Gas Exchange

Cells require a lot of energy to perform all the tasks they need to perform; can you think of any examples of those tasks?

Nerve impulses, active transport of molecules, muscle contraction, warmth

To do these tasks the cell requires chemical energy from glucose, and atmospheric oxygen

For single-celled organisms, glucose and oxygen can simply diffuse over the cell membrane on its own.

But what about a cell contained deep within a big organism like an elephant or a human?

It needs a complex system to transport the molecules to cells

The heart pumps blood to the lungs where it picks up oxygen. This oxygen diffuses into the blood and is carried on a special protein called "haemoglobin"

This oxygen-rich blood is sent back to the heart, where it is pumped to the body

On the way, the blood picks up the carbon dioxide waste and is returned to the heart

There are a few experiments that can be done in the lab to investigate exercise and breathing.

You can detect carbon dioxide in gases by using lime water.

You can also measure the rate and amount of breathing.

There are certain diseases that impede the ability of gas to exchange properly. Can you think of any?

Pollution kills around 9400 people in London every year

Breathing in smoke and fumes can cause blockages in the alveoli

Pollution can also cause an asthma attack

Asthma is a condition caused by inflammation of the airways and lungs

Asthma causes wheezing, breathlessness, chest tightness, and coughing at night or early in the morning

It is caused by inflammation (what does that mean?)

Asthma can be treated with anti-inflammatory medicine

Asthma attacks can be serious

Smoking is one of the leading causes of lung disease and kills around 7 million people per year (incl one million non-smokers)

It contains chemicals which damage DNA, which can lead to cancer

It also causes tar to block up alveoli

It also causes inflammation

People used to think smoking was healthy!

When carbon dioxide is absorbed in the blood, it is made up of an acid (carbolic acid)

The brain can detect the pH of the blood

When the pH drops, it speeds up the rate of breathing to expel the carbon dioxide

People with severe lung disease often have acidic blood due to this and have a fast pulse and breathing. This can be fatal