respiration

• The chemical energy stored in glucose must be released by all cells through a series of enzyme-controlled reactions called respiration.  
• The living organisms are unable to use energy from glucose directly and so uses the energy released from the breakdown of glucose to make ATP which the body can use
• The energy from the breakdown of glucose is used to build up ATP from ADP and Pi.
• 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.
• how is atp made from the breakdown of glucose?

  A) ADP

  B) pi

  
• how is energy released when it is needed from the stored atp?

  A) ADP

  B) pi

  
• Examples of cellular processes that use energy are:

  • Protein synthesis
  • Cell division
  • Muscle contraction

  Some energy is also lost as heat.
• aerobic respiration: glucose + oxygen → carbon dioxide + water + energy
• aerobic respiration stage 1:

  During aerobic respiration glucose is broken down to two molecules of pyruvate, releasing enough energy to yield two molecules of ATP. occurs in the cytoplasm.
• aerobic respiration stage 1:

  A) 2 ATP

  B) pyruvate

  C) pyruvate

  
• In the second stage of aerobic respiration, each pyruvate is broken down to carbon dioxide and water, releasing enough energy to yield a large number of ATP molecules. occurs in the mitochondria
• 2nd stage of aerobic respiration:

  A) many ATP

  B) carbon dioxide + water

  
• Since the second stage of aerobic respiration releases the greatest number of ATP and takes place in the mitochondria, the higher the energy requirement of a cell the greater the number of mitochondria present in that cell. For example a muscle cell which requires a lot of energy in order to contract will have a greater number of mitochondria than a skin cell.
• The pyruvates can only be broken down into many atp if oxygen is present, 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.