Enzymes

Question 1

What are enzymes?

Answer 1

biological catalysts

Enzymes speed up chemical reactions in biological systems.

Question 2

What properties do all enzymes have?

Answer 2

• are globular proteins
• specific (only have one substrate)
• have an active site
• affected by temperature and pH

These properties are crucial for enzyme function and efficiency.

Question 3

What are anabolic reactions?

Answer 3

reactions that construct molecules from smaller units

Anabolic reactions require energy, examples include protein synthesis and building biological molecules.

Question 4

What are catabolic reactions?

Answer 4

reactions that break molecules down into smaller units

Catabolic reactions release energy, examples include digestion and respiration.

Question 5

What are intracellular enzymes?

Answer 5

enzymes that react within a cell

Examples include catalase and DNA polymerase.

Question 6

What are extracellular enzymes?

Answer 6

enzymes released from cells, which work outside of cells

Examples include amylase and trypsin.

Question 7

Describe the lock and key hypothesis.

Answer 7

• active site is complementary to a specific substrate
• when substrate binds to active site, enzyme-substrate complex is formed
• enzyme-product complex is formed after the substrate has reacted and products have formed
• enzyme holds substrate so that the right atom groups are close enough to react

This hypothesis illustrates how enzymes and substrates interact specifically.

Question 8

Describe the induced fit hypothesis.

Answer 8

• when the substrate enters, the active site changes shape slightly
• initial interactions are weak but they change the enzyme’s tertiary structure
• this weakens bonds and therefore lowers the activation energy

This hypothesis emphasizes the dynamic interaction between enzymes and substrates.

Question 9

What factors affect enzyme action?

Answer 9

• temperature
• pH
• substrate concentration
• enzyme concentration
• presence of inhibitors
• presence of cofactors

Each factor can significantly influence enzyme activity and stability.

Question 10

How does an increase in temperature affect the rate of enzyme action?

Answer 10

• increase in temp increases kinetic energy
• enzymes and substrates move faster
• active site and substrate collide more frequently
• more enzyme-substrate complexes

Past 38°C, the rate decreases as the enzyme denatures.

Question 11

What is the temperature coefficient?

Answer 11

Q10

For enzyme controlled reactions, the rate of reaction doubles with each 10°C increase, therefore Q10 = 2.

Question 12

What is denaturing (of an enzyme)?

Answer 12

change in tertiary structure of an enzyme (because bonds are broken)

The active site irreversibly changes shape and no longer has a complementary shape to the substrate.

Question 13

What is an optimum pH (for enzymes)?

Answer 13

the pH where the enzyme’s active site remains the correct shape

Enzymes have specific pH ranges for optimal activity.

Question 14

Why do too acidic/too alkali conditions affect enzyme action?

Answer 14

• H+ ions interact with polar R-groups of amino acids
• when the concentration of H+ changes, the degree of interactions between R-groups changes

The pH affects the structure and function of the enzyme’s active site.

Question 15

What is an enzyme inhibitor?

Answer 15

a substance/molecule that slows down the rate of an enzyme-controlled reaction

Inhibitors affect the enzyme’s active site or its ability to function.

Question 16

Why do enzymes need to be inhibited?

Answer 16

to regulate enzyme-controlled reactions

This regulation helps control the amount of products produced.

Question 17

What are the two types of enzyme inhibitors?

Answer 17

• competitive inhibitors
• non-competitive inhibitors

Each type affects enzyme activity differently.

Question 18

What is a competitive inhibitor?

Answer 18

a molecule that has a similar shape to the substrate and can fit into the enzyme’s active site

Competitive inhibitors block the substrate from entering the active site.

Question 19

How does a competitive inhibitor affect the rate of reaction?

Answer 19

reduces rate of reaction

It does not change Vmax but takes longer to reach it.

Question 20

What is a non-competitive inhibitor?

Answer 20

a molecule that binds to the allosteric site on an enzyme

It changes the shape of the active site, affecting enzyme function.

Question 21

How does a non-competitive inhibitor affect the rate of reaction?

Answer 21

reduces rate of reaction and causes rate to plateau sooner

Increasing enzyme or substrate concentration won’t affect the inhibitor’s effect.

Question 22

What is end product inhibition?

Answer 22

when the product of a reaction acts as an inhibitor to the enzyme that produced it

This process is reversible and non-competitive.

Question 23

Why can end product inhibition be a good thing?

Answer 23

excess products aren’t made

This prevents resource wastage.

Question 24

What are enzyme cofactors?

Answer 24

non-protein components on enzymes that help them catalyze reactions

Cofactors can be essential for enzyme activity.

Question 25

How are enzyme cofactors obtained?

Answer 25

* from diet * inorganic cofactors are from minerals (e.g., iron, zinc, calcium) * coenzymes are from vitamins (e.g., vitamin B3 and B5) ## Footnote Proper nutrition is essential for maintaining enzyme function.

Question 26

What are coenzymes?

Answer 26

cofactors that are organic molecules ## Footnote Coenzymes often assist in enzyme reactions by carrying chemical groups.

Question 27

What is the cofactor for amylase?

Answer 27

chlorine ions (Cl-) ## Footnote Amylase requires this cofactor for its activity.

Question 28

What is the prosthetic group of carbonic anhydrase?

Answer 28

zinc ions (Zn2+) ## Footnote This prosthetic group is crucial for the enzyme's catalytic function.

Question 30

What effect does heat have on enzyme activity?

Answer 30

Heat increases kinetic energy, causing molecules to collide more frequently and with more force ## Footnote This results in an initial increase in the rate of reaction.

Question 31

What happens to enzymes when the temperature is increased beyond a certain point?

Answer 31

Ionic and hydrogen bonds break in the tertiary structure, leading to loss of specificity in the active site ## Footnote This process is known as denaturation.

Question 32

What is the temperature coefficient (Q10)?

Answer 32

Q10 shows how much the rate of reaction changes when the temperature rises by 10 degrees ## Footnote For every 10-degree rise, the rate of reaction doubles.

Question 33

What is the Q10 value from 0 to 40 degrees?

Answer 33

Q10 is 2 ## Footnote This indicates the rate of reaction doubles with each 10-degree increase in temperature.

Question 34

How does pH affect enzymes?

Answer 34

It affects the charge of the amino acid side chain and interferes with the tertiary structure ## Footnote Each enzyme has an optimum pH based on its location in the body.

Question 35

What is the optimum pH for enzymes in the stomach?

Answer 35

Acidic ## Footnote Stomach enzymes work best in low pH environments.

Question 36

What is the optimum pH for enzymes in the small intestine?

Answer 36

Alkaline ## Footnote Small intestine enzymes function optimally in higher pH environments.

Question 37

What is the effect of increasing substrate concentration on the rate of reaction?

Answer 37

Increasing substrate concentration increases the rate of reaction to a point ## Footnote When all enzyme active sites are occupied, the rate levels off.

Question 38

What occurs when all enzyme active sites are occupied?

Answer 38

The rate of reaction levels off and cannot increase further ## Footnote This is due to saturation of the enzyme.