AQA Biology 2

Everything you need for the AQA Biology 2 exam

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  • Created on: 21-05-12 16:15
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GCSE BIOLOGY REVISON
Plant cells
Cell wall ­ made of cellulose, strengthens the cell.
Vacuole ­ filled with cell sap, helps to support the cell.
Cytoplasm ­ where most chemical reactions in the cell takes place.
Nucleus ­ controls what the cell does and contains genetic information.
Ribosomes ­ where protein synthesis occurs.
Chloroplasts ­ contain chlorophyll that is where photosynthesis takes place.
Cell membrane ­ controls movement in and out of the cell.
Animal cells
Cytoplasm ­ where most chemical reactions take place.
Ribosomes ­ where protein synthesis occurs.
Cell membrane ­ controls movement in and out of the cell.
Nucleus ­ controls what the cell does and contains genetic information.

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Specialized cells
Root hair cells ­ have tiny hair like structure, which increases the
surface area of the cell enabling it to absorb water and ions more
efficiently.
Palisade cells ­ are column shaped cells on the upper surface of a leaf.
They are packed with chloroplasts for photosynthesis.
Xylem ­ these cells are long, thin and hollow cells that contain
cytoplasm. They transport water through the stem and root.…read more

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Carbon dioxide diffused from the air
Water from the soil
Chlorophyll in the leaves
Two things are produced ­
Glucose ­ for biomass and energy
Oxygen ­ released into the atmosphere
Light energy is absorbed by green chlorophyll found in chloroplasts.
Some of the glucose produced goes straight to provide energy for the cells
respiration, but some is stored as starch.…read more

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The sun is the source of energy for all living organisms.
In green plants photosynthesis captures solar energy, which is then stored in
the substances, which make up the cells of the plant. It is then passed onto
organisms, which then eat the plant. The transfer of energy can be represented
in a food chain.
Pyramids of biomass
The mass of living material is called biomass. At each stage of a food chain the
biomass is less than it was at the previous stage.…read more

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Transfer of energy and biomass
Biomass and energy are lost at every stage of a food chain because materials
and energy are lost in an organisms waste. Energy is also released through
respiration and lost as heat energy.
More heat energy is lost in warm-blooded animals whose bodies must be kept
at a constant high temperature which are higher than their surroundings.…read more

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Living things remove materials from the environment for growth and other
processes but when they die or excrete waste these materials are returned to
the environment.
They are broken down by then microorganisms. This decay process releases
substances substances used by plants for growth.
Microorganisms digest materials faster in warm, moist conditions where there
is plenty of oxygen.
Humans deliberately use microorganisms in ­
Sewage works to break down human waste.
Compost heaps to break down plant material waste.…read more

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Maintain a constant temperature in colder surroundings.
Make proteins in plants from amino acids.
Aerobic respiration
Aerobic respiration releases energy through the break down of glucose
molecules, by combining them with oxygen inside living cells (mostly takes
place in the mitochondria).
Glucose + oxygen carbon dioxide + water + energy
Outside living cells
Digestive enzymes are produced by specialised cells in glands in the lining of
the gut.
The enzymes pass out of the cells into the gut where they meet the food
molecules.…read more

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It emulsifies fats, meaning it breaks down large drops of fats into small
droplets to increase the surface area, which enables the lipase enzyme
to work much faster.
Use of enzymes in the home and industry
Some microorganisms produce enzymes, which can be used to out benefit.
At home biological detergents may contain ­
Protease enzymes to break down things like blood and food stains.
Lipase enzymes to break down oil and grease stains.…read more

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More water is lost when it is hot, and more water has to
be taken by food and drink to balance this.
Too Cold Too Hot
A - Hair muscles pull hairs on D - Hair muscles relax. Hairs
end. lie flat so heat can escape.
B - Hairs trap air to create an E - Sweat secreted by sweat
insulating layer. glands. Cools skin by
C - Blood flow in capillaries evaporation.
decreases.…read more

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Of the 23 pairs of chromosomes in the human body cells, one pair is the sex
chromosome.
In females, these are identical and are called X chromosomes.
In males, one is much shorter than the other. The shorter one is called
the Y chromosome and the longer one is called the X chromosome.
Offspring inherit one sex chromosome from the mother and one from
the father.…read more

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