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KS3 Biology
8B Respiration

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8B Respiration
Contents
Releasing energy
The circulation system
Summary activities
The breathing system
Anaerobic respiration

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The body needs a constant supply of energy which
comes from digested food.
Glucose from digested carbohydrate is an important
substance that contains stored chemical energy .
How is digested food used by the body?
When glucose reacts with oxygen a lot of energy is
released.
The release of energy from glucose is called…
In the body’s cells, glucose and oxygen react to release
energy . Some of this is released as heat and the rest is
used by the cells.
respiration

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from the
digestive
system
from the
breathing
system
useful!useful!waste
product
exhaled
waste
product
exhaled
This type of respiration is called aerobic respiration because
energy is released with oxygen.
Respiration is the process that the body uses to release
energy from digested food (glucose):
What is respiration?
carbon
dioxideglucose oxygen water energy
How do the glucose and oxygen needed for aerobic
respiration get to the all the body’s cells?

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Aerobic respiration: word equation activity

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When something burns, heat and light energy are
released and carbon dioxide and water are also produced,
so combustion is similar to respiration.
Burning is the reaction between a fuel and oxygen.
This reaction is called combustion:
Comparing respiration and combustion
carbon
dioxidefuel oxygen water
However, combustion is different because it is not a
controlled reaction. Respiration is a controlled reaction
which slowly releases energy from food in the body’s cells
and the cells do not catch fire!

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8B Respiration
Contents
Releasing energy
The circulation system
Summary activities
The breathing system
Anaerobic respiration

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The dissolved food and
oxygen needed for
respiration are carried
around the body by the
circulation system.
The circulation system
includes the blood, blood
vessels, the heart and
the lungs.
Which part of the
circulation system
actually carries dissolved
food and oxygen to the
body’s cells?
The body’s transport system
body’s
cells
body’s
cells
lungslungs

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The blood carries oxygen and dissolved food to all the body’s
cells so that respiration can take place.
Blood

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The heart is made of very special
muscle called cardiac muscle.
This is because it has to keep
beating for the whole of a
person’s life!
If you tried to do the same action
repeatedly (like the heart does),
your muscles would get tired and
after a while stop working.
Your beating heart
For example, if you keep clenching and unclenching your
hand, it will get tired and may even start to get cramp.
Why is it important for respiration that the heart keeps
beating?

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What happens to the pulse rate whilst
someone is running?
The body needs to release more energy:
 so oxygen and glucose need to reach
muscle cells quickly;
 so blood is pumped around the body faster;
 so the pulse is faster.
Different types of activity
What happens to the pulse rate whilst
someone is sleeping?
The body needs to release less energy:
 so oxygen and glucose need to reach muscle cells slowly;
 so blood is pumped around the body slower;
 so the pulse is slower.

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8B Respiration
Contents
Releasing energy
The circulation system
Summary activities
The breathing system
Anaerobic respiration

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The breathing system is used by the body
to get the oxygen needed for respiration.
It is also use to get rid of the waste product
of respiration, the gas carbon dioxide.
Breathing in and breathing out are separate
processes in the body:
What is breathing?
Breathing in is also known as inhalation. When you inhale
you breathe in air, including oxygen, into your lungs.
Breathing out is also known as exhalation. When you
exhale you breathe out the contents of our lungs and getting
rid of the waste gas carbon dioxide.

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Inhalation

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In the lungs, oxygen travels to thousands of tiny air sacs
called alveoli. These are covered with tiny blood vessels.
The alveoli
The alveoli give the lungs a huge surface area which is equal
in size to the area of a tennis court!

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Gas exchange takes place in the alveoli–oxygen is transferred
into the blood and carbon dioxide moves out of the blood.
Each alveolus has a thin wall so that gas exchange between
Gas exchange
the lungs and the blood can take place quickly.

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Exhalation

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What are the differences between inhaled and exhaled air?
inhaled air
nitrogen (78%)
oxygen (21%)
carbon dioxide (0.04%)
other
Comparing inhaled and exhaled air
How could you test for the differences between inhaled and
exhaled air?
exhaled air
nitrogen (78%)
oxygen (17%)
carbon dioxide (4%)
other

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8B Respiration
Contents
Releasing energy
The circulation system
Summary activities
The breathing system
Anaerobic respiration

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When the body is able to supply the cells with the oxygen and
glucose that they need, it carries out aerobicaerobic respiration.
Anaerobic respiration
When the body cannot supply the cells with the oxygen
needed to break down glucose, then it has to carry out
anaerobicanaerobic respiration. Energy is released without oxygen:
Aerobic and anaerobic respiration
Aerobic respiration
carbon
dioxideglucose oxygen water energy
lactic
acid energyglucose

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When anaerobic respiration takes place, the lactic acid
produced soaks the muscle cells and prevents muscles from
doing their job. This causes fatigue and sometimes cramp.
After activity that has lead to anaerobic
respiration, the person involved pants
and breathes heavily.
This happens because they need lots of
oxygen to get rid of lactic acid that has
built up in their body.
Not enough oxygen!
lactic
acid energyglucose
carbon
dioxide
lactic
acid oxygen water

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Anaerobic respiration: word equation activity

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8B Respiration
Contents
Releasing energy
The circulation system
Summary activities
The breathing system
Anaerobic respiration

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Glossary
aerobic – The type of respiration that occurs with oxygen.
alveoli – Tiny air sacs in the lungs where gas exchange
takes place.
anaerobic – The type of respiration that occurs without
oxygen.
exhalation – The process of breathing out.
glucose – A type of sugar that the body releases energy
from during respiration.
inhalation – The process of breathing in.
respiration – The process that the body uses to release
energy from digested food.

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Anagrams

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Multiple-choice quiz