Respiration

• The primary source of energy in cells is

  glucose.
• The chemical energy in glucose cannot be used

  directly by cells.
• The energy is converted into a usable form by

  the process called respiration.
• Respiration involving oxygen is known as

  AEROBIC respiration.
• Respiration in the absence of oxygen is

  known as FERMENTATION.
• Heat energy is released by a respiring

  organism
• Glucose is the main source of energy in a

  living cell.
• Organisms use energy for:

  
  

  -Muscle cell contraction

  
  

  -Cell division

  
  

  -Protein synthesis

  
  

  -Transmitting nerve impulses
• Energy released by respiration is stored

  in the form of adenosine triphosphate

  (ATP)
• Glycolysis

  
  

  -Does not require oxygen

  
  

  -Occurs in cytoplasm

  
  

  -Each molecule of glucose is broken

  down into 2 pyruvate molecules and

  generates 2 molecules of ATP in the

  process.
• Aerobic stage

  
  

  -Takes place in the mitochondria.

  
  

  -When oxygen is available, each

  molecule of pyruvate is broken down

  completely into carbon dioxide and

  water.

  
  

  -This releases enough energy to yield

  a large number of ATP molecules

  (36 molecules of ATP).
• Fermentation – takes place in the

  cytoplasm
• Lactate and O2 debt

  
  

  Animal cells

  
  

  -Lactate builds up in muscle (working)

  cells and bloodstream and causes muscle

  fatigue

  
  

  -O2 required to breakdown lactate.

  
  

  -Body has built up an O2 debt

  
  

  -Debt repaid during rest period

  
  

  -Lactate converted back to pyruvate and

  enters aerobic respiration