Overview
Today's lecture introduced aerobic respiration, focusing on glycolysis and the prep steps, with a comparison to photosynthesis and anaerobic respiration.
Respiration vs. Photosynthesis
- Respiration converts glucose and oxygen into ATP, carbon dioxide, and water, essentially reversing photosynthesis.
- Photosynthesis occurs in chloroplasts; respiration mainly happens in mitochondria.
- Both plant and animal cells conduct respiration in mitochondria.
Types of Respiration
- Aerobic respiration requires oxygen, produces up to 38 ATP per glucose, and is efficient and sustainable.
- Anaerobic respiration occurs without oxygen, produces only 2 ATP per glucose, and results in lactic acid or alcohol as by-products.
Overview of Aerobic Respiration Steps
- Both aerobic and anaerobic respiration start with glycolysis, producing 2 ATP.
- Aerobic respiration continues with prep steps, the Krebs cycle (2 ATP), and the electron transport chain (34 ATP).
- Total ATP yield for aerobic respiration is about 38 per glucose molecule.
Stored Energy Molecules
- ATP, NADH, and FADH2 are rechargeable molecules that store and transfer energy within the cell.
- NADPH is used in photosynthesis, not in respiration; remember 'P' for photosynthesis.
Glycolysis
- Glycolysis breaks down one glucose (6 carbons) into two pyruvate molecules (3 carbons each).
- The process uses 2 ATP and produces 4 ATP (net gain: 2 ATP).
- Generates 2 NADH per glucose for use in later steps.
The Prep Steps
- Occur only in aerobic respiration when oxygen is present.
- Each pyruvate (3 carbons) is converted to Acetyl CoA (2 carbons) by adding Co-enzyme A and using NAD+.
- Produces 2 Acetyl CoA, 2 NADH, and 2 COâ‚‚ per glucose; carbon count remains balanced.
Molecule Tally So Far
- Net 2 ATP produced after glycolysis.
- 4 NADH molecules generated (2 from glycolysis, 2 from prep steps).
- No FADH2 produced yet.
Key Terms & Definitions
- Aerobic Respiration — Energy production using oxygen; highly efficient.
- Anaerobic Respiration — Energy production without oxygen; low efficiency.
- Glycolysis — First step in glucose breakdown, occurs in cytoplasm, yields pyruvate and ATP.
- Pyruvate — Three-carbon molecule from glycolysis, enters further steps if oxygen is present.
- Acetyl CoA — Two-carbon molecule formed from pyruvate during prep steps.
- ATP (Adenosine Triphosphate) — Main energy currency of the cell.
- NADH, FADH2 — Electron carriers storing energy for ATP production.
Action Items / Next Steps
- Review the glycolysis and prep steps processes.
- Prepare for next lecture on the Krebs cycle and electron transport chain.