[BIOCHEMISTRY] PACOP PINK

Proverbs 16:3

B. nucleolus

1. This region in the nucleus is the site of ribosome assembly.

A) nuclear membrane

B) nucleolus

C) chromatin

D) chromosome

C. internal cellular membrane

2. Which of the following cellular structures is unique in eukaryotes?

A) plasma membrane

B) ribosomes

C) internal cellular membrane

D) golgi apparatus

C. peroxisomes

3. These organelles consist of membranous sacs containing powerful oxidase enzymes, and they use molecular oxygen (O2) to detoxify harmful substances

A) lysosomes

B) golgi apparatus

C) peroxisomes

D) mitochondria

B. Svedberg

4. The cellular particles are often referred by their sedimentation coefficient value, for example, 70s ribosomes that is expressed in terms of 10^-13 seconds. The abbreviation "s" stands for

A) subunit

B) Svedberg

C) seconds

D) none of the above

D. mitochondria

5. These are organelles that contain the enzymes for pyruvate oxidation, citric acid cycle, beta-oxidation of fatty acids, oxidative phosphorylation, and ETC.

A) golgi apparatus

B) lysosomes

C) nucleus

D) mitochondria

A) The endoplasmic reticulum is a system of fluid-filled cisterns.

📌RATIONALE:

The ER consists of interconnected membranous tubules and flattened sacs (cisterns) filled with fluid.

• Rough ER (studded with ribosomes) handles protein synthesis, not smooth ER

• Smooth ER is the site of lipid synthesis, not rough ER

6. Which of the following is/are true?

A) The endoplasmic reticulum is a system of fluid-filled cisterns

B) The smooth endoplasmic reticulum is responsible for protein synthesis

C) The rough endoplasmic reticulum is a site of lipid synthesis

D) All of the above

B. I and III

• Vacuole

• Cell wall

7. Some organelles are specific to plant or animal cells. Which of the following organelles are present in plant cells only?

I. Vacuole

II. Nuclear envelope

III. Cell wall

IV. lysosomes

A) I only

B) I and III

C) II and IV

D) I-IV

A. A virus contains only one type of nucleic acid, either DNA or RNA

8. Viruses are not cellular, but are rather termed as "biological entities". The main reason why viruses are considered acellular entities is because _______

A) A virus contains only one type of nucleic acid, either DNA or RNA

B) A virus is very small compared to bacteria

C) A virus is pathogenic

D) Scientists cannot classify viruses under the 5 kingdoms of Whittaker

C. plasmids

9. _______ are small, extrachromosomal circular DNA molecules found in prokaryotes

A) nucleoli

B) genes

C) plasmids

D) histones

C. II and III

• Plasmids are found in many types of bacteria

• Plasmids replicate independently of the main chromosome

10. Which of the following statements is/are correct regarding plasmids?

I. Plasmids are either DNA or RNA molecules

II. Plasmids are found in many types of bacteria

III. Plasmids replicate independently of the main chromosome

IV. Each cell contains only a single copy of plasmid

A) III only

B) I and III

C) II and III

D) II-IV

B. plant cell wall-cellulose

11. The diversity of the different cell types among various organisms lies in their chemical nature. Which of the following pairs is/are accurate?

A) bacterial cell membrane-peptidoglycan

B) plant cell wall-cellulose

C) animal cell membrane-nucleic acid

D) none of the above

B. The disease "bovine spongiform encephalogpathy" or "mad cow disease " is one disease attributed to prions

📌Rationale: Bovine spongiform encephalopathy (BSE) is indeed caused by prions.

• Prions are infectious agents composed only of protein, with no nucleic acid (this is what makes them unique)

12. Which of the following statements is/are true of prions?

A) A prion is an infectious agent that contains both proteins and nucleic acid

B) The disease "bovine spongiform encephalopathy" or "mad cow disease " is one disease attributed to prions

C) Both statements are correct

D) Both statements are false

D. All of the above

• Nuclear membrane

• Nucleoli

• Chromatin

13. Which of the following structures is/are present in the nucleus?

A) nuclear membrane

B) nucleoli

C) chromatin

D) all of the above

E) A and B only

D. None of the above

14. Which of the following is an active process?

A) Transport of molecules through protein pores

B) Transmembrane transport through carrier molecules

C) Both A and B

D) None of the above

B. Facilitated diffusion is saturable, simple passive diffusion is not

15. Which of the following statements differentiates simple passive diffusion from facilitated diffusion?

A) Facilitated diffusion is an active process

B) Facilitated diffusion is saturable, simple passive diffusion is not

C) Both statements are correct

D) None of the above

C. Na-K pump

16. Which of the following is affected by digitalis glycosides and ouabain?

A) sodium-glucose cotransport system

B) Ca-Na exchanger

C) Na-K pump

D) All of the above

B. Sodium

📌Rationale: Sodium is co-transported with glucose via the SGLT1 (sodium-glucose linked transporter) in intestinal epithelial cell

17. Which of the following ions is co-transported with glucose in the small intestine?

A) potassium

B) sodium

C) calcium

D) magnesium

A. peptidoglycan

18. The nature of the cell wall of the bacteria is used in their classification. Which of the following is cross-linked, multi-layered polysaccharide-peptide complex used as the basis of Gram staining?

A) peptidoglycan

B) teichoic acids

C) ergosterol

D) phospholipids

D. lipids

📌Rationale: Lipids are not biopolymers — they aren't made of repeating monomer units linked together like true polymers.

19. Which of the following is not a biopolymer?

A) nucleic acids

B) carbohydrates

C) amino acids

D) lipids

C. Nucleotides are also known as nucleoside phosphates

20. Which of the following statements is/are correct?

A) Adenine is nucleoside

B) Adenosine is a nucleotide

C) Nucleotides are also known as nucleoside phosphates

D) All of the above

D) all of the above

• Cytosol

• Inclusions

• Mitochondrion

21. Which of the following is/are found inside the cytoplasm?

A) cytosol

B) inclusions

C) mitochondrion

D) all of the above

E) A and B only

B. Guanosine

22. Which of the following is a nucleoside?

A) guanine

B) guanosine

C) guanosine monophosphate

D) Any of the above

B) carbon-2

23. Which carbon in the sugars is responsible for the difference between the two nucleic acids?

A) carbon-1

B) carbon-2

C) carbon-3

D) none of the above

A. DNA contains thymine, RNA contains uracil

24. Which of the following statements is/are true regarding nucleic acid primary structure?

A) DNA contains thymine, while RNA contains uracil

B) Adenine and guanine are pyrimidines

C) Uracil is a purine

D) All of the above

E) Only A and B

A. hydroxyl group, hydrogen

25. The ribose in RNA is converted to deoxyribose in DNA by replacing ___ in RNA with ___

A) hydroxyl group, hydrogen

B) hydrogen, hydroxyl group

C) oxygen, hydroxyl group

D) hydroxyl group, oxygen

A. The ability of certain anticodons to pair with codons that differ at the third base

26. What is wobble?

A) The ability of certain anticodons to pair with codons that differ at the third base

B) An error in translation induced by streptomycin

C) A mechanism that allows for a peptide extension in the 50s subunit of the ribosome

D) thermal motions leading to local denaturation of the DNA double helix

C. phosphodiester bond

27. What type of bond connects successive monomer units through a phosphate residue attached to hydroxyl on the 5' carbon of one unit with the 3' hydroxyl of the next?

A) hydrogen bond

B) covalent bond

C) phosphodiester bond

D) None of the above

A) Phosphate group

28. Which of the following groups is responsible for the acidic character of nucleic acids?

A) Phosphate group

B) Nucleotides

C) A and B

D) None of the above

B) Adenine and Guanine

29. Which of the following are purine bases?

A) Adenine and Thymine

B) Adenine and Guanine

C) Cytosine and Thymine

D) Cytosine and Uracil

B. thymine

📌Rationale:

• Thymine is found only in DNA, replaced by uracil in RNA.

• Uracil is present only in RNA, not DNA

30. Which of the following nitrogenous bases is present only in DNA?

A) adenine

B) thymine

C) cytosine

D) uracil

A. adenine and thymine

31. Which of the following base pairs is bonded by a double bond?

A) Adenine and thymine

B) Cytosine and guanine

C) Adenine and guanine

D) Cytosine and thymine

C. three

32. How many hydrogen bonds are formed between cytosine and guanine?

A) one

B) two

C) three

D) no hydrogen bonds are formed between them

B. Adenine binds to thymine, cytosine binds to guanine

33. The DNA structure is a double helix containing chains which are complementary. Which of the following statements best describes complementarity?

A) In the chains, each end of the helix contains the 5' end of one strand and the 3' end of the other

B) Adenine binds to thymine, and cytosine binds to guanine

C) Several codons may code for the same amino acid

D) All of the above

B. antiparallel

34. Each end of the DNA double helix contains the 5' end of one strand and the 3' end of the other strand - this statement describes what characteristic of the DNA structure?

A) complementary

B) antiparallel

C) semiconservative replication

D) base pairing

D. glycosidic bond

35. What do you call the bond between the 1' carbon of the sugar and the base nitrogen?

A) hydrogen bond

B) covalent bond

C) phosphodiester bond

D) glycosidic bond

A. Some nucleic acid bases are capable of tautomerization

36. Which of the following statements is correct?

A) Some nucleic acid bases are capable of tautomerization

B) All enzymes are proteins

C) Both A and B

D) Both are incorrect

B. They have 6-membered ring structure

37. Which of the following statements best describes pyrimidine bases?

A) They have a 5-membered ring structure.

B) They have a 6-membered ring structure.

C) Adenine and guanine are pyrimidine bases.

D) Some examples include caffeine, theophylline and theobromine.

B. False

📌Rationale:

• Nucleosides = base + sugar only

• Nucleotides = base + sugar + phosphate.

38. The primary difference between nucleosides and nucleotides is the presence of phosphate group in the former - this statement is:

A) True

B) False

C. 6 codons = 1 amino acid

📌Rationale: Degeneracy means multiple codons can code for the same amino acid.

39. Which of the following best describes the degeneracy of the genetic code?

A) 1 codon = 1 amino acid

B) 1 codon = 6 amino acids

C) 6 codons = 1 amino acid

D) none of the above

C. 1, 2 and 3

40. Deoxyribonucleic acid is a double stranded polynucleotide. The base content of DNA displays three sets of equivalent pairs. Which f the following equations are true?

1. A = T,2. C = G, 3. A + G = T + C, A + G is not always equal to T + C

A) 3 only

B) 1 and 2

C) 1, 2 and 3

D) 1, 2 and 4

B. B-DNA

41. Which of the following is the most common form of DNA?

A) A-DNA

B) B-DNA

C) Z-DNA

D) All of the following occur in the same frequency in nature.

D) semiconservative replication

42. When the two strands of the DNA double helix are separated, each strand can serve as a template for the replication of a new complementary strand. This describes _____

A) DNA replication

B) transcription

C) complementarity of base pairing

D) semiconservative replication

D. 1, 2 and 4

• DNA consists of a two-stranded double helix

• Pairing is A-T and G-C

• The chains were complementary and antiparallel

43. Which fo the following is correct according to the Watson-Crick model for DNA?

1. DNA consists of a two-stranded double helix

2. Pairing is A-T and G-C

3. The primary structure of nucleic acids is composed of a double helix stabilized by H-bonds

4. The chains were complementary and antiparallel

A) 3 only

B) 1 and 2

C) 1, 2 and 3

D) 1, 2 and 4

A. cytosine-guanine

44. The following base pairs form minor groove

A) cytosine-guanine

B) adenine-thymine

C) adenine-uracil

D) A and B only

C. Okazaki fragments

45. These are discontinuous stretches in which the lagging strand is initially synthesized during DNA replication

A) enhancer

B) operon

C) Okazaki fragments

D) primer

D. primer

46. A short piece of nucleic acid (DNA or RNA), base-paired with a DNA template strand and provides a free 3'-OH end from which DNA polymerase can extend a DNA strand

A) enhancer

B) operon

C) Okazaki fragments

D) primer

C. III

47. DNA polymerase type ___ has a 5' to 3' polymerase activity and a 3' to 5' proofreading exonuclease activity,

A) I

B) II

C) III

D) IV

A. I

48. This DNA polymerase is primarily involved in repairing DNA

A) DNA polymerase I

B) DNA polymerase II

C) DNA polymerase III

D) DNA polymerase IV

E. B and C

• The B form of the DNA is the most common in biological systems

• The breaking of H-bonds caused by high temperature is called melting

49. Which of the following statements is/are true regarding the secondary structure of nucleic acids?

A) Guanine forms base pairs with adenine via 2 hydrogen bonds

B) The B form of the DNA is the most common in biological systems

C) The breaking of H-bonds caused by high temperature is called melting

D) A and B

E) B and C

B. 3-4-2-5-1

50. What is the sequence of the major events in DNA replication?

1. DNA ligase joins DNA fragments of the lagging strand, creating a single DNA molecule

2. DNA polymerase at the replication fork synthesizes DNA in 5' to 3' direction. There are two strands, the leading and the lagging strands.

3. DNA double helix is opened by helicase

4. Primase creates a temporary RNA primer for each DNA strand

5. DNA polymerase removes DNA primer and fills the gaps between Okazaki fragments

A) 1-3-5-4-2

B) 3-4-2-5-1

C) 1-2-5-4-3

D) 4-3-2-5-1

A. Xeroderma pigmentosum

51. This is a rare human disorder, which progresses to photosensitivity, caused by an inherited exonuclease deficiency

A) Xeroderma pigmentosum

B) Bloom's syndrome

C) Fanconi's anemia

D) Hodgkin's lymphoma

C. guanine

52. Alkylating agents are used in the treatment of Hodgkin's diseases and leukemias. Their main mechanism of action is to alkylate this nitrogenous base.

A) adenine

B) cytosine

C) guanine

D) thymine

D. Rifampicin

53. The chemotherapeutic agent binds to bacterial RNA polymerase.

A) Pyrazinamide

B) Actinomycin D

C) Bleomycin

D) Rifampicin

E. A and B

• RNA polymerase, unlike DNA polymerase does not require a primer

• DNA polymerase is a nuclease

NOTE: RNA polymerase lacks proofreading/nuclease activity

54. Which of the following statements is/are true?

A) RNA polymerase, unlike DNA polymerase does not require a primer

B) DNA polymerase is a nuclease

C) RNA polymerase is a nuclease

D) All of the above

E) A and B

B. AUG

55. Which of the following is a codon for methionine?

A) UAG

B) AUG

C) UGA

D) UAA

B. transversional

56. This DNA mutation occurs when a purine replaces a pyrimidine, or vice-versa

A) transitional

B) transversional

C) insertion

D) frame-shift

A. transitional

57. A purine replaces another purine in ____ mutations

A) transitional

B) transversional

C) insertion

D) frame-shift

D. all of the above

• Insertion

• Deletion

• Transition

58. Which of the following is/are point mutations?

A) insertion

B) deletion

C) transition

D) all of the above

E) A and B

D. benzopyrene

59. This mutagenic substance is obtained from smoking cigarettes. It intercalates with DNA and causes frameshifts

A) tar

B) nicotine

C) coal

D) benzopyrene

C. introns

60. This refers to the noncoding regions that alternate with coding regions in the polypeptide sequence,

A) exon

B) promoters

C) introns

D) repressor

C. Z-DNA

61. This DNA duplex has a special left-handed helical structure

A) A-DNA

B) B-DNA

C) Z-DNA

D) F-DNA

D. Intercalates with minor groove of the double helix

62. Which of the following statements best describes the mechanism of action of Dactinomycin (Actinomycin D)?

A) binds to the bacterial RNA polymerase

B) binds to the 30s subunit

C) binds to 50s subunit

D) intercalate with the minor groove of the double helix

A. transitional

63. 2-Aminopyrine is no longer used clinically. It has been found out to replace adenine (6-aminopurine) or guanine in DNA resulting to bone marrow toxicity. 2-Aminopyrine exhibits what type of mutation?

A) transitional

B) transversional

C) frameshift

D) deletion

A. Transcription is the synthesis of RNA from DNA

64. Which of the following is/are true regarding the central dogma of molecular biology?

A) Transcription is the synthesis of RNA from DNA

B) The process of replication produces new RNA.

C) Reverse transcription is impossible.

D) All of the above.

B. Transcription

65. Actinomycin D, an antineoplastic drug, intercalates between two GC pairs in DNA. Which of the following processes does it inhibit?

A) Translation

B) Transcription

C) DNA Repair

D) Replication

B. reverse transcription

66. Tumor-producing RNA viruses synthesize DNA from RNA in the process called ____.

A) transcription

B) reverse transcription

C) translation

D) reverse translation

D. DNA polymerase

📌Note: DNA polymerase I (in prokaryotes) has 5'→3' exonuclease activity that removes RNA primers and replaces them with DNA nucleotides

67. This enzyme is responsible for removing the RNA primer in DNA.

A) Excinuclease

B) DNA ligase

C) RNA polymerase

D) DNA polymerase

C. eukaryote-methionine

68. Which of the following pairs is an accurate pairing of the organism and its start codon?

A) eukaryote-formylmethionine

B) prokaryote-methionine

C) eukaryote-methionine

D) none of the above

B. uric acid

69. Humans catabolize purines to _______.

A) urea

B) uric acid

C) allantoin

D) B and C

A. operator

70. This refers to the set of prokaryotic structural genes, which are transcribed as a unit, along with regulatory elements controlling their expression.

A) operon

B) operator

C) inducer

D) repressor

C. gouty arthritis

71. When the serum urate levels exceed the solubility limit, the crystals of sodium urate accumulate in soft tissues and joints and causes an inflammatory reaction known as ________

A) Lesch Nyhan syndrome

B) osteomalacia

C) gouty arthritis

D) Von Gierke's disease

C. Lysine and arginine are basic amino acids

72. Which of the following statements about amino acids is true?

A) Acidic amino acids bear a positive charge at pH 7.0

B) All amino acids have a chiral carbon.

C) Lysine and arginine are basic amino acids.

D) All of the above.

A. nonsense

73. This type of mutation occurs when the codon containing the changed base may become a termination codon.

A) nonsense

B) missense

C) silent

D) transitional

C. silent

74. The result of a point mutation that occurs when UCA (coding for serine) is converted to UCU (also coding for serine) is called

A) nonsense

B) missense

C) silent

D) transitional

C. neutral

75. Glutamine and asparagine amino acids are ____.

A) acidic

B) basic

C) neutral

D) nonpolar

A. cystine is a dimer of cysteine.

76. Which statement is true?

A) Cystine is a dimer of cysteine.

B) Cysteine is more stable that cystine.

C) Both statements are correct.

D) Both statements are false.

E. A and B

• Histidine

• Arginine

77. Which of the following amino acids contain(s) basic side chains?

A) histidine

B) arginine

C) leucine

D) all of the above

E) A and B

C. Both A and B

• Cysteine

• Methionine

78. Which of the following amino acids contain(s) side chains with sulfur atom?

A) methionine

B) cysteine

C) Both A and B

D) Neither A nor B

A. proline

79. Which of the following amino acids is responsible for disrupting the alpha-helix because its imino group is not geometrically compatible with the righthanded spiral of the alpha helix?

A) proline

B) valine

C) leucine

D) glycine

B. proline

80. Which of the following amino acids has an imino group?

A) phenylalanine

B) proline

C) tyrosine

D) A and B

E) All of the above

E. all of the above

• Serine

• Threonine

• Tyrosine

81. Which of the following amino acids possess(es) a hydroxyl group, which renders it/them polar?

A) serine

B) threonine

C) tyrosine

D) only A and B

E) All of the above

D. peptide bonds

82. What stabilizes the primary structure of proteins?

A) salt bridges

B) hydrophobic bonds

C) disulfide bonds

D) peptide bonds

E) All of the above

C. tyrosine

83. Which of the following amino acids possesses a phenolic hydroxyl group?

A) serine

B) threonine

C) tyrosine

D) A and B

E) All of the above

B. pI = (pK1 + pK2)/2

84. The isoelectric pH is the pH midway between pK values on either side of the isoelectric process. Which of the following equations gives an accurate estimate of iPH?

A) pI = pK1 + pK2

B) pI = (pK1 + pK2)/2

C) pI = (pK1 + pK2) x 2

D) pI = pK1 > pK2

A. 6.02

85. Using the equation of pI, calculate the pI (isoelectric pH) of alanine. pK1 (R-COOH) = 2.35; pK2 (R-NH3+) = 9.69.

A) 6.02

B) 12.04

C) 24.08

D) 5.0

C. protein

86. Thyroxine, which is chemically 3,5,3'5'-tetraiodothyronine, is used as a precursor for thyroid hormones. What type of biopolymer is thyroxine?

A) carbohydrate

B) lipid

C) protein

D) nucleic acid

D. dehydration

87. Peptide bond, a type of amide bond, binds the amino terminal of one amino acid to the carboxyl end of another. What type of process is involved in the formation of peptide bonds?

A) oxidation

B) hydration

C) reduction

D) dehydration

D. all of the above

• The C-N bond in the peptide linkage has a partial double bond property that makes it rigid.

• Neither the C=O nor the N-H in the peptide bond can dissociate.

• Each amino acid in a polypeptide chain is called a residue.

88. Which of the following statements is correct?

A) The C-N bond in the peptide linkage has a partial double bond property that makes it rigid.

B) Neither the C=O nor the N-H in the peptide bond can dissociate.

C) Each amino acid in a polypeptide chain is called a residue.

D) All of the above.

A. primary

89. This structure of peptides refers to the order of amino acids in the polypeptide chain/s and the location of the disulfide bonds.

A) primary

B) secondary

C) tertiary

D) quaternary

B. secondary

📌Rationale: Secondary structure refers to local, regular folding patterns (like alpha helices and beta sheets) formed by amino acid residues near each other in the linear sequence, stabilized by hydrogen bonds.

90. This refers to the spatial arrangements of amino acid residues close to one another in the linear sequence of a polypeptide chain.

A) primary

B) secondary

C) tertiary

D) quaternary

C. tertiary

91. The overall arrangement and interrelationship of various regions or domains, and individual amino acid residues of a single polypeptide chain is ______.

A) primary

B) secondary

C) tertiary

D) quaternary

B. secondary

92. Alpha-helix and beta-pleated sheets belong to what structure?

A) primary

B) secondary

C) tertiary

D) quaternary

B. secondary

93. Random coils and triple helices are examples to what protein structure?

A) primary

B) secondary

C) tertiary

D) quaternary

C. tertiary

94. Fibrous and globular proteins belong to what protein structure?

A) primary

B) secondary

C) tertiary

D) quaternary

D. quaternary

95. The arrangement of polypeptide chains in relation to one another in a multi-chained protein refers to what structure?

A) primary

B) secondary

C) tertiary

D) quaternary

B. Edman

96. What do you call the principal method for determining the primary structure of polypeptides? For its initial step, it utilizes phenylisocyanate, which combines with the terminal amino acid of the polypeptide.

A) Grignard

B) Edman

C) Molisch

D) Zollinger

C. 1-3

97. Which of the following bonds are found in the quaternary structure of polypeptides?

1. Hydrogen

2. Electrostatic

3. Hydrophobic

4. Covalent

A) 3 only

B) 1 only

C) 1-3

D) all of the above

A. 1 only

98. Denaturation is a randomization of the conformation of a polypeptide chain. Chemical agents like strong acids or bases, heat, detergents, etc. are involved in this process. Which of the following structure remain unaffected with denaturation?

1. Primary, 2. Secondary, 3. Tertiary, 4. Quaternary

A) 1 only

B) 1 and 2

C) 1-3 only

D) 1-4

E) All of the above.

• Fibrous proteins are water-insoluble

• Globular proteins are water-soluble

• Proteins lose their biologic activity after denaturation

• Denaturation of proteins is sometimes irreversible

99. Which of the following statements is true?

A) Fibrous proteins are water-insoluble

B) Globular proteins are water-soluble

C) Proteins lose their biologic activity after denaturation.

D) Denaturation of proteins is sometimes irreversible.

E) All of the above.

E. B and C

• Threonine

• Tryptophan

100. Which of the following is/are example(s) of essential amino acids?

A) tyrosine

B) threonine

C) tryptophan

D) A and B

E) B and C