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Respiration – Revision Pack (B3)
Aerobic Respiration:
The symbol equation for aerobic respiration:
C6H12O6 + 6O2→ 6CO2 + 6H2O
Glucose + oxygen → carbon dioxide + water
Measuring Respiration Rate:
Two different experiments can be used to measure rate of respiration. These two
ways involve:
-
Measuring how much oxygen is used up (the faster it’s consumed, the faster
the respiration rate
The rate at which carbon dioxide is made
The rate of oxygen consumption can be used as an estimate of metabolic rate
because aerobic respiration requires oxygen using the respiratory quotient (RQ)
formula:
RQ = carbon dioxide produced / oxygen used
The rate of respiration is influenced by changes in temperature and pH. This is
because enzymes are involved in respiration, and their activity varies with
temperature and pH.
Anaerobic Respiration:
Muscles often don’t receive sufficient oxygen during exercise. They start to use
anaerobic respiration as well as aerobic respiration. The word equation is:
Glucose  Lactic Acid (+ energy)
Anaerobic respiration makes lactic acid which builds up in muscles. This can cause
extreme pain and fatigue (tiredness).
It also released much less energy per glucose molecule than aerobic respiration.
Oxygen debt is when the incomplete breakdown of glucose results in the build up of
lactic acid.
Sometimes during recovery the heart rate and breathing rate stay high; this is
because:
-
Rapid blood flow allows the lactic acid to be carried away to the liver
Extra oxygen can be supplied, enabling the liver to break down the lactic
acid
ATP:
ATP is a substance that is used as the energy source for many processes in cells. ATP
is produced as a result of respiration. For example, one glucose molecule can
release enough energy during respiration for the production of:
Respiration – Revision Pack (B3)
-
38 ATP molecules by aerobic respiration
-
2 ATP molecules by anaerobic respiration
PPQ(1):
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PPQ(2):
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PPQ(3):
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Mark Schemes:
PPQ(1):
PPQ(2):
PPQ(3):
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PPQ(4):
PPQ(5):
PPQ(6):