Biology Section One - Life and Cells (AQA)

Important notes from the AQA Additional Science revison guide on section one of biology, Life and Cells. This includes topics such as DNA and Osmosis, with higher tier material included.

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CELLS

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Animal Cells

Most animal cells contain the following:

1) Necleus - contains genetic material that control the activities of the cell

2) Cytoplasm - gel like substance where most chemical reactions occur. It contains enzymes which control these.

3) Cell Membrane - Holds the cell together and controls what goes in and out.

4) Mitochondria - Where most respiaration reaction takes place. Resperation releases energy which the cells need to work.

5) Ribsomes - these are where protiens are made in the cell.                                                          


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Plant Cells

Plants cells usually contain what the animal cells have, plus a few extras:

1) Rigid Cell Wall - Made of cellulose. It supports the cell and strenghtens it.

2) Permenant Vacuole - Contains cell sap, a weak solution of sugar and salts.

3) Chloroplasts - These are where photosynthesis occurs, which makes food for the plant. They containtain a geen substance called chlorophyll.

                                 

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Specialized Cells - Palisade Leaf Cells

Palisade Leaf Cells are adapted for photosnythesis in the following ways:

1) They're packed whith chloroplasts for photosynthesis.

2) Their tall shape means a big surface area allowing more CO2 to be absorbed.

3) They're thin, so a lot of them can be packed into the top of a leaf, allowing more photosynthesis to occur.


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Specialized Cells - Guard Cells

Guard cells are adapted to pen and close pores in the following ways:

1) They have a special kidney shape to open and close pores

2) When the plant has plenty of water the guard cells become turgid (plump). This makes the stomata open so gasses can exchange for photosynthesis

3) When the plant is short of water the cells become flaccid (floppy) making the stomata close to stop water vapor escaping.

4) Thin outer walls and thicker inner walls make the opening and closing work.

5) They're sensitive to light so close at night to save water without losing out on photosynthesis.


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DNA

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DNA Fingerprinting

All DNA is unique (unless your an identical twin like me, in which case your DNA is the same)

DNA fingerprinting is a way of comparing DNA samples to see if they come from the same person

It is most commonly used by the police to solve crime problems

It can also be used in paternity tests to check if a man is really the father of a child

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