Respiration

• Energy in our universe remains constant. Energy is neither created nor destroyed.
• Forms of energy


  • Potential energy (stored energy)
  • Kinetic energy (energy due to motion)
• Autotrophs


  Plants that manufacture their own food
• Heterotrophs


  Animals that cannot make their own food and obtain energy by eating plants (herbivores) or other animals (carnivores)
• Cellular respiration


  Releases the energy in food, so that the organism can get the energy it requires
• When oxygen is available to a cell

  Aerobic respiration takes place and lots of energy is released and stored as ATP
• When oxygen is not available to a cell

  Anaerobic respiration occurs and little energy is released
• Mitochondrion


  • Organelle in which the process of aerobic respiration is completed
  • Has a double membrane
  • Contains cristae
  • Contains matrix
• Aerobic respiration


  1. Glycolysis (occurs in the cytosol)

  2. Krebs cycle (occurs in the mitochondrion)

  3. Oxidative phosphorylation (occurs in the mitochondrion)
• During aerobic respiration, 1 glucose molecule will produce a net product of 38 high energy ATP molecules
• Glycolysis


  1. Glucose is broken down to form pyruvic acid in the cytosol

  2. Pyruvic acid contains energy-rich hydrogen atoms
• Krebs Cycle


  1. Pyruvic acid enters the mitochondrion and joins a cyclic series of reactions

  2. CO2 and energised hydrogen atoms are released
• Oxidative Phosphorylation


  1. The energised hydrogen atoms are used to make 36 ATP molecules

  2. The de-energised hydrogen atoms combine with oxygen to form water
• ATP


  • Carrier of energy in a cell
  • Formed when ADP+P+energy forms ATP
  • Breaks down to ADP+P to release energy for the cell
• Anaerobic respiration is a catabolic (breaking down) reaction that occurs in both plant and animal cells, when oxygen is not available in the cell
• Anaerobic respiration in plant and yeast cells

  1. Energy-rich glucose is broken down to ethanol (alcohol)

  2. Carbon dioxide and some energy is released
• Beer making


  • Yeast is allowed to ferment under anaerobic conditions to produce alcohol
• Bread making


  • Yeast breaks down sugar via anaerobic respiration to produce ethanol and CO2
  • CO2 forms pockets of "air", causing the dough to rise
• Anaerobic respiration in animal cells

  1. Food (e.g. glucose) is broken down to yield some energy and lactic acid

  2. Lactic acid can be converted back to pyruvic acid when oxygen becomes available