enzymes as biological catalysts

Question 1

what do enzymes do

Answer 1

• speed up the rate at which a reaction reaches equilibrium
• Bind and stabilize the transition state
• Reduce activation energy by providing an alternative reaction pathway

Question 2

what are enzymes S

Answer 2

Specific - have a limited range of substrates

Question 3

what are enzymes P

Answer 3

Potent - can convert many substrate molecules into product per second

Question 4

what are isozymes

Answer 4

Isoforms of enzymes - catalyze the same reaction but have different properties and structure

Question 5

what are phosphorylation reactions carried out by

Answer 5

protein kinases

Question 6

Cofactors:

Answer 6

metal ions required for enzymatic activity

Question 7

Coenzymes:

Answer 7

organic molecules required for enzymatic activity

Question 8

Prosthetic groups:

Answer 8

tightly bound coenzymes

Question 9

Apoenzyme:

Answer 9

enzyme without cofactor

Question 10

Holoenzyme:

Answer 10

enzyme with cofactor

Question 11

describe substrate binding

Answer 11

• Substrate binds to active site
• Active site contains amino acids for catalytic activity

Question 12

describe the lock and key model

Answer 12

Active site of unbound enzyme is complementary to the shape of the substrate

Question 13

decribe the induced fit model

Answer 13

• Binding of a substrate induces a conformational change in the enzyme
• Results in a complementary fit

Question 14

describe how temperature and PH affect enzymes

Answer 14

• Each enzyme will have an optimum - at either side of the optimum, enzyme activity will decrease
• Active site can be altered by extreme temperature/pH