1.1 The chemical reactions inside cells are controlled by enzymes.
1.1.1 During aerobic respiration (respiration that
uses oxygen) chemical reactions occur that use
glucose and oxygen and release energy.
18.104.22.168 Aerobic respiration takes place continuously in both plants and animals.
22.214.171.124.1 Most of the reactions in aerobic respiration take place inside mitochondria.
126.96.36.199.1.1 Aerobic respiration is summarised by the equation:
glucose + oxygen ➞ carbon dioxide + water (+ energy)
188.8.131.52.1.1.1 Energy that is released during respiration
is used by the organism. The energy may
be used to build larger molecules from
smaller ones, to enable muscles to contract
in mammals and birds, to maintain a steady
body temperature in colder surroundings in
plants and to build up sugars, nitrates and
other nutrients into amino acids which are
then built up into proteins.
184.108.40.206.220.127.116.11 During exercise the heart rate increases and the
rate and depth of breathing increases.
18.104.22.168.22.214.171.124.1 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.
126.96.36.199.188.8.131.52.1.1 Muscles store glucose as
glycogen, which can then be
converted back to glucose for
use during exercise.
2 B2.6.2 Anaerobic Respiration
2.1 During exercise, if insufficient oxygen is reaching the muscles they
use anaerobic respiration to obtain energy.
2.1.1 Anaerobic respiration is the
incomplete breakdown of
glucose and produces lactic
184.108.40.206 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.
220.127.116.11.1 If muscles are subjected to long periods of vigorous activity they become fatigued; 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.