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biology MCQs

11th • Chapter 03

49 Questions TextBook
1

Enzymes are a group of biologically active molecules primarily composed of what?

A
Lipids
B
Carbohydrates
C
Proteins
D
Nucleic acids
2

The catalytic activity of an enzyme is restricted to a small portion of its structure known as the:

A
Binding region
B
Active site
C
Substrate pocket
D
Reaction center
3

What is the reactant in an enzyme-catalyzed reaction called?

A
Product
B
Co-factor
C
Substrate
D
Catalyst
4

A non-protein part essential for the proper functioning of some enzymes is known as a:

A
Co-factor
B
Apoenzyme
C
Holoenzyme
D
Polypeptide
5

If a detachable co-factor is an inorganic ion like Mg2+, it is known as an:

A
Activator
B
Prosthetic group
C
Coenzyme
D
Inhibitor
6

When a non-protein part is covalently bonded to an enzyme, it is called a:

A
Coenzyme
B
Activator
C
Holoenzyme
D
Prosthetic group
7

A non-protein part that is loosely attached to the protein part of an enzyme is known as a:

A
Prosthetic group
B
Coenzyme
C
Apoenzyme
D
Activator
8

Coenzymes are closely related to, and often derived from:

A
Minerals
B
Proteins
C
Vitamins
D
Fats
9

An enzyme with its coenzyme or prosthetic group removed is designated as an:

A
Apoenzyme
B
Holoenzyme
C
Active enzyme
D
Zymogen
10

An activated enzyme consisting of a polypeptide chain and a cofactor is known as a:

A
Apoenzyme
B
Substrate
C
Holoenzyme
D
Inhibitor
11

Enzymes involved in photosynthesis are typically found in which organelle?

A
Mitochondria
B
Ribosomes
C
Nucleus
D
Chloroplasts
12

Enzymes involved in cellular respiration are found in the:

A
Chloroplasts
B
Mitochondria
C
Cytoplasm
D
Ribosomes
13

Which of the following is a key characteristic of all enzymes?

A
They are fibrous proteins
B
They are globular proteins
C
They are used up in the reaction
D
They alter the end products
14

Enzymes increase the rate of reaction by lowering the:

A
Temperature
B
pH
C
Substrate concentration
D
Activation energy
15

The inactive form of the protein-digesting enzyme pepsin is called:

A
Trypsin
B
Pepsinogen
C
Chymotrypsin
D
Amylase
16

According to the mechanism of enzyme action, what does 'ES' in the equation E + S ⇌ ES stand for?

A
Enzyme separation
B
Energy source
C
Enzyme-substrate complex
D
Effective solution
17

In a metabolic pathway, the product of one enzymatic reaction often serves as the what for the next enzyme?

A
Inhibitor
B
Co-factor
C
Substrate
D
Activator
18

The active site of an enzyme is composed of which two regions?

A
Binding site and catalytic site
B
Primary and secondary site
C
Alpha and beta site
D
Core and peripheral site
19

Who proposed the 'Lock and Key' model for enzyme-substrate interaction in 1890?

A
Daniel Koshland
B
Louis Pasteur
C
Emil Fischer
D
James Watson
20

The 'Lock and Key' model describes the active site as a/an:

A
Flexible structure
B
Rigid structure
C
Unstable structure
D
Temporary structure
21

Who proposed the 'Induced Fit Model' as a modification of the 'Lock and Key Model' in 1959?

A
Emil Fischer
B
Daniel Koshland
C
Robert Hooke
D
F. Sanger
22

According to the 'Induced Fit Model', what happens when a substrate binds to an enzyme?

A
The enzyme is denatured
B
It induces a change in the enzyme's structure
C
The reaction stops
D
The substrate becomes an inhibitor
23

If the enzyme concentration is doubled while substrate is unlimited, the reaction rate will:

A
Halve
B
Remain constant
C
Double
D
Increase by four times
24

When all active sites of an enzyme are occupied by substrate molecules, the enzyme is said to be:

A
Denatured
B
Inhibited
C
Saturated
D
Activated
25

What is the term for the specific temperature at which an enzyme works at its maximum rate?

A
Boiling point
B
Melting point
C
Optimum temperature
D
Absolute temperature
26

What is the optimum temperature for most enzymes in the human body?

A
25°C
B
37°C
C
45°C
D
50°C
27

The loss of an enzyme's globular structure and activity due to excessive heat or extreme pH is called:

A
Saturation
B
Inhibition
C
Activation
D
Denaturation
28

For every 10°C rise in temperature, the rate of an enzyme-catalyzed reaction generally:

A
Halves
B
Doubles
C
Triples
D
Remains unchanged
29

What is the term for the narrow range of pH where an enzyme functions most effectively?

A
Neutral pH
B
Acidic pH
C
Basic pH
D
Optimum pH
30

What is the optimum pH for the enzyme pepsin, found in the stomach?

A
2.00
B
4.50
C
7.60
D
9.00
31

What is the optimum pH for the enzyme sucrase?

A
2.00
B
4.50
C
6.80
D
9.70
32

The optimum pH for salivary amylase is approximately:

A
4.50
B
5.50
C
6.80
D
7.60
33

What is the optimum pH for arginase?

A
5.50
B
7.00
C
9.00
D
9.70
34

A chemical substance that reacts with an enzyme to block its active site is called an:

A
Activator
B
Substrate
C
Inhibitor
D
Coenzyme
35

Inhibitors that occupy the active site by forming covalent bonds are typically classified as:

A
Reversible
B
Competitive
C
Irreversible
D
Non-competitive
36

An inhibitor whose effect can be neutralized by increasing substrate concentration is called a:

A
Reversible inhibitor
B
Irreversible inhibitor
C
Permanent inhibitor
D
Denaturing agent
37

A competitive inhibitor works because it has a structural similarity to the:

A
Enzyme
B
Substrate
C
Product
D
Co-factor
38

A non-competitive inhibitor binds to the enzyme at a point called the:

A
Catalytic site
B
Binding site
C
A site other than the active site
D
The active site
39

How do non-competitive inhibitors affect the enzyme's structure?

A
They do not alter it
B
They strengthen it
C
They alter it, preventing catalysis
D
They make it more flexible
40

Malonic acid acts as a competitive inhibitor for the enzyme succinic dehydrogenase, blocking the conversion of:

A
Fumaric acid to malic acid
B
Succinic acid to fumaric acid
C
Malonic acid to succinic acid
D
Fumaric acid to succinic acid
41

The small amount of amino acids in the active site is responsible for:

A
Maintaining the enzyme's shape
B
Catalytic activity
C
Connecting to co-factors
D
Storing energy
42

Pepsin is produced in an inactive form to prevent it from:

A
Digesting the cell that produces it
B
Reacting with the wrong substrate
C
Working outside the digestive tract
D
Being denatured by acid
43

What type of bonds in an enzyme are broken by extreme changes in pH?

A
Peptide bonds
B
Hydrogen bonds and ionic bonds
C
Covalent bonds
D
Ester bonds
44

Enzymes which are integral parts of ribosomes are involved in the synthesis of:

A
Lipids
B
Carbohydrates
C
DNA
D
Proteins
45

In an enzyme to enzyme chain, the product of one step becomes the _______ for the next step.

A
inhibitor
B
cofactor
C
substrate
D
activator
46

Reversible inhibitors form what kind of linkages with the enzyme?

A
Strong covalent bonds
B
Weak linkages
C
Permanent bonds
D
Peptide bonds
47

The part of the active site that helps in recognizing and binding a proper substrate is the:

A
Catalytic site
B
Allosteric site
C
Binding site
D
Inhibitory site
48

Which model of enzyme action suggests that the active site is not rigid?

A
Lock and Key Model
B
Induced Fit Model
C
Template Model
D
Fischer Model
49

Which of these metal ions can act as a co-factor?

A
Na+
B
K+
C
Cl-
D
Zn2+