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1 of © Boardworks Ltd 2011 Respiration
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Respiration
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Releasing energy
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Aerobic respiration
Glucose is an important substance that contains stored chemical energy. When glucose reacts with oxygen, energy is released.
All living organisms need a constant supply of energy. This is because all life processes use energy.
This reaction is called aerobic respiration. It takes place continuously in plants and animals, and in some micro-organisms.
Respiration is controlled by enzymes. Like other enzyme-controlled reactions, it can be affected by pH and temperature.
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What is respiration?
Aerobic respiration is the process of releasing energy through the oxidation of glucose molecules.
The energy is transferred to small molecules called ATP, which cells use as an immediate source of energy.
oxygencarbondioxide
glucose + + water ( energy)+
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Equation for aerobic respiration
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Cells and respiration
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How do cells get oxygen and energy?
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Respiration and the circulatory system
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How is energy used?
Cells use the ATP produced during respiration to do work.
movement – enabling muscles to contract
Where might ATP be used?
thermoregulation in mammals and birds
active transport – moving molecules against a concentration gradient.
biosynthesis – building new molecules, cells and tissues
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Building new molecules
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Respiration during exercise
the arteries supplying the muscles dilate.
These changes increase blood flow to the muscles, which increases the supply of oxygen and glucose and removes carbon dioxide more quickly.
During exercise several changes occur:
the heart rate increases
the rate and depth of breathing increases
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How does exercise affect heart rate?
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Heart calculations
Heart rate gives a measure of how healthy a person’s heart is, but there are also two other important measurements:
cardiac output is the volume of blood that is pumped by the heart each minute
stroke volume is the volume of blood pumped with each heartbeat.
cardiac output = stroke volume × heart rate
Andrew’s resting heart rate is 70 bpm and his stroke volume is 60 ml. When he exercises, his heart rate increases to 140 bpm and his stroke volume increases to 120 ml.
What is the increase in his cardiac output in litres per minute?
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Testing for the products of respiration
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Respiration rate
Aerobic respiration uses oxygen and produces carbon dioxide.
An increase in the rate of oxygen use and carbon dioxide production indicates an increase in the overall rate of respiration.
Measuring the rate of oxygen consumption can give an estimate of the metabolic rate. This measure indicates how quickly the body is using energy from respiration.
respiratory quotient (RQ) = O2 used
CO2 produced
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Glossary
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Multiple-choice quiz
