Biology Unit 2.6 - Aerobic and Anaerobic Respiration

Biology Unit 2.6 - Aerobic and Anaerobic Respiration

1. Aerobic Respiration

   • The chemical reactions inside cells are controlled by enzymes
   • During aerobic respiration (respiration that uses oxygen) chemical reactions occur that...
     • use glucose and oxygen
     • release energy
   • Aerobic respiration is continuous in both animals and plants
   • Most of the reactions in aerobic respiration take place inside mitochondria
   • Aerobic respiration is summarised by the equation... glucose + oxygen -> carbon dioxide + water +energy
   • Energy that is released during respiration is used by the organism The energy may be used...
     • To build larger molecules from smaller ones
     • In animals, to enable muscles to contract
     • In mammals and birds, to maintain a steady body temperature in colder surroundings
     • In plants to build up sugars, nitrates and other nutrients into amino acids which are then built up into proteins
   • During exercise a number of changes take place...
     • The heart rate increases
     • The rate and depth of breathing increases
     • These changes increase the blood flow to the muscles and so increase the supply of sugar and oxygen and increase the rate of removal of carbon dioxide
   • Muscles store glucose as glycogen which can then be converted back to glucose for use during exercise

2. Anaerobic Respiration

   • During exercise, if insufficient oxygen is reaching the muscles they use anaerobic respiration to obtain energy
   • Anaerobic respiration is the incomplete breakdown of glucose and produces lactic acid (OUCH!!!)
   • As the breakdown of glucose is incomplete, much less energy is released than during aerobic respiration
     • Anaerobic respiration results in an oxygen debt that has to be repaid in order to oxidise lactic acid to carbon dioxide and water
   • If muscles are subjected to long periods of vigorous activity they become fatigued, i.e. they stop contracting efficiently
     • One cause of muscle fatigue is the build-up of lactic acid in the muscles. Blood flowing through the muscles removes the lactic acid.