Enzymes

Question 1

enzymes are ….. proteins

Answer 1

globular

Question 2

ribozymes

Answer 2

catalytic RNA molecules with no protein component

Question 3

apoenzymes

Answer 3

protein component

Question 4

holoenzymes

Answer 4

whole enzyme

Question 5

active site

Answer 5

where the substrate binds

Question 6

enzyme functions

Answer 6

lower activation energy

increase rate of spontaneous reactions

Question 7

addition of an enzymes lower the

Answer 7

activation energy

Question 8

delta G =

Answer 8

Delta H - T delta S

Question 9

enzymes form non-covalent bonds with substrate molecules called the

Answer 9

binding energy

Question 10

binding energy allows the enzymes to

Answer 10

take the reaction through a different path of reaction intermediates

Question 11

how do enzymes reduce the activation energy?

Answer 11

entropy reduction

desolvation

induced fit

Question 12

desolvation

Answer 12

weak bonds between substrate and enzymes replaced with H bonds

Question 13

Vo

Answer 13

initial velocity

Question 14

low substrate concentration gives you an

Answer 14

increase in Vo

Question 15

when [S] becomes so large that Vo changes are vanishingly small you get

Answer 15

maximum reaction velocity

Vmax

Question 16

E + (K1) gives ES which gives

Answer 16

E + P (k2)

Question 17

K1 is a ……….. reaction

Answer 17

reversible

Question 18

K2 occurs ………. than K1

Answer 18

slower

Question 19

Study of initial rates of reaction are termed

Answer 19

steady state kinetics

Question 20

Rate limiting step of enzymatic reactions is the breakdown of

Answer 20

ES complex to give free enzymes and product

Question 21

Half of Vmax is

Answer 21

michealis constant

Question 22

the
substrate concentration at
which the initial reaction
rate is half of the maximum
reaction rate

Answer 22

Km

Question 23

the ratio of rate constant for breakdown of ES to E + S compared to the rate constant for formation of ES from E + S

Answer 23

Km

Question 24

Larger Km indicates a

Answer 24

less stable ES complex

Question 25

Smaller Km indicates a

Answer 25

more stable ES complex

Question 26

Km indicates the ……. for a substrate

Answer 26

affinity

Question 27

Glucose + ATP =

Answer 27

glucose-6-phosphate + ADP

Question 28

Glucokinase and hexokinase catalyse

Answer 28

glucose to glucose 6 phosphate

Question 29

Glucokinase Km and Vmax are both

Answer 29

high

Question 30

Hexokinase Km and Vmax are both

Answer 30

low

Question 31

what increases after a meal

Answer 31

glucokinase

Question 32

when blood glucose is low - it is released from the liver via

Answer 32

gluconeogenesis

Question 33

when blood sugar levels are low

Answer 33

Glucokinase also low

Question 34

isoenzymes

Answer 34

different enzymes that catalyse the same reaction

Question 35

hexokinase is in

Answer 35

muscle

Question 36

Glucokinase is in the

Answer 36

liver

Question 37

electrophoresis is useful to

Answer 37

separate plasma protein

Question 38

elevation of CK2 indicates

Answer 38

myocardial infarction

Question 39

Catalysing reaction with two or more substrates usually involved

Answer 39

transfer of groups from one substrate to the other

Question 40

In an ordered sequential reaction mechanism the enzyme exists in a ………….. structure

Answer 40

ternary

Question 41

Lactate dehydrogenase catalyses

Answer 41

pyruvate to lactate

co enzyme needed: NADH

Question 42

example of random sequential mechanism

Answer 42

phosphocreatine from creatine

Question 43

Allosteric enzymes are made up of

Answer 43

many subunits, which contain many active sites

Question 44

3 things that can change the way an enzyme functions

Answer 44

temperature

pH

inhibitors

Question 45

feedback inhibition

Answer 45

build up at the end product of a pathway can slow the entire pathway

Question 46

allosteric effectors bind to a site that is not the ……….. which changes the enzymes structure

Answer 46

active site

Question 47

allosteric enzymes

concerted model

Answer 47

each subunit exists in two different conformations

one binds substrate and the other doesn’t

Question 48

allosteric enzymes

sequential model

Answer 48

no flipping between conformation sites

substrate binding causes a change in ONE subunit

Question 49

Different ways inhibitors can effect enzymes

Answer 49

Competitive inhibitor

Non-competitive inhibitor

Irreversible inhibitor

Feedback inhibition

Question 50

Proproteins can be cleaved to give active enzyme by

Answer 50

proteases