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AQA GCSE Biology ­ Unit 2 summary notes
















AQA




GCSE Biology




Unit 2




Summary Notes












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AQA GCSE Biology ­ Unit 2 summary notes




12.1 Animal and Plant Cells

Cells

Cells are the smallest unit of life.
All living things are made of cells.
Most human cells, like most other animal cells, have the following parts:
o nucleus
o cytoplasm
o cell membrane
o mitochondria
o…

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AQA GCSE Biology ­ Unit 2 summary notes




Permanent vacuole filled with cell sap in plant cells.
Other facts:
The chemical reactions inside cells are controlled by enzymes.
Examples:
o Enzymes for respiration are in the mitochondria.
o Enzymes for photosynthesis are in the chloroplasts.
o Enzymes for protein synthesis…

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12.2 Movement into and out of cells

To get into or out of cells, dissolved substances have to cross the cell membranes.
Solutes = particles in solution eg glucose, sodium ions, chloride ions.
Solvent = liquid in which the particles are dissolved…

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Osmosis in animal cells:


If animal cells are placed in a solution that has a higher solute concentration
than the cytoplasm, then water will leave the cell by osmosis, until it shrinks
and dies.


If animal cells are placed in a solution…

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12.3 Photosynthesis

Photosynthesis

Photo = light
Synthesis = making of (glucose)
Photosynthesis = making glucose using light

Complex definition:
A process in green plants that produces complex organic chemicals (glucose) from simple
inorganic chemicals (carbon dioxide and water) using light energy.

More…

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A palisade mesophyll cell:





Factors that limit the rate of photosynthesis

1) Temperature
A low temperature will limit the rate as the molecules will move less and therefore the reaction
happens slower

2) Carbon dioxide
A shortage of CO2 will limit the…

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Farmers artificially manipulate the environment in which they grow plants.
They grow plants in greenhouses or in polythene tunnels.
They can control the temperature in greenhouses using heaters and ventilation.
They can artificially increase the carbon dioxide levels.
They can control the…

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12.4 Energy flow in ecosystems

Food Chains

Radiation from the Sun is the source of energy for most communities of living organisms.
Green plants capture a small part of the solar energy which reaches them.
This energy is stored in the substances…

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Diagrams that display the numbers of organisms at each trophic level in a food chain
Each block is drawn to scale.
These do not necessarily represent amount of biomass:







Pyramids of biomass

The biomass at each stage can be drawn to scale…

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