ENZYMES MCQS

TOP ENZYMES MCQS

1. What is the primary role of enzymes in biological systems?

a) They act as catalysts to speed up chemical reactions
b) They provide energy for cellular reactions
c) They store genetic information
d) They break down proteins

2. Enzymes are typically made up of which macromolecule?

a) Lipids
b) Proteins
c) Carbohydrates
d) Nucleic acids

3. The specific region of the enzyme where the substrate binds is called the:

a) Allosteric site
b) Binding site
c) Active site
d) Catalytic site

4. What type of structure are most enzymes classified as?

a) Fibrous
b) Globular
c) Linear
d) Cylindrical

5. Which type of bond stabilizes the secondary structure of an enzyme?

a) Covalent bonds
b) Hydrogen bonds
c) Ionic bonds
d) Van der Waals forces

6. The tertiary structure of an enzyme refers to its:

a) Linear sequence of amino acids
b) Arrangement of alpha helices and beta sheets
c) Three:dimensional folding of the entire polypeptide chain
d) Combination of multiple polypeptide chains

7. What is the primary characteristic of a competitive inhibitor?

a) It binds to the active site of the enzyme
b) It binds to an allosteric site
c) It changes the shape of the enzyme
d) It increases the rate of reaction

8. An example of a digestive enzyme that works at a low pH is:

a) Trypsin
b) Pepsin
c) Amylase
d) Lipase

9. At what temperature do most human enzymes operate optimally?

a) 25°C
b) 50°C
c) 37°C
d) 60°C

10. What happens to an enzyme when it is exposed to high temperatures?

a) Its activity increases
b) It becomes denatured
c) It forms new active sites
d) It speeds up indefinitely

11. Non:competitive inhibitors bind to:

a) A site other than the active site
b) The active site
c) The substrate
d) The product

12. What happens to enzyme activity as the pH moves away from the optimal range?

a) The activity increases
b) The activity decreases
c) The enzyme denatures
d) The enzyme becomes more specific

13. The process of increasing the rate of a chemical reaction without being consumed is called:

a) Metabolism
b) Catalysis
c) Anabolism
d) Hydrolysis

14. Which type of enzyme catalyzes the transfer of functional groups?

a) Oxidoreductases
b) Transferases
c) Hydrolases
d) Lyases

15. Which enzyme type adds or removes atoms to form double bonds?

a) Lyases
b) Ligases
c) Isomerases
d) Hydrolases

16. Which enzyme type rearranges atoms within a molecule?

a) Hydrolases
b) Isomerases
c) Lyases
d) Oxidoreductases

17. Which enzyme type catalyzes reactions that involve joining two molecules together?

a) Oxidoreductases
b) Isomerases
c) Lyases
d) Ligases

18. Which of the following affects the rate of enzyme activity?

a) pH
b) Temperature
c) Inhibitors
d) All of the above

19. An enzyme that catalyzes oxidation:reduction reactions belongs to which class?

a) Transferases
b) Ligases
c) Oxidoreductases
d) Hydrolases

20. Enzyme inhibitors that resemble the substrate and bind to the active site are called:

a) Non:competitive inhibitors
b) Allosteric inhibitors
c) Competitive inhibitors
d) Reversible inhibitors

21. What happens when an enzyme is denatured?

a) Its structure is altered, and it loses function
b) It increases its activity
c) It binds more efficiently to substrates
d) It becomes a better catalyst

22. Enzyme activity is highest when the enzyme is:

a) Frozen
b) At its optimal temperature
c) Denatured
d) Not bound to a substrate

23. Which of the following is true about enzyme specificity?

a) Enzymes are specific to their substrates
b) Enzymes work on multiple substrates
c) Enzymes catalyze all types of reactions
d) Enzymes work equally well at all pH levels

24. What does the active site of an enzyme bind to?

a) The substrate
b) The product
c) The inhibitor
d) The enzyme itself

25. In which type of inhibition does the inhibitor bind to the enzyme away from the active site?

a) Non:competitive inhibition
b) Competitive inhibition
c) Uncompetitive inhibition
d) Reversible inhibition

26. Which enzyme is responsible for breaking down starch into sugars?

a) Lipase
b) Amylase
c) Protease
d) Pepsin

27. Enzyme activity can be measured by:

a) The rate of product formation
b) The increase in temperature
c) The presence of inhibitors
d) The amount of substrate

28. Which of the following is true about competitive inhibitors?

a) They compete with the substrate for the active site
b) They bind to an allosteric site
c) They cannot be overcome by increasing substrate concentration
d) They make the enzyme non:functional permanently

29. What happens to the reaction rate when the substrate concentration is increased in the presence of a competitive inhibitor?

a) The reaction rate decreases
b) The reaction stops
c) The reaction rate increases up to a point
d) The reaction rate is unaffected

30. Enzymes are:

a) Consumed in reactions
b) Reused after reactions
c) Destroyed after use
d) Unchanged but not reused

31. What type of reaction does hydrolase catalyze?

a) Transfer of functional groups
b) Hydrolysis of bonds
c) Formation of double bonds
d) Rearrangement of molecules

32. Which term refers to the enzyme’s loss of function due to a structural change?

a) Inhibition
b) Denaturation
c) Activation
d) Catalysis

33. Which enzyme is involved in DNA replication?

a) DNA polymerase
b) Pepsin
c) Amylase
d) Lactase

34. What is the optimum pH for most human enzymes?

a) 7
b) 2
c) 5
d) 10

35. Which is NOT a factor that affects enzyme activity?

a) pH
b) Temperature
c) DNA sequence
d) Inhibitors

36. A change in the enzyme’s three:dimensional structure can lead to:

a) Increased reaction rate
b) Loss of enzyme activity
c) Formation of new active sites
d) Improved specificity

37. Enzymes are specific to their substrates due to:

a) Random binding
b) The shape of the active site
c) The shape of the inhibitor
d) The pH of the environment

38. Which factor does NOT denature enzymes?

a) High temperature
b) Low substrate concentration
c) Extreme pH levels
d) High salt concentration

39. Which enzyme breaks down proteins into smaller peptides?

a) Amylase
b) Lipase
c) Protease
d) Nuclease

40. What is the term for an enzyme that has its structure altered but returns to function when normal conditions are restored?

a) Denatured
b) Irreversibly inhibited
c) Reversibly inhibited
d) Permanently destroyed

ENZYMES MCQS ENZYMES MCQS ENZYMES MCQS ENZYMES MCQS

Enzymes

The biological catalysts that accelerate chemical reactions in living organisms, having a crucial role in facilitating metabolic processes, such as digestion, energy production, and DNA replication.

Biology and its branches

Most enzymes are proteins, though a few RNA molecules can act as enzymes (ribozymes).

Cofactors: Non:protein chemical compounds or metallic ions required for enzyme activity. Prosthetic Groups: Tightly bound, permanent non:protein components of enzymes essential for their function.

Coenzymes: Organic molecules that temporarily bind to enzymes, assisting in catalysis.

Structure of Enzymes

Enzymes are primarily globular proteins. They have specific three:dimensional shape which is essential for their function. The enzyme’s active site is where the substrate binds, facilitating the chemical reaction.

Primary Structure: The linear sequence of amino acids.
Secondary Structure: Folding into alpha helices and beta:pleated sheets due to hydrogen bonding.
Tertiary Structure: The overall three:dimensional shape of the enzyme.
Quaternary Structure: Structure formed by multiple polypeptide chains.

Types of Enzymes

Enzymes are classified into six main categories based on the type of reaction they catalyze:

Oxidoreductases: Catalyze oxidation:reduction reactions.
Transferases: Transfer functional groups between molecules.
Hydrolases: Catalyze hydrolysis reactions.
Lyases: Add or remove atoms to form double bonds.
Isomerases: Rearrange atoms within a molecule.
Ligases: Join two molecules together using covalent bonds.

Factors Affecting Enzyme Activity

1. pH

Enzymes function best at a specific pH. Changes in pH can denature the enzyme, altering its shape and reducing its effectiveness.

Pepsin (found in the stomach): Optimum pH = 2 (acidic).
Amylase (found in saliva): Optimum pH = 7 (neutral).
Trypsin (found in the small intestine): Optimum pH = 8 (slightly basic).
Optimum temperature

Most enzymes work best at a particular temperature. High temperatures can cause enzyme denaturation, while low temperatures reduce activity.

Pepsin: Optimum temperature = 37°C (human body temperature).
Amylase: Optimum temperature = 37°C.
Trypsin: Optimum temperature = 37°C.
Plant and bacterial enzymes can have different temperature optima, ranging from 20°C to 80°C depending on the organism.
Inhibitors

Non:competitive Inhibitors: Bind elsewhere on the enzyme, altering its shape and reducing function.

Competitive Inhibitors: Bind to the active site, competing with the substrate.