Unit 3 - Cellular Respiration

Cellular respiration: Aerobic process that oxidizes fuel molecules and generates ATP for cellular work.

Photosynthesis vs Cellular Respiration: Photosynthesis occurs in the chloroplast (reactants: water, CO₂, light energy; products: glucose and O₂); cellular respiration occurs in the mitochondria (reactants: glucose and O₂; products: water, CO₂, ATP, and heat).

Life on Earth is solar-powered because: Plants capture sunlight to make energy-rich compounds, which are used by organisms through cellular respiration to fuel life processes.

Relationship between breathing and cellular respiration: Breathing provides the oxygen needed for cellular respiration to produce ATP from glucose.

Overall chemical equation for cellular respiration: C₆H₁₂O₆ + 6O₂ → 6H₂O + 6CO₂ + Energy (ATP).

How the body uses ATP: Powers muscle contraction, nerve signaling, metabolism, and protein synthesis.

Kilocalorie (kcal): A unit of heat equal to 1,000 calories; used to measure food energy, also known as a “Calorie.”

How glucose releases energy during cellular respiration: Through glycolysis, the Krebs cycle, and the electron transport chain, transferring energy to ATP.

Redox reactions in cellular respiration: Electrons are transferred from glucose to oxygen, releasing energy gradually to form ATP.

NADH role: Carries electrons to the electron transport chain from glycolysis and the Krebs cycle.

Electron Transport Chain (ETC): Uses electron energy to pump protons and produce ATP.

Oxygen role in ETC: Final electron acceptor, forms water, and allows ETC to keep working.

Glycolysis location: Cytoplasm

Pyruvate Oxidation location: Mitochondrial matrix

Citric Acid Cycle location: Mitochondrial matrix

Oxidative Phosphorylation location: Inner mitochondrial membrane

Glycolysis reactants/products/ATP: Reactants: glucose, 2 ATP; Products: 2 pyruvate, 2 NADH, 2 net ATP.

Pyruvate Oxidation reactants/products: Reactants: 2 pyruvate, 2 NAD+, 2 CoA; Products: 2 acetyl CoA, 2 NADH, 2 CO₂.

Citric Acid Cycle reactants/products: Reactants: 2 acetyl CoA; Products: 2 ATP, 6 NADH, 2 FADH₂, 4 CO₂.

Oxidative Phosphorylation reactants/products: Reactants: NADH, FADH₂, O₂, ADP; Products: 34 ATP, 2 H₂O.

Total ATP yield per glucose: About 36–38 ATP depending on efficiency and cellular conditions.

Fermentation purpose: Regenerates NAD⁺ so glycolysis can continue without oxygen.

Alcohol fermentation reactants/products: Reactants: 2 pyruvate + 2 NADH; Products: 2 ethanol, 2 CO₂, 2 NAD⁺.

Lactic acid fermentation reactants/products: Reactants: 2 pyruvate + 2 NADH; Products: 2 lactate, 2 NAD⁺.

Does fermentation produce ATP?: No, it only allows glycolysis to continue.

Glycolysis evolutionary history: An ancient pathway from early anaerobic life, still central in most organisms.

Carbs, fats, and proteins as fuel: Broken down into glucose, fatty acids, and amino acids and fed into glycolysis, Krebs cycle, and ETC for ATP production.

Why fats yield more ATP than carbs or proteins: Fats have more carbon-hydrogen bonds for oxidation, producing more ATP.

Nutrients in biosynthesis: Provide building blocks (sugars, amino acids, fatty acids) for making cell components like proteins and lipids.

Oxidation (OIL): Loss of electrons.

Reduction (RIG): Gain of electrons.

ETC pumps protons by: Using energy from electrons to actively transport H⁺ into intermembrane space.

Chemiosmosis: Flow of H⁺ through ATP synthase to power ATP production.

Why oxygen is essential in ETC: It accepts electrons; without it, ATP production stops.

Intermediates: Molecules formed and used during steps between starting and final products.