Year 8 Biology Topic Respiration

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KS3 Biology

8B Respiration


8B Respiration

Contents

Releasing energy

The circulation system

Summary activities

The breathing system

Anaerobic respiration


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


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?

carbondioxideglucose oxygen water energy

How do the glucose and oxygen needed for aerobic respiration get to the all the body’s cells?


Aerobic respiration: word equation activity


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

carbondioxidefuel 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!


8B Respiration

Contents

Releasing energy


Summary activities




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’scells

body’scells

lungslungs


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

Blood


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?


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.


8B Respiration

Contents

Releasing energy


Summary activities




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.


Inhalation


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 equalin size to the area of a tennis court!


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.


Exhalation


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


8B Respiration

Contents

Releasing energy


Summary activities




When the body is able to supply the cells with the oxygen and glucose that they need, it carries out aerobicaerobic respiration.

Anaerobic respirationWhen the body cannot supply the cells with the oxygen needed to break down glucose, then it has to carry out anaerobic anaerobic respiration. Energy is released without oxygen:

Aerobic and anaerobic respiration

Aerobic respiration

carbondioxideglucose oxygen water energy

lacticacid energyglucose


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!

lacticacid energyglucose

carbondioxide

lacticacid oxygen water


Anaerobic respiration: word equation activity


8B Respiration

Contents

Releasing energy


Summary activities




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.


Anagrams


Multiple-choice quiz

Year 8 Biology Topic Respiration

Technology

alveoli oxygen

oxygen travels

bloodthe blood carries

waste product of respiration

digested food glucose

body slower

release of energy

muscle cells