Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

3. Energy & Cell Processes

Krebs Cycle

Anatomy & Physiology

3. Energy & Cell Processes

Krebs Cycle

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Multiple Choice

Which of the following is needed as a reactant for the first step of the citric acid cycle?

Acetyl-CoA

ATP

FADH2

NADH

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Verified step by step guidance

Begin by understanding the citric acid cycle, also known as the Krebs cycle, which 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.

Identify the first step of the citric acid cycle: the combination of Acetyl-CoA with oxaloacetate to form citrate. This is a key step where Acetyl-CoA is a necessary reactant.

Recognize that Acetyl-CoA is produced from pyruvate in the mitochondria through a process called pyruvate decarboxylation, which is catalyzed by the pyruvate dehydrogenase complex.

Understand that ATP, FADH2, and NADH are not direct reactants in the first step of the citric acid cycle. Instead, they are involved in other parts of cellular respiration, such as oxidative phosphorylation and electron transport chain.

Conclude that Acetyl-CoA is the correct reactant needed for the first step of the citric acid cycle, as it combines with oxaloacetate to initiate the cycle.