1.8

• ATP (Adenosine Triphosphate)


  High-energy chemical
• Glucose


  A simple sugar used by cells for respiration
• Glycogen


  Animals store glucose as glycogen in their liver and muscle tissues
• Glycolysis


  1. The process by which glucose (the respiratory substrate) is broken down into pyruvate

  2. Involves the phosphorylation of glucose and intermediates (during the energy investment stage) which leads to the generation of more ATP during the energy pay off stage

  3. Results in a net gain of ATP
• Liver


  The large organ, beside the stomach, which has many functions, including processing substances absorbed by the digestive system and a role in the storage of the body's carbohydrate
• Myoglobin


  Oxygen-storing protein
• Oxygen debt


  The amount of extra oxygen required by the body for recovery after vigorous exercise
• Pyruvate


  The substance produced by the breakdown of glucose in the cytoplasm during the first stage of aerobic respiration and fermentation
• Oxygen debt during long periods of vigorous activity

  1. Lactate levels accumulate

  2. Build-up of lactate produces an oxygen debt

  3. Glycogen reserves in the muscles become low as more glucose is used for respiration

  4. Muscle fatigue occurs
• After exercise


  1. Oxygen debt is repaid when exercise is complete

  2. Allows respiration to provide the energy to convert lactate back to pyruvate and glucose in the liver

  3. Glycogen levels in the liver and muscles can then be restored

  4. Breathing rate and heart rate do not return to normal straight away as these processes require oxygen
• During vigorous exercise, the muscle cells do NOT get sufficient oxygen to support the electron transport chain
• Lactate metabolism in the fermentation pathway

  1. Pyruvate is converted to lactate

  2. Occurs in the cytoplasm of the cell

  3. Muscles continue to contract, but less efficiently

  4. Involves the transfer of hydrogen ions from the NADH, produced during glycolysis, to pyruvate in order to produce lactate

  5. Removal of hydrogen ions for NADH regenerates the NAD needed to maintain ATP production through glycolysis
• Lactate metabolism results in much less ATP being produced in the fermentation pathway than in aerobic respiration
• Justify


  You must give reasons to support the SQA's suggestions or conclusions, e.g. this might be by identifying an appropriate relationship and the effect of changing variables
• Outline


  Provide a brief summary of the content. It should be more detailed than just listing, but not as detailed as describe
• Predict


  You must suggest what may happen based on available information
• Show that


  You must use biological knowledge and mathematics to prove something, e.g. a given value
• Types of skeletal muscle

  • Slow-twitch muscle fibres
  • Fast-twitch muscle fibres
• Slow-twitch muscle fibres


  • Contract relatively slowly but can sustain contractions for longer as they use oxygen well
  • Useful for endurance activities such as long-distance running, cycling or cross-country skiing
• Fast-twitch muscle fibres


  • Contract relatively quickly, over short periods as they do not use oxygen well
  • Useful for activities such as sprinting or weight-lifting
• Most human muscle tissue contains a mixture of both slow-and fast-twitch muscle fibres
• Athletes show distinct patterns of muscle fibres that reflect their sporting activities