21. The Generation of Biochemical Energy

Which one of the following catabolism stages produces NADH?

The overall equation in this section,

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shows the cycle between photosynthesis and oxidation. Pathways operating in opposite directions cannot be exergonic in both directions.

a. Which of the two pathways in this cycle is exergonic and which is endergonic?

Each of these reactions is involved in one of the four stages of metabolism shown in Figure 21.4. Identify the stage in which each reaction occurs.

a. Hydrolysis of starch to produce glucose

Each of these reactions is involved in one of the four stages of metabolism shown in Figure 21.4. Identify the stage in which each reaction occurs.

b. Oxidation of NADH coupled with synthesis of ATP

Each of these reactions is involved in one of the four stages of metabolism shown in Figure 21.4. Identify the stage in which each reaction occurs.

c. Conversion of glucose to acetyl-CoA

What is the difference between digestion and metabolism?

Arrange the following events in the order in which they occur in a catabolic process: electron transport, digestion, oxidative phosphorylation, citric acid cycle.

What key metabolic intermediate is formed from the catabolism of all three major classes of foods: carbohydrates, lipids, and proteins?

Why is ∆G a useful quantity for predicting the favorability of biochemical reactions?

The following reactions occur during the catabolism of glucose. Which are exergonic? Which is endergonic? Which proceeds farthest toward products at equilibrium?

b. Phosphoenol pyruvate + H₂O → Pyruvate + Phosphate(P_i)

∆G = ―14.8 kcal/mol (―61.9 kJ/mol)

What is the difference between catabolism and anabolism?

Why is it important that the macronutrients calcium and phosphorus be ingested in approximately equal amounts?

Look up the structures of vitamin C and vitamin E on the Web, and identify the functional groups in these vitamins.

What is the relationship between vitamin A and β-carotene? (Hint: Look up the structures on the Web.)

Vitamins are a diverse group of compounds that must be present in the diet. List four functions of vitamins in the body.

What criteria make a compound a vitamin?

What is the relationship between vitamins and enzymes?

Why is daily ingestion of vitamin C more critical than daily ingestion of vitamin A?

If you use a flame to burn a pile of glucose completely to give carbon dioxide and water, the overall reaction is identical to the metabolic oxidation of glucose. Explain the differences in the fate of the energy released in each case.

Identify each of the following as catabolic or anabolic:

a. synthesis of lipids from glycerol and fatty acids

Identify each of the following as catabolic or anabolic:

d. digestion of proteins in the stomach

Identify each of the following as catabolic or anabolic:

a. digestion of fats to fatty acids and glycerol

Identify each of the following as catabolic or anabolic:

c. synthesis of nucleic acids from nucleotides

What is the purpose of digestion in stage 1?

Identify each pathway as anabolic or catabolic.

a. gluconeogenesis

Identify each pathway as anabolic or catabolic

b. citric acid cycle