CH 9

✅ CHAPTER 9 — LEARNING OBJECTIVES ANSWERED (Using Your Slides Only)

🔷 CONCEPT 9.1 — Oxidation & Reduction

1. Define oxidation and reduction. Identify oxidized vs. reduced species.

  • Oxidation = loss of electrons.
    Slide quote: “the loss of electrons from a substance is called oxidation”

  • Reduction = gain of electrons.
    Slide quote: “the addition of electrons to a substance is called reduction”

How to identify them:

  • The molecule that loses electrons is oxidized.

  • The molecule that gains electrons is reduced.

2. Analyze simple redox example

Example: Na + Cl → Na⁺ + Cl⁻

• Na loses an electron → oxidized

• Cl gains an electron → reduced

Slide quote: “Na → Na⁺ + e⁻; Cl + e⁻ → Cl⁻”

Example: Methane combustion (CH₄ + O₂ → CO₂ + H₂O)

• Carbon in CH₄ loses electrons → oxidized

• Oxygen gains electrons → reduced

Slide quote: “O atoms… attract electrons… partial ‘gain’ of electrons by O atoms”

CONCEPT 9.2 — Glycolysis, Fermentation, Cellular Respiration

1. Sketch/location of pathways

  • Glycolysis: cytoplasm (all cells)
    Slide quote: “Glycolysis occurs in the cytoplasm”

  • Pyruvate oxidation + Citric Acid Cycle: mitochondrial matrix (eukaryotes)

  • ETC + Oxidative phosphorylation: inner mitochondrial membrane

  • Prokaryotes: all steps occur in cytosol or plasma membrane
    Slide quote: “In prokaryotes, the electron transport chain is embedded in the plasma membrane”

2. Fermentation

Occurs in cytosol when no O₂ is present.
Regenerates NAD⁺ so glycolysis can continue.
Slide quote: “Fermentation uses mechanisms to regenerate NAD+”

🔷 CONCEPT 9.3 — Pyruvate Oxidation & Energy Flow

1. How pyruvate enters mitochondria

  • Eukaryotes: transported into mitochondria via a transport protein.
    Slide quote: “Pyruvate enters a mitochondrion… Transport protein”

  • Aerobic prokaryotes: pyruvate oxidation occurs in cytosol.
    Slide quote: “This occurs in the cytosol for aerobic prokaryotes”

2. Where most energy remains after glycolysis

  • Energy is still in pyruvate.
    Slide quote: “Most of the energy in glucose remains stored in the pyruvate molecules”

3. Three reactions of pyruvate processing

Pyruvate dehydrogenase performs:

  1. Carboxyl group oxidized → CO₂ released

  2. NAD⁺ reduced → NADH

  3. Remaining 2‑C fragment + CoA → acetyl‑CoA
    Slide quote: “Oxidation… releasing CO₂… Reduction of NAD⁺… forming acetyl CoA”

4. Consequences of inhibiting pyruvate dehydrogenase

If PDH is blocked:

  • No acetyl‑CoA

  • Citric acid cycle stops

  • NADH/FADH₂ production drops

  • ATP from oxidative phosphorylation collapses

  • Pyruvate builds up → fermentation increases

5. How NADH & FADH₂ feed the ETC

They donate electrons to the ETC.
Slide quote: “NADH and FADH₂ donate electrons to the electron transport chain”

🔷 CONCEPT 9.4 — ETC, Proton Gradient, ATP Synthase

1. Composition of ETC

  • Located in inner mitochondrial membrane

  • Made of multiprotein complexes (I–IV)

  • Includes cytochromes with iron-containing heme groups
    Slide quote: “Most molecules… are proteins… including several cytochromes”

2. How proton pumping creates proton‑motive force

Electron flow releases energy → pumps H⁺ into intermembrane space.
Slide quote: “Energy… is used to pump H⁺… establishing a proton‑motive force”

3. ATP synthase structure/function

  • Rotor

  • Stator

  • Internal rod

  • Catalytic knob
    H⁺ flow spins rotor → ATP produced.
    Slide quote: “H⁺ moves into binding sites on the rotor… causing it to spin… catalyzes phosphorylation of ADP to ATP”

4. How energy is conserved

Electron transfers → proton gradient → chemiosmosis → ATP.
Slide quote: “Maintaining the H⁺ gradient couples redox reactions… to ATP synthesis”

🔷 CONCEPT 9.5 — Fermentation & Anaerobic Respiration

1. Anaerobic respiration

Uses ETC but final electron acceptor ≠ O₂.
Example: sulfate → produces H₂S.
Slide quote: “Some organisms use sulfate… H₂S is made as a by‑product”

2. How NAD⁺ is regenerated in fermentation

Electrons from NADH are transferred to pyruvate or derivatives.
Slide quote: “Fermentation… oxidizes NADH by transferring electrons to pyruvate”

3. Predict end products with alternative acceptors

  • Sulfate → H₂S

  • Nitrate → NO₂⁻ or N₂

  • CO₂ → methane (in methanogens)

4. Steps & products of alcohol fermentation

  • Pyruvate → acetaldehyde + CO₂

  • Acetaldehyde → ethanol (regenerates NAD⁺)
    Slide quote: “The first step releases CO₂… the second step produces NAD⁺ and ethanol”

5. Steps & products of lactic acid fermentation

  • Pyruvate reduced directly → lactate

  • No CO₂ released
    Slide quote: “Pyruvate is reduced directly by NADH to form lactate… no release of CO₂”

🔷 CONCEPT 9.6 — Metabolic Connections

1. Where proteins, fats, carbs enter pathways

Slide quote: “The catabolism of various molecules from food” diagram shows:

  • Carbs → glucose → glycolysis

  • Fats → glycerol (glycolysis) + fatty acids (acetyl‑CoA)

  • Proteins → amino acids → pyruvate, acetyl‑CoA, or citric acid cycle intermediates

2. Define deamination & beta oxidation

  • Deamination: removing amino groups from amino acids before entering pathways.

  • Beta oxidation: breaking fatty acids into acetyl‑CoA units.

3. Predict effects of high fatty acid influx

  • More acetyl‑CoA

  • Citric acid cycle speeds up (if energy demand high)

  • If ATP is high → acetyl‑CoA diverted to fat synthesis

  • NADH buildup slows the cycle (feedback inhibition)