Chapter 24

Question 1

Energy of activation?

Answer 1

• certain amount of energy to initiate a rxn

- energy level that ensures that random collision of molecules will result in a rxn

Question 2

What are enzymes? Function in a rxn?

Answer 2

• proteins that act as catalysts
• lower the activation energy
• increase rate of rxn, end products form faster
• not consumed in the rxn

Question 3

Lock and key model of enzymes?

Answer 3

enzymes work as catalysts because on the surface of each enzyme there is an active site that matches a specific substrate. They bind with substrate to form an enzyme substrate complex to catalyze specific rxns. Substrate is split in two in the product

Question 4

What factors determine rate of a rxn?

Answer 4

• amount and activity of enzyme
• amount of substrate
• temp
• pH of cell

Question 5

How does increasing temp affect enzyme activity?

Answer 5

at low temps, fewer interactions happen between substrate and enzyme. at higher temps, more substrate binds to the active site of enzymes

Question 6

At normal body temp, most rxns take place too slow to maintain life. How do we still survive?

Answer 6

enzymes are most effective near body temp, so they speed up these rxns without having to increase body temp

Question 7

During exercise, what are the changes in pH that affect enzyme activity?

Answer 7

muscle contractions cause pH to decrease which creates an optimal pH range for enzyme activity

Question 8

During intense exercise, when lactates accumulates, what changes in pH affect enzyme activity?

Answer 8

pH decreases below optimal range which is a possible cause of fatigue

Question 9

What happens when concentration of enzyme is lower than substrate?

Answer 9

• the concentration of enzyme limits the rate of rxn

- increasing the concentration of enzyme will increase the rate of rxn

Question 10

What happens when concentration of substrate is lower than enzyme?

Answer 10

• concentration of substrate limits the rate of rxn

- add more substrate to speed up rate of rxn

Question 11

What do the plateaus on the enzyme-substrate graph represent?

Answer 11

the point at which addition of more enzyme or substrate will have no effect

Question 12

Rate limiting enzyme?

Answer 12

• control rate of rxn
• found near beginning of series of rxns
• controlled by modulators

Question 13

How do modulators work?

Answer 13

-negative feedback system

Question 14

Phosphofructokinase (PFK)? Modulators for it?

Answer 14

• rate limiting enzyme if Glycolysis
• ATP, ADP, Pi are modulators
• Increased ADP and Pi stimulate PFK
• Increased ATP inhibit PFK