Biology Chapter 6: Cellular Respiration

Study Notes

Purpose: Breaks down glucose into two pyruvate molecules, producing ATP and NADH.
Location: Cytoplasm.
Phases:
- Energy Investment Phase: Consumes 2 ATP molecules.
- Energy Payoff Phase: Produces 4 ATP molecules and 2 NADH.
Major Products:
- 2 Pyruvate
- 2 NADH
Net Gain: 2 ATP

Mechanism: Occurs when oxygen is unavailable. Regenerates NAD⁺ from NADH to allow glycolysis to continue. Produces lactate in animals or ethanol and CO₂ in yeast/plants.
Purpose: Ensures ATP production during anaerobic conditions.

Purpose: Oxidizes acetyl-CoA to CO₂, generating NADH and FADH₂. These carry high-energy electrons to the Electron Transport Chain (ETC).
Location: Mitochondrial matrix.
Key Molecules Involved:
- Reactants/Inputs:
  - Acetyl-CoA (from pyruvate oxidation)
  - NAD⁺ (electron carrier)
  - FAD (electron carrier)
  - ADP + Pi
- Products/Outputs:
  - 3 NADH (per acetyl-CoA)
  - 1 FADH₂ (per acetyl-CoA)
  - 1 ATP (via substrate-level phosphorylation)
  - 2 CO₂ (per acetyl-CoA)
Key Points:
- Per Acetyl-CoA (1 Cycle): 3 NADH, 1 FADH₂, 1 ATP, and 2 CO₂ are produced.
- Per Glucose Molecule (2 Acetyl-CoA, meaning 2 turns of the cycle): 6 NADH, 2 FADH₂, 2 ATP, and 4 CO₂ are produced.
- NADH and FADH₂ are essential for transferring high-energy electrons to the ETC for ATP generation.

Purpose: Uses electrons from NADH and FADH₂ to create a proton gradient for ATP synthesis.
Location: Inner mitochondrial membrane.
Energy and Molecule Flow:
- Protons are pumped into the intermembrane space, creating a gradient.
- Electrons move through protein complexes (I-IV).
- ATP synthase uses the gradient to convert ADP + Pi into ATP.
- Oxygen acts as the final electron acceptor, forming water.

Photosynthesis:
- Location: Chloroplasts
- Converts light energy into chemical energy (glucose).
- Key Processes: Light-dependent reactions and Calvin Cycle.
Cellular Respiration:
- Location: Mitochondria
- Converts glucose into usable energy (ATP).
- Key Processes: Glycolysis, Krebs Cycle, ETC.
Similarities: Both involve energy transformations and electron carriers.
Differences: Photosynthesis stores energy while respiration releases it. They have opposite reactants and products.

Photosynthesis:
- Internal factors: Chlorophyll concentration and enzyme activity.
- External factors: Light intensity, CO₂ concentration, and temperature.
Cellular Respiration:
- Internal factors: Enzyme levels and substrate availability.
- External factors: Oxygen levels and temperature.
Predictions: High light/CO₂ levels increase photosynthesis. Low oxygen inhibits aerobic respiration. Extreme temperatures disrupt enzyme function in both processes.