GCSE AQA Biology 2 Respiration & Exercise

GCSE AQA Biology 2 Respiration & Exercise

1. Respiration

   • Involves reactions catalysed by enzymes
   • All living things respire to release energy from food
   • Respiration: The process of releasing energy from glucose, which goes on in every cell

2. Aerobic respiration

   • Respiration using oxygen
     • Most efficient way to release energy from glucose
   • Goes on all the time in plants & animals
   • Most reactions happen inside mitochondria
   • Glucose + oxygen ---> carbon dioxide + water + ENERGY
   • Energy released is used to...
     • Build up larger molecules from smaller ones
       • Like proteins from amino acids
     • (In animals) allow muscles to contract
       • Which allows them to move about
     • (In mammals & birds) keep body temp. steady
     • (In plants) build sugars, nitrates & other nutrients into amino acids, then proteins

3. Exercise increases heart rate

   • Muscles made of muscle cells - aerobically respire to contract muscles
     • Increase in muscle activity requires more glucose & oxygen to be supplied & extra carbon dioxide to be removed - blood has to flow at faster rate
   • Physical activity increases...
     • Breathing rate & makes you breathe more deeply - to meet demand for extra oxgen
     • Speed at which heart pumps

4. Glycogen is used during exercise

   • Some glucose from food stored as glycogen
   • Glycogen mainly stored in liver - each muscle has own store
   • During vigorous exercise, muscles use glucose rapidly - some of the glycogen is converted back to glucose (to provide more energy)

5. Anaerobic respiration

   • Respiration without oxygen
     • Doesn't release as much energy as aerobic
   • Incomplete breakdown of glucose
     • Glucose ---> ENERGY + lactic acid
   • Causes lactic acid build up in muscles - painful & causes muscle fatigue
     • Muscle fatigue: when muscles get tired & stop contracting efficiently
   • Can allow use of muscles for longer
   • Leads to oxygen debt
     • Have to 'repay' oxygen that didn't reach muscles in time
       • Have to breathe hard for a while after stopping to get more oxgygen into blood - blood flows through muscles to remove lactic acid by oxidising it to carbon dioxide & water
         • While high levels of carbon dioxide & lactic acid detected - pulse & breathing rate stay high