Biology Paper 2

• Gas exchange occurs at the alveoli, where oxygen diffuses into the bloodstream and carbon dioxide diffuses out.
• Air enters through the nose or mouth and passes down the trachea (windpipe) into the bronchioles.
• The main function of the respiratory system is to exchange gases between the body and the environment.
• Aerobic respiration


  1. NAD+ + anaerobic (no O2) -> glucose

  2. Hexophosphorylation: adding 2 inorganic (P) -> glycolysis: Phosphorylation + -> Cell

  3. Link reaction: decarboxylation -> oxidation of pyruvate

  4. Krebs Cycle: enzyme-controlled -> matrix of mitochondria

  5. Oxidative (ETC): ATP production- inner mitochondrial membrane
• Coenzymes


  Helper transfer molecules of energy that carry e- or H+
• Dehydrogenase enzymes


  Family of enzymes (in ETC)
• Chemiosmosis Theory: ETC produces electrochemical gradient
• Glycolysis + Krebs produce 4 ATP, ETC produces 30 ATP, total 34 ATP for aerobic respiration
• Oxygen is the final electron acceptor in the ETC
• Anaerobic respiration


  1. Glycolysis -> pyruvate -> lactate or ethanol

  2. Regenerates NAD+ to be reused in glycolysis
• Oxygen debt


  When O2 demand exceeds supply, leading to anaerobic respiration and buildup of lactic acid
• Anaerobic respiration is important to regenerate NAD+ to be reused in glycolysis for ATP production
• Respiratory quotient (RQ)


  Ratio of CO2 produced to O2 consumed, indicates respiratory substrate
• Using a respirometer


  1. Measures O2 uptake of respiring organisms

  2. Absorbs CO2 (into soda-lime) changing gas volume

  3. Measures volume/pressure changes with manometer
• Substrate can be identified from RQ value
• Inaccuracies can occur if KOH doesn't properly absorb CO2, so water should be used instead