Gluconeogenesis, Glycogen, and the Pentose Phosphate Pathway

SCI260 – Introduction to Biochemistry

Lesson 5

In this week’s class, we discussed gluconeogenesis, glycogen metabolism, and the

pentose phosphate pathway and their roles in glucose metabolism. Based on the topics

discussed in Lecture #5, please answer each of the following questions.

1. Which enzyme-catalyzed reactions are shared between the gluconeogenesis and

glycolysis pathways? (Note: just provide the name of the enzyme that catalyzes

each of the shared reactions).

2. Why are some enzymes needed only in the gluconeogenesis pathway and not in

the glycolysis pathway?

3. Which one of the following reactions only occurs during gluconeogenesis (i.e.,

not during glycolysis)?

a. 1,3-bisphosphglycerate into 3-phosphoglycerate

b. Glucose 6-phosphate into fructose 6-phosphate

c. Oxaloacetate into Phosphoenolpyruvate

d. Phosphoenolpyruvate into Pyruvate

4. An increase in glucagon levels can __________.

a. Promote the degradation of glycogen (i.e., glycogenolysis)

b. Occurs during the fasting state (starvation)

c. Promotes the synthesis of glycogen

d. A and B

5. A high school girl who is self-conscious about her appearance has been fasting for

several days to fit into a dress she intentionally bought a size too small for a

school dance. Which of her organs/tissues is producing the glucose that is being

synthesized through gluconeogenesis?

a. Red blood cells

b. Muscles

c. Liver

d. Brain

6. Why do only some tissues (e.g., liver) contain the enzyme glucose-6-

phosphatase?

7. What are the main products of the pentose phosphate pathway, and how does

the cell use them?

8. How many molecules of ATP are produced during the metabolism of one (1)

molecule of glucose through the pentose phosphate pathway?

9. Which two (2) molecules are produced during the pentose phosphate pathway

that are also produced during glycolysis?

10. Describe two (2) specific things that make NADH and NADPH different from each

other (Note: consider the structural and biological properties of the two

molecules).

You may use your textbook and/or the internet to assist you. You will earn 10 points for

correctly answering each question (maximum points earned = 100 points).