Enzymes and Their Functions

Question 1

What role do catalysts play in chemical reactions?

Answer 1

Catalysts accelerate the rate of chemical reactions without changing the equilibrium.

Question 2

Enzymes are categorized as what type of catalyst?

Answer 2

Biological catalysts (biocatalysts).

Question 3

How efficient are enzymes compared to typical catalysts?

Answer 3

One enzyme molecule can act on ~1000 substrates, making their catalysis extremely rapid.

Question 4

What happens if an enzyme is missing in a metabolic pathway?

Answer 4

It blocks the pathway, halting the associated metabolic process.

Question 5

What is the term for the reactant an enzyme acts on?

Answer 5

Substrate

Question 6

Why are enzymes considered “highly specific”?

Answer 6

They typically act on only one substrate (e.g., lactase only breaks down lactose).

Question 7

List four key characteristics of enzymes.

Answer 7

1. Mostly proteins.
2. Water-soluble.
   3.Heat-labile (denature with heat).
   4.Contain 16% nitrogen by weight.

Question 8

What is the name of the site where a substrate binds to an enzyme?

Answer 8

Active site (or catalytic site).

Question 9

What distinguishes a simple protein enzyme from a conjugated enzyme?

Answer 9

Simple enzymes are only proteins; conjugated enzymes have a protein (apoenzyme) and a non-protein part (cofactor).

Question 10

What term describes the complete, functional form of a conjugated enzyme?

Answer 10

Holoenzyme (apoenzyme + cofactor)

Question 11

What are coenzymes often derived from?

Answer 11

Vitamin B derivatives.

Question 12

Describe the two steps in the mechanism of enzyme action.

Answer 12

1. Substrate binds to the enzyme’s active site, forming an enzyme-substrate (ES) complex.
2. ES complex splits into products, releasing the original enzyme.

Question 13

List the five steps of an enzymatic reaction.

Answer 13

1. Substrate approaches active site.
2. ES complex forms.
3. Substrate → products.
4. Products released.
5. Enzyme recycled.

Question 14

What does the Lock and Key Theory state about enzyme-substrate binding?

Answer 14

The active site’s shape exactly fits the substrate, like a key in a lock (proposed by Emil Fischer

Question 15

How does the Induced Fit Theory differ from Lock and Key?

Answer 15

The active site changes shape upon substrate binding for a better fit (proposed by Daniel Koshland).

Question 16

Name the six classes of enzymes.

Answer 16

1. Oxidoreductases
2. Transferases
3. Hydrolases
4. Lyases
5. Isomerases
6. Ligases

Question 17

What is the function of hydrolases?

Answer 17

Catalyze hydrolysis reactions (break bonds using water).

Question 18

Which enzyme class joins molecules using ATP?

Answer 18

Ligases.

Question 20

Why might babies be lactose intolerant?

Answer 20

Temporary deficiency in lactase enzyme after weaning.

Question 21

What is a prosthetic group in enzymes?

Answer 21

A tightly bound, non-protein cofactor (e.g., heme in hemoglobin).

Question 22

What are enzymes?

Answer 22

Enzymes are proteins that act as biological catalysts, increasing the rate of chemical reactions without being consumed.

Question 23

What is a coenzyme?

Answer 23

A coenzyme is a small organic molecule that assists enzymes in facilitating chemical reactions, often derived from vitamins.

Question 24

What are the two main types of enzymes?

Answer 24

Simple enzymes (composed only of protein) and complex (conjugated) enzymes (composed of an apoenzyme and a cofactor).

Question 25

What factors affect enzyme activity?

Answer 25

Temperature, pH, substrate concentration, and enzyme concentration.

Question 26

What is enzyme inhibition?

Answer 26

Enzyme inhibition is the process by which a substance slows down or stops the normal catalytic function of an enzyme.

Question 27

What are the types of enzyme inhibition?

Answer 27

1. Reversible Competitive Inhibition 2. Reversible Non-competitive Inhibition 3. Irreversible Inhibition

Question 28

What is the difference between a cofactor and a coenzyme?

Answer 28

A cofactor is an inorganic ion (e.g., metal ions like Zn²⁺), while a coenzyme is an organic molecule (often derived from vitamins) that assists enzyme activity.

Question 29

What is the significance of enzyme specificity?

Answer 29

Enzyme specificity refers to the ability of an enzyme to catalyze a reaction for only one substrate or a group of similar substrates, ensuring precise biochemical reactions.

Question 30

What is the "Lock and Key" model of enzyme action?

Answer 30

The "Lock and Key" model suggests that the active site of the enzyme is a rigid structure that fits only a specific substrate, like a key fits into a lock.

Question 31

What is the role of allosteric enzymes?

Answer 31

Allosteric enzymes have multiple binding sites and can be regulated by molecules that enhance or inhibit their activity, affecting the enzyme's overall function.

Question 32

What are isoenzymes?

Answer 32

Isoenzymes are different forms of an enzyme that catalyze the same reaction but are found in different tissues, allowing for tissue-specific regulation.