3.5.2 Respiration

Aerobic Respiration

requires oxygen → carbon dioxide, water and ATP

Anaerobic Respiration

absence of oxygen → Lactate(animals)/ ethanol and carbon dioxide(plants & fungi) and a little amount of ATP

Mitochondria

Organelles where aerobic respiration occurs

Cristae

Inner mitochondrial membrane folds → contains the electron transport chain for oxidative phosphorylation and ATP synthase enzyme channels

The Matrix

Contains enzymes required for catalysis of the link reaction and Krebs cycle

Glycolysis

Occurs in the cytoplasm - both aerobic and anaerobic respiration

Glycolysis Reaction

Glucose is phosphorylated by ATP = ADP and Hexose Biphosphate → 2 molecules of Triose Phosphate

Triose Phosphate

Each Triose Phosphate is oxidised → 2 molecules of Pyruvate

NAD

Coenzyme that collects H+ and is reduced → 2 reduced NAD molecules

Substrate Level Phosphorylation

4 ATP are produced by substrate level phosphorylation

The Link Reaction

Pyruvate is actively transported into matrix of the mitochondria

Acetate

Pyruvate is oxidised → Acetate

Decarboxylation

Pyruvate is decarboxylated - loses CO2

Acetyl Coenzyme A

Acetate + Coenzyme A (CoA) → Acetyl coenzyme A (Acetyl CoA)

Krebs Cycle

Acetyl CoA enters Krebs cycle in the matrix - cycle happens once for every pyruvate

Citrate

Acetyl CoA combines with 4-Carbon Oxaloacetate → 6-Carbon Citrate

NADH Production

The H+ released produces NADH

Oxidative Phosphorylation

Energy carried by electrons provided by reduced coenzymes(NADH & FADH) to generate lots of ATP

Electron Transport Chain

Involves Electron Transport Chain and Chemiosmosis

ATP Synthase

H+ moves down electrochemical gradient into the matrix by ATP Synthase which provides the energy needed to combine ADP + Pi → ATP

Final Electron Acceptor

Oxygen - final electron acceptor - combines with H+ and Electrons at the end of the electron transport chain → Water

ATP Yield

2.5 ATP = one NADH, 1.5 ATP = one FADH

Anaerobic Respiration Purpose

Main purpose of anaerobic respiration is to generate NAD for glycolysis which allows a small amount of ATP to be made

Lactate

Pyruvate produced in glycolysis is reduced using NADH = lactate - lactic acid

Respiratory Quotient (RQ)

Respiratory Quotient = Volume of Co2 produced / Volume of O2 used