B9: Respiration


B9.1: Aerobic Respiration

  • cellular respiration is an exothermic reaction that occurs continuously in living cells.

glucose + oxygen -----> carbon dioxide + water + energy transferred to the environment. 

  • the energy transferred supplies all the energy needed for living processes. 
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B9.2: The Response to Exercise

  • the energy that is transferred during respiration is used to enable muscles to contract.
  • during exercise the human body responds to the increased demand for energy.
  • body responses to exercised
    • increased heart rate, breathing rate and breath volume
    • glycogen stores in muscles are converted to glucose for cellular respiration.
    • the flow of oxygenated blood to the muscles increases.
  • these act to increase the supply of glucose and oxygen to muscles are removal of carbon dioxide from the muscles. 
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B9.3: Anaerobic Respiration

  • if muscles work for a long time, they become fatigues and don't contract efficiently. if they don't get enough oxygen they respire anaerobically. 
  • anaerobic respiration is respiration without oxygen. glucose is incompletely broken down and forms lactic acid in animals. 
  • the anaerobic breakdown of glucose produces less energy that aerobic respiration.
  • after exercise oxygen is needed to break down the lactic acid. the amount of oxygen needed is called oxygen debt.
  • anaerobic respiration in plants and some microorganisms like yeast produce ethanol and carbon dioxide. 
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B9.4: Metabolism and the Liver

  • metabolism is the sum of all the reactions in the body
  • the energy transferred by respiration in cells is used by an organism for the enzyme-controlled processes of metabolism which creates new molecules.
  • metabolism includes the converion of glucose to starch, glycogen and cellulose. 
  • it also includes the formation of lipid molecules, the use of glucose and nitrate ions to form amino acids which are used to synthesise proteins and breakdown excess protein into urea. 
  • blood flows through the muscles and transports lactic acid to the liver where it is converted back into glucose. 
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