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2ND YEAR MBBS DAY 6-BIOCHEM

Total questions: 80

Worksheet time: 3600secs

Name
Class
Date
1.

A child presents with developmental delay and photosensitivity. DNA repair defect is suspected. Which mechanism is most likely impaired?

a)

Base excision repair

b)

Nucleotide excision repair

c)

Mismatch repair

d)

Non-homologous end joining

2.

A mutation causes replacement of guanine with adenine. This is classified as:

a)

Transversion

b)

Transition

c)

Frameshift

d)

Nonsense mutation

3.

Xeroderma pigmentosum patients are prone to skin cancers due to inability to repair:

a)

Deaminated bases

b)

Thymine dimers

c)

Double-strand breaks

d)

Alkylated bases

4.

During DNA replication, removal of RNA primers is performed by:

a)

DNA polymerase α

b)

DNA polymerase β

c)

DNA polymerase I

d)

DNA polymerase III

5.

A frameshift mutation is most likely caused by:

a)

Point mutation

b)

Insertion or deletion

c)

Silent mutation

d)

Missense mutation

6.

Which RNA has anticodon sequence?

a)

mRNA

b)

rRNA

c)

tRNA

d)

snRNA

7.

Which factor recognizes the TATA box during transcription?

a)

RNA polymerase II

b)

Sigma factor

c)

TBP (TATA binding protein)

d)

CAP protein

8.

A nonsense mutation leads to:

a)

Altered amino acid

b)

Elongated protein

c)

Premature termination

d)

No change in protein

9.

Which enzyme adds the poly-A tail to mRNA?

a)

RNA polymerase

b)

Poly-A polymerase

c)

DNA ligase

d)

RNase

10.

Which histone is NOT part of nucleosome core?

a)

H2A

b)

H2B

c)

H3

d)

H1

11.

In prokaryotes, transcription and translation occur:

a)

In nucleus

b)

In cytoplasm simultaneously

c)

Separately

d)

In mitochondria

12.

Codon AUG codes for:

a)

Valine

b)

Methionine

c)

Tryptophan

d)

Stop signal

13.

Which mutation does NOT alter amino acid sequence?

a)

Missense

b)

Nonsense

c)

Silent

d)

Frameshift

14.

Telomerase is a:

a)

DNA-dependent DNA polymerase

b)

RNA-dependent DNA polymerase

c)

RNA polymerase

d)

Restriction enzyme

15.

Which process increases genetic diversity?

a)

DNA replication

b)

Crossing over

c)

Translation

d)

Transcription

16.

Which RNA removes introns?

a)

mRNA

b)

tRNA

c)

snRNA

d)

rRNA

17.

Lac operon is an example of:

a)

Repressible operon

b)

Inducible operon

c)

Constitutive operon

d)

Attenuated operon

18.

Which enzyme proofreads DNA during replication?

a)

DNA polymerase α

b)

DNA polymerase β

c)

DNA polymerase III

d)

RNA polymerase

19.

CpG islands are associated with:

a)

Gene silencing

b)

Promoter regions

c)

Exons only

d)

Telomeres

20.

Which mutation is most severe?

a)

Silent

b)

Missense

c)

Nonsense

d)

Conservative substitution

21.

Which base pairing occurs in DNA?

a)

A–U

b)

A–T

c)

G–U

d)

C–U

22.

Which enzyme synthesizes RNA primer?

a)

DNA polymerase I

b)

DNA polymerase III

c)

Primase

d)

Helicase

23.

Which process uses aminoacyl-tRNA synthetase?

a)

Transcription

b)

Translation

c)

Replication

d)

Splicing

24.

Operons are found in:

a)

Eukaryotes

b)

Prokaryotes

c)

Mitochondria only

d)

Nucleus

25.

Which DNA repair mechanism fixes mismatched bases?

a)

NER

b)

BER

c)

Mismatch repair

d)

SOS repair

26.

Okazaki fragments are found on:

a)

Leading strand

b)

Lagging strand

c)

Both strands

d)

Neither strand

27.

Which codon signals termination?

a)

AUG

b)

UAA

c)

UGG

d)

GCU

28.

Which histone modification increases transcription?

a)

Deacetylation

b)

Acetylation

c)

Methylation

d)

Phosphorylation

29.

Which enzyme unwinds DNA helix?

a)

Ligase

b)

Helicase

c)

Topoisomerase

d)

Primase

30.

Which RNA is structural component of ribosome?

a)

mRNA

b)

tRNA

c)

rRNA

d)

snRNA

31.

Mutation causing substitution of chemically similar amino acid is:

a)

Non-conservative

b)

Conservative

c)

Nonsense

d)

Frameshift

32.

DNA ligase requires:

a)

NAD+ / ATP

b)

FAD

c)

GTP

d)

CoA

33.

Shine-Dalgarno sequence is found in:

a)

Eukaryotic mRNA

b)

Prokaryotic mRNA

c)

rRNA

d)

tRNA

34.

Which process forms phosphodiester bonds?

a)

Translation

b)

Replication

c)

Transcription

d)

All of the above

35.

Which enzyme removes supercoiling?

a)

Ligase

b)

Helicase

c)

Topoisomerase

d)

Polymerase

36.

Which mutation inserts stop codon?

a)

Missense

b)

Silent

c)

Nonsense

d)

Frameshift

37.

Which polymerase synthesizes mitochondrial DNA?

a)

DNA pol α

b)

DNA pol β

c)

DNA pol γ

d)

DNA pol δ

38.

Which RNA transports amino acids?

a)

mRNA

b)

rRNA

c)

tRNA

d)

snRNA

39.

Which base is absent in RNA?

a)

Adenine

b)

Guanine

c)

Cytosine

d)

Thymine

40.

Gene silencing via methylation occurs at:

a)

Histones

b)

CpG islands

41.

A patient with pyruvate kinase deficiency presents with hemolytic anemia. The main defect is in:

a)

ATP generation

b)

NADH production

c)

CO2 formation

d)

Acetyl-CoA synthesis

42.

Rate-limiting enzyme of glycolysis is:

a)

Hexokinase

b)

Phosphofructokinase-1

c)

Pyruvate kinase

d)

Aldolase

43.

Arsenic inhibits glycolysis by blocking:

a)

Hexokinase

b)

Glyceraldehyde-3-phosphate dehydrogenase

c)

Pyruvate kinase

d)

Enolase

44.

Net ATP produced in glycolysis is:

a)

1

b)

2

c)

4

d)

6

45.

Which step of glycolysis is irreversible?

a)

Aldolase

b)

Enolase

c)

Phosphofructokinase-1

d)

GAPDH

46.

NADH produced in cytosol enters mitochondria via:

a)

Malate-aspartate shuttle

b)

Cori cycle

c)

Pentose pathway

d)

Urea cycle

47.

TCA cycle occurs in:

a)

Cytosol

b)

Mitochondrial matrix

c)

Inner membrane

d)

Outer membrane

48.

Which TCA enzyme is inhibited by fluoroacetate?

a)

Citrate synthase

b)

Aconitase

c)

Isocitrate dehydrogenase

d)

α-ketoglutarate dehydrogenase

49.

Rate-limiting enzyme of TCA cycle is:

a)

Citrate synthase

b)

Aconitase

c)

Isocitrate dehydrogenase

d)

Malate dehydrogenase

50.

Which TCA step produces NADH?

a)

Succinate → fumarate

b)

Malate → oxaloacetate

c)

Citrate → isocitrate

d)

Acetyl-CoA → citrate

51.

ETC occurs in:

a)

Cytosol

b)

Mitochondrial matrix

c)

Inner mitochondrial membrane

d)

Outer membrane

52.

Cyanide poisoning inhibits:

a)

Complex I

b)

Complex II

c)

Complex IV

d)

ATP synthase

53.

Most ATP is produced at:

a)

Glycolysis

b)

TCA

c)

ETC

d)

Pentose pathway

54.

Uncouplers of oxidative phosphorylation cause:

a)

Increased ATP

b)

Decreased O2 consumption

c)

Heat production

d)

Decreased electron flow

55.

Glycogen is stored mainly in:

a)

Brain

b)

Kidney

c)

Liver & muscle

d)

RBCs

56.

Rate-limiting enzyme of glycogenesis:

a)

Glycogen phosphorylase

b)

Glycogen synthase

c)

Branching enzyme

d)

Debranching enzyme

57.

Von Gierke disease is due to deficiency of:

a)

Glucose-6-phosphatase

b)

Glycogen synthase

c)

Phosphorylase

d)

Debranching enzyme

58.

McArdle disease affects:

a)

Liver

b)

Muscle

c)

Brain

d)

RBC

59.

Glycogen phosphorylase requires:

a)

Biotin

b)

Pyridoxal phosphate

c)

Thiamine

d)

FAD

60.

Cori cycle involves:

a)

Liver & muscle

b)

Liver & brain

c)

Kidney & muscle

d)

RBC & kidney

61.

Which hormone activates glycogenolysis?

a)

Insulin

b)

Glucagon

c)

Thyroxine

d)

Cortisol

62.

Insulin promotes:

a)

Glycogen breakdown

b)

Gluconeogenesis

c)

Glycogenesis

d)

Lipolysis

63.

ATP yield per glucose aerobically is approximately:

a)

12

b)

24

c)

30–32

d)

40

64.

ETC Complex II uses:

a)

NADH

b)

FADH2

c)

Cytochrome c

d)

ATP

65.

Succinate dehydrogenase is part of:

a)

TCA only

b)

ETC only

c)

Both TCA & ETC

d)

Glycolysis

66.

Which enzyme converts glucose to glucose-6-phosphate in liver?

a)

Hexokinase

b)

Glucokinase

c)

PFK-1

d)

Pyruvate kinase

67.

Glucokinase has:

a)

Low Km

b)

High Km

c)

No insulin regulation

d)

Found in muscle only

68.

Which step of glycolysis produces ATP by substrate-level phosphorylation?

a)

Glucose → G6P

b)

1,3-BPG → 3-PG

c)

F6P → F1,6BP

d)

PEP → Pyruvate

69.

ETC final electron acceptor is:

a)

NAD+

b)

FAD

c)

Oxygen

d)

Cytochrome c

70.

Which TCA intermediate is glucogenic?

a)

Acetyl-CoA

b)

Citrate

c)

Oxaloacetate

d)

Ketone bodies

71.

ATP synthase is also called:

a)

Complex I

b)

Complex II

c)

Complex IV

d)

Complex V

72.

Which enzyme deficiency causes fasting hypoglycemia?

a)

Hexokinase

b)

Glucose-6-phosphatase

c)

PFK-1

d)

Pyruvate kinase

73.

Which pathway provides NADPH?

a)

Glycolysis

b)

TCA

c)

Pentose phosphate pathway

d)

ETC

74.

ETC proton gradient exists across:

a)

Outer membrane

b)

Inner membrane

c)

Matrix

d)

Cytosol

75.

Muscle glycogen cannot maintain blood glucose due to lack of:

a)

Hexokinase

b)

Glucose-6-phosphatase

c)

PFK-1

d)

Glycogen synthase

76.

ATP-yielding step in TCA is:

a)

Citrate synthase

b)

Succinyl-CoA synthetase

c)

Aconitase

d)

Malate dehydrogenase

77.

ETC inhibitor Rotenone blocks:

a)

Complex I

b)

Complex II

c)

Complex III

d)

Complex IV

78.

Which enzyme catalyzes conversion of lactate to pyruvate?

a)

LDH

b)

Pyruvate kinase

c)

Enolase

d)

Aldolase

79.

Glycolysis occurs in RBCs because:

a)

Mitochondria absent

b)

High oxygen

c)

High ATP

d)
80.

Which condition increases glycolysis?

a)

High ATP

b)

High citrate

c)

High AMP

d)

High acetyl-CoA

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