AQA Additional Science Biology - Cells

Taken from the AQA Science Revision Guide, just thought I'd share it on here anyway :)

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  • Created on: 28-04-12 11:15
Preview of AQA Additional Science Biology - Cells

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B2.1 Cells
1.1 Animal and Plant Cells
Animal and Plant cells have some structures in
common they have:
A nucleus to control the cells activities
Cytoplasm where many chemical reactions
take place
A cell membrane that controls the movement
of materials
Mitochondria where energy is released during
aerobic respiration
Ribosomes where proteins are made
Plant cells also have:
A rigid cell wall for support
Chloroplasts that contain chlorophyll for
A permanent vacuole containing cell sap
Key Points
Animal and plant cells have structures that
enable them to do their jobs.
Plant cells have some structures which
animal cells don't have.

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B2.1 Cells
1.2 Specialised Cells
When an egg is fertilised it begins to grow and develop.
At first there is a growing ball of cells. Then as the organism gets bigger, some of the cells
change and become specialised.
There are many different types of specialised cells, e.g.:
Some cells in plants may become xylem or root hair cells.
Some cells in animals will develop into nerve or sperm cells.…read more

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B2.1 Cells
1.3 How do substances get in and out of cells?
Molecules move randomly because of the energy they have.
Diffusion is the random movement of molecules from an area of high concentration to an area of
lower concentration.
The larger the difference in concentration, the faster the rate of diffusion.…read more

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B2.1 Cells
1.4 Osmosis
Osmosis is the movement of water.
Just like diffusion, the movement of molecules is random and requires no energy from the cell.
Osmosis is the diffusion of water across a partially permeable membrane from a dilute solution
to a more concentrated solution. No solute molecules can move across the membrane. The cell
membrane is partially permeable.
Water is needed to support cells and because chemical reactions take place in solution.…read more


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