Notes from own school work and CGP AQA Biology Revision Guide

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  • Created on: 09-02-11 18:38
Preview of Cells

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The Structure and Function of an Animal Cell
Nucleus ­ controls all the activites of the cell. It
also contains the genetic material needed for
making new cells or new organisms.
Cytoplasm ­ a liquid gel in which most of the
chemical reactions needed for life take place.
One of the most important of these is
Cell Membrane ­ controls the passage of
substances in and out of the cell.
Ribosomes ­ where protein synthesis takes
place. All the proteins needed in the cell are
made here.
Mitochondria ­ structures in the cytoplasm where oxygen is used and most of the energy is released
during respiration.
The Structure and Function of a Plant Cell
A plant cells contains three extra features:
Cell Wall ­ made of cellulose, gives the cell strength and
Chloroplasts ­ found in the green areas of the plant. They
are green because they contain a green substance called
chlorophyll. They absorb light energy to make food by
Permanent Vacuole ­ a space in the cytoplasm that is filled
with cell sap made up of a weak solution of sugar and salts.
The vacuole keeps the cells rigid in order to support the plant.
Enzymes in the Cell
Cell chemistry works because each reaction is controlled by an enzyme.
They are made up of proteins.
Found in both plant and animal cells.
Enzymes increase the rate of reacion.
They are specific ­ each enzyme controls only one reaction.
Most of the enzymes controlling the reactions of:
- Respiration are found in the mitochondria.
- Photosynthesis are found in the chloroplasts.
- Protein syntehsis are found on the surface of the ribosomes.
Specialised Cells
Name Diagram Location Role in the Body Adaptation

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Contains haemoglobin to carry oygen.
To carry oxygen Biconcave shape increases surface
Blood ­ they
Red to cells and area for maximum uptake.
travel around
Blood carbon dioxide No nucleus to carry more haemoglobin.
the body
Cell back from the Flexible shape to squeeze through
cells. capillaries.
Lots of cytoplasm to support the many
To fuse with the
divisions that the cell undergoes once
Egg sperm cell to
Ovaries fertilised.
Cell produce a zygote
or fertilised egg. Huge food reserves to feed the embryo.…read more

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These membranes select which particles pass through. Small
particles can usually pass through by diffusion quite easily but large particles can not pass through.
- The Medium: the state of medium in which particles are moving can affect their rate. Diffusion is
slowest in solids, then liquids and most rapid in gases.
- Diffusion Gradient: the difference in concentration between two areas. Diffusion always occurs from
the region of high concentration to the region of low concentration. The steeper the gradient the bigger
the difference.…read more


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