Enzymes

Question 1

Enzymes vs Catalysts

Answer 1

They’re : faster, work in milder conditions, have greater specificity, and the potential to be regulated.

Question 2

Relationship between G and the activation energy

Answer 2

inverse and exponential

Question 3

Binding of reactants in enzyme active sites provides…

Answer 3

Substrate specificity and catalytic power

Question 4

Substrate binding promotes reactions by…

Answer 4

Reducing entropy, desolvation of the substrate to expose reactive groups, alignment of reactive functional groups of the enzyme with the substrate, distortion of substrates, induced fit of the enzyme in response to substrate binding.

Question 5

Transition-state analogs

Answer 5

are stable compound whose structures resemble unstable transition states

Question 6

VMax=

Answer 6

maximum velocity of the enzyme

Question 7

What is Km

Answer 7

is [S] required to reach 1/2 Vman

Question 8

V0=

Answer 8

Vmax[S]/Km + [S]

Question 9

An inhibitor is…

Answer 9

a compound that binds to an enzyme to interfere with its activity.

Question 10

inhibitors prevent ____ & ____

Answer 10

formation of ES, the breakdown to E and P

Question 11

Reversible inhibitors…

Answer 11

bind to the enzyme by non-covalent interactions

Question 12

Irreversible inhibitors

Answer 12

form stable covalent bonds with the enzyme to inactivate the enzyme

Question 13

suicidal inactivators

Answer 13

are initially unreactive but are converted to a reactive species that inactivates the enzyme. Also called Biochemical trojan horses or Mechanism-based inactivators

Question 14

Digestive enzymes cleave ________ _______ in protein substrates

Answer 14

peptide bonds

Question 15

Where are digestive enzymes made and stored

Answer 15

pancreas (inactive zymogens)

Question 16

How are zymogens activated

Answer 16

selective proteolysis

Question 17

What does trypsin cleave by

Answer 17

Lys and Arg

Question 18

Chymotryposin cleave by

Answer 18

Phe and Tyr

Question 19

What does Elastase cleave by

Answer 19

Gly and Ala

Question 20

How are enzymes regulated?

Answer 20

Long term-control amount of the enzyme that is present, short-term adjusting the activity of a constant quantity of the enzyme

Question 21

covalent modification

Answer 21

phosphorylation, methlation, glyosylation

Question 22

non-covalent modification

Answer 22

allosteric regulation

Question 23

Kinases add ______

Answer 23

phosphoryl goups

Question 24

phosphatases remove ____

Answer 24

phosphoryl groups

Question 25

what is the most common post-translation covalent modification

Answer 25

phosporylation

Question 26

Co-factors

Answer 26

are inorganic ions

Question 27

Co-enzymes

Answer 27

organic molecules

Question 28

Prosthetic Group

Answer 28

A co-factor or Co-enzyme that is tightly associated with the enzyme

Question 29

Active Site

Answer 29

The portion of the enzyme (E) responsible for binding the substrate leading to the formation of an Enzyme-Substrate complex (ES)

Question 30

Activation energy between S & P determines ______

Answer 30

rate

Question 31

Difference between the free energy between S & P determines

Answer 31

equilibrium

Question 32

Two forms of binding effects

Answer 32

substrate binding, transition-state stabilization

Question 33

Two forms of chemical effects

Answer 33

Acid/Base Catalysis, covalent catalysis

Question 34

An increased interaction of the enzyme and substrate occurs in the

Answer 34

transition state

Question 35

The active site must be

Answer 35

similar enough to substrate to ensure specificity but different enough to promote change

Question 36

An antibody against the transition state analog may also

Answer 36

bind the substrate

Question 37

rate of reaction=

Answer 37

products/time

Question 38

Enzymatic catalysis

Answer 38

involves the formation of a enzyme-substrate complex where the substrate is bound in the active site of the enzyme

Question 39

Enzyme turnover number

Answer 39

number of molecules of substrate converted to product per unit time under saturating conditions

Question 40

How is the enzyme turnover number calculated

Answer 40

Vmax/[E]t

Question 41

Lineweaver Burk plots

Answer 41

1) describe relationship between Vo & [S] 2) double reciprocal of 1/Vo & 1/[S] 3) more precise method of kinetics analysis 4) used to determine Vmax & Km

Question 42

Competitive inhibitors resemble the

Answer 42

substrate

Question 43

Competitive inhibitors bind to the

Answer 43

binds to the free enzyme (E)

Question 44

For competitive inhibition how are Vmax and Km changed

Answer 44

same, increased

Question 45

Uncompetitive inhibitors bind to

Answer 45

ES

Question 46

For uncompetitive inhibition how are Vmax and Km changed

Answer 46

decreased, decreased, therefore lines are parallel

Question 47

Enzymatic pathways controlled by

Answer 47

negative feedback

Question 48

Allosteric enzymes are regulated by

Answer 48

metabolic intermediates

Question 49

Allosteric enzymes ___ obey MMK

Answer 49

don't, have sigmoidal curves

Question 50

Are allosteric enzymes fast or slow

Answer 50

slow

Question 51

Allosteric enzymes often catalyse

Answer 51

branch-point reactions

Question 52

Structure of allosteric enzyme

Answer 52

quaternary

Question 53

allosteric modulators bind

Answer 53

non-covalently to allosteric enzymes

Question 54

Phosphorylation activates ____ and inactivates _____

Answer 54

catabolic, anabolic