How many final high-energy molecules are produced in phase C of the citric acid cycle?

• A. 2
• B. 4
• C. 1
• D. 3

Answer: (D)

Verified step by step guidance

1. Understand that the citric acid cycle, also known as the Krebs cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate derived from carbohydrates, fats, and proteins into carbon dioxide.
2. Recognize that the citric acid cycle produces high-energy molecules such as ATP, NADH, and FADH2, which are used in the electron transport chain to produce ATP.
3. Identify that phase C of the citric acid cycle refers to the steps where high-energy molecules are produced. Specifically, these steps include the conversion of succinyl-CoA to succinate, which produces GTP (or ATP), and the conversion of succinate to fumarate and malate to oxaloacetate, which produce FADH2 and NADH, respectively.
4. Count the high-energy molecules produced in these steps: 1 GTP (or ATP), 1 FADH2, and 1 NADH.
5. Conclude that the total number of high-energy molecules produced in phase C of the citric acid cycle is 3, which includes 1 GTP (or ATP), 1 FADH2, and 1 NADH.