B9-Respiration

• Respiration


  Also called cellular respiration, the reactions of respiration occur inside cells
• Aerobic respiration


  Respiration that occurs with oxygen
• Every living cell needs energy and this energy is released from food (glucose) by a series of chemical reactions called respiration
• The reactions of respiration occur 24 hours a day, continuously, in all living cells
• Respiration


  An exothermic reaction which means energy is transferred to the environment
• An organism will receive all the energy it needs for living processes as a result of the energy transferred from respiration
• Why living organisms need energy

  • For chemical reactions
  • To build larger molecules from smaller ones
  • For keeping warm
  • To keep a steady body temperature in a cold environment
• Aerobic respiration


  Glucose + oxygen -> carbon dioxide + water
• Aerobic respiration occurs inside mitochondria continuously
• Glucose is oxidised by oxygen to transfer the energy the organism needs to perform its functions
• Aerobic respiration releases a large amount of energy from each glucose molecule
• Anaerobic respiration


  Respiration that occurs without oxygen
• Anaerobic respiration in animal cells

  Glucose -> lactic acid
• During hard exercise, muscles cells are respiring so fast that the blood cannot transport enough oxygen to meet their needs
• The muscle cells switch to use ANAEROBIC RESPIRATION to transfer energy
• Glucose is not completely broken down to carbon dioxide and water, so less energy is transferred. An end product called lactic acid is formed
• Anaerobic respiration in plant and yeast cells

  Glucose -> ethanol + carbon dioxide
• Anaerobic respiration in yeast cells is called fermentation, which is economically important in the manufacture of alcoholic drinks and bread
• Respiration summary


  • Aerobic respiration: Oxygen required, end products carbon dioxide and water, complete oxidation of glucose, high efficiency of energy transfer
  • Anaerobic respiration in animal cells: Oxygen not required, end product lactic acid, incomplete oxidation of glucose, low efficiency of energy transfer
  • Anaerobic respiration in plant and yeast cells: Oxygen not required, end products ethanol and carbon dioxide, incomplete oxidation of glucose, low efficiency of energy transfer
• Response to exercise


  1. Heart rate increases to pump oxygenated blood faster

  2. Breathing rate and breath volume increase to increase oxygen entering bloodstream
• If insufficient oxygen is supplied to the muscle cells then anaerobic respiration occurs during exercise
• Response to exercise (HT only)

  1. Lactic acid builds up in muscle cells

  2. Blood transports lactic acid to liver

  3. Liver oxidises lactic acid and converts it back to glucose

  4. Oxygen debt - extra oxygen required to remove all lactic acid from cells
• Metabolism


  The sum of all reactions in a cell or body
• Metabolic reactions


  • Conversion of glucose to starch
  • Conversion of glucose and nitrate ions to amino acids and proteins
  • Conversion of glucose to cellulose
  • Conversion of glucose to glycogen
  • Formation of lipids from glycerol and fatty acids
  • Breakdown of proteins to form urea
• Organisms use the energy transferred by respiration for the continual enzyme controlled processes of metabolism