Structure of cells

This and the following pages conform the content included in :
Science Education Key Learning Area, Biology Curriculum and Assessment Guide (Advaned Level), Jointly prepared by the Curriculum Development Council and the Hong Kong Examination Authority 2002

1.2

*	the ultrastructures and their functions in plant and animal cells : nucleus, cell wall, cell membrane, vacuole, chloroplast, mitochondrion, lysosome, ribosome, endoplasmic reticulum and Golgi apparatus.
*	the fluid mosaic model of membranes.
*	the structure of prokaryotic cells and eukaryotic cells.

Suggested Reading :

(1)	Advanced-level Biology for Hong Kong, by Y.K. Ho, SNP Manhattan Press (H.K.) Ltd. Bk 1, pp. 33-59
(2)	BIOLOGY for Advanced Level, 4th ed., by Glenn and Susan Toole, Stanley Thornes pp.47, 50 - 66
(3)	A-level Biology, by Phillips and Chilton, Oxford University Press pp. 37 - 45
(4)	Biology : Principles and Processes, by Roberts, Reiss and Monger, Nelson Internatioinal pp. 151 - 171

Cells are the building unit of multicellular organisms. They may have different size and different shape. Normally, cells can be divided into two major types, the procaryotic cells and the eucaryotic cells. Procaryotic cells have no membranous structures inside, but eucaryotic cells do. Within the group of eucaryotic cells, there are two major types also. They are plant cells and animal cells.

The size of cells may vary from 12 microns to 8 microns. Normally, plant cells are larger. they may reach up to the diameter of 12 microns. Animal cells are normally smaller. Normally, the size would be around 8 micron or so.

Some cells are round in shape, as red blood cells, but others can be very thin and long, as the nerve cells.

Some cells are irregular in shape, but some other may change their shape from time to time.

In contrast with the multicellular organism, the organisms containing only one cell are called the unicellular organisms. As their bodies are not the aggregation of cells, some scientists just call them acellular organisms.

(28.08.2006)

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