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C1.2 Cell Respiration

C1.2.1 ATP

  • ATP is the molecule that distributes energy in cells

  • Structure: Adenine + ribose + three phosphate groups

  • Properties:

    • Soluble in water

    • stable at pH levels close to neutral

    • cannot pass freely through phospholipid bilayer

    • easily removable/reattachable third phosphate group through hydrolysis and condensation

    • hydrolysis of ATP → small amount of energy

C1.2.2 Life processes that need ATP

  • Synthesizing macromolecules

    • anabolic reaction, endothermic

  • Active transport

    • against concentration gradient

  • cellular movement

    • changing shape of cell

C1.2.3 Energy transfers during conversions between ATP and ADP

  • ATP → ADP + Pi + energy

    • Hydrolysis - addition of water to break bonds between third phosphate group

  • ADP + Pi + energy→ ATP

    • Phosphorylation - remove water from ADP and add third phosphate group

  • Small amount of energy released

    • ATP has more potential energy than ADP

C1.2.4 Cell Respiration for producing ATP

  • Cell respiration: Uses oxygen and produces carbon dioxide

    • carbon compounds oxidized to produce ATP

    • energy used to produce ATP

  • Gas exchange: oxygen enters cells through membrane while carbon dioxide exits the cells

  • Living organisms require ATP to perform its activities - continuous cellular respiration

  • common substrate is glucose

C1.2.5 Anaerobic vs Aerobic Respiration

  • Aerobic: Glucose + oxygen → carbon dioxide + water + ATP

    • Glycolysis - Krebs Cycle - Electron Transport Chain

  • Anaerobic: Glucose → Lactic acid/alcohol + carbon dioxide + ATP

    • Glycolysis - Fermentation

C1.2.6 Variables affecting rate of respiration

  • Temperature, glucose/oxygen levels

  • Respirometer

C1.2.7 Role of NAD

  • Oxidation: Removal of electrons

  • Reduction: Gaining electrons

  • NAD is an electron carrier during cellular respiration

    • 2 H atoms are removed from the reduced substance

    • One splits into proton and electron

    • Electron is absorbed, cation released

    • NAD accepts the H remaining

C1.2.8 Conversion of glucose to pyruvate

  • Glycolysis

    • Occurs in cytosol

    • Glucose (6C) → Pyruvate (3C)

    • Occurs in both aerobic and anaerobic respiration

    • example of metabolic pathway

  1. Phosphorylation of glucose molecule

  2. Lysis → 2 G3P

  3. oxidation - removing hydrogen → reducing NAD+ to NADH

  4. ATP formation

  • Produces 2 ATP and 2 NADH

C1.2.9. Pyruvate → lactate (Anaerobic)

  • pyruvate undergoes fermentation

  • yeast oxidize NADH back to NAD by gaining 2H

  • convert pyruvate to lactate/alcohol

  • require NAD for glycolysis, will run out unless regenerated in fermentation

C1.2.10 Pyruvate → alcohol

  • pyruvate decarboxylates, releases CO2 → ethanal (oxidizes NADH) → ethanol

  • used in brewing and baking

C1.2.11 Oxidation and decarboxylation of pyruvate in Link Reaction

  • aerobic respiration

  • Link reaction occurs in mitochondrial matrix

  • Decarboxylation - release CO2

  • Oxidation - removing 2 electrons → accepted by NAD

  • Binding of acetyl group and coenzyme A → Acetyl CoA

  • 2 pyruvate → 2 acetyl CoA, 2 CO2, 2 NADH

C1.2.12 Oxidation and decarboxylation of acetyl groups in Krebs Cycle

  • occurs in mitochondrial matrix

  • Acetyl CoA (2C) + oxaloacetate (4C) → citrate (6C)

  • decarboxylation of citrate → oxaloacetate and CO2

    • occurs twice

    • 6C → 5C → 4C

  • formation of ATP, NADH and FADH2

    • NADH x3, FADH2 x1, ATPx1, H2Ox1 per cycle

  • Substrate-level phosphorylation

  • NADH and FADH2 carry electrons to electron transport chain

  • 1 glucose: 6 NADH, 2 FADH2, 2 ATP, 4 CO2, 2 H2O

C1.2.13 Transfer of energy to electron transport chain

  • occurs in intermembrane space

  • only in presence of oxygen

  • NADH and FADH2 are oxidized → electrons to electron carrier proteins

C1.2.14 Generation of Proton Gradient by flow of electrons

  • Electrons in the chain release energy at each stage of the ETC

    • used to pump protons across the inner mitochondrial membrane (matrix → intermembrane space)

    • creates concentration gradient

C1.2.15 Chemiosmosis

  • H+ ions move from matrix to intermembrane space through ATP synthase - chemiosmosis

  • ATP synthase - integral protein channel

  • Energy provided by proton gradient is used to synthesize ATP with ADP and Pi - oxidative phosphorylation

C1.2.16 Role of Oxygen

  • Oxygen is the final electron acceptor

  • Requires oxygen to accept electrons from NADH

  • Formation of hydrogen helps maintain proton concentration gradient

  • Total ATP: Glycolysis (2) + Krebs (2) + Oxidative Phosphorylation (34) → 38 ATP