B4 revision notes OCR GCSE

revision notes based on the OCR B4 section of the text book

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  • Created on: 25-11-11 17:45
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Biology revision B4 Nick wills
What affects the Rate of Photosynthesis?
the surface area the larger the
leaf the more energy it can
absorb from the sun
the thickness of the leaf a thick
leaf will have lots of cells for the
gases to travel through
A network of 'veins' these
support the leaf and carry water
in and Glucose out.
A stomata to allow gases to
pass in and out by diffusion
Chlorophyll to absorb sunlight
Air spaces inside the leaf
mean that the leaf has a large
internal surface areatovolume
The top layer of cells, the upper epidermis, has NO chloroplasts and so is transparent.
This means the light hitting the leaf passes straight through to palisade mesophyll layer,
(which contains most of the leafs chloroplasts)
The air sacs in the spongy mesophyll layer allow gases to diffuse between the stomata
and the photosynthesising cells.
Carbon dioxide diffuses in and oxygen diffuses out.
The waxy top layer called the cuticle is waterproof.
Osmosis ­ the movement of water from an area of high concentration to an area of low
Turgid ­ the vacuole of a plant is filled with water
Flaccid ­ the Cell loses more water than is taken in
so is floppy.
Lysis When an animal cell fills up with water and
Crenation shrinking of red blood cells due to the loss
of water by osmosis
Transpiration the loss of water from plant leaves

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Biology revision B4 Nick wills
Tissue Process What is moved Structure
Xylem Transpiration Moves water and minerals from roots to Columns of hollow, dead
leaves reinforced cells
Phloem Translocation Moves food substances from leaves to Columns of living cells
rest of plant
The rate of Transpiratation can be increased by
Light levels increasing
Dry and not humid
Temperature increase.…read more

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Biology revision B4 Nick wills
1st organism is the producer. The others are all consumers as they cannot produce their
own food
Each level in a food chain is called a trophic level.…read more

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Biology revision B4 Nick wills
Saprophytic nutrition ­ the type of feeding done by the bacteria and fungi
Preserving food
Canning Canning involves cooking food, sealing it in sterile cans or jars, and boiling the containers to
kill or weaken any remaining bacteria as a form of sterilization.…read more


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