Enzymes – Online MCQs Test – Biology MCAT

1. Fischer in 1898 proposed:

Key-Lock Theory

Catalyst Fit Theory

Enzyme Lock Theory

Induce Fit Theory

2. Penicillin blocks the active site of an enzyme that many bacteria use for:

Synthesis of proteins

ATP hydrolysis

Cellular respiration

Synthesis of cell-wall

3. Enzymes function because of their particular shape or conformation. Which level of protein structure is most directly responsible for the shape of a protein?

Tertiary

Primary

Quaternary

Secondary

4. Decarboxylases and Dehydratases, are enzymes included in class:

Hydrolases

Lyases

Transferase

Ligases

5. Biological control for the regulation of most of the enzyme is provided by:

Competitive Inhibition

Feed-back Inhibition

Allosteric Inhibition

Non-competitive Inhibition

6. An enzyme acts by

Decreasing the pH

Increasing the pH

Reducing the energy of activation

Increasing the energy of activation

7. If the non-protein part is covalently bonded to enzyme, it is known as a:

Co-factor

Coenzyme

Prosthetic group

Holoenzyme

8. Which of the following is not an attribute of enzymes?

They are used up in reactions.

They are specific in nature.

They speed up the rate of biochemical reactions.

They are proteinaceous in nature.

9. Regarding enzyme molecules:

No relation with substrate

Greater in size than the substrate

Of same size as substrate

Smaller in size than the substrate

10. Substances which decrease the activity of enzyme are called:

Co-enzymes

Inhibitors

Apo-enzymes

Activators

11. All of the following are correct about enzymes EXCEPT

Enzymes are assisted by cofactors

Enzymes are affected by changes in temperature but not changes in pH

Enzymes lower the energy of activation

Enzymes are organic catalysts

12. Which statements are correct for all enzymes?

2 and 4 only

1 and 4 only

1, 2, 3 and 4

1, 2 and 3 only

13. Concerning enzyme activity at O°C, which of the following statement is correct?

Activity is reduced to minimum but enzymes are destroyed.

Activity is reduced to minimum but enzymes are not destroyed.

Activity is increased to maximum but enzymes are not destroyed.

Activity is increased to maximum but enzymes are destroyed.

14. Concerning effects of Radiation on enzymes:

generally activated by UV-rays and inactivated by X-rays

generally inactivated by both, UV-rays and X-rays

generally activated by exposure to UV-rays & X-rays

generally inactivated by UV-rays and activated by X-rays

15. Which of the following statements is not correct?

All enzymes are proteins

All enzymes are biocatalysts

All proteins are enzymes

All enzymes are thermo-labile

16. In plants enzymes are present

In all the living cells of paint body

Only in parenchyma

Only in leaves

Only in flowers

17. All of the following are correct about enzymes EXCEPT

They are proteins

The mechanism by which enzymes work is known as lock and key

They are assisted by vitamins and minerals

They denature at high temperatures

18. Most vitamins are:

Co-enzymes

Non-competitive inhibitors

Co-factors

Competitive inhibitors

19. When an enzyme-induced product inhibits enzymatic activity, inhibition is called

Non-competitive inhibition

Feedback inhibition

None of the above

Competitive inhibition

20. Vitamins are essential for the body because:

Prosthetic groups of enzymes are synthesized from them

Co enzyme of enzyme is synthesized from them

Some activators have direct link with them

They are part of some enzyme

Enzymes-Medical College Admission Test Preparation Notes