We know that the hydrolysis of ATP to ADP is spontaneous and will reach an equil

Question

We know that the hydrolysis of ATP to ADP is spontaneous and will reach an equilibrium in a test tube. Cells actively maintain relatively high levels of ATP far from equilibrium. These levels are refered to as ________.

Natural levels

Activation state

Exergonic state

Steady state

Question 2

The first and second laws of thermodynamics can be combined to provide us with an understanding of Gibbs free energy. How does this help us as cell biologists?

This allows us to determine how fast a reaction will occur.

This allows us to determine the Vmax of an enzyme catalyzed reaction.

This allows us to determine the activation energy of a chemical reaction.

This allows us to predict how favorable or unfavorable a biochemical reaction will be.

Question 3

The converstion of ADP to ATP has a G°' of +7.3 kcal/mol. Which energy molecule would be the most likely one to be used in a coupled reaction to regenerate ATP from ADP?

Glycerol-3-phosphate (G°' = -2.18 kcal/mol)

S-adenosylmethionine (G°' = - 6.11 kcal/mol)

Glucose-6-phosphate (G°' = -3.3 kcal/mol)

Phosphoenolpyruvate (G°' = -14.86 kcal/mol)

Question 4

Which of the following amino acids can form hydrogen bonds?

Phenylalanine

Leucine

Arginine

Valine

Question 5

Given the equation G = H - TS, which set of conditions would result in a reaction that is unambiguously nonspontaneous?

Entropy stays the same and there is no change in enthalpy.

Entropy decreases and the reaction is endothermic.

Entropy decreases and the reaction is exothermic.

Entropy increases and the reaction is endothermic.

Entropy increases and the reaction is exothermic.

Question 6

You are working with an enzyme named altase. You denature altase in the presence of urea. If altase were denatured no further by the addition of mercaptoethanol, what would that suggest to you about the enzyme?

The enzyme has no disulfide bonds

The enzyme has refolds immediately

The enzyme has cofactors that prevent denaturation

The enzyme has strong ionic interaction

Question 7

Which of the following tripeptides would be most likely to be soluble in an organic solvent like benzene (C6H6)?

N-Arg-Lys-Pro-C

N-Pro-Phe-Leu-C

N-Phe-Ala-Gln-C

N-Glu-Asp-Gly-C

N-Leu-Ala-Lys-C

Question 8

What happens in a reaction that contains a noncompetitive inhibitor?

The Km shifts but the Vmax remains the same.

The Km shifts and so does the Vmax.

The Km and Vmax both remain the same.

The Km remains the same but the Vmax is shifted.

Question 9

Virtually all chemical changes that take place in cells require ________, molecules that greatly increase the rate at which a chemical reaction occurs.

DNA

Enzymes

Carbohydrates

Lipids

Question 10

Doubling the concentration of enzyme will ______ the Vmax and _____ the KM.

halve, halve

double, double.

not alter, double.

not change, not alter.

double, not alter.

A)

Natural levels

B)

Activation state

C)

Exergonic state

D)

Steady state

Explanation / Answer

1. Answer : D : Steady state

Steady state is an unchanging condition where ATP levels are maintained.

2. Answer : D : This allows us to predict how favorable or unfavorable a biochemical reaction will be.

The change in Gibbs free energy provides information about the reaction whether it can be spontaneous or non-spontaneous.

4. Answer : C : Arginine

Arginine is the positively charged amino acid which can form hydrogen bonding. Leucine, valine and phenylalanine are hydrophobic amino acids which cannot form hydrogen bonding.

5. Answer : B : Entropy decreases and the reaction is endothermic.

Enothermic needs heat energy for the reaction to proceed while exothermic reaction liberates heat. When entropy is high, reaction will be spontaneous but when entropy is low, reaction will be non-spontaneous.

7. Answer : B : N-Pro-Phe-Leu-C

Benzene is hydrophobic solvent so only hydrophobic amino acids will be soluble. Only option B has all three hydrophobic amino acids.

8. Answer : The Km remains the same but the Vmax is shifted.

An enzyme inhibitor does not bind at the same site as the substrate. Kmax is independent of substrate and enzyme concentration. Vmax is dependent on enzyme concentration.

9. Answer : B : Enzymes

Enzymes enhances the rate of chemical reaction. But DNA, carbohydrates and lipids does not do so.

10. Answer : E : double, not alter.

Kmax is independent of substrate and enzyme concentration. Vmax is dependent on enzyme concentration

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