Topic 4 - Bioenergetics

• Metabolism

  The sum of all reactions in a cell or the body. The energy transferred in the cells by repiration is used in the processes (controlled by enzymes) of metabolism to make new molecules
• Examples of metabolic reactions

  1. Glucose molecules being conveyed to starch, glycogen and cellulose by being joined together.
  2. A glycerol molecule and 3 molecules of fatty acids forming a lipid molecule
  3. Glucose and nitrate ions forming amino acids to form proteins
  4. reactions in respiration
  5. Urea foing from breakdown of proteins
• Respiration (endo or eox)

  Exothermic as eerily transferred to surroundings

  Can take place aerobicslly (with oxygen) or anaerobically (without oxygen)
• Aerobic respiration

  Uses oxygen, yeilds the most energy, most of the reactions that make up it occur in the mitochondria
• aerobic respiration equation


  Glucose + oxygen = carbon dioxide + water

  C6H12O6 + O2 = CO2 + H2O
• anaerobic respiration

  occurs when there is not enough oxygen, does not yield as much energy as aerobic, used as last resort, eg during a sprint, oxidation of glucose is incomplete
• Anaerobic respiration equation


  In animals:

  glucose - lactic acid

  In plants :

  glucose - ethanol + carbon dioxide
• Response to exercise


  More energy needed for muscle contraction, so respiration has to occur faster, so more oxygen needs to be supplied to cells, done by:

  1. Heart rate increasing
  2. breathing rate increasing
  3. breath volume increasing
• oxygen debt


  If not enough oxygen then anaerobic used. Lactic acid is a byproduct and builds up creating oxygen debt.

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


  Muscle tire and don’t contract properly. Blood flowing through the muscles transports the lactic acid to the liver where it is converted back to glucose
• Uses of glucose from photosynthesis

  1. Respiration
  2. converted into insoluble starch for storage (in roots, stems and leaves)
  3. To produce fat or oil for storage (in seeds)
  4. To produce cellulose to strengthen cell walls
  5. Combined with nitrates top form amino acids which produce proteins
• photosynthesis

  the process by which plants make glucose from sunlight. It is an endothermic reaction in which energy is transferred from the environment to the chloroplasts by light
• Photosynthesis equation


  Carbon dioxide + water -- light-- glucose + oxygen
• Factors affecting rate of photosynthesis

  1. Temperature
  2. light intensity
  3. carbon dioxide concentration
  4. amount of chlorophyll
• Factor: temperature


  An increase in temperature means increase in rate. As reaction is controlled by enzymes the trend continues up to a certain temperature until the enzymes begin to denature and rate of reaction decreases
• Factor: light intensity


  For most plants, higher the light intensity, the faster the rate of reaction
• Carbon dioxide concentration


  Carbon dioxide is needed to make glucose. As concentration of CO2 increases, so does the rate of reaction
• Factor: amount of chlorophyll


  Chlorophyll is essential. If levels are decreased through a magnesium deficiency, then the rate also decreases
• Rate of photosynthesis required practical

  1. Pondweed is placed in a test tube full with water and top is sealed with a bung.
  2. A capillary tube also containing water leads into the test tube, and is attached with a syringe
  3. A lamp is placed at a measured distance from the test tube
  4. oxygen is priced forming a gas tube in the capillary tube
  5. the distance the bubble has moved is measured using a ruler to calculate volume odd oxygen produced.
  6. Repeat with distant distance from lamp to test light intensity as a factor
• Limiting factors


  Any of the factors may become a limiting factor. This is a n environmental condition which in low levels restricts any increase in photosynthesis. Despite increases in other factors the rate will not increase any more. This can be seen on a graph as the curve levels off.
• Knowledge of limiting factors in farming


  Can enhance the conditions in a greenhouse for greater rate of photosynthesis which will increase growth leading to increase profits.
• Inverse proportion


  Describes a relationship between two factors which involving one increasing while one decreasing. The light intensity is inversely proportional to the sauté of the distance called the inverse square law.

  Light intensity ∝ 1/distance 2