BIOL 112 - CITRIC ACID CYCLE, ETC, FERMENTATION

Q1: Which two enzymes in glycolysis require ATP consumption?

A1: Hexokinase and Phosphofructokinase.

Q2: Which enzyme catalyzes the last step of glycolysis?

A2: Pyruvate kinase.

Q3: What is the net ATP yield of glycolysis per glucose?

A3: 2 ATP net (4 produced, 2 consumed).

Q4: How many NADH are produced in glycolysis per glucose?

A4: 2 NADH.

Q5: Which enzyme produces NADH in glycolysis?

A5: Glyceraldehyde 3-phosphate dehydrogenase.

Q6: Which electron carrier is produced during glycolysis?

A6: NADH (not FADH₂, GTP, or water).

Q7: What are the three irreversible steps in glycolysis?

A7: Steps catalyzed by Hexokinase, Phosphofructokinase, and Pyruvate kinase.

Q8: What effect does Fructose-2,6-bisphosphate have on glycolysis?

A8: It activates Phosphofructokinase, stimulating glycolysis.

Q9: What regulates Phosphofructokinase (PFK)?

A9: Inhibited by ATP, citrate, and H⁺; activated by AMP and Fructose-2,6-BP.

Q10: Which statement is FALSE: PFK-1 is activated by ATP, AMP, or F-2,6-BP?

A10: False: PFK-1 is inhibited by ATP.

Q11: What happens to pyruvate in the presence of oxygen?

A11: It's converted to Acetyl-CoA by pyruvate dehydrogenase in the mitochondrial matrix.

Q12: How many NADH are produced during pyruvate oxidation per glucose?

A12: 2 NADH (1 per pyruvate).

Q13: When does CoA attach to pyruvate?

A13: Upon transport into the mitochondria.

Q14: Where does the TCA cycle occur?

A14: Mitochondrial matrix.

Q15: What is the main goal of the TCA cycle?

A15: To reduce NAD⁺ and FAD into NADH and FADH₂ for electron transport.

Q16: What are the products per one turn of the TCA cycle?

A16: 3 NADH, 1 FADH₂, 1 ATP (or GTP), 2 CO₂.

Q17: What enzyme catalyzes FADH₂ production?

A17: Succinate dehydrogenase.

Q18: What are the 8 reactions of the TCA cycle (just substrates)?

A18: Acetyl-CoA → Citrate → Isocitrate → α-Ketoglutarate → Succinyl-CoA → Succinate → Fumarate → Malate → Oxaloacetate.

Q19: Mnemonic for TCA intermediates?

A19: Citrate Is Krebs' Special Substrate For Making Oxaloacetate.

Q20: What is the net reaction of the TCA cycle?

A20: Acetyl-CoA + 3 NAD⁺ + FAD + GDP + Pᵢ → 2 CO₂ + CoA + 3 NADH + FADH₂ + GTP.

Q21: What TCA intermediates are used elsewhere?

A21:

• OAA → gluconeogenesis or amino acids

• Citrate → fatty acid synthesis

• α-KG → glutamate

• Succinyl-CoA → heme, chlorophyll

Q22: How many total NADH and FADH₂ are generated before ETC?

A22: 10 NADH and 2 FADH₂ per glucose.

Q23: What is the total ATP yield per glucose (range)?

A23: 30–32 ATP (2 from glycolysis, 2 from TCA, rest from ETC).

Q24: Where do NADH and FADH₂ donate electrons in ETC?

A24:

• NADH → Complex I

• FADH₂ → Complex II

Q25: What does Complex I do?

A25: Accepts e⁻ from NADH, pumps 4 H⁺.

Q26: What does Complex II do?

A26: Accepts e⁻ from FADH₂ (no H⁺ pumped).

Q27: What does Complex III do?

A27: Transfers e⁻ via cytochrome C to Complex IV, pumps 4 H⁺.

Q28: What does Complex IV do?

A28: Transfers e⁻ to ½ O₂ → H₂O, pumps 2 H⁺.

Q29: What drives ATP synthesis in the ETC?

A29: Proton (H⁺) gradient across inner mitochondrial membrane.

Q30: What enzyme uses the proton gradient to synthesize ATP?

A30: ATP synthase.

Q31: What is the full name for each ETC complex?

A31:

• Complex I: NADH-Q reductase

• Complex II: Succinate-Q reductase

• Complex III: Ubiquinol/cytochrome c oxidoreductase

• Complex IV: Cytochrome c oxidase

Q32: What is FALSE about the H⁺ gradient?

A32: That the pH of the matrix is greater than the intermembrane space before ATP synthesis (it's actually lower).

Q33: How do electrons cascade in the ETC?

A33: From lower to higher affinity carriers; O₂ pulls them down the chain.

Q34: What happens to pyruvate when O₂ is absent?

A34: It undergoes fermentation to regenerate NAD⁺.

Q35: What are the two fermentation types and their products?

A35:

• Ethanol fermentation (yeast/prokaryotes): ethanol

• Lactic acid fermentation (humans): lactic acid

Q36: What is the byproduct of converting pyruvate to acetaldehyde?

A36: CO₂.

Q37: What is TRUE about alcohol fermentation?

A37: It generates CO₂ and NAD⁺.