Phosphocreatine (PCr) is used to replenish ATP levels during bursts of intense exercise.

PCr -> creatine + Pi G=-43kJ/mol

ATP -> ADP + Pi G=-30.5 kJ/mol

What is the overall delta G for the following reaction?

PCr + ADP -> creatine + ATP

-12.5 kJ/mol

Favorable reactions release energy

Favorable reactions increase entropy

Catabolic reactions are generally favorable

The hydrolysis of ATP is a favorable reaction

The following statements refer to thermodynamically favorable reactions?

Enzymes strain bonds in the substrate when forming the transition state

cat

vaires between enzymes

Enzymes cannot alter the delta G for a reaction or make an unfavorable reaction favorable.

Which of the following statements applies to enzyme catalysts?

Question 2 Spring 08

In general, which of the following is an important factor for enzyme catalysis in the cell?

means the estimate of the dissociation constant of the E from S. High K

means weak binding

Notice the mutant has a lower Km so tighter binding

The single amino acid substitution results in a mutant enzyme that binds substrate more tightly

What can you conclude from the K

of the mutant and wild type enzymes?

The initial velocity of the wild type enzyme at a substrate concentration of 10mM is 50

moles/min

Think logically fist, Vmax decreased in the mutant and so did the Km- this is classic uncompetitive inhibition.

At K

is equal to 1/2 V

max

ii.

Anywhere in the rectangle, so from 0-K

then the velocity is proportional to concentration

iii.

The initial velocity of the wild type enzyme at a substrate concentration of 5 mM is 25

moles/min

What can you conclude from the V

max

of the mutant and wild type enzymes?

Activation energy determines the velocity of a reaction- the higher the activation energy, the slower the reaction

Enzyme increase the rate of a reaction by binding the transition state better than they bind substrate

Turnover number refers to the amount of substrate converted to product per mole of enzyme per unit of time

Vmax is dependent on enzyme concentration

The following statements refer to enzyme catalysis. Which of the following are true?

Glucokinase has a lower affinity for glucose than hexokinase because it has a higher Km so less tightly bound

Hexokinase is saturated at the concentration of glucose in blood following a meal

Glucokinase catalyzes the phosphorylation of glucose in liver

10.

Km increase, Vmax constant

In the Lineweaver-Burk plot of 1/V against 1/[S] for an enzyme catalyzed reaction, the presence of a competitive inhibitor will:

11.

Remember that Alcohol dehydrogenase is used to convert ethanol to acid aldehyde normally

Ethanol slows the conversion of methanol to formaldehyde by acting as a competitive inhibitor

Methanol is highly toxic because it is converted to formaldehyde in a reaction catalyzed by the enzyme alcohol dehydrogenase

(ADH):

NAD+ + MeOH -> NADH + H+ + HCHO

Part of the medical treatment for methanol poisoning is to administer large amounts of ethanol-enough to cause intoxication

under normal circumstances.

12.

Which of the following graphs would explain why ethanol is an effective treatment for methanol poisoning.

13.

Correct Answers only

Old Exam 2

Friday, March 01, 2013

11:58

Biochem Page 1