Enzymes Kinetics, Inhibition, and Control Ch.12

Question 1

What will reduce the amount of cholesterol that we make?

Answer 1

Atorvastatin (Lipitor)

Question 2

What does kinetics refer to?

Answer 2

Rates

Question 3

What doe enzyme kinetic rates refer to?

Answer 3

Reaction rates

Question 4

What do reaction rates refer to?

Answer 4

the formation of product as a function of time.

Question 5

What is the job of an enzyme?

Answer 5

To enhance the rate of the reaction.

Question 6

If the Michaelis-Menten Equation for Enzyme Kineticas is determined early in its course what is considered?

Answer 6

products is considered to be low and K-2 ( rate constants) drops out of the equation. Back reaction is negligible.

Question 7

What is KM?

Answer 7

A constant describing the affinity of an enzyme for its substrate.

Question 8

In KM, the lower the constant what can be determined?

Answer 8

The higher the affinity for the substrate.

Question 9

What gives half maximal VMAX?

Answer 9

KM is the S.

Question 10

What is KM unique for?

Answer 10

each substrate of a given enzyme.

Question 11

What is Kcat?

Answer 11

take the Vmax/ total enzyme concentration and it gives you the value of the turnover number.

Question 12

What is the turnover number?

Answer 12

how fast the enzyme will come to a state that it can do it again.

Question 13

What doe the most efficient reactions reflect a need for?

Answer 13

speed

Question 14

KM should be what in vivo concentrations?

Answer 14

10^-2

Question 15

Ethyl Ester is not something that happens in the cell normally what?

Answer 15

The 10^-1 is too big of a concentration to exist inside the cell naturally.

Question 16

Why do enzyme inhibitors react reversably or irreversably with an enzyme?

Answer 16

to alter its Km and or Vmax values.

Question 17

What alters the KM or Vmas values?

Answer 17

Enzymes inhibitors that interact reversibly or irreversibly with an enzyme

Question 18

What does a competitive inhibitor bind to?

Answer 18

the enzymes active site

Question 19

What does a competitive inhibitor increase?

Answer 19

the apparent Km for the reaction

Question 20

What does an uncompetitive enzyme inhibitor affect?

Answer 20

catalytic activity such that both the apparent KM and the apparent Vmax decreases.

Question 21

A mixed enzyme inhibitor alters both what?

Answer 21

catalytic activity and substrate binding.

Question 22

What will occur with a mixed enzyme inhibitor?

Answer 22

Apparent Vmax decreases and the apparent KM may increase or decrease.

Question 23

What occurs in competitive inhibition?

Answer 23

The inhibitor binds to the enzyme’s substrate binding site.

Question 24

What does the inhibitor resemble in competitive inhibition?

Answer 24

the inhibitor structurally resembles the substrate but not always obvious to the eye.

Question 25

What is pyrazole?

Answer 25

a competitive inhibitor of alcohol dehydrogenase.

Question 26

What is tamiflu (oseltamivir)?

Answer 26

it is a competitive inhibitor of influenze neurominidase.

Question 27

What does Oseltamivir do?

Answer 27

Hydrolizes sialic acid.

Question 28

What is Adenosine Deaminase?

Answer 28

Transition State Analog Inhibitor.

Question 29

What two enzymes does HIV make?

Answer 29

reverse transcriptase and a protease.

Question 30

What is the reverse transcriptase that HIV makes do?

Answer 30

Replicate genome

Question 31

What does the protease that HIV makes do?

Answer 31

cleaves its polyprotein precursor into functional proteins.

Question 32

What is the most important point in regards to competitive enzyme inhibition?

Answer 32

inhibition can be overcome at high substrate concentration.

Question 33

What occurs in the uncompetitve enzyme inhibition?

Answer 33

inhibitor binds to the ES complex.

Question 34

What do allosteric effectors bind to?

Answer 34

multisubunit enzymes

Question 35

What are multisubunit enzymes?

Answer 35

aspartate transcarbamoylase

Question 36

What does the binding of allosteric effectors to multisubunit induce?

Answer 36

cooperative conformational changes that alter the enzyme's catalytic activity.

Question 37

What can phosphorylation and dephosphorylation of an enzyme such as glycogen phosphorylase control?

Answer 37

its activity by shifting the equilibrium between more active and less active conformations.

Question 38

What is the first committed step in the biosynthesis of pyrimidines?

Answer 38

aspartate transcarbamoylase reaction.

Question 39

What is significant of the allosteric effectors: ATCase reaction graphs?

Answer 39

the curves are sigmoidal because the substrates bind cooperatively.

Question 40

Why does the pyrimidine biosynthesis ATCase feedback inhibition is activated by ATP?

Answer 40

To coordinate purine and pyrimidine biosynthesis (need equal amounts for RNA and DNA)

Question 41

What is the important point of ATCase: T-State vs R-state?

Answer 41

the regulatory subunits impose coopertivity on the catalytic subunits.

Question 42

What do regulatory subunits repress?

Answer 42

the catalytic subunits' activity.

Question 43

Allosteric effects of a different molecule binds to an enzyme to what?

Answer 43

modify its activity

Question 44

CTP binds to what?

Answer 44

regulatory subunits to cause substrate binding site to close.

Question 45

Why does CTP cause substrate binding site to close?

Answer 45

inhibit enzyme activity

Question 46

What does CTP undergo this feedback inhibition?

Answer 46

it is the endproduct of the pathway

Question 47

What does ATP bind to in allosteric effect of enzyme activity?

Answer 47

To regulatory subunits to cause the substrate binding site to open and enhances activity.

Question 48

ATP is the product of what?

Answer 48

a parallel pathway.

Question 49

What does the parallel pathways mean when the ATP is the product of parallel pathways?

Answer 49

purine and pyrimidine nucleotides need to be present in nearly in equal amounts.

Question 50

Why do purines and pyrimidine nucleotides needs to be present in nearly equal amounts?

Answer 50

this serves to balance the levels of nucleotides in the cell.

Question 51

How is phosphorylation controlled?

Answer 51

by covalent modification.

Question 52

What is G1P a product of?

Answer 52

Glycogen phosphorylase

Question 53

Rabbit muscle glycogen phosphorylase causes a masking loop to do what?

Answer 53

move out of the way of the active site.

Question 54

What is atorvastatin (lipitor)?

Answer 54

inhibitor of HMG CoA reductase-rate limiting step in cholesterol synthesis.