Cell Respiration (Higher Level)

Content Statements

• Role of NAD: Carrier of hydrogen, oxidized by removal during respiration.
• Glycolysis: Conversion from glucose to pyruvate, yielding ATP and reduced NAD.
• Anaerobic Respiration:
  • Pyruvate to lactate conversion regenerates NAD.
  • Used in yeast for brewing and baking.
• Aerobic Respiration:
  • Link reaction of pyruvate oxidation and decarboxylation.
  • Krebs cycle: Oxidation of acetyl groups, yields ATP and reduced NAD.
  • Electron Transport: Energy transfer via reduced NAD in mitochondria.
  • Chemiosmosis: Synthesis of ATP.
  • Oxygen as a terminal electron acceptor.
• Energy Substrates: Differences between lipids and carbohydrates.
• Mitochondrial Adaptations: For ATP production.

Energy Conversions

• Organic Molecules: Store energy in chemical bonds, converted by cell respiration.
  • ATP: Immediate energy source, released when hydrolyzed to ADP.
  • Hydrogen Carriers: Transitional energy, transfer electrons and protons.
• ATP Production:
  • Substrate Level Phosphorylation: Direct from molecules.
  • Oxidative Phosphorylation: Indirect via hydrogen carriers, requires O2.

Types of Cell Respiration

• Anaerobic Respiration:
  • Partial glucose digestion to pyruvate, no oxygen, low ATP yield.
  • Occurs in cytosol.
• Aerobic Respiration:
  • Complete glucose breakdown to CO2 and H2O, requires oxygen.
  • High yield of ATP, requires mitochondria.

Glycolysis

• Initial stage for both anaerobic and aerobic respiration.
• Splits glucose into pyruvate, using 2 ATP and producing 4 ATP (net gain 2 ATP).
• Produces NADH from NAD.

Fermentation

• Occurs if oxygen is absent, allows glycolysis to continue.
• Plants & Yeasts: Pyruvate converts to ethanol and CO2.
• Animals: Pyruvate to lactic acid, reversible with oxygen presence.

Aerobic Respiration Processes

• Link Reaction:
  • Pyruvate transported to mitochondria, forms acetyl CoA.
  • Releases CO2 and reduces NAD to NADH.
• Krebs Cycle:
  • Acetyl CoA combines with a 4C compound, continuing in a cycle.
  • Produces CO2, ATP, NADH, and FADH2.
• Electron Transport Chain:
  • NADH and FADH2 release electrons, energizing protons in the matrix.
  • Forms an electrochemical gradient, diffuses back via ATP synthase (chemiosmosis) producing ATP.
  • Oxygen combines with electrons and protons to form water.

Energy Sources

• Carbohydrates: Preferred for both respiration types, easy digestion and transport.
• Lipids: Used aerobically, more energy per gram, broken into acetyl CoA bypassing glycolysis.