Page 25 - 新思维科学学生用书8 样章

1 Respiration

Using energy to stay alive

Our bodies need energy for many different reasons. For example:

We use energy when we move We use energy to send electrical We use energy to keep our bodies
around. impulses along neurones. warm when it is cold.

All of our energy comes from the food that we eat. Carbohydrates are especially good for giving us
energy.

When we eat food containing carbohydrates, our digestive system breaks the carbohydrates down to
a kind of sugar called glucose. The glucose goes into our blood. The blood delivers glucose to every

cell in the body. The cells use the glucose to get the energy that they need.

Releasing energy from glucose

Energy must be changed from one type to another, or be transferred,
in order to do something.

The energy in glucose is locked up inside it. Glucose is an energy
store. Before your cells can use the energy, it has to be released from

the glucose.

This is done by tiny structures called mitochondria that are found
inside cells. Most cells have many mitochondria inside them. glucose oxygen
Mitochondria release energy from glucose, so that the cells can
use the energy.

The mitochondria carry out a chemical reaction called aerobic energy
released
respiration. Aerobic means that is uses oxygen, from the air.
Here is the word equation for aerobic respiration:

glucose + oxygen → carbon dioxide + water
water carbon dioxide

In this reaction, some of the energy inside the glucose is released. Energy is released from glucose
This is done in a very controlled way. Just a little bit of energy is inside mitochondria
released at a time – just enough for the cell’s needs.

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