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Quiz on Proteins and Enzymes

Total questions: 75

Worksheet time: 38mins

Name
Class
Date
1.

Proteins are considered the engine of which of the following?

a)

Human brain

b)

Working human cell

c)

Digestive system

d)

Skeletal muscles

2.

Which of the following is not a function of proteins?

a)

Catalysis

b)

Storage

c)

Structure

d)

Photosynthesis

3.

The building blocks of proteins are:

a)

Lipids

b)

Amino acids

c)

Nucleotides

d)

Fatty acids

4.

Peptide bonds are also known as:

a)

Ester bonds

b)

Amide bonds

c)

Ionic bonds

d)

Hydrogen bonds

5.

How many natural amino acids are commonly found in proteins?

a)

18

b)

19

c)

20

d)

21

6.

The only amino acid that is not chiral is:

a)

Alanine

b)

Glycine

c)

Serine

d)

Leucine

7.

Which group differentiates amino acids from each other?

a)

Amino group

b)

Carboxyl group

c)

R group

d)

Hydrogen atom

8.

The bond between two cysteine residues forms:

a)

Hydrogen bond

b)

Disulfide bond

c)

Ionic bond

d)

Peptide bond

9.

The secondary structure of a protein includes:

a)

β-pleated sheets and α-helices

b)

Disulfide bridges

c)

Peptide linkages

d)

Amino acid residues

10.

In an α-helix, how many amino acids are present per turn?

a)

2.5

b)

3.0

c)

3.6

d)

4.0

11.

Which amino acid disrupts the α-helix due to its cyclic structure?

a)

Glycine

b)

Proline

c)

Tyrosine

d)

Phenylalanine

12.

β-pleated sheets are stabilized mainly by:

a)

Covalent bonds

b)

Hydrogen bonds

c)

Peptide bonds

d)

Ionic bonds

13.

A β-turn typically consists of how many amino acids?

a)

2

b)

3

c)

4

d)

5

14.

Standard β-sheet is how many amino acids long?

a)

2

b)

3

c)

4

d)

5-6

15.

The tertiary structure of proteins is stabilized primarily by:

a)

Peptide bonds

b)

Interactions between R-groups

c)

DNA binding

d)

Van der Waals forces only

16.

Interaction of multiple tertiary chains forms a:

a)

Primary structure

b)

Secondary structure

c)

Quaternary structure

d)

Coiled coil

17.

Which of the following proteins is fibrous?

a)

Collagen

b)

Hemoglobin

c)

Myoglobin

d)

Amylase

18.

Globular proteins are primarily:

a)

Structural

b)

Functional

c)

Insoluble in water

d)

Non-reactive

19.

Fibrous proteins are primarily:

a)

Structural

b)

Functional

c)

Insoluble in water

d)

Non-reactive

20.

Which type of protein has an axial ratio > 10?

a)

Globular

b)

Fibrous

c)

Enzymatic

d)

Membrane

21.

Denaturation of proteins affects which of the following?

a)

Primary structure

b)

Secondary and tertiary structure

c)

Amino acid sequence

d)

Peptide bond formation

22.

Which factor can denature a protein?

a)

Heat

b)

pH change

c)

Chemicals

d)

All of the above

23.

A dipeptide contains how many amino acids?

a)

1

b)

2

c)

3

d)

4

24.

A peptide bond is formed by which reaction?

a)

Oxidation

b)

Dehydration

c)

Reduction

d)

Hydrolysis

25.

The N-terminus of a polypeptide contains which functional group?

a)

Carboxyl

b)

Amine (-NH₂)

c)

Hydroxyl

d)

Carbonyl

26.

The C-terminus of a polypeptide contains which functional group?

a)

Amine

b)

Carboxyl (-COOH)

c)

Amide

d)

Alcohol

27.

A peptide bond connects:

a)

Two nitrogen atoms

b)

Carboxyl and amino groups

c)

Two hydroxyl groups

d)

Two carboxyl groups

28.

Sulfur-containing amino acids include:

a)

Methionine and cysteine

b)

Serine and threonine

c)

Tyrosine and tryptophan

d)

Alanine and glycine

29.

Aromatic amino acids absorb UV light and include:

a)

Phenylalanine, tyrosine, tryptophan

b)

Alanine, glycine, valine

c)

Lysine, arginine, histidine

d)

Leucine, isoleucine, methionine

30.

Histidine contains which unique side chain?

a)

Pyrrole ring

b)

Imidazole ring

c)

Benzene ring

d)

Sulfur group

31.

Proline is unique because:

a)

It is achiral

b)

It has a secondary amine

c)

It has a disulfide bridge

d)

It is aromatic

32.

Glycine is the only amino acid that is:

a)

Non-polar

b)

Achiral

c)

Polar

d)

Aromatic

33.

Enzymes are:

a)

Structural lipids

b)

Biological catalysts

c)

RNA molecules only

d)

Hormones

34.

The compound on which an enzyme acts is called the:

a)

Cofactor

b)

Substrate

c)

Inhibitor

d)

Product

35.

The complex formed during catalysis is known as:

a)

Active complex

b)

Enzyme–substrate complex

c)

Reaction complex

d)

Cofactor system

36.

Enzymes affect which of the following?

a)

Equilibrium

b)

Rate of reaction

c)

Product formation

d)

Substrate energy

37.

Apoenzyme is:

a)

Protein part of enzyme

b)

Cofactor

c)

Active enzyme

d)

Product

38.

Coenzymes are:

a)

Non-protein molecules that assist enzymes

b)

Amino acid residues

c)

Protein chains

d)

Inhibitors

39.

A holoenzyme is composed of:

a)

Apoenzyme + cofactor

b)

Enzyme + inhibitor

c)

Product + enzyme

d)

Protein + substrate

40.

Enzymes lower activation energy by:

a)

Stabilizing the transition state

b)

Increasing reactant energy

c)

Changing product energy

d)

Releasing heat

41.

Enzymes lower activation energy by:

a)

Stabilizing the transition state

b)

Increasing reactant energy

c)

Changing product energy

d)

Releasing heat

42.

Enzymes are generally composed of:

a)

Lipids

b)

Globular proteins

c)

Carbohydrates

d)

RNA

43.

The region of the enzyme where substrate binds is called the:

a)

Active site

b)

Regulatory site

c)

Catalytic pocket

d)

Cofactor region

44.

The rate of an enzyme-catalyzed reaction increases with substrate concentration until:

a)

The enzyme becomes saturated

b)

The enzyme denatures

c)

The reaction stops

d)

Product accumulates

45.

The Michaelis constant (Km) represents:

a)

Substrate concentration at half Vmax

b)

Product concentration

c)

Maximum velocity

d)

Enzyme stability

46.

Competitive inhibitors bind to the:

a)

Active site

b)

Allosteric site

c)

Substrate

d)

Product

47.

Non-competitive inhibitors bind:

a)

To another site on the enzyme

b)

To substrate

c)

To product

d)

To cofactors

48.

Uncompetitive inhibitors bind only to the:

a)

Free enzyme

b)

Enzyme–substrate complex

c)

Product

d)

Coenzyme

49.

The Lock-and-Key model describes the enzyme as:

a)

Rigid and complementary to substrate

b)

Flexible active site

c)

Dynamic cofactor

d)

Inactive form

50.

The Induced-Fit model describes the enzyme as:

a)

Adapting its shape to the substrate

b)

Unchanged by binding

c)

Rigid in structure

d)

Destroyed during binding

51.

Feedback inhibition is an example of:

a)

Allosteric regulation

b)

Covalent modification

c)

Denaturation

d)

Enzyme activation

52.

An allosteric enzyme is typically involved in:

a)

Regulation of metabolic pathways

b)

Transport

c)

Replication

d)

Digestion

53.

The Lineweaver–Burk plot is used to determine:

a)

Enzyme kinetic constants

b)

pH effect

c)

Molecular weight

d)

Denaturation point

54.

Which class of enzymes catalyzes oxidation–reduction reactions?

a)

Transferases

b)

Hydrolases

c)

Oxidoreductases

d)

Ligases

55.

Transferases catalyze reactions that involve:

a)

Electron transfer

b)

Group transfer

c)

Hydrolysis

d)

Isomerization

56.

Hydrolases carry out:

a)

Hydrolysis of bonds using water

b)

Formation of double bonds

c)

Group transfer

d)

Electron transport

57.

Lyases catalyze:

a)

Bond breaking without water

b)

Phosphate transfer

c)

ATP formation

d)

Oxidation

58.

Isomerases catalyze:

a)

Formation of isomers from one molecule

b)

Bond cleavage

c)

ATP hydrolysis

d)

Lipid oxidation

59.

Ligases catalyze:

a)

Joining of two substrates using ATP

b)

Breaking of peptide bonds

c)

Protein denaturation

d)

Hydrogen bonding

60.

Which enzyme class does hexokinase belong to?

a)

Transferase

b)

Oxidoreductase

c)

Hydrolase

d)

Isomerase

61.

Pyruvate decarboxylase is an example of a(n):

a)

Lyase

b)

Hydrolase

c)

Isomerase

d)

Transferase

62.

Which enzyme class forms new bonds between molecules using ATP?

a)

Ligases

b)

Oxidoreductases

c)

Transferases

d)

Hydrolases

63.

The universal energy molecule of the cell is:

a)

NADH

b)

ATP

c)

GTP

d)

Glucose

64.

The breakdown of glucose to pyruvate is called:

a)

Glycolysis

b)

Gluconeogenesis

c)

Krebs cycle

d)

Fermentation

65.

The net ATP gain in glycolysis is:

a)

1

b)

2

c)

4

d)

6

66.

The citric acid cycle occurs in the:

a)

Cytoplasm

b)

Mitochondria

c)

Nucleus

d)

Ribosome

67.

The final electron acceptor in aerobic respiration is:

a)

Oxygen

b)

NADH

c)

ATP

d)

Glucose

68.

The enzyme that synthesizes ATP using the proton gradient is:

a)

ATP synthase

b)

Kinase

c)

Dehydrogenase

d)

Oxidase

69.

Fermentation produces:

a)

Lactic acid

b)

CO₂ and water

c)

Oxygen

d)

Glucose

70.

The main electron carrier in glycolysis is:

a)

NAD⁺

b)

FAD

c)

ATP

d)

GTP

71.

The process of glucose breakdown in the absence of oxygen is called:

a)

Aerobic respiration

b)

Fermentation

c)

Oxidation

d)

Photolysis

72.

During aerobic respiration, the majority of ATP is produced by the:

a)

Glycolytic pathway

b)

Citric acid cycle

c)

Electron transport chain

d)

Fermentation pathway

73.

The enzyme that synthesizes ATP during oxidative phosphorylation is:

a)

Kinase

b)

ATP synthase

c)

Phosphatase

d)

Dehydrogenase

74.

Which of the following is not a product of aerobic respiration?

a)

Carbon dioxide

b)

Water

c)

Glucose

d)

ATP

75.

The final electron acceptor in the electron transport chain is:

a)

Carbon dioxide

b)

Oxygen

c)

NADH

d)

ATP

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