enzymes

Question 1

enzymes are ___

Answer 1

specialized proteins that act as catalysts

Question 2

enzymes speed up chemical reactions by

Answer 2

lowering the activation energy

Question 3

enzymes are specific to a particular

Answer 3

substrate (reactant)

Question 4

all reactions require an

Answer 4

activation energy (must be overcome for reaction to occur)

Question 5

catalysts reduce the

Answer 5

activation energy, but do not affect the free energy change

Question 6

catalysts can only

Answer 6

speed up a reaction that would occur normally

Question 7

substrate:

Answer 7

the reactant that an enzyme works on (binds to active site on enzyme)

Question 8

enzyme names usually end in

Answer 8

“ase”

Question 9

enzyme-substrate complex: substrates bind to a depression on the surface of enzymes known as the

Answer 9

active site, to form an enzyme-substrate complex

Question 10

active site:

Answer 10

where substrate binds to enzyme (lock and key model)

Question 11

induced fit:

Answer 11

protein undergoes conformational shape to accommodate substrate (caused by functional groups interactions)

Question 12

enzyme-substrate complex

Answer 12

substrate attached to enzyme

Question 13

factors affecting enzyme activity rate

Answer 13

temperature
pH
concentration

Question 14

factors affecting enzymes: temperature

Answer 14

• reaction rates increase as temp increases
• peaks at 37-40 C then drops rapidly
• e.g. egg frying

Question 15

factors affecting enzymes: pH

Answer 15

• enzymes function within optimal pH
• stomach pH, small intestine pH

Question 16

factors affecting enzymes: concentration of substrate molec.s

Answer 16

• reaction rate increases as concentration increases (up to a point)
• limiting factor in reaction may be amount of substrate/amount of available enzyme

Question 17

cofactors:

Answer 17

inorganic substances that aid in enzyme activity

Question 18

coenzymes:

Answer 18

organic enzymes that aid in enzyme activity

Question 19

cofactors vs coenzymes

Answer 19

• cofactors are inorganic, coenzymes are organic
• both bind to the active site of enzymes

Question 20

competitive inhibitors:

Answer 20

compete with substrate for enzymes active site
- block active site
- reversible, overcome by increasing substrate concentration
- e.g. drugs: CO, cyanide

Question 21

competitive inhibitors are overcome by

Answer 21

increasing substrate

Question 22

non competitive inhibitors bind to enzyme at

Answer 22

allosteric site (not active site)
- cause conformation change in enzyme
- prevent normal substrate from binding
- loss of enzyme activity

Question 23

cells control enzyme activity to coordinate

Answer 23

cellular activities

Question 24

allosteric sites:

Answer 24

receptor sites that bind substances that inhibit/stimulate enzyme activity

Question 25

activators may bind

Answer 25

allosterically controlled enzymes to stabilize its shape and keep all active sites available

Question 26

allosteric inhibitors:

Answer 26

bind to allosteric site + stabilize inactive form of enzyme

Question 27

feedback inhibition:

Answer 27

a method used by cells to control metabolic pathways involving a series of reactions

Question 28

feedback inhibition is when a product formed later in a sequence of reactions

Answer 28

allosterically inhibits an enzyme that catalyzes the reaction earlier on