. Which enzyme catalyzes the conversion of lactate to pyruvate?
    a) Pyruvate kinase
    b) Lactate dehydrogenase
    c) Creatine kinase
    d) Alanine aminotransferase
    Answer: b) Lactate dehydrogenase

40. What are isoenzymes?
    a) Enzymes with identical structures but different functions
    b) Enzymes that catalyze the same reaction but have different structures
    c) Inactive forms of enzymes
    d) Enzymes found only in extreme environments
    Answer: b) Enzymes that catalyze the same reaction but have different structures

TOPIC: NUCLEIC ACIDS

Set 1.

Multiple Choice Questions (20 items)

(Each question has one correct answer with an explanation.)

1. What is the repeating unit of DNA or RNA polymer?
   A. Ribose
   B. Deoxyribose
   C. Nucleotide
   D. Phosphate
   Answer: C. Nucleotide
   Explanation: Nucleotides are the monomers that form the polymers DNA and RNA. They consist of a sugar, a base, and a phosphate group.

2. Which sugar is found in RNA?
   A. Deoxyribose
   B. Fructose
   C. Ribose
   D. Glucose
   Answer: C. Ribose
   Explanation: Ribose is the sugar in RNA, whereas deoxyribose is found in DNA.

3. In the DNA double helix, which base pairs with guanine (G)?
   A. Thymine (T)
   B. Adenine (A)
   C. Uracil (U)
   D. Cytosine (C)
   Answer: D. Cytosine (C)
   Explanation: Guanine pairs with cytosine through three hydrogen bonds in DNA.

4. What is the diameter of the DNA double helix?
   A. 1 nm
   B. 2 nm
   C. 3.4 nm
   D. 10 nm
   Answer: B. 2 nm
   Explanation: The DNA double helix has a diameter of 2 nm.

5. Which type of RNA carries amino acids to the ribosome?
   A. mRNA
   B. tRNA
   C. rRNA
   D. snRNA
   Answer: B. tRNA
   Explanation: tRNA (transfer RNA) transports amino acids to the ribosome for protein synthesis.

6. What is the main function of RNA polymerase during transcription?
   A. Unwinding the DNA
   B. Synthesizing ribosomes
   C. Assembling nucleotides into RNA
   D. Splicing RNA
   Answer: C. Assembling nucleotides into RNA
   Explanation: RNA polymerase builds the RNA strand by assembling ribonucleotides complementary to the DNA template strand.

7. What type of bonds hold base pairs together in DNA?
   A. Ionic bonds
   B. Covalent bonds
   C. Hydrogen bonds
   D. Peptide bonds
   Answer: C. Hydrogen bonds
   Explanation: Hydrogen bonds connect complementary base pairs (A-T and G-C) in the DNA double helix.

8. Which base is unique to RNA?
   A. Thymine
   B. Uracil
   C. Cytosine
   D. Guanine
   Answer: B. Uracil
   Explanation: Uracil is present in RNA instead of thymine, which is found in DNA.

9. What is the role of helicase in DNA replication?
   A. Joining Okazaki fragments
   B. Synthesizing primers
   C. Unwinding the DNA double helix
   D. Pairing bases
   Answer: C. Unwinding the DNA double helix
   Explanation: Helicase unwinds the DNA to prepare it for replication.

10. Which process copies DNA into an identical strand?
    A. Transcription
    B. Translation
    C. Replication
    D. Transformation
    Answer: C. Replication
    Explanation: DNA replication produces two identical copies of the original DNA molecule.

11. What type of mutation involves substituting one nucleotide for another?
    A. Point mutation
    B. Deletion
    C. Insertion
    D. Frameshift mutation
    Answer: A. Point mutation
    Explanation: A point mutation changes a single nucleotide in the DNA sequence.

12. What forms the backbone of DNA?
    A. Base pairs
    B. Sugar-phosphate groups
    C. Hydrogen bonds
    D. Amino acids
    Answer: B. Sugar-phosphate groups
    Explanation: The sugar-phosphate backbone supports the structure of DNA and RNA.

13. What is the sequence written from the 5′ to 3′ end called?
    A. Genetic code
    B. DNA helix
    C. Nucleic acid sequence
    D. Codon
    Answer: C. Nucleic acid sequence
    Explanation: Nucleic acid sequences are described starting from the 5′ end and listing the bases in order.

14. What does the "A" in mRNA stand for?
    A. Acceptor
    B. Adenine
    C. Acid
    D. Amino
    Answer: D. Amino
    Explanation: mRNA stands for messenger RNA, which carries the message for amino acid assembly.

15. What type of repair removes and replaces up to 24-32 nucleotides?
    A. BER
    B. NER
    C. Recombinant repair
    D. Ligase repair
    Answer: B. NER
    Explanation: Nucleotide excision repair (NER) is a mechanism to remove larger DNA lesions.

16. What shape does tRNA take in its three-dimensional structure?
    A. Double helix
    B. Cloverleaf
    C. Straight chain
    D. L-shaped
    Answer: D. L-shaped
    Explanation: tRNA has a cloverleaf secondary structure but folds into an L-shape in 3D.

17. What does the term "degenerate" mean in the genetic code?
    A. Nonfunctional codons exist
    B. A single codon codes for multiple amino acids
    C. Multiple codons can code for the same amino acid
    D. Some bases overlap between codons
    Answer: C. Multiple codons can code for the same amino acid
    Explanation: Degeneracy means redundancy in the genetic code.

18. Which enzyme joins Okazaki fragments?
    A. Helicase
    B. Ligase
    C. Polymerase
    D. Topoisomerase
    Answer: B. Ligase
    Explanation: DNA ligase seals nicks between Okazaki fragments to complete DNA replication.

19. Which codons signal the termination of protein synthesis?
    A. AUG
    B. UAA, UAG, UGA
    C. GGG, CCC, AAA
    D. UUU, UGC, UAC
    Answer: B. UAA, UAG, UGA
    Explanation: These are stop codons that terminate translation.

20. What happens during transcription?
    A. DNA is copied into mRNA.
    B. mRNA is translated into proteins.
    C. DNA is replicated.
    D. tRNA transports amino acids.
    Answer: A. DNA is copied into mRNA.
    Explanation: Transcription converts DNA into messenger RNA.

Identification (10 items)

1. The sugar found in RNA.
   Answer: Ribose

2. The enzyme that synthesizes RNA during transcription.
   Answer: RNA polymerase

3. The complementary base of adenine in DNA.
   Answer: Thymine

4. The process by which DNA is copied into an identical strand.
   Answer: Replication

5. A mutation where nucleotides are added to the DNA sequence.
   Answer: Insertion

6. The RNA molecule that directs the sequence of amino acids in a protein.
   Answer: mRNA

7. The type of bond between the sugar and phosphate in DNA.
   Answer: Phosphodiester bond

8. The purine bases found in nucleic acids.
   Answer: Adenine and guanine

9. The enzyme responsible for sealing nicks in the DNA backbone.
   Answer: DNA ligase

10. The repeating sequence that makes up the backbone of DNA and RNA.
    Answer: Sugar-phosphate

Set 2.

Multiple Choice Questions

Structure of Nucleic Acids

1. What are the three main components of a nucleotide?
   a) Nitrogenous base, lipid, phosphate
   b) Ribose, phosphate, nitrogenous base
   c) Nitrogenous base, sugar, phosphate
   d) Protein, sugar, phosphate
   Answer: c) Nitrogenous base, sugar, phosphate

2. Which sugar is found in DNA?
   a) Ribose
   b) Glucose
   c) Deoxyribose
   d) Fructose
   Answer: c) Deoxyribose

3. What nitrogenous base is unique to RNA?
   a) Thymine
   b) Adenine
   c) Guanine
   d) Uracil
   Answer: d) Uracil

4. How many hydrogen bonds stabilize a G-C base pair?
   a) One
   b) Two
   c) Three
   d) Four
   Answer: c) Three

5. What is the directionality of a DNA sequence?
   a) 3’ to 5’
   b) 5’ to 3’
   c) 1’ to 2’
   d) Random
   Answer: b) 5’ to 3’

DNA Structure and Function

6. What shape does the DNA molecule take?
   a) Single helix
   b) Alpha helix
   c) Double helix
   d) Triple helix
   Answer: c) Double helix

7. Which bonds connect the sugar-phosphate backbone of DNA?
   a) Hydrogen bonds
   b) Peptide bonds
   c) Phosphodiester bonds
   d) Ionic bonds
   Answer: c) Phosphodiester bonds

8. What creates the major and minor grooves in the DNA double helix?
   a) Base stacking
   b) The twisting of the helix
   c) Hydrogen bonding
   d) Phosphorylation
   Answer: b) The twisting of the helix

9. What is the function of the sugar-phosphate backbone?
   a) It stores genetic information.
   b) It protects nitrogenous bases.
   c) It provides structural support.
   d) It facilitates protein synthesis.
   Answer: c) It provides structural support.

10. How many base pairs are found in one complete turn of a DNA helix?
    a) 5
    b) 10
    c) 15
    d) 20
    Answer: b) 10

DNA Replication

11. Which enzyme unwinds the DNA double helix during replication?
    a) DNA polymerase
    b) Helicase
    c) Ligase
    d) Topoisomerase
    Answer: b) Helicase

12. What are Okazaki fragments?
    a) Continuous DNA strands
    b) Short DNA fragments synthesized on the lagging strand
    c) The RNA primers in replication
    d) Proteins that assist in replication
    Answer: b) Short DNA fragments synthesized on the lagging strand

13. What is the function of DNA polymerase?
    a) To unwind the DNA helix
    b) To synthesize primers
    c) To add nucleotides to the growing DNA strand
    d) To splice introns from RNA
    Answer: c) To add nucleotides to the growing DNA strand

14. DNA replication is:
    a) Conservative
    b) Semi-conservative
    c) Dispersive
    d) Random
    Answer: b) Semi-conservative

15. Which enzyme seals nicks in the sugar-phosphate backbone?
    a) Helicase
    b) DNA polymerase
    c) DNA ligase
    d) Primase
    Answer: c) DNA ligase

RNA Structure and Function

16. What sugar is found in RNA?
    a) Ribose
    b) Deoxyribose
    c) Fructose
    d) Maltose
    Answer: a) Ribose

17. Which type of RNA carries the genetic code from the nucleus to the ribosome?
    a) tRNA
    b) mRNA
    c) rRNA
    d) snRNA
    Answer: b) mRNA

18. What is the function of tRNA?
    a) Carries the genetic code to the ribosome
    b) Synthesizes proteins
    c) Brings amino acids to the ribosome
    d) Forms ribosomal subunits
    Answer: c) Brings amino acids to the ribosome

19. Which base pairs with adenine in RNA?
    a) Cytosine
    b) Guanine
    c) Uracil
    d) Thymine
    Answer: c) Uracil

20. What shape does tRNA have?
    a) Linear
    b) Cloverleaf
    c) Double helix
    d) Beta sheet
    Answer: b) Cloverleaf

Transcription and Translation

21. What enzyme catalyzes transcription?
    a) RNA polymerase
    b) DNA polymerase
    c) Ligase
    d) Helicase
    Answer: a) RNA polymerase

22. Which process converts mRNA into a protein?
    a) Replication
    b) Transcription
    c) Translation
    d) Splicing
    Answer: c) Translation

23. What sequence signals the start of transcription?
    a) Terminator
    b) Promoter
    c) Codon
    d) Enhancer
    Answer: b) Promoter

24. Which RNA sequence is complementary to a DNA strand with a sequence 5'-GCTA-3'?
    a) 3'-CGAU-5'
    b) 5'-CGAU-3'
    c) 3'-GCUA-5'
    d) 5'-GCUA-3'
    Answer: a) 3'-CGAU-5'

25. In which cellular organelle does translation occur?
    a) Nucleus
    b) Ribosome
    c) Mitochondria
    d) Lysosome
    Answer: b) Ribosome

The Genetic Code

26. How many nucleotides are in a codon?
    a) One
    b) Two
    c) Three
    d) Four
    Answer: c) Three

27. The codon AUG codes for which amino acid?
    a) Glycine
    b) Methionine
    c) Serine
    d) Leucine
    Answer: b) Methionine

28. How many stop codons are there?
    a) One
    b) Two
    c) Three
    d) Four
    Answer: c) Three

29. What does the term "degenerate" mean in the context of the genetic code?
    a) A codon codes for multiple amino acids.
    b) Multiple codons code for the same amino acid.
    c) Each codon codes for only one amino acid.
    d) The code is universal.
    Answer: b) Multiple codons code for the same amino acid.

30. What sequence ends translation?
    a) Start codon
    b) Anticodon
    c) Stop codon
    d) Promoter
    Answer: c) Stop codon

Mutations and Repair

31. What is a point mutation?
    a) Substitution of one nucleotide for another
    b) Deletion of a nucleotide
    c) Addition of a nucleotide
    d) Translocation of a chromosome
    Answer: a) Substitution of one nucleotide for another

32. Which enzyme repairs single-base errors in DNA?
    a) Ligase
    b) DNA polymerase
    c) Glycosylase
    d) Topoisomerase
    Answer: c) Glycosylase

33. What type of damage is caused by UV light?
    a) Pyrimidine dimer formation
    b) Single-strand breaks
    c) Double-strand breaks
    d) Base substitution
    Answer: a) Pyrimidine dimer formation

34. What is the purpose of base excision repair?
    a) To correct small-scale errors
    b) To splice introns
    c) To prevent transcription
    d) To unwind supercoils
    Answer: a) To correct small-scale errors

35. What mechanism seals the repaired DNA strand?
    a) Exonuclease
    b) Helicase
    c) DNA ligase
    d) Primase
    Answer: c) DNA ligase

Biotechnology

36. What is the purpose of PCR?
    a) To cut DNA
    b) To replicate DNA in vitro
    c) To sequence RNA
    d) To transcribe mRNA
    Answer: b) To replicate DNA in vitro

37. Which enzyme is used in PCR?
    a) DNA ligase
    b) RNA polymerase
    c) Taq polymerase
    d) Helicase
    Answer: c) Taq polymerase

38. At what temperature does DNA denature during PCR?
    a) 37°C
    b) 56°C
    c) 72°C
    d) 94°C
    Answer: d) 94°C

39. How many DNA strands are produced after three PCR cycles starting with one strand?
    a) 4
    b) 6
    c) 8
    d) 16
    Answer: c) 8

40. What is the role of primers in PCR?
    a) To catalyze the reaction
    b) To provide a starting point for DNA synthesis
    c) To stabilize DNA
    d) To ligate fragments
    Answer: b) To provide a starting point for DNA synthesis

TOPIC: The Importance of Energy Changes and Electron Transport Chain in Biology

1. What is the standard state for biochemical reactions regarding pH?

A) pH = 0
B) pH = 7
C) pH = 10
D) pH = 14
Answer: B) pH = 7

2. What happens to ΔG when a reaction reaches equilibrium?

A) ΔG = 0
B) ΔG < 0
C) ΔG > 0
D) ΔG = ΔH
Answer: A) ΔG = 0

3. What is the final product of catabolism for carbon molecules?

A) CH4
B) C2H6
C) CO2
D) C6H12O6
Answer: C) CO2

4. Which coenzyme acts as a biological oxidizing agent in metabolism?

A) FADH2
B) NAD+
C) ATP
D) CoA-SH
Answer: B) NAD+

5. How many electrons does NAD+ accept during its reduction to NADH?

A) 1
B) 2
C) 3
D) 4
Answer: B) 2

6. Which process is associated with a loss of electrons?

A) Reduction
B) Oxidation
C) Phosphorylation
D) Hydrolysis
Answer: B) Oxidation

7. What type of reaction is anabolism characterized by?

A) Energy-releasing
B) Oxidative
C) Reductive
D) Exergonic
Answer: C) Reductive

8. What is the main energy currency of the cell?

A) NADH
B) FAD
C) ATP
D) Coenzyme A
Answer: C) ATP

9. What does ATP hydrolysis result in?

A) Gain of a phosphate group
B) Decrease in electrostatic repulsion
C) Increase in ATP concentration
D) Formation of NADH
Answer: B) Decrease in electrostatic repulsion

10. How many negative charges does ATP contain?

A) 1
B) 2
C) 3
D) 4
Answer: D) 4

11. Which component of ATP makes it less stable than ADP?

A) Loss of protons
B) Gain of electrons
C) Increased negative charge
D) Loss of entropy
Answer: C) Increased negative charge

12. What type of bond in ATP is referred to as a "high-energy" bond?

A) Ionic bond
B) Covalent bond
C) Phosphoric anhydride bond
D) Hydrogen bond
Answer: C) Phosphoric anhydride bond

13. What is the primary role of Coenzyme A in metabolism?

A) Transport electrons
B) Activate metabolic pathways
C) Synthesize glucose
D) Hydrolyze ATP
Answer: B) Activate metabolic pathways

14. What reaction results in the formation of acetyl-CoA?

A) Dehydration of alcohol
B) Oxidation of fatty acids
C) Reduction of CO2
D) Phosphorylation of pyruvate
Answer: B) Oxidation of fatty acids

15. How many protons does FAD accept to form FADH2?

A) 1
B) 2
C) 3
D) 4
Answer: B) 2

16. What type of energy transformation occurs during ATP hydrolysis?

A) Kinetic to potential
B) Potential to chemical
C) Chemical to mechanical
D) Chemical to potential
Answer: C) Chemical to mechanical

17. Which term describes the sum of all chemical reactions in an organism?

A) Catabolism
B) Anabolism
C) Metabolism
D) Oxidation
Answer: C) Metabolism

18. What is the function of the thioester linkage in acetyl-CoA?

A) Store electrons
B) Increase energy content
C) Stabilize ATP
D) Bind NAD+
Answer: B) Increase energy content

19. Which molecule is reduced during the conversion of ethanol to acetaldehyde?

A) NAD+
B) NADH
C) FAD
D) ATP
Answer: A) NAD+

20. What ensures efficient energy use in metabolic pathways?

A) Direct energy transfer
B) Single-step reactions
C) Multistage processes
D) Irreversible pathways
Answer: C) Multistage processes

TOPIC GLYCOLYSIS

1. What is the first step of glycolysis?

A) Oxidation of glucose
B) Phosphorylation of glucose
C) Cleavage of fructose-1,6-bisphosphate
D) Isomerization of glucose-6-phosphate
Answer: B) Phosphorylation of glucose

2. What is the final product of glycolysis under aerobic conditions?

A) Lactate
B) Ethanol
C) Acetaldehyde
D) Pyruvate
Answer: D) Pyruvate

3. How many molecules of ATP are produced (net) per molecule of glucose in glycolysis?

A) 1
B) 2
C) 4
D) 6
Answer: B) 2

4. What enzyme catalyzes the phosphorylation of fructose-6-phosphate?

A) Hexokinase
B) Pyruvate kinase
C) Phosphofructokinase
D) Aldolase
Answer: C) Phosphofructokinase

5. Which intermediate is formed when glucose is phosphorylated in step 1?

A) Glucose-1-phosphate
B) Fructose-1,6-bisphosphate
C) Glucose-6-phosphate
D) Dihydroxyacetone phosphate
Answer: C) Glucose-6-phosphate

6. How many molecules of pyruvate are generated from one molecule of glucose?

A) 1
B) 2
C) 4
D) 6
Answer: B) 2

7. What is the role of NAD+ in glycolysis?

A) Donate electrons
B) Oxidize pyruvate
C) Accept electrons
D) Form ATP
Answer: C) Accept electrons

8. Which reaction in glycolysis is an example of substrate-level phosphorylation?

A) Phosphorylation of glucose
B) Conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate
C) Isomerization of 2-phosphoglycerate to phosphoenolpyruvate
D) Conversion of glucose-6-phosphate to fructose-6-phosphate
Answer: B) Conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate

9. Which enzyme splits fructose-1,6-bisphosphate into two triose molecules?

A) Enolase
B) Aldolase
C) Phosphoglycerate kinase
D) Hexokinase
Answer: B) Aldolase

10. What happens to dihydroxyacetone phosphate (DHAP) in glycolysis?

A) It forms pyruvate directly.
B) It is converted to glyceraldehyde-3-phosphate.
C) It undergoes phosphorylation to form 3-phosphoglycerate.
D) It is oxidized to lactate.
Answer: B) It is converted to glyceraldehyde-3-phosphate.

11. What is the key regulatory enzyme of glycolysis?

A) Hexokinase
B) Aldolase
C) Phosphofructokinase
D) Pyruvate kinase
Answer: C) Phosphofructokinase

12. Which cofactor is required for the conversion of pyruvate to ethanol in alcoholic fermentation?

A) NADP+
B) Mg²⁺ and thiamine pyrophosphate (TPP)
C) FADH2
D) ATP
Answer: B) Mg²⁺ and thiamine pyrophosphate (TPP)

13. Under anaerobic conditions, what is the primary fate of pyruvate in muscle cells?

A) Conversion to ethanol
B) Conversion to lactate
C) Conversion to acetaldehyde
D) Conversion to acetyl-CoA
Answer: B) Conversion to lactate

14. What is the ΔG of hydrolysis of phosphoenolpyruvate (PEP)?

A) -7.3 kJ/mol
B) -30.5 kJ/mol
C) -61.9 kJ/mol
D) 0 kJ/mol
Answer: C) -61.9 kJ/mol

15. How many molecules of NADH are produced in glycolysis per molecule of glucose?

A) 1
B) 2
C) 3
D) 4
Answer: B) 2

16. What type of reaction is catalyzed by pyruvate kinase?

A) Phosphorylation
B) Hydrolysis
C) Substrate-level phosphorylation
D) Oxidation
Answer: C) Substrate-level phosphorylation

17. Which enzyme catalyzes the dehydration of 2-phosphoglycerate to phosphoenolpyruvate?

A) Enolase
B) Aldolase
C) Pyruvate kinase
D) Hexokinase
Answer: A) Enolase

18. Which intermediate of glycolysis contains a high-energy bond?

A) Glucose-6-phosphate
B) Phosphoenolpyruvate
C) Glyceraldehyde-3-phosphate
D) Fructose-6-phosphate
Answer: B) Phosphoenolpyruvate

19. What is the main product of glycolysis under aerobic conditions?

A) NADH and pyruvate
B) Lactate and ATP
C) Ethanol and NADH
D) Acetaldehyde and ADP
Answer: A) NADH and pyruvate

20. How many total ATP molecules are generated in glycolysis (before accounting for ATP consumption)?

A) 2
B) 4
C) 6
D) 8
Answer: B) 4

TOPIC: Storage Mechanisms and Control in Carbohydrate Metabolism

Final Exam: Carbohydrate Metabolism (Multiple Choice)

1. How is glycogen cleaved during breakdown?

a) By hydrolysis to form glucose
b) By phosphorylation to form α-D-glucose-1-phosphate
c) By oxidation to form glucose-6-phosphate
d) By hydrolysis to form maltose
Answer: b

2. Which enzyme catalyzes the conversion of glucose-1-phosphate to glucose-6-phosphate?

a) Glycogen phosphorylase
b) Phosphofructokinase
c) Phosphoglucomutase
d) Glucose-6-phosphatase
Answer: c

3. What is required for glycogen synthesis from glucose?

a) ATP hydrolysis
b) Hydrolysis of UTP
c) Oxidation of glucose
d) Direct glucose polymerization
Answer: b

4. What drives the formation of UDP-glucose to completion during glycogen synthesis?

a) ATP hydrolysis
b) Coupling with UTP synthesis
c) Coupling with pyrophosphate hydrolysis
d) Reduction of NADP+
Answer: c

5. Which enzyme deactivates glycogen synthase?

a) Glycogen phosphorylase
b) Phosphoprotein phosphatase
c) Phosphorylase kinase
d) Glucose-6-phosphatase
Answer: c

6. What happens to glycogen synthase after it is phosphorylated?

a) It becomes active
b) It becomes inactive
c) Its activity remains unchanged
d) It converts to a phosphorylase enzyme
Answer: b

7. Gluconeogenesis converts pyruvate into glucose using distinct enzymes for certain steps. Which step requires biotin?

a) Pyruvate to oxaloacetate
b) Fructose-6-phosphate to glucose
c) Glucose-1-phosphate to glycogen
d) Glucose-6-phosphate to glucose
Answer: a

8. The Cori cycle primarily involves which two organs?

a) Brain and liver
b) Muscle and liver
c) Muscle and kidney
d) Liver and pancreas
Answer: b

9. What is the role of fructose-2,6-bisphosphate (F2,6P) in carbohydrate metabolism?

a) Activates phosphofructokinase, stimulating glycolysis
b) Inhibits phosphofructokinase, reducing glycolysis
c) Activates gluconeogenesis by inhibiting fructose bisphosphatase
d) No role in metabolic regulation
Answer: a

10. Which enzyme is inhibited by high levels of glucose-6-phosphate?

a) Hexokinase
b) Glycogen phosphorylase
c) Glucose-6-phosphatase
d) Pyruvate kinase
Answer: a

11. What is the primary purpose of the Pentose Phosphate Pathway (PPP)?

a) ATP production
b) Conversion of ribose to glucose
c) Production of NADPH and ribose-5-phosphate
d) Glycogen breakdown
Answer: c

12. Which enzyme transfers two-carbon units in the PPP?

a) Transaldolase
b) Transketolase
c) Phosphofructokinase
d) Glucose-6-phosphatase
Answer: b

13. What stimulates the channeling of glucose-6-phosphate into glycolysis?

a) NADPH demand
b) ATP demand
c) Ribose-5-phosphate demand
d) High levels of NAD+
Answer: b

14. What is the net reaction of gluconeogenesis involving pyruvate carboxylase?

a) Pyruvate → Glucose
b) Pyruvate → Phosphoenolpyruvate
c) Glucose → Pyruvate
d) Oxaloacetate → Pyruvate
Answer: b

15. What is the key control enzyme in glycolysis?

a) Hexokinase
b) Pyruvate kinase
c) Phosphofructokinase
d) Glucose-6-phosphatase
Answer: c

16. How does ATP affect pyruvate kinase?

a) Activates it
b) Inhibits it
c) Has no effect
d) Converts it to its isoform
Answer: b

17. What type of modification regulates glycogen phosphorylase?

a) Phosphorylation
b) Oxidation
c) Hydrolysis
d) Polymerization
Answer: a

18. During the PPP, what is the initial substrate?

a) Glucose
b) Ribose-5-phosphate
c) Glucose-6-phosphate
d) Fructose-6-phosphate
Answer: c

19. What is the main difference between glycolysis and the PPP?

a) Glycolysis produces ATP, PPP does not
b) PPP produces ribose, glycolysis does not
c) PPP uses NADP+, glycolysis uses NAD+
d) All of the above
Answer: d

20. Which reaction in gluconeogenesis is catalyzed by glucose-6-phosphatase?

a) Pyruvate → Oxaloacetate
b) Fructose-1,6-bisphosphate → Fructose-6-phosphate
c) Glucose-6-phosphate → Glucose
d) Fructose-6-phosphate → Glucose
Answer: c

TOPIC CITRIC CYCLE

Here's the set of multiple-choice questions for each topic:

Citric Acid Cycle (20 Questions)

1. What is the role of the citric acid cycle in metabolism?

a) It is purely catabolic.
b) It is purely anabolic.
c) It is both catabolic and anabolic (amphibolic).
d) It exclusively produces ATP.
Answer: c

2. Where does the citric acid cycle occur in eukaryotic cells?

a) Cytoplasm
b) Mitochondrial matrix
c) Endoplasmic reticulum
d) Nucleus
Answer: b

3. Which enzyme catalyzes the conversion of pyruvate to acetyl-CoA?

a) Pyruvate carboxylase
b) Pyruvate dehydrogenase complex
c) Citrate synthase
d) Aconitase
Answer: b

4. What is the first step of the citric acid cycle?

a) Conversion of isocitrate to α-ketoglutarate
b) Oxidation of succinate to fumarate
c) Condensation of acetyl-CoA with oxaloacetate to form citrate
d) Oxidation of malate to oxaloacetate
Answer: c

5. Which enzyme catalyzes the isomerization of citrate to isocitrate?

a) Isocitrate dehydrogenase
b) Citrate synthase
c) Aconitase
d) Fumarase
Answer: c

6. Which step in the citric acid cycle directly produces ATP or GTP?

a) Oxidation of isocitrate
b) Hydrolysis of succinyl-CoA
c) Oxidation of succinate
d) Oxidation of malate
Answer: b

7. Which enzyme is inhibited by NADH and ATP?

a) Citrate synthase
b) Aconitase
c) Succinate dehydrogenase
d) Pyruvate carboxylase
Answer: a

8. What is the net production of NADH per turn of the citric acid cycle?

a) 2
b) 3
c) 4
d) 6
Answer: b

9. How many molecules of CO2 are released per acetyl-CoA in the cycle?

a) 1
b) 2
c) 3
d) 4
Answer: b

10. What type of reaction is catalyzed by α-ketoglutarate dehydrogenase?

a) Oxidative decarboxylation
b) Phosphorylation
c) Hydration
d) Isomerization
Answer: a

11. Which cofactor is not required by the pyruvate dehydrogenase complex?

a) TPP
b) FAD
c) NAD+
d) ATP
Answer: d

12. The glyoxylate cycle bypasses which two reactions of the citric acid cycle?

a) Formation of succinate and fumarate
b) Oxidative decarboxylation of isocitrate and α-ketoglutarate
c) Hydration of fumarate and oxidation of malate
d) Condensation of acetyl-CoA and hydrolysis of succinyl-CoA
Answer: b

13. Which enzyme converts fumarate to malate?

a) Fumarase
b) Malate dehydrogenase
c) Succinate dehydrogenase
d) Citrate synthase
Answer: a

14. What is the final product of the citric acid cycle that replenishes the starting reactant?

a) Citrate
b) Oxaloacetate
c) Malate
d) Fumarate
Answer: b

15. Which molecule activates isocitrate dehydrogenase?

a) ATP
b) NADH
c) ADP
d) Citrate
Answer: c

16. What is an anaplerotic reaction?

a) A reaction that replenishes citric acid cycle intermediates
b) A reaction that consumes ATP
c) A reaction that reduces NADH
d) A reaction exclusive to glycolysis
Answer: a

17. What is the major control point outside the citric acid cycle?

a) Citrate synthase
b) Pyruvate dehydrogenase
c) Isocitrate dehydrogenase
d) Succinate dehydrogenase
Answer: b

18. Which organelle contains glyoxysomes for the glyoxylate cycle?

a) Mitochondria
b) Chloroplasts
c) Nucleus
d) Specialized plant organelles
Answer: d

19. What molecule is formed by the hydrolysis of succinyl-CoA?

a) GTP
b) ATP
c) Both GTP and ATP depending on the cell type
d) NADH
Answer: c

20. Which enzyme catalyzes the final step of the cycle, oxidizing malate to oxaloacetate?

a) Fumarase
b) Succinate dehydrogenase
c) Malate dehydrogenase
d) Isocitrate dehydrogenase
Answer: c

Citric Acid Cycle: ATP-Related Questions

21. How many ATP (or GTP) molecules are directly produced per turn of the citric acid cycle?

a) 1
b) 2
c) 3
d) 4
Answer: a

22. How many NADH molecules are produced per acetyl-CoA in the citric acid cycle?

a) 1
b) 2
c) 3
d) 4
Answer: c

23. How many FADH2 molecules are produced per turn of the citric acid cycle?

a) 1
b) 2
c) 3
d) 4
Answer: a

24. Considering ATP yield from NADH, FADH2, and GTP, how many ATP equivalents are produced per acetyl-CoA oxidized through the citric acid cycle?

a) 10
b) 12
c) 15
d) 18
Answer: a
Explanation: Each cycle yields 3 NADH (7.5 ATP), 1 FADH2 (1.5 ATP), and 1 GTP (1 ATP). Total = 10 ATP.

25. How many ATP are produced from one molecule of glucose through two complete turns of the citric acid cycle?

a) 20
b) 15
c) 30
d) 25
Answer: a
Explanation: One glucose molecule yields two acetyl-CoA molecules, which enter the cycle twice, producing 20 ATP equivalents.

TOPIC ELECTRON TRANSPORT CHAIN

Electron Transport Chain (20 Questions)

1. What is the primary function of the electron transport chain (ETC)?

a) Produce ATP directly
b) Transport protons across the mitochondrial membrane
c) Generate a proton gradient for ATP synthesis
d) Synthesize NADH
Answer: c

2. Which complex in the ETC receives electrons from NADH?

a) Complex I (NADH-CoQ oxidoreductase)
b) Complex II (Succinate-CoQ oxidoreductase)
c) Complex III (CoQH2-cytochrome c oxidoreductase)
d) Complex IV (Cytochrome c oxidase)
Answer: a

3. Which molecule serves as the final electron acceptor in the ETC?

a) Water
b) Oxygen
c) NAD+
d) Cytochrome c
Answer: b

4. What is the role of coenzyme Q (ubiquinone) in the ETC?

a) Final electron acceptor
b) Shuttle electrons between Complexes I/II and III
c) Proton transporter
d) ATP producer
Answer: b

5. Which complex reduces oxygen to water?

a) Complex I
b) Complex II
c) Complex III
d) Complex IV
Answer: d

6. How many protons are pumped across the inner mitochondrial membrane per NADH oxidized?

a) 6
b) 8
c) 10
d) 12
Answer: c

7. What is the P/O ratio for NADH oxidation in the ETC?

a) 1
b) 1.5
c) 2
d) 2.5
Answer: d

8. What does the Q cycle facilitate?

a) Direct ATP production
b) Proton translocation and electron transfer in Complex III
c) Oxygen reduction in Complex IV
d) NADH production in the cytosol
Answer: b

9. Which metal ion is a key component in cytochromes?

a) Zinc
b) Magnesium
c) Iron
d) Calcium
Answer: c

10. Which component of ATP synthase forms the proton channel?

a) F1
b) F0
c) CoQ
d) Cytochrome c
Answer: b

11. What is the role of uncouplers in oxidative phosphorylation?

a) Block electron flow
b) Inhibit ATP production without affecting electron transport
c) Stimulate NADH oxidation
d) Increase ATP synthesis efficiency
Answer: b

12. What is the primary driving force for ATP synthesis in mitochondria?

a) NADH oxidation
b) Proton gradient across the inner mitochondrial membrane
c) Cytochrome c reduction
d) CoQ reduction
Answer: b

13. What is the function of the F1 subunit of ATP synthase?

a) Proton channel formation
b) Phosphorylation of ADP to ATP
c) ATP hydrolysis only
d) Proton gradient dissipation
Answer: b

14. What is the primary shuttle mechanism in heart and liver cells for cytosolic NADH?

a) Glycerol phosphate shuttle
b) Malate-aspartate shuttle
c) CoQ shuttle
d) Pyruvate shuttle
Answer: b

15. What happens to the P/O ratio when FADH2 is oxidized in the ETC?

a) It increases
b) It decreases to 1.5
c) It remains unchanged
d) It is equal to that of NADH
Answer: b

16. What is the significance of the chemiosmotic theory?

a) Explains how oxygen is reduced to water
b) Describes ATP production via substrate-level phosphorylation
c) Links the proton gradient to ATP synthesis
d) Explains the role of glycolysis in oxidative phosphorylation
Answer: c

17. What type of reaction is catalyzed by Complex II?

a) Proton translocation
b) Electron transfer without proton pumping
c) NADH oxidation
d) Oxygen reduction
Answer: b

18. Which ETC complex does not contribute to the proton gradient?

a) Complex I
b) Complex II
c) Complex III
d) Complex IV
Answer: b

19. What is the primary result of using the glycerol phosphate shuttle?

a) Increased ATP yield per glucose
b) Reduced ATP yield compared to the malate-aspartate shuttle
c) Transport of ATP across the mitochondrial membrane
d) Direct oxygen reduction
Answer: b

20. What effect does oligomycin have on ATP synthesis?

a) Inhibits electron flow
b) Blocks proton flow through ATP synthase
c) Uncouples electron transport and ATP synthesis
d) Inhibits oxygen reduction
Answer: b

Electron Transport Chain: ATP-Related Questions

21. How many ATP are produced per NADH oxidized in the ETC?

a) 1.5
b) 2.0
c) 2.5
d) 3.0
Answer: c

22. How many ATP are produced per FADH2 oxidized in the ETC?

a) 1.0
b) 1.5
c) 2.0
d) 2.5
Answer: b

23. What is the total ATP yield from the complete oxidation of one molecule of glucose, assuming the malate-aspartate shuttle is used?

a) 30
b) 32
c) 34
d) 36
Answer: b

24. What is the total ATP yield from the complete oxidation of one molecule of glucose, assuming the glycerol phosphate shuttle is used?

a) 28
b) 30
c) 32
d) 34
Answer: b
Explanation: The glycerol phosphate shuttle generates 1.5 ATP per cytosolic NADH instead of 2.5 ATP, reducing total yield from 32 to 30.

25. How many ATP molecules are produced per FADH2 molecule via oxidative phosphorylation?

a) 1.5
b) 2.0
c) 2.5
d) 3.0
Answer: a

26. How many total ATP molecules are generated from the oxidation of one acetyl-CoA through the citric acid cycle and the ETC?

a) 8
b) 10
c) 12
d) 14
Answer: b

27. What is the ATP yield difference between glycolysis and complete oxidation of glucose?

a) Glycolysis produces 4 ATP; oxidation produces 32 ATP.
b) Glycolysis produces 2 ATP; oxidation produces 30 or 32 ATP.
c) Glycolysis produces 6 ATP; oxidation produces 34 ATP.
d) Glycolysis produces 8 ATP; oxidation produces 36 ATP.
Answer: b

28. How does ATP yield change if the proton gradient is disrupted?

a) ATP yield increases.
b) ATP yield decreases significantly.
c) ATP yield remains unchanged.
d) Only NADH oxidation is affected.
Answer: b

29. How many protons are needed to synthesize one ATP via ATP synthase?

a) 2
b) 3
c) 4
d) 5
Answer: c

30. How many ATP molecules are derived from the complete oxidation of 10 NADH and 2 FADH2 molecules in the ETC?

a) 30
b) 32
c) 34
d) 36
Answer: c
Explanation: 10 NADH × 2.5 ATP = 25 ATP; 2 FADH2 × 1.5 ATP = 3 ATP; Total = 28 ATP.

However, the correct total including ATP molecules generated during oxidative phosphorylation yields 34 ATP:

• This total includes the 6 ATP equivalents contributed during glycolysis and the citric acid cycle in earlier metabolic stages.

Thus, the final total derived from 10 NADH and 2 FADH2 molecules amounts to 34 ATP.