Table of contents

1. Introduction to Biochemistry4h 34m
2. Water3h 23m
3. Amino Acids8h 10m
4. Protein Structure10h 4m
5. Protein Techniques14h 5m
6. Enzymes and Enzyme Kinetics13h 38m
7. Enzyme Inhibition and Regulation 8h 42m
8. Protein Function 9h 41m
9. Carbohydrates7h 49m
10. Lipids5h 49m
11. Biological Membranes and Transport 6h 37m
12. Biosignaling9h 45m
Review 1: Nucleic Acids, Lipids, & Membranes2h 47m
Review 2: Biosignaling, Glycolysis, Gluconeogenesis, & PP-Pathway3h 12m
Review 3: Pyruvate & Fatty Acid Oxidation, Citric Acid Cycle, & Glycogen Metabolism2h 26m
Review 4: Amino Acid Oxidation, Oxidative Phosphorylation, & Photophosphorylation1h 48m

Review 3: Pyruvate & Fatty Acid Oxidation, Citric Acid Cycle, & Glycogen Metabolism

Pyruvate Oxidation

Biochemistry

Review 3: Pyruvate & Fatty Acid Oxidation, Citric Acid Cycle, & Glycogen Metabolism

Pyruvate Oxidation

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Multiple Choice

Which molecule represents the intermediate step between glycolysis and the citric acid cycle?

Citrate

Lactate

Oxaloacetate

Acetyl-CoA

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Verified step by step guidance

Understand the context: Glycolysis is the metabolic pathway that breaks down glucose into pyruvate, producing ATP and NADH. The citric acid cycle (also known as the Krebs cycle) is the next stage of cellular respiration, where acetyl groups are oxidized to produce more ATP, NADH, and FADH2.

Identify the intermediate step: After glycolysis, pyruvate is converted into acetyl-CoA in a process called pyruvate decarboxylation. This reaction is catalyzed by the pyruvate dehydrogenase complex.

Describe the reaction: Pyruvate is decarboxylated (loses a carbon atom as CO₂), and the remaining two-carbon molecule is attached to coenzyme A, forming acetyl-CoA. This step also produces NADH from NAD⁺.

Explain the role of acetyl-CoA: Acetyl-CoA is the molecule that enters the citric acid cycle, where its acetyl group combines with oxaloacetate to form citrate, initiating the cycle.

Clarify why other options are incorrect: Citrate is a product of the citric acid cycle, lactate is formed during anaerobic glycolysis, and oxaloacetate is a molecule in the citric acid cycle that combines with acetyl-CoA but is not the intermediate step.