The

is the top part of the body, it is separated from the lower part by the

The lungs are protected by the

and are surrounded by

When air is breathed in, it passes through the

and splits into two tubes called

which split progressively into

which end in air sacs called

The lungs contain millions of air sacs called

that are surrounded by a network of

diffuses out of the alveoli and

diffuses in.

The equation for breathing rate is

Large

organisms have different

for exhanging and

materials.

A tissue is a group of

An organ is a group of

A system is a group of

Enzymes are

that speed up

in the body.

They are large

made up of chains of

A catalyst is a substance that increases the

without being changed or

in the reaction.

Enzymes are

to certain substrates, each

is a different shape to

a different substrate, which also changes

slightly for a better

Temperature and

effect the

of an enzyme. If it is too

it will

the enzyme, so it cannot

the reaction.

It also cannot be too

otherwise there is not enough

for them to catalyse efficiently.

Rate is a measure of how much something

The equation for rate is

the unit for rate is

In

enzymes are produced by cells and then released into the

to mix with food. Large molecules such as

are too big to pass through the walls of the

so the enzymes

the molecules, making them smaller and

so they can be absorbed into the