Respiration

• Principles of Respiration


  Cellular respiration is an exothermic reaction which is continuously occurring in living cells.

  The chemical process of respiration releases energy.

  The energy transferred supplies all the energy needed for living processes to occur in organisms as a whole.
• Uses of Energy Released from Respiration

  Chemical reactions to build larger molecules from smaller molecules e.g. protein synthesis.

  Muscle contraction to allow movement.

  Keeping warm to maintain suitable body temperature for enzyme action.
• Aerobic Respiration

  Glucose + Oxygen → Carbon Dioxide + Water.

  C6H12O6 + 6O2 → 6CO2 + 6H2O.

  Takes place in the mitochondria.
• Anaerobic Respiration

  Glucose → Lactic Acid.

  Respiration without oxygen. Results in the incomplete breakdown of glucose into lactic acid.

  Occurs when the body can't supply enough oxygen for aerobic respiration e.g. during vigorous exercise.

  Releases much less energy than in aerobic respiration because oxidation of glucose is incomplete.
• Anaerobic Respiration in Plants and Yeast Cells

  Glucose → Ethanol + Carbon Dioxide.

  Anaerobic respiration in yeast cells is called fermentation.

  Fermentation is economically important in the manufacture of bread (release of CO2 causes bread to rise) and alcoholic drinks (ethanol is a type of alcohol).
• Comparisons between Aerobic and Anaerobic Respiration

  .

  A) Needed/Not Needed

  B) Needed/Not Needed

  C) Complete/Incomplete

  D) Complete/Incomplete

  E)

  F) In Animal Cells and in Yeast

  G) A lot/A little

  H) A lot/A little

  
• Response to Exercise

  When exercising, the number of muscle contractions increases, therefore there is a greater energy demand, which means that the muscles need more oxygen for aerobic respiration.

  Body reacts to increased demand of oxygen by increasing breathing rate and breath volume and increasing heart rate so that more oxygenated blood is supplied to the muscles.
• Response to Vigorous Exercise

  During vigorous exercise, the body may not be able to supply sufficient oxygen to the muscles.

  Therefore some of the energy will have to come from anaerobic respiration.

  Anaerobic respiration releases much less energy and results in formation of lactic acid as a waste product.

  An oxygen debt is created causing individual to continue breathing heavily after exercise stops.

  Muscles become fatigued and stop contracting efficiently due to lactic acid build-up.
• Oxygen Debt

  After vigorous exercise, the body must deal with the build-up of lactic acid by oxidising it to form carbon dioxide and water, resulting in the individual continuing to breathe heavily when exercise stops.

  Oxygen debt is the amount of extra oxygen needed after exercise to react with the accumulated lactic acid and remove it from cells.
• Metabolism

  The sum of all reactions in a cell or the body and these reactions happen all the time.

  The energy transferred by respiration in cells is used for the continual enzyme controlled processes of metabolism that synthesise new molecules.

  Enzymes control all the reactions occurring in cells; often the products of one reaction are the reactants of another.
• Metabolic reactions

  Conversion of glucose into cellulose in plants to build and strengthen cell walls.

  Conversion of glucose into glycogen in animals and starch in plants for storage.

  Formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids to form triglycerides which are used for insulation and energy storage.

  Use of glucose and nitrate ions to form amino acids which are used to synthesise proteins in plants.

  Breakdown of glucose in respiration to release energy.

  Breakdown of excess proteins to form urea for excretion in animals.