Enzymes

Question 1

what are catalysts

Answer 1

substance that speeds up chemical reactions without itself being chemically changed at the end of the reaction

Question 2

what is activation energy

Answer 2

amount of energy required to bring reactant molecules into their transition state

Question 3

what is metabolism

Answer 3

sum of all chemical reactions within a body of an organism

*catabolism (break down) + anabolism (break up)

Question 4

what are enzymes

Question 5

what are 2 examples of catabolism

Answer 5

respiration
decomposition of hydrogen peroxide

Question 6

what are 2 examples of anabolism

Answer 6

protein synthesis
photosynthesis

Question 7

what are 2 characteristics of enzymes

Answer 7

small amount can affect change of large amount of substrate molecules
enzymes are unaffected by reactions and are reusable

Question 8

what is a substrate

Answer 8

reactant that the enzyme acts on

Question 9

what is an enzyme-substrate complex

Answer 9

when an enzyme binds to a substrate(s)

Question 10

what is a product

Answer 10

conversion from substrate after catalytic action of enzyme

Question 11

what is an active site

Answer 11

pocket/groove on surface of protein where catalysis occurs

Question 12

describe the lock-and-key hypothesis

Answer 12

• reaction catalysed by each enzyme is very specific
• only substrate molecule with complementary shape can fit into active site
• enzyme is lock, substrate is key

Question 13

how does temperature affect the rate of enzyme activity

Answer 13

• at low temp., enzyme is inactive/activity is slow
• as temp. rises, rate of enzyme activity increases until optimum temp. is reached
• beyond optimum temp., reaction slows down and eventually stops
• at high temp., enzyme denatures

*denaturation usually irreversible, unlike inactivity
*graph is steeper on the decrease
*human enzymes: 35-40 degrees
*enzymes are 2 times as active for each 10-degree increase until optimum temp.

Question 14

how does pH affect the rate of enzyme activity

Answer 14

• enzymes denature at extreme pH
• however, enzymes in stomach optimum pH is 2, small intestine is 8
• graph is symmetrical
• most enzymes have optimum pH of 6-8

Question 15

how does substrate concentration affect the rate of enzyme activity

Answer 15

• as substrate conc. increases from low conc., rate of binding to available active sites increases
• at high substrate conc., active sites of all enzymes occupied and enzymes are saturated

Question 16

how does enzyme concentration affect the rate of enzyme activity

Answer 16

• rate of reaction directly proportional to enzyme concentration
• provided that temp. and pH constant, conc. of substrate is high/in excess