Exam 3: Carbohydrate Metabolism

Question 1

Name the reactants and number of which are involved in glycolysis.

Answer 1

1 Glucose
2 ATP
2 NAD+
2 Pi
4 ADP

Question 2

Name the end products and number of which are involved in glycolysis.

Answer 2

2 Pyruvate
4 ATP
2 NADH

Question 3

In glycolysis, glucose is ultimately converted into _________.

Answer 3

…pyruvate.

Question 4

Where does glycolysis occur?

Answer 4

In the cytosol of the cell.

Question 5

Describe where the preparatory phase starts and ends.

Answer 5

It begins with the phosphorylation of glucose and ends with the production of glyceraldehyde 3-phosphate.

Question 6

Describe where the payoff phase begins and ends.

Answer 6

It begins with the oxidative conversion glyceraldehyde 3-phosphate and ends with the production of pyruvate and the second production of ATP.

Question 7

Properly trace the reactions through glycolysis.

Answer 7

Glucose > Glucose-6P > Fructose-6P > Fructose-1,6P > Glyceraldehyde-3P + Dihydroxyacetone phosphate > (2) Glyceraldehyde-3P > (2) 1,3-BPG > (2) 3-Phosphoglycerate > (2) 2-Phosphoglycerate > (2) Phosphoenolphyruvate > (2) Pyruvate

Question 8

Properly trace the enzymes that drive the reactions through glycolysis.

Answer 8

1. Hexokinase
2. Phosphohexose isomerase
3. Phosphofructokinase-1
4. Aldose
5. Triose phosphate isomerase
6. Glyceraldehyde 3-phosphate dehydrogenase
7. Phosphoglycerate kinase
8. Phosphoglycerate mutase
9. Enolase
10. Pyruvate kinase

Question 9

What is the first committed step of glycolysis and why?

Answer 9

Step 3, the second priming reaction of fructose 6-phosphate to fructose 1,6-bisphosphate. This is the first committed reaction because all products previously may have been utilized in other reactions, but once fructose 1,6-bisphosphate is produced, it must continue through glycolysis.

Question 10

List the reactions that use ATP in glycolysis.

Answer 10

Steps 1., 3., 7., and 10.

Question 11

What are fermentation reactions?

Answer 11

Reactions that occur to generate ATP without the consumption of oxygen.

Question 12

What is the Cori Cycle?

Answer 12

The process by which lactate from lactic acid fermentation is cycled though the blood to the liver and, with the aid of ATP, synthesizes glucose in gluconeogenesis during recovery.

Question 13

What enzyme are humans incapable of producing that would allow us to ferment alcohol?

Answer 13

Pyruvate decarboxylase.

Question 14

Where do glycolysis and gluconeogenesis respectively occur?

Answer 14

Glycolysis occurs mainly in the brain and muscles, whereas gluconeogenesis occurs mainly in the liver.

Question 15

Explain bypass reactions in gluconeogenesis.

Answer 15

There are steps in glycolysis that are irreversible which must be bypassed in gluconeogenesis.

Question 16

Name the products and reactants of the three bypass reactions.

Answer 16

1. Pyruvate > Oxaloacetate > Phosphoenolpyruvate
2. Fructose 1, 6 - Bisphosphate > Fructose 6 - Phosphate + Pi
3. Glucose 6 - Phosphate > Glucose + Pi

Question 17

Where does gluconeogenesis occur?

Answer 17

Within the cytosol and mitochondria.

Question 18

Why must oxaloacetate be converted into malate or PEP before being exported?

Answer 18

There is no transporter for oxaloacetate in mitochondria.

Question 19

What is the role of glycogenin?

Answer 19

To generate the protein core of glycogen and catalyzes the addition of the first 8 residues.

Question 20

What is the role of glycogen-branching enzyme?

Answer 20

To transfer 6 to 7 glucose monomers from the growing chain to the C6 hydroxyl group of a glucose on the same chain or another chain to make an a1-6 connection.

Question 21

What is the role of glycogen synthase?

Answer 21

To add more glucose monomers to both branches.

Question 22

What is the function of the pentose phosphate pathway?

Answer 22

Generates Nucleotides, Coenzymes, DNA, and RNA while along the way the reduction of NADP+ is needed for the generation of fatty acids, sterols, and steroids that can aide in the repair in oxidative damage.

Question 23

What does the pentose phosphate pathway use to generate the main products of NADPH and ribose 5-phosphate?

Answer 23

Glucose 6-phosphate.