Overview
This lecture explains cellular respiration, focusing on how mitochondria convert food and oxygen into ATP, the cell's usable energy.
Mitochondria & Cellular Respiration Basics
- Mitochondria are organelles responsible for converting food and oxygen into ATP, providing energy for cellular functions.
- Cellular respiration is the process used by aerobic organisms to extract energy from food using oxygen.
- ATP (adenosine triphosphate) is the cell's energy currency, constantly recycled to meet cellular demands.
- Humans recycle about 100 pounds of ATP daily via cellular respiration.
Stages of Cellular Respiration
- The process has three main stages: glycolysis, the citric acid (Krebs) cycle, and oxidative phosphorylation.
- Glycolysis occurs in the cytoplasm, breaking glucose into pyruvate, yielding 2 ATP and NADH.
- Pyruvate enters mitochondria, is oxidized, releasing CO2 and forming a two-carbon molecule for the citric acid cycle.
- The citric acid (Krebs) cycle produces CO2, 1 ATP, 3 NADH, and 1 FADH2 per turn; it cycles twice per glucose.
- Oxidative phosphorylation, occurring in mitochondrial membranes, uses an electron transport chain to create a proton gradient.
- The proton gradient drives ATP synthase, producing about 30 ATP per glucose molecule.
- Electrons at the end of the chain combine with oxygen and protons to form water.
Anaerobic Respiration & Fermentation
- Some organisms can release energy without oxygen using anaerobic respiration or fermentation.
Key Terms & Definitions
- Mitochondria — Organelles that generate ATP through cellular respiration.
- Cellular respiration — Metabolic process converting glucose and oxygen into ATP, CO2, and water.
- ATP (Adenosine Triphosphate) — Main energy carrier in cells.
- Glycolysis — The first stage of respiration; breaks down glucose into pyruvate in the cytoplasm.
- Citric Acid Cycle (Krebs Cycle) — A series of reactions in mitochondria that generates electron carriers.
- Oxidative Phosphorylation — Final stage where electron transport creates a proton gradient to drive ATP production.
- NAD+/NADH, FADH2 — Electron carriers in cellular respiration.
- ATP Synthase — Enzyme that synthesizes ATP using a proton gradient.
Action Items / Next Steps
- Prepare to learn about photosynthesis in the next lecture.
- Optional: Visit biointeractive.org/crashcourse for classroom resources and further study materials.