Page 32 - 新思维科学学生用书8 样章

1.5 Blood

Questions

1 Look at the photograph on the previous page of blood
viewed through a microscope.

Approximately how many times more red blood cells

are there than white blood cells?
2 The photograph on the right was taken with a
powerful electron microscope. A red blood cell and a white blood cell

What differences can you see between the red blood cell and the white blood cell?

Plasma

Plasma is the liquid part of blood. It is mostly water. The red and white blood cells are transported

around the body in the blood plasma. Plasma also has many other different substances dissolved in
it. For example, glucose, dissolved in blood plasma, is transported from the digestive system to every
cell.

You will remember that carbon dioxide is produced in every body cell, by respiration. The carbon
dioxide dissolves in blood plasma and is carried away from the cells. The blood takes it to the lungs,
where the carbon dioxide diffuses out and is breathed out in your expired air.

Red blood cells

Stage 7, Topic 1.3 described how the structure of red blood cells is related to their function. Now you
are going to think about this in a little bit more detail.

Red blood cells are very unusual cells. They do not have a nucleus and they do not have
mitochondria. They are full of a red pigment called haemoglobin. It is haemoglobin that makes

blood look red. The structure of a red blood cell is related to its function.

cell membrane
There is no nucleus, to make
more room for haemoglobin. cytoplasm
The cytoplasm contains a red
pigment called haemoglobin,
which carries oxygen.
There are no mitochondria in
the cytoplasm.

A red blood cell

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