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Nicola Fitzhugh

Biology Unit 1 Revision

Observing Cell Structure

There are two types of microscopes:
1. Light (up to X1500 and low resolution)
2. Electron (up to X500000 and high resolution)

Resolution is how well small, close objects can be seen
separately. High resolution produces detailed images of

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Nicola Fitzhugh

The fluid mosaic is a phospholipid bilayer with scattered
The cell surface membrane is for transport (partially
permeable) and recognition or signalling (e.g. receptor
molecules for hormones).

Passive transport (diffusion/facilitated diffusion) does not
use energy, while active transport does and is against a
concentration gradient.

Osmosis is…

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Nicola Fitzhugh

They are specialised for their function (e.g. epithelial or
guard cells).

Cells are organised into tissues (e.g. squamous or ciliated
epithelium; xylem/phloem), which are organised into organ

Gaseous Exchange

The alveolus wall is an efficient exchange surface as it is
only one cell thick. It is moist…

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Nicola Fitzhugh

Inhaling (inspiration):
1. Diaphragm contracts to become flatter and pushes
digestive organs down.
2. External intercostal muscles contract to raise ribs.
3. Volume of chest cavity increases.
4. Pressure in chest cavity drops below atmospheric
5. Air moves into lungs.

Exhaling (expiration)
1. Diaphragm relaxes and is…

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Nicola Fitzhugh

The right ventricle wall (thinner) only has to pump blood to
the lungs.

Atrial walls are very thin since they only have to pump
blood a short distance into the ventricles.

Cardiac cycle: chambers fill; ventricles contract (cuspid
valves close, "lub" sound); atria contract (semi-lunar
valves close, "dub'…

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Nicola Fitzhugh

The waterproof Casparian strip in endodermis cells forces
water into the symplast. This creates root pressure in the

The transpiration stream pulls water up the xylem.
Cohesion holds water molecules together.
Adhesion holds them to the xylem walls.

Plant Transport ­ Translocation and Phloem

Phloem is a…


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