Overview
This lecture introduces metabolism and cellular respiration, explaining key concepts, pathways, and differences between aerobic and anaerobic processes.
Metabolism Overview
- Metabolism refers to all chemical reactions within a living organism.
- It is divided into catabolism (breaking down molecules for energy) and anabolism (building molecules using energy).
Cellular Respiration Basics
- Cellular respiration is the process by which cells extract energy from glucose.
- It occurs in three main stages: glycolysis, Krebs cycle, and electron transport chain (ETC).
- The overall equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP).
Steps of Cellular Respiration
- Glycolysis happens in the cytoplasm, breaking glucose into two pyruvate molecules and producing 2 ATP.
- Krebs cycle occurs in the mitochondria, generating electron carriers (NADH and FADH₂) and CO₂.
- ETC uses electrons from NADH and FADH₂ to create a proton gradient that powers ATP synthesis (oxidative phosphorylation).
Aerobic vs. Anaerobic Respiration
- Aerobic respiration requires oxygen and produces up to 38 ATP per glucose.
- Anaerobic respiration (fermentation) occurs without oxygen, producing less ATP and generating lactic acid or ethanol as byproducts.
Regulation of Metabolism
- Enzymes control metabolic pathways and are regulated by feedback mechanisms.
- ATP, ADP, and other metabolites act as signals to increase or decrease pathway activity.
Importance of Respiration
- Respiration provides ATP, which powers cellular activities such as muscle contraction and biosynthesis.
Key Terms & Definitions
- Metabolism — all chemical reactions in an organism.
- Catabolism — metabolic pathways that break down molecules and release energy.
- Anabolism — pathways that build molecules and consume energy.
- Cellular respiration — process of converting glucose into ATP, CO₂, and H₂O.
- Glycolysis — first stage of cellular respiration, splitting glucose into pyruvate.
- Krebs cycle — produces electron carriers and releases CO₂.
- Electron transport chain (ETC) — final stage producing most ATP using electron carriers.
- ATP (Adenosine triphosphate) — main energy currency of the cell.
- Fermentation — anaerobic process generating ATP and byproducts like lactic acid.
Action Items / Next Steps
- Review metabolic pathway diagrams and stages of respiration.
- Practice writing and explaining the overall respiration equation.
- Read assigned textbook sections on cellular respiration and metabolism.