Enzymic Kinetics

Question 1

What are Michaelis-Menten kinetics and Lineweaver-Burk plots used for?

Answer 1

To determine the Km and Vmax of an enzyme

To distinguish different types of enzyme inhibition

Question 2

_____________reaction is a type of chemical reaction in which the rate of reaction is directly proportional to the concentration of one reactant

Answer 2

First order

Question 3

What is happening in a zero order reaction?

Answer 3

the rate of the reaction is independent of the concentration of the reactant(s)

Question 4

How does hexokinase contrast glucokinase?

Answer 4

It has a lower Vmax, lower Km, and turns off by high concentrations of glucose-6-P

Question 5

What same reaction do both hexokinase and glucokinase catalyze?

Answer 5

Glucose —- glucose - 6 - phosphate

The phosphorylation of glucose.

Question 6

Where is glucokinase found?

Answer 6

In the liver. Nutrients are absorbed from the intestine and go to the liver first, which allows glucokinase to convert excess glucose from a meal to glycogen.

Question 7

High ________ = high capacity to convert substrate to product.

Answer 7

Vmax

Question 8

What is significant about adding a P to glucose?

Answer 8

When glucose is phosphorylated, it becomes glucose-6-phosphate, which is an intermediate in both glycolysis (the breakdown of glucose for energy) and glycogenesis (the synthesis of glycogen for energy storage). The addition of a phosphate group makes it less likely for glucose-6-phosphate to leave the cell, effectively trapping the glucose molecule inside the cell for further metabolic processing.

Question 9

______ also helps determine enzyme efficiency.

Answer 9

Km

Question 10

Which is a more efficient enzyme, one with a larger or smaller value for Kcat/Km?

Answer 10

smaller

Question 11

What does Kcat measure?

Answer 11

speed of P formation once ES has been made

Question 12

What does Km measure?

Answer 12

binding affinity of E and S to make ES

Question 13

Enzymes with very important physiological function tend to be very ____________.

Answer 13

efficient

Question 14

What is the general purpose of carbonic anhydrase?

Answer 14

catalyze the interconversion between carbon dioxide (CO2) and bicarbonate ion (HCO3-)

aids in acid/base balance

Question 15

What is the general purpose of triose phosphate isomerase?

Answer 15

catalyze the interconversion between two three-carbon sugar molecules: dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P). (GLYCOLYSIS)

Question 16

What is the general purpose of fumarase?

Answer 16

fumarase catalyzes the reversible hydration reactions (CAC)

Question 17

What is the general purpose of acetylcholinesterase?

Answer 17

regulate the neurotransmitter acetylcholine (ACh) in chemical synapses

Question 18

_________ kinetics also aids in the study of enzyme inhibition.

Answer 18

M & M

Question 19

What are 3 types of reversible inhibition?

Answer 19

1.) competitive
2.) uncompetitive
3.) noncompetitive

Question 20

The inhibition of an enzyme can be ________ or ________

Answer 20

Reversible or irreversible

Question 21

In (reversible/irreversible) inhibition, the inhibitor can leave, restoring the enzyme to its uninhibited level of activity

Answer 21

reversible

Question 22

In (reversible/irreversible) inhibition, the inhibitor remains permanently bound to the enzyme.

Answer 22

irreversible

Question 23

In (competitive/ noncompetitive) inhibition, the inhibitor competes with substrate for binding at the active site.

Answer 23

competitive

Question 24

In (competitive/uncompetitive) inhibition, the inhibitor does not compete with the substrate for the active site and cannot bind to enzyme alone.

Answer 24

uncompetitive

Question 25

a (competitive/uncompetitive) inhibitor exerts control by binding to the enzyme-substrate complex.

Answer 25

uncompetitive

Question 26

In _____________ control, the binding of a regulator at one site on a protein affects the protein’s ability to bind another molecule at a different site.

Answer 26

allosteric

Question 27

In allosteric control, binding of a regulator changes the shape of an enzyme, which type of bonding is usually implemented?

Answer 27

noncovalent intermolecular forces

Question 28

allosteric control (always/never) involves shape change of the enzyme.

Answer 28

always

Question 29

Which is more common, competitive or uncompetitive inhibition?

Answer 29

competitive

Question 30

G-6-P inhibition of hexokinase is an example of what type of inhibition?

Answer 30

reversible, noncompetitive

Question 31

What kind of bond is formed in irreversible inhibition?

Answer 31

covalent

Question 32

(zero/first/second) order reactions are often observed when the reaction is limited by factors other than reactant concentration, such as surface area or enzyme activity.

Answer 32

zero

Question 33

V = Vmax [S] / (Km + [S])

What is this equation and what does it tell us?

Answer 33

Michaelis-Menten kinetics

Determines how much affinity an enzyme has for a substrate

Question 34

(M&M)

V= ______

Answer 34

Speed your at

Question 35

(M&M)

Vmax= ________

Answer 35

max speed conversion

Question 36

(M&M)

S = _______

Answer 36

substrate concentration

Question 37

(M&M)

Km = __________

Answer 37

substrate at 1/2 Vmax

how much substrate it takes for enzyme to function at 50% of its capability

Question 38

In competitive inhibition, the Km is (increased/reduced/unaffected) and the vmax is (increased/reduced/unaffected). What would the LB plot look like?

Answer 38

increased/unaffected/crossed (like 2 lightsabers in a fight=competition)

Question 39

In uncompetitive inhibition, the Km is (increased/decreased/unaffected) and the vmax is (increased/decreased/unaffected). What would the LB plot look like

Answer 39

reduced/reduced/parallel-shifted up (looks like the 2 parallel lines, Un- = Up!)

Question 40

In non competitive (mixed) inhibition, the Km is (increased/decreased/unaffected) and the vmax is (increased/decreased/unaffected). What would the LB plot look like

Answer 40

unaffected/reduced/ ((non-Km-petitive) Km does not move so the x-intercept stays the same)