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 Heart2h 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

Why is the citric acid cycle called a "cycle"?

The acetyl CoA that enters the cycle is regenerated in the last step of the pathway.

NAD⁺ and FAD are recycled.

All of the carbon from glucose is cycled back into the atmosphere as carbon dioxide.

NADH is cycled down the electron transport chain.

The four-carbon acid that accepts the acetyl CoA in the first step of the cycle is regenerated by the last step of the cycle.

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Verified step by step guidance

Understand the structure of the citric acid cycle: It is a series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

Identify the key components involved: The cycle begins with the combination of acetyl-CoA and a four-carbon molecule called oxaloacetate, forming a six-carbon molecule called citrate.

Recognize the cyclical nature: As the cycle progresses, citrate undergoes a series of transformations, eventually regenerating oxaloacetate, which can then combine with another acetyl-CoA molecule to begin the cycle anew.

Clarify the role of oxaloacetate: The regeneration of oxaloacetate is crucial because it allows the cycle to continue processing acetyl-CoA molecules, making it a true cycle.

Connect the concept to the question: The citric acid cycle is called a 'cycle' because the four-carbon acid (oxaloacetate) that accepts the acetyl CoA in the first step is regenerated by the last step of the cycle, allowing the process to repeat continuously.