1 of 33© Boardworks Ltd 2008. 2 of 33© Boardworks Ltd 2008 Releasing energy.

1 of 33 © Boardworks Ltd 2008


Releasing energy


How is digested food used by the body?

Glucose, from digested carbohydrates, is an important substance that contains stored chemical energy.

When glucose reacts with oxygen, a lot of energy is released.

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.

What is the release of energy from glucose called?

The body needs a constant supply of energy which comes from digested food.


What is respiration?

Respiration is the process that the body uses to release energy from digested food (glucose):

This type of respiration is called aerobic respiration because energy is released in the presence of oxygen.

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

oxygencarbondioxide

glucose + + water ( energy)+

from the digestive system

from the respiratory

system

waste product

(exhaled)

waste product

(exhaled)


Testing for the products of respiration


How do cells get oxygen and glucose?


The equation for aerobic respiration


Respiration and combustion

Burning is the reaction between a fuel and oxygen. This reaction is called combustion:

During combustion, heat and light energy are released and carbon dioxide and water are also produced, so combustion is similar to respiration.

The difference between combustion and respiration is that combustion is not a controlled reaction. Respiration is a controlled reaction that slowly releases energy from food in the body’s cells and the cells do not catch fire!

fuel oxygen carbon dioxide water+ +


Respiration and combustion


The circulatory system


Circulation

The dissolved food and oxygen needed for respiration are carried around the body by the circulatory system.

Which part of the circulatory system actually carries dissolved food and oxygen to the body’s cells?

The circulatory system includes the blood, blood vessels, the heart and the lungs.


Blood


Your beating heart

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.

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?


Ideas about circulation


Measuring pulse

The heart pumps blood around the body in the blood vessels. Each time it pumps it causes the blood vessels to throb. This is called a pulse.

1. Hold out one hand with the palm facing up.

3. Press these fingers lightly on the underside of the other wrist, just under the thumb bone.

2. Put the index and middle fingers of your other hand together.

To take your pulse:


Different types of activity

During sleep, the pulse falls. This causes blood to be pumped around the body more slowly. This means that oxygen and glucose take longer to reach muscle cells.

During exercise, the pulse rises. This causes blood to be pumped around the body more quickly, which increases the amount of oxygen and glucose that can reach muscle cells.

What happens to the pulse while someone is running?

What happens to the pulse while someone is sleeping?


The breathing system


What is breathing?

The breathing system is used by the body to get the oxygen needed for respiration.

Breathing in and breathing out are separate processes in the body.

It is also used to get rid of one of the waste products of respiration: the gas, carbon dioxide.

Breathing in is called inhalation. When you inhale, you breathe air, including oxygen, into your lungs.

Breathing out is called exhalation. When you exhale you breathe out the contents of your lungs and get rid of the waste gas carbon dioxide.


Inhalation and exhalation


The alveoli


Gas exchange


Comparing inhaled and exhaled air

What are the differences between inhaled and exhaled air?

How could you test for the differences between inhaled and exhaled air?

Inhaled Air Exhaled Air

Oxygen: 21% Oxygen: 16%

Carbon dioxide: 0.04% Carbon dioxide: 4%

Water vapour: small amount

Water vapour: large amount

What are the main differences?


Respiration


Anaerobic respiration


Aerobic and anaerobic respiration

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

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

lactic acidglucose energy+

oxygencarbondioxide

glucose + + water ( energy)+


Not enough oxygen!

When anaerobic respiration takes place, lactic acid is also produced.

glucose lactic acid energy+

After exercise the body needs to remove the lactic acid before it causes damage to cells.

Lactic acid builds up in the muscle cells and prevents the muscles doing their job. This is thought to cause fatigue and sometimes cramp.


Oxygen debt

The amount of oxygen needed to remove all the lactic acid after exercise is called an oxygen debt.

oxygen waterlactic acid carbon dioxide+ +

After activity that has lead to anaerobic respiration, the person involved breathes heavily and their heart rate remains high to supply the body with the oxygen it needs.

Lactic acid is broken down by oxygen.


How does running affect your pulse?


Anaerobic respiration equations


Summary activities


Glossary


Anagrams


Multiple-choice quiz

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