A
Cell Membrane.
This controls what goes in and out of the cell
Cytoplasm.
This
has the thickness of wallpaper paste. It is where the chemical
reactions take place.
A
nucleus.
This is the 'brain' of the cell. It contains the genetic material
(DNA) and tells the cell what to do.
Only
plant cells contain:
A
Cell Wall. It support the plant cell and is very strong.
It is made out of a substance called cellulose.
A
Vacuole.
This is filled with a liquid called cell sap. It helps the cell
to maintain its shape.
Chloroplasts.
These are green discs that allow the plant to make food by photosynthesis.
They contain a chemical called chlorophyll. Plant tissues which
contain them appear green.
In the
sections below some functions of specialized animal and plant
cells are described.
Red
Blood Cells
Red
blood cells are adapted to carry oxygen around the body in blood
vessels. A red blood cell has a small size to enable it to fit
through capillaries and a biconcave shape (see the picture below
- it looks a bit like a Werther's Original sweet). Red blood
cells are flexible and contain the chemical haemoglobin
which binds to oxygen to carry it around the body.
The
shape of the red blood cell provides a large surface area to
help it take in oxygen and release it rapidly. The flexible
shape helps it to fit through narrow capillaries.
In
the lungs haemoglobin in the red blood cells combines with oxygen
to form oxyhaemoglobin
Oxygen
+ Haemoglobin Oxyhaemoglobin
When
the red blood cells reach tissues oxyhaemoglobin breaks down
to release oxygen:
Oxyhaemoglobin
Oxygen + Haemoglobin
White
Blood Cells
White
blood cells are bigger than red blood cells and have a flexible
shape. White blood cells help to protect our body against disease.
The diagrams below show how white blood cells can 'eat' bacteria
cells which have entered the body.
Palisade
Cells
Palisade
cells contain lots of chloroplasts and are found near to the
top surface of the leaf. The chloroplasts aborb light energy
and make food (glucose) for the plant using photosynthesis.
The chloroplasts give plants their green colour. The diagram
below shows cells in a plant leaf. The palisade cells can be
seen just below the top surface of the leaf.
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2005 drparry.co.uk. All Rights Reserved.
Oxyhaemoglobin
