Friday, 20 October 2017

CELLS - AN INTRODUCTION

Cells
Cells are very small. They are the basic building blocks of all animals and plants. 


Animal cells usually have an irregular shape, and plant cells usually have a regular shape
Cells are made up of different parts. It is easier to explain what these parts are by using diagrams like the ones below.
Animal and plant cells both have a cell membrane, cytoplasm, and a nucleus. Plant cells also have chloroplasts, a vacuole and a cell wall.

Animal cells and plant cells both contain:
  • cell membrane, cytoplasm, nucleus
Plant cells also contain these parts, not found in animal cells:
  • chloroplasts, vacuole, cell wall
The table summarises the functions of these parts.

Part
Function
Found in
Cell membrane
Controls what substances can get into and out of the cell.
Plant and animal cells
Cytoplasm
Jelly-like substance, where chemical reactions happen. In plant cells there's a thin lining, whereas in animal cells most of the cell is cytoplasm.
Plant and animal cells
Nucleus
Controls what happens inside the cell. Carries genetic information.
In exams don't call the nucleus the 'brain' of the cell. That is not a good description and will not get you marks.
Plant and animal cells
Chloroplast
Where photosynthesis happens – chloroplasts contain a green substance called chlorophyll.
Plant cells only
Vacuole
Contains a liquid called cell sap, which keeps the cell firm.
Plant cells only
Cell wall
Made of a tough substance called cellulose, which supports the cell.
Plant cells only

From: BBC BiteSize

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