Respiration

• We need energy for movement. Humans and other mammals need energy to keep warm. Lastly, we need energy for chemical reactions to build larger molecules. For example, proteins are made by chemically joining amino acids.
• The energy we need is supplied by a process called cellular respiration.
• Respiration is an exothermic reaction because it releases energy, and respiration takes place continually in all living cells.
• There are two types of respiration: aerobic respiration, and anaerobic respiration.
• What is the word equation for aerobic respiration?

  Here it is, but in a picture.

  
• Aerobic respiration releases a great deal of energy. This is because the glucose molecule has been fully oxidised.
• What is the symbol equation for aerobic respiration?

  Here it is, but in a picture.

  
• Muscle cells, need a great deal of energy for contraction. But under certain conditions, the amount of oxygen is limited. When there is a shortage of oxygen, muscle cells respire anaerobically.
• What is the word equation for anaerobic respiration?

  Here it is, but in a picture.

  
• Anaerobic respiration does not require any oxygen. Anaerobic respiration releases much less energy than aerobic respiration. This is because in anaerobic respiration, the oxidation of glucose is incomplete.
• Anaerobic respiration can also take place in plant cells and in yeast cells.
• Anaerobic respiration equation in plant and yeast cells.

  Here it is, but in a picture.

  
• Anaerobic respiration in yeast cells is called fermentation, we use this reaction to make alcoholic drinks, like beer.
• The alcohol in these drinks is ethanol, and that is produced by fermentation.
• We use yeast to make bread, and here the carbon dioxide produced by fermentation is useful. This creates bubbles in the dough, causing the bread to rise.
• Cellular respiration is the process of transferring energy from the breakdown of glucose.

  • It is a universal chemical process which is continuously occurring in all living cells.
  • Every process happening in your body requires energy.
• The energy transferred by respiration cannot be immediately or directly used by the cell.

  • Energy is stored in the form of a special molecule of called ATP.
  • ATP can then be used in cellular processes where energy is required.
  • An analogy of ATP is a rechargeable battery which can store potential energy and release it as kinetic energy.
  • Once the energy has been depleted the battery can be recharged.
• Cellular respiration is controlled by enzymes, consequently the rate can be affected by temperature and pH.
• Although most of the energy generated through respiration uses glucose as a substrate, organisms can break down other molecules to be used in respiration.

  • Proteins, lipids (fats) and other carbohydrates can all be utilised.
• Most aerobic respiration takes place in the mitochondria.

  • Aerobic respiration is the complete breakdown of glucose to release a relatively large amount of energy for use in cell processes and reactions.
  • Large amounts of energy in the form of ATP can be generated.
  • Aerobic respiration can produce approximately 32 molecules of ATP per molecule of glucose.
• Cellular respiration is an exothermic reaction as it transfers energy to the environment in the form of heat.

  • This is one of the reasons why our bodies heat-up when we exercise.
  • The heat generated through aerobic respiration.
• Anaerobic respiration releases much less energy than aerobic respiration as it involves the incomplete breakdown of glucose.

  • Only 2 molecules of ATP are produced for every molecule of glucose.
• Anaerobic respiration in animals:

  • Bodies can only deliver so much oxygen to muscle cells for aerobic respiration.
  • When oxygen becomes a limiting factor, glucose is broken down without it, producing lactic acid instead.
  • The glucose has not been fully broken down meaning there is still energy stored within the bonds of lactic acid molecules.
• Lactic acid and oxygen debt:

  • Lactic acid builds up in muscle cells and lowers the pH of the muscle tissue (making the conditions more acidic).
  • Acidic conditions can denature the enzymes in cells.
  • Lactic acid will eventually be broken down using oxygen to produce carbon dioxide and water as waste products.
  • The amount of oxygen required to break down the lactic acid that has built up is referred to as the 'oxygen debt'
  • The process of breaking down the lactic acid is known as ‘repaying the oxygen debt’.
• Anaerobic respiration in plants and fungi:

  • Plants and fungi can respire without oxygen as well, breaking down glucose in the absence of oxygen to produce ethanol and carbon dioxide.
  • Under certain conditions plants need to utilise anaerobic respiration.
  • If plants are in waterlogged soil, there is little or no oxygen available.
  • The plant root cells will respire anaerobically.
• Anaerobic respiration in yeast (a unicellular fungi) is called fermentation.

  • Fermentation is economically important in the manufacture of bread (where the carbon dioxide produced helps the dough to rise) and in brewing (where the ethanol produced makes beer).
• Comparing Aerobic & Anaerobic Respiration Table:


  Here it is...