BIOCHEM FINAL QUESTIONS

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Which of the following is a carrier of ONLY protons?


1. Acids and bases
2. NADH
3. FADH2
4. Metals

1

Which of the following is **NOT** a characteristic of the mitochondrial inner membrane?


1. It has high concentration of proteins necessary for ATP synthesis 
2. It is used in oxidative phosphorylation
3. It is where glycolysis occurs  
4. The electron transport chain takes place in it

3

What inhibits complex III?


1. Rotenone
2. Antimycin A
3. Malonate
4. Cyanide

2

Which factor in complex 5 is responsible for ATP synthesis:


1. F1
2. F0
3. F1F0 ATP synthase
4. a and b 

1

Which enzyme is responsible for the transport of ATP to the cytosol?


1. F1F0 ATP synthase
2. Adenine nucleotide translocase
3. Phosphatase
4. None

2

Which of the following carriers transfers a pair of electrons with a proton?


1. FADH2
2. FMNH2
3. NADH
4. QH2

3

Which complex is not involved when Succinate is used?


1. Complex II
2. Complex III
3. Complex IV 
4. Complex I

4

Which two complexes yield QH2?


1. Complex I and II
2. Complex III and IV
3. Complex I and V
4. Complex II and IV

1

Within complex 5, where does the entry of protons occur?


1. The stalk of b subunits
2. The ring of membrane-bound γ subunits
3. The interface between the rotor and stator
4. The cylinder of αβ subunits

3

Which of the following is true for both Complex 1 and Complex 2? 


1. Succinate provides the hydride
2. Electrons pass through Fe-S complexes
3. FAD is used
4. There is proton movement

2

Which of the following is the overall reaction for proteins within complex 3?


1. QH2+2 cytochrome cox  → Q+2 Cytochrome *c*red
2. Dihydroxyacetone -P +NADH ↔ Glycerol-P +NAD+
3. Glycerol-P +Q→ Dihydroxyacetone-P+QH2
4.  QH2+ 2H+ matrix → Q+4H+cyto

4

Complex III is also known as Q-cytochrome c reductase because


1. it takes electrons from QH2 and reduces cytochrome c.
2. it take electrons from QH2 and oxidizes cytochrome c.
3. it takes part in a step in the Krebs cycle. 
4. All of the above 

1

Select all the choices involved in the electron transport chain:


1. Complex 1
2. Complex 2
3. Complex 3
4. Complex 4 
5. Complex 5

1,2,3,4

Which of the following statements is true regarding the difference between the fed state and fasting state?

a. in the fed state, the blood’s fatty acid concentration is low as there is an

abundance of glucose from the food recently consumed that can be used for

energy.

b. In the fasting state, the blood’s fatty acid concentration is high as the brain releases amylopectin to hydrolyze stored triacylglycerols to make free fatty acids.

c. Fatty acid concentrations in the fed state are about 100 times as much as fatty

acid concentrations in the fasting state.

d. A and B are correct.

a

Which of the following statements is true regarding the steps of fatty acid oxidation?

a. the activation and transport steps occur in the cytosol while the beta-oxidation step occurs in the mitochondrial matrix

b. the activation step is metabolically irreversible

c. a and b are both correct

d. none of the above

b

which of the following is not true regarding sphingolipids?

a. Sphingolipids are a variation of lipids that use Serine as a backbone rather than glycerol.

b. sphingolipids can help to regulate apoptosis

c. sphingolipids are a variation of lipids that use threonine as a backbone rather than glycerol

d. sphingolipids can help cells to grow and migrate

c

which of the following lipoproteins is primarily responsible for transporting dietary lipids from the intestines to other tissues?

a. chylomicrons

b. VLDL

c. LDL

d. HDL

a

what is the primary site of absorption for dietary lipids?

a. stomach

b. small intestine

c. large intestine

d. esophagus

b

what is the principal regulatory site of fatty avid biosynthesis?

a. malonyl CoA formation

b. carboxylation of acetyl CoA

c. pyruvate carboxylase reaction

d. propionyl CoA carboxylase reaction

b

what are most of the lipids in the body stored as?

a. lipoproteins

b. cholesterol

c. triacylglycerols

d. cholesteryl esters

c

what enzymes catalyze the hydroxylation steps of cholesterol and its derivatives, such as those evident in cholate?

a. phenylalanine hydroxylase

b. cytochrome C

c. cytochrome P450

d. asparagine

c

what is the first step in fatty acid oxidation?

a. activation where fatty acid is converted to acyl-CoA

b. transport where acyl-CoA is transported to the mitochondria

c. b-oxidation where acyl-CoA is converted to acetyl-CoA

d. transport where acyl-CoA is transported to the cytosol

a

how is acyl-CoA transported to mitochondria?

a. diffuses directly into membrane

b. uses an active transport

c. uses a carnitine shuttle and is an indirect movement

d. acyl-CoA is not transported to mitochondria

c

which of the following is a key enzyme involved in fatty acid biosynthesis?

a. pyruvate dehydrogenase

b. phosphofructokinase

c. acetyl-CoA carboxylase

d. isocitrate dehydrogenase

c

which cell has the role of fatty acid oxidation and ketone body synthesis?

a. liver cells

b. fat cells

c. beta cells

d. muscle cells

a

which of the following is false about carnitine?

a. carnitine ester is derived from fatty acyl-CoA

b. carnitine is expelled through the cytosol (it is recycled back into the cytosol)

c. it is a shuttle used for transporting fatty acyl-CoA into the inner mitochondrial membrane

d. carnitine acyl transferase is the enzyme used to catalyze conversion of fatty acyl-carnitine to fatty actyl-CoA

b

what is the function and location of the Urea Cycle?

a. the urea cycle occurs in the liver and is used to metabolize nitrogen containing compounds

b. the urea cycle occurs in the kidney and is used to excrete nitrogen

c. the urea cycle occurs in the liver and is used to excrete nitrogen

d. the urea cycle occurs In the kidney and is used to metabolize nitrogen containing compounds

c

which of the following enzymes is involved in the urea cycle?

a. pyruvate kinase

b. isocitrate dehydrogenase

c. carbamoyl phosphate synthetase

d. glucose-6-phosphatase

c

which organ is primarily responsible for the urea cycle?

a. liver

b. kidneys

c. pancreas

d. stomach

a

what is the second step of the urea cycle?

a. formation of citrulline

b. formation of argininosuccinate

c. formation of ornithine

d. formation of urea

a

what enzyme catalyzes the condensation step when citrulline and aspartate arrives in cytosol?

a. carbamoyl-P-synthetase

b. glutamate DH

c. amino acid transferase

d. arginosuccinate synthase

d

in the urea cycle, what 3 amino acids are converted to glutamate?

a. arginine, proline, histidine

b. lysine, histidine, aspartate

c. arginine, lysine, histidine

d. aspartate, proline, lysine

a

which of the following molecules is a key precursor for triaglycerol formation?

a. glucose

b. glycerol

c. fructose

d. alanine

b

in the urea cycle, which two molecules in the cytosol exit the cycle?

a. ornithine and urea

b. ornithine and fumarate

c. urea and fumarate

d. urea and arginine

c

what is a ribosome?

a. an organelle made of rRNA and protein and is made of two subunits. its main function is to translate mRNA to protein

b. an organelle made of rRNA and protein and is made of three subunits. its main function is to transcribe DNA to mRNA

c. an organelle made of rRNA and protein and is made of two subunits. its main function is to translate DNA to mRNA

d. an organelle made of rRNA and protein and is made of three subunits. its main function is to transcribe mRNA to protein

a

a codon is a group of 3 nucleic bases in RNA that ribosomes use to translate into the amino acids of a protein. how many codon combinations can be made in an RNA sequence?

a. 19

b. 20

c. 61

d. 64

d

what is the term used to describe modifications made to a protein during its synthesis on the ribosome?

a. post-translational modifications

b. co-translational modifications

c. pre-translational modifications

d. in vitro modifications

b

which organelle is responsible for most co-translational modifications of proteins?

a. nucleus

b. endoplasmic reticulum

c. golgi apparatus

d. mitochondria

b

what is the term used to describe modifications made to a protein after its synthesis on the ribosome?

a. post-translational modifications

b. co-translational modifications

c. pre-translational modifications

d. in vitro modifications

a

which of the following is not a type of RNA?

a. ribosomal

b. messenger

c. transfer

d. replication

d

where does DNA replication occur?

a. cytoplasm

b. endoplasmic reticulum

c. nucleus

d. mitochondria

c

how many distinct RNA polymerase enzymes exist in eukaryotes?

a. 2

b. 5

c. 1

d. 3

d

what positively and negatively regulates the protein mTOR?

a. activated by insulin, inhibited by AMP kinase

b. activated by ornithine, inhibited by GSK3

c. activated by ornithine, inhibited by insulin

d. activated by AMP kinase, inhibited by insulin

a

what is the enzyme involved in the rate limiting step of glycogen synthesis?

a. glycogen synthetase

b. glycogen synthase

c. glycogen phosphorylase

d. glycogen reductase

b

which of the following is true regarding gluconeogenesis?

a. gluconeogenesis is a pathway that is the exact reverse of glycolysis

b. gluconeogenesis is a pathway that can be used to create glucose from non-carbohydrate precursors

c. gluconeogenesis is a pathway that can be used to create glucose from carbohydrate precursors

d. gluconeogenesis is a pathway that only occurs in plants

b

what is the role of glucagon in glycogenolysis?

a. to activate glycogen phosphorylase

b. to inhibit glycogen phosphorylase

c. to activate glycogen synthase

d. to promote glycogenesis

a

how does glucagon promote the activation of glycogen phosphorylase?

a. by increasing the levels of cyclic AMP in the liver

b. by increasing insulin sensitivity

c. by decreasing the levels of glucose in the liver

d. by inhibiting gluconeogenesis

a

the process of glycogenolysis is sped up by

a. glucagon

b. insulin

c. glucose

d. ATP

a

under anaerobic conditions, the product of glycolysis is:

a. fructose-6-phosphate

b. lactic acid

c. pyruvic acid

d. oxaloacetic acid

b

in carbohydrate pathways related to glycolysis, what is the role of AMPK?

a. can lead to overall stimulation of glycogen deposition

b. entry of glucose into the cytosol

c. directly phosphorylates and inhibits glycogen synthase

d. all of the above

e. both A and C

e

which enzyme catalyzes the conversion of glucose-6-P to glucose?

a. fructose-2,6-P2

b. NAD+

c. glucose-6-phosphatase

d. GLUT7

c

what is one reaction Ribulose-5-P undergoes?

a. epimerase

b. phosphatase

c. mutase

d. kinase

a

Which of the following choices best represents the difference in physiological context of glucose metabolism between the liver and the muscles?

a. the muscles are a selfish group of organs, using stored glycogen and glucose as fuel to support muscle contractions

b. the liver is a selfless organ, controlling the levels of glucose in the body so that other bodily tissues and cells can get the required amount of glucose needed for energy

c. both A and B are true

d. none of the above

c

what is the rate limiting step in gluconeogenesis and what enzyme(s) catalyze(s) this reaction?

a. step: pyruvate to acetyl CoA; enzyme: pyruvate dehydrogenase

b. step: pyruvate to phosphoenolpyruvate; enzymes: pyruvate carboxylase and phosphoenolpyruvate carboxykinase

c. step: pyruvate to lactase; enzyme: lactate dehydrogenase

d. step: ozaloacetate to phosphoenolpyruvate; enzyme: phosphoenolpyruvate carboxykinase

b

from what 2 substances is urea formed?

a. amino acids and ammonia

b. amino acids and glucose

c. nitrogen and glucose

d. nitrogen and fatty acids

a

which amino acid is present in the urea cycle?

a. serine

b. glycine

c. tryptophan

d. aspartate

d

which amino acids are involved in transporting nitrogen via blood?

a. alanine and glycine

b. alanine and glutamine

c. glutamine and glycine

d. glycine and serine

b

how many ATP(s) are needed to form carbamoyl phosphate?

a. 1 ATP

b. 2 ATP

c. 3 ATP

d. 4 ATP

b

what is an allosteric activator of carbamoyl phosphate synthetase I?

a. nitrogen

b. glutamate

c. acetyl CoA

d. N-acetyl-glutamate

d

where does the first two steps of urea cycle occur?

a. cytosol

b. mitochondria

c. mitochondria and cytosol

d. cell membrane

b

which of the following reactions are metabolically irreversible?

a. glutamine synthetase

b. glutamate DH

c. transaminase

d. serine hydroxymethyltransferase

c

what is the rate limiting enzyme in the Urea cycle?

a. ornithine transcarbamlase

b. carbamoyl-P-synthetase

c. carbamoyl-P synthase

d. none of these

b

what two molecules exit the urea cycle in the cytosol?

a. aspartate and citrulline

b. fumarate and aspartate

c. fumarate and urea

d. citrulline and urea

c

what is an importance of cholesterol?

a. essential component of the plasma membrane

b. storage of lipids and proteins

c. it is a precursor to steroid hormones

d. a and c

d

what substances are found in the DNA replication process?

a. okazaki fragments

b. RNA primers

c. neither a nor b

d. both a and b

d

what is the process of central dogma?

a. DNA → RNA → protein

b. DNA → DNA → RNA → protein

c. RNA → DNA → protein

d. DNA → RNA → RNA → protein

b

in which process is topoisomerase required?

a. translation

b. replication

c. both a and b

d. neither

b

which type of RNA polymerase catalyzes the first reactions that add bases to single-stranded DNA?

a. diase

b. triase

c. primase

d. quatrase

c

which of the following categorizes excision repair?

a. correcting an incorrect base inserted during normal replication

b. fixing damage to a DNA sequence after replication

c. reorganizing pairs of bases after replication

d. none of the above

b

which enzymes catalyze change in DNA supercoils?

a. polymerases

b. ligase

c. topoisomerases

d. helicase

c

which of the following classes of RNA found in the transcription phase of DNA replication is responsible for carrying amino acids?

a. siRNA

b. transfer RNA

c. ribosomal RNA

d. messenger RNA

b

which base pairs in DNA require more energy to break and why

a. AT because it has more bonds

b. AT because it has less bonds

c. GC because it has more bonds

d. GC because it has less bonds

c

which of the following is an example of co-translational modification?

a. lipidation

b. folding

c. splicing

d. disulfide formation

b

what is necessary for the termination step of translation?

a. reading the stop codon

b. recognizing the start codon of a different sequence

c. hydrolysis reaction

d. both a and c

d

what is used as an energy source to make the peptide longer in the elongation step?

a. ATP

b. GTP

c. NADH

d. ADP

b

what is the size of the large subunit of eukaryotes?

a. 40

b. 50

c. 60

d. 70

c

what is the start codon?

a. AUG

b. UAA

c. GUA

d. UGA

a

which of the following is NOT an example of post-translational modification?

a. splicing

b. O glycosylation

c. disulfide formation

d. N glycosylation

d

which of the following is not true about bacteria?

a. transcription and translation take place simultaneously

b. the first amino acid added is fMet

c. the recognition sequence is called Shine Dalgarno Sequence

d. the smaller ribosomal subunit Is 40s

d

what large substance is necessary for degrading protein?

a. proteasome

b. RNase

c. glycogen

d. phosphatase

a

why is it important to degrade proteins?

a. to avoid energy waste

b. to avoid unnecessary occupation of space in cell

c. to give energy to neighboring cells

d. both a and b

d

which is an example of co-translational modifications?

a. ubiquitination

b. folding

c. de-formylation

d. b and c

d

fatty acid concentration in the blood is higher in the fed state than the fasting state

a. true

b. false

c. they have the same concentration in the blood

b

where does beta oxidation occur during fatty acid oxidation?

a. cytosol

b. mitochondrial matrix

c. endoplasmic reticulum

d. plasma membrane

b

the urea cycle forms intermediates for what other pathway?

a. DNA replication

b. the krebs cycle

c. glycolysis

c

aspartate and citrulline are condensed into ___ with the help of what enzyme?

a. urea, DNA polymerase

b. glucose, argininosuccinate synthase

c. urea, argininosuccinate synthase

c

aspartate and citrulline must be maintained at what ratio?

a. 1:2

b. 2:1

c. 1:1

d. 3:1

c

carbamoyl phosphate is converted to what molecule?

a. aspartate

b. citrulline

c. glucose

b

what 2 molecules are carriers of nitrogen in the urea cycle?

a. aspartate and citrulline

b. arginine and tryptophan

c. aspartate and threonine

a

what is the largest class of relatively short lived molecules?

a. sugar

b. acids

c. eicosanoids

c

the urea cycle begins in the mitochondria

a. true

b. false

a

the requirement of urea synthesis is a reflection of the amount of cytosolic ___

a. proteins

b. OH-

c. argininosuccinate synthase

d. PFK

c

how many carbons do fatty acids contain?

a. 12, 15, or 19 carbons

b. 14, 16, or 18 carbons

c. 14, 15, or 16 carbons

b

how many carbons are removed at a time by beta oxidation from the chain of fatty acids?

a. none

b. one

c. two

d. four

c

which of the following is not a function of sphingolipids?

a. cell growth

b. cell migration

c. regulation of apoptosis

d. ATP synthesis

d

in what 3 forms do humans excrete nitrogen through the kidneys?

a. creatine, uric acid, and minor amounts of free ammonia

b. water, uric acid, and serine

c. serine, minor amounts of ammonia, and water

d. creatinine, water, and ammonia

a

all of these statements are true except?

a. nitrogen is excreted as urea

b. the urea cycle occurs in the liver

c. urea cycle is related to the synthesis of carbohydrates

d. the formation of ammonia and amino acids are resulted from the cycle

c

how many levels of regulation does the urea cycle occur at?

a. one

b. two

c. three

d. four

c

where does urea go after it is excreted from the body?

a. liver

b. kidney

c. lungs

d. aspartate

b

which amino group enters the urea cycle first?

a. citrulline

b. ornithine

c. argininosuccinate

d. carbamoyl phosphate

d