22. Carbohydrate Metabolism

Classify each one of the following reactions as phosphorylation (P), isomerization (I), or neither (N).

a) ____ Conversion of glucose into glucose-6-phosphate.

b) ____ Conversion of glucose-6-phosphate into fructose-6-phosphate.

c) ____ Conversion of DHAP into G3P.

d) ____ Cleavage of fructose-1,6-bisphosphate into DHAP and G3P.

Which one of the following compound pairs is produced by cleavage of fructose-1,6-bisphosphate?

Which enzyme catalyzes the oxidation of glyceraldehyde-3-phosphate in reaction 6 of glycolysis?

What is the energy output of reaction 7 of glycolysis (1,3-bisphosphoglycerate to 3-phosphoglycerate)?

What product is formed when phosphoglycerate mutase moves the phosphate group in 3-phosphoglycerate?

Identify each step in glycolysis that is an isomerization.

Glucose 6-phosphate is in a pivotal position in metabolism. Depending on conditions, glucose 6-phosphate follows one of several pathways. Under what conditions do the following occur?

b. Hydrolysis to free glucose

Glucose 6-phosphate is in a pivotal position in metabolism. Depending on conditions, glucose 6-phosphate follows one of several pathways. Under what conditions do the following occur?

d. Glycogenesis

In Figure 22.3, compare the starting compound (glucose) and the final product (pyruvate).

a. Which is oxidized to a greater extent?

The pathway that converts glucose to acetyl-CoA is often referred to as an “aerobic oxidation pathway.”

(b) Thinking back to Chapter 20, where does molecular oxygen enter the picture?

Which cells, liver, muscle, or brain, use the following pathways?

a. Glycolysis

Which glycolysis reactions are catalyzed by the following enzymes?

a. Pyruvate kinase

Which glycolysis reactions are catalyzed by the following enzymes?

d. Phosphoglycerate mutase

Review the 10 steps in glycolysis (Figure 22.3) and then answer the following questions:

c. Which step is a dehydration?

What two types of reactions convert glycerol to dihydroxyacetone phosphate? <IMAGE>

 Identify each of the following as a six-carbon or a three-carbon compound and arrange them in the order in which they occur in glycolysis: (18.4)

a. 3-phosphoglycerate

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State if each of the following processes release or require ATP: (18.4, 18.5, 18.6)

f. first six reactions of glycolysis