Question

1. Four metabolites (C, J, M, X and Z) are known to be in a pathway that ultimately produces J.

Which of the following situations would be the best indicator that the flux through a pathway needs to be decreased?

Select one:

a. The concentration of the starting compound continually increases.

b. The last enzyme in the pathway is at 0.01 V_max.

c. The end product of the pathway increases in concentration.

2. Cells live because of the continuous chemical reactions going on inside them. They obtain the enregy they need to survive from the tendency of these reactions to:

Select one:

a. proceed toward equilibrium.

b. involve high energy intermediates.

3. A certain reaction, M→N, that is in a metabolic pathway has a ∆G' of +18 kJ/mol. Based on this information, on could conclude that, in the cell:

Select one:

a. the concentration of M is kept extremely high.

b.  the concentration of N is kept extremely low.

4. Which components of ATP synthase are responsible for the synthesis of ATP?

Select one:

a. The α-subunits.

b. The F_o component.

5. When a mixture of glucose 6-phosphate and fructose 6-phosphate is incubated with the enzyme phosphohexose isomerase at 25°C, the final mixture contains twice as much glucose 6-phosphate as fructose 6-phosphate. Which of the following statements is most nearly correct when applied to the reaction below?

Select one:

a.  ∆G’° = + 1.7 kJ/mol

b. ∆G’° is extremely large and negative

c. ∆G’° = - 1.7 kJ/mol

d. ∆G’° is extremely large and positive

Answer 1

Answer 1:

When there is more than one metabolite in a pathway, then the best indicator of success of the pathway is end product. The end product can act as a signal to regulate the pathway and flux of substrates. This is known as negative feedback mechanism. Thus, the correct choice should be:

(c) The end product of the pathway increases in concentration.

Answer 2:

Cells need energy to perform different tasks of growth as well as cell repair. The energy is obtained via generation of high energy intermediate molecules like ATP, NADH. Thus, the correct choice should be:

(B) involve high energy intermediates.