Deck 11: Chemical Logic of Metabolism

Question 1

Substrate-level phosphorylation is a term given to the loss of free energy when ATP is hydrolyzed.

Answer 1

False

Question 2

A futile cycle is:

A) the citric acid cycle.
B) two reactions or pathways that share substrates and products, and result in no net gain of ATP.
C) two opposing cellular reactions that are independently controlled.
D) an endergonic reaction that uses up ATP.
E) the reoxidation of NAD+ from NADH.

Answer 2

B

Question 3

Calculate the amount of ATP in kg that is turned over by a resting human every 24 hours. Assume that a typical human contains ~50g of ATP (Mr 505) and consumes ~8000 kJ of energy in food each day. The energy stored in the terminal anhydride bond of ATP under standard conditions is 30.6 kJmol-1. Assume also that the dietary energy is channeled through ATP with an energy transfer efficiency of ~50%.

Answer 3

66 kg

Question 4

Which of the following can be used as a metabolic control mechanism?

A) Enzyme compartmentation
B) Action of hormones
C) Covalent modification of an enzyme
D) Regulation of enzyme degradation
E) All of the above

Question 5

Which of the following produces the largest number of reducing equivalents when oxidized?

A) Glucose
B) NADPH
C) NADH
D) Palmitic acid
E) A hydrogen atom

Question 6

Under physiological conditions the complete oxidation of glucose to carbon dioxide and water in the presence of oxygen has a △G of -2900 kJ/mol glucose. This process can be coupled to the synthesis of ~32 mol ATP. The △G of the coupled reactions to make ATP is -1300 kJ/mol glucose. Calculate the △G for the synthesis of ATP from ADP.

Question 7

Enzyme-catalyzed sequential reactions that make up a metabolic pathway are normally separated in the cell for equal access to reactants.

Question 8

An enzyme that catalyzes a committed step in a metabolic pathway has a high ________.

Question 9

Catabolic processes involve degradation of complex molecules into simpler molecules with the net release of chemical energy.

Question 10

The main energy-coupling compound in biochemical reactions that allows thermodynamically unfavorable processes to become favorable is ________.

Question 11

ATP has a high phosphoryl group transfer potential because:

A) it is chemically unstable.
B) it has a high rate of spontaneous hydrolysis at physiological pH and temperature.
C) it exhibits resonance stabilization prior to hydrolysis.
D) it has three phosphate groups.
E) cleavage of either of its two phosphoanhydride bonds proceeds with a large negative △Go' of hydrolysis.

Question 12

The standard free energy change in physiological conditions (△G∘') for the reaction catalyzed by malate dehydrogenase in the citric acid cycle
malate + NAD+ oxaloacetate + NADH + H+
is ~+29 kJmol-1
Calculate the actual △G' at 37∘C if Keq' is 1.02 × 10-5

Question 13

Reactions in metabolic pathways that are subject to regulation are those that are displaced far from ________.

Question 14

The anabolic and catabolic processes of cellular metabolism can be coupled by ATP.

Question 15

Name the type of reaction that involves reversible electron transfer from a donor to an acceptor.