respiration

• When glucose is broken down, bonds are broken, and this releases energy.
• The living organisms are unable to use energy from glucose directly and so uses it to produce an energy rich molecule which the body can use. This molecule is ATP.
• The energy from the breakdown of glucose is used to build up ATP from ADP and Pi.
• ADP + Pi -energy in -> ATP
• When energy is needed, the reverse happens. ATP is broken down into ADP and Pi releasing energy. This energy used for a number of cellular processes.
• ATP -energy out-> ADP +Pi
• Examples of cellular processes that use energy are:

  • Protein synthesis
  • Cell division
  • Muscle contraction
  • Transmission of nerve impulses
• Some energy is also lost as heat.
• Aerobic respiration is the breakdown of glucose in the presence of Oxygen.
• Stage 1

  Glucose → Pyruvate

  This yields a small quantity of ATP.
• Stage 2 (oxygen required)

  Pyruvate → Carbon Dioxide + Water

  This yields a large amount of energy.

  The products here are carbon dioxide and water, completing the full breakdown of glucose.
• Respiration can be summarised in the following equation:

  Glucose + Oxygen → Carbon Dioxide + Water (ATP)
• It starts in the cytoplasm and ends in the mitochondria.
• It initially yields 2 molecules of ATP (stage 1) and further releases a lot of energy to produce a large number of ATP.
• As most energy is produced in the mitochondria, cells requiring a lot of energy will have a lot of mitochondria in comparison to other cells.
• Fermentation in animals is the breakdown of glucose in the absence of oxygen.
• Glucose → Pyruvate ↔ Lactate
• The product of this reaction is Lactate. This reaction is reversible, and lactate can be converted back into pyruvate in the presence of oxygen.
• It only takes place in the cytoplasm and only releases a small amount of energy, enough to produce only the initial 2 molecules of ATP.
• Fermentation in plants and fungal cells is the breakdown of glucose in the absence of oxygen.
• Glucose → Ethanol + Carbon dioxide
• The products of fermentation here are Ethanol and carbon dioxide. This reaction is not reversible due to the loss of carbon dioxide.
• It only takes place in the cytoplasm and only releases a small amount of energy, enough to produce only the initial 2 molecules of ATP.