Understanding Plant Respiration: Key Notes 🌿
⚡ How Mitochondria Make ATP
Mitochondria use a proton gradient to power ATP production with ATP synthase (Complex V). This complex has two parts:
- 🔹 F₁: The “head” that builds ATP from ADP + inorganic phosphate.
- 🔹 F₀: The tunnel in the inner membrane letting protons (\(4H^+\) per ATP!) flow from the intermembrane space into the matrix.
Proton flow through \(F_0\) spins \(F_1\) like a turbine ⚙️, creating ATP! (See Figure 12.5 for structure)
📊 The Respiratory Balance Sheet (Glucose → ATP)
Theoretical ATP yield per glucose molecule: 38 ATP ✨…but only if we assume:
- ⛓️ All steps happen in order: Glycolysis → Krebs cycle → Electron Transport Chain (no overlap).
- 🧪 All glycolysis-made NADH enters mitochondria for ATP production.
- 🚫 No intermediates are used to build other molecules.
- 🍬 Only glucose is used (no fats/proteins enter mid-pathway).
Real life is messier! Cells use pathways simultaneously, pull intermediates for building blocks, and adjust based on needs. But this 38 ATP model helps us appreciate energy efficiency! 💡
🔁 Fermentation vs. Aerobic Respiration
| Fermentation | Aerobic Respiration | |
|---|---|---|
| Glucose Breakdown | Partial (→ pyruvic acid) | Complete (→ CO₂ + H₂O) |
| ATP Gain | Only 2 ATP per glucose 😅 | ~38 ATP per glucose 🎉 |
| NADH → NAD⁺ | Slow oxidation | Fast & vigorous! |
🔄 Respiration: The Amphibolic Pathway
Respiration isn’t just breaking stuff down! It’s a two-way street (amphibolic):
- 🔽 Catabolism (Breakdown):
- Fats → Glycerol (→ PGAL) & Fatty acids (→ Acetyl CoA)
- Proteins → Amino acids → Pyruvate/Acetyl CoA/Krebs intermediates
- 🔼 Anabolism (Building):
- Acetyl CoA from respiration → Fatty acids
- Krebs intermediates → Amino acids → Proteins
👉 Key Idea: Respiratory intermediates (like Acetyl CoA) are shared hubs for breaking AND building molecules! 🔄
🌟 NEET Must-Knows
- ATP Synthase Mechanism: \(F_0\) (proton channel) + \(F_1\) (ATP factory), requires \(4H^+\) per ATP.
- Theoretical ATP Yield: 38 ATP/glucose in aerobic respiration (and its 4 assumptions).
- Fermentation vs Aerobic: 2 ATP (incomplete) vs 38 ATP (complete breakdown).
- Amphibolic Pathway: Respiration supports BOTH breakdown (catabolism) AND synthesis (anabolism).
- Substrate Entry Points: Fats/proteins enter respiration as glycerol, fatty acids (→ Acetyl CoA), or amino acids.
