Respiration
1 of 21
© Boardworks Ltd 2011
Releasing energy
2 of 21
© Boardworks Ltd 2011
Aerobic respiration
All living organisms need a constant supply of energy.
This is because all life processes use energy.
Glucose is an important substance that contains stored
chemical energy. When glucose reacts with oxygen,
energy is released.
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.
3 of 21
© Boardworks Ltd 2011
What is respiration?
Aerobic respiration is the process of releasing energy
through the oxidation of glucose molecules.
glucose
+
oxygen 
carbon
dioxide
+
water ( + energy)
The energy is transferred to small molecules called ATP,
which cells use as an immediate source of energy.
4 of 21
© Boardworks Ltd 2011
Equation for aerobic respiration
5 of 21
© Boardworks Ltd 2011
Cells and respiration
6 of 21
© Boardworks Ltd 2011
7 of 21
© Boardworks Ltd 2011
How do cells get oxygen and energy?
8 of 21
© Boardworks Ltd 2011
Respiration and the circulatory system
9 of 21
© Boardworks Ltd 2011
10 of 21
© Boardworks Ltd 2011
How is energy used?
Cells use the ATP produced during respiration to do work.
Where might ATP be used?
 movement – enabling muscles
to contract
 thermoregulation in mammals
and birds
 biosynthesis – building new
molecules, cells and tissues
 active transport – moving molecules against a
concentration gradient.
11 of 21
© Boardworks Ltd 2011
Building new molecules
12 of 21
© Boardworks Ltd 2011
13 of 21
© Boardworks Ltd 2011
Respiration during exercise
During exercise several
changes occur:
 the heart rate increases
 the rate and depth of
breathing increases
 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.
14 of 21
© Boardworks Ltd 2011
How does exercise affect heart rate?
15 of 21
© Boardworks Ltd 2011
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?
16 of 21
© Boardworks Ltd 2011
Testing for the products of respiration
17 of 21
© Boardworks Ltd 2011
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) =
18 of 21
CO2 produced
O2 used
© Boardworks Ltd 2011
19 of 21
© Boardworks Ltd 2011
Glossary
20 of 21
© Boardworks Ltd 2011
Multiple-choice quiz
21 of 21
© Boardworks Ltd 2011