MCAT Biology Ch2: Enzymes Kap

Question 1

endothermic

Answer 1

requires energy input

Question 2

exothermic

Answer 2

energy is given off

Question 3

enzymes

Answer 3

-lower activation energy, not G or H; increase rate of rxn , not changed or consumed in course of rxn; specific for particular rxn or class of rxns

Question 4

substrate

Answer 4

upon which an enzyme acts

Question 5

enzyme-substrate complex

Answer 5

complex between enzyme and substrate

Question 6

active site

Answer 6

location w/in enzymes where substrate is held during chem rxn

Question 7

two theories of how enzymes and sub interact

Answer 7

1. lock and key 2. induced fit

Question 8

the lock and key theory

Answer 8

enzyme’s active site (lock) in perfect conformation w/ substrate (key); no alter of 3rd or 4th structure upon binding of substrate

Question 9

the induced fit theory

Answer 9

squeeze –> change conformation (endo) –> adjust –> relax –> exo and release substrate
-wrong substrate doesn’t cause change in conformation–> no rxn

Question 10

cofactors

Answer 10

enzymes require these nonprotein molecules in order to be effective

Question 11

apoenzymes

Answer 11

enzymes w/o cofactors

Question 12

holoenzymes

Answer 12

enzymes w/ cofactors

Question 13

prosthetic groups

Answer 13

tightly bound factors on enzyme

Question 14

coenzymes

Answer 14

small organic group cofactors, vast majority are vitamins

Question 15

saturation

Answer 15

inviting more substrates will not change the rate of rxn

Question 16

maximum velocity, Vmax

Answer 16

at saturation rate, enzyme is working at this

Question 17

enzyme temp 10 C inc

Answer 17

enzymes catalyzed rxns double in rate as a result

Question 18

pH of pepsin in stomach

Answer 18

2

Question 19

pH of pancreatic enzymes of smalll intestin

Answer 19

8.5

Question 20

ability to control when enzymes work

Answer 20

allosteric effects and inhibition

Question 21

allosteric site

Answer 21

have multiple binding site on enzymes; other site that can regulate availability of active site; binding many consist of either allosteric activators or inhibitors (differ in effect)

Question 22

allosteric enzyme

Answer 22

alternate between inactive and active form

Question 23

allosteric activator

Answer 23

shift causes active site more available to substrate

Question 24

allosteric inhibitor

Answer 24

shift causes active site less available to substrate; binding of this or repressor may alter the affinity of enzymes for its substrate

Question 25

types of inhibition

Answer 25

feedback, reversible, irreversible

Question 26

feedback inhibition

Answer 26

products of enzyme bind to earlier enzyme, making unavailable for other substrates to use

Question 27

three types of reversible inhibition

Answer 27

competitive, noncompetitive, and uncompetitive

Question 28

competitive inhibition (reversible)

Answer 28

occupy active site, substrate can’t access if inhibitor there; can be overcome by adding more substrate (substrate to inhibitor ratio higher), since likely to bind to it.

inc. in Km

Question 29

noncompetitive inhibition (reversible)

Answer 29

inhibitor binds to allosteric site instead of active site –> change in enzyme conformation –> can’t be overcome even by adding more substrate

Km remains unchanged but Vmax dec.

Question 30

irreverisible inhibition (reversible)

Answer 30

active site made permanently available or enzymes permanently altered; enzyme no longer make products; have to synthesis new one through transcription and translation

Question 31

zymogens (ex: trypsinogen for trypsin)

Answer 31

to avoid dangers of dangerous released enzymes, secreted as this inactive form; contain (active) domani and reg. domain. Reg. domain must be either removed or altered to expose active site. (apoptotic enzymes similar fashion)

Question 32

enzymes

Answer 32

often break down or create molecules that would be damaging to cell if were released into cytoplasm

Question 33

enzymes

Answer 33

are pH and temp sensitive, w/ optimal activity at specific pH ranges and temp

Question 34

vitamin cofactors

Answer 34

deficiencies in these can result in devasting diseases

Question 35

two majors classes of vitamins

Answer 35

fat and water soluble

Question 36

Km

Answer 36

can asses enzyme’s affinity for substrate by noting this

Question 37

low Km

Answer 37

enzyme high affinity for substrate; low [S] required for 50% enzyme saturation

Question 38

high Km

Answer 38

low affinity of enzyme for substrate

Question 39

Km

Answer 39

concentration of substrate required for the enzyme to reach half it’s velocity.

Question 40

digestive enzymes

Answer 40

chew up fat, proteins, and carb (same compound our body makes) => coordinated manner using feedback mech and other substances so doesn’t chew up body!

Question 41

cooperative binding of hemoglolbin

Answer 41

sig. binding curve

Question 42

feedback inhibition

Answer 42

how many of hormones in body are regulated

often product binds to allosteric site to cause chage

Question 43

enzymes

Answer 43

change rate (kinetics) at which eq. is reached

Question 44

cofactors

Answer 44

tend to be either metal cations or small organic molecules

Question 45

temp and pH in enzyme

Answer 45

can result in denaturing of enzyme and loss of activity owing to 2, 3, and 4th structure