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AQA GCSE Biology ­ Unit 2 summary notes
B2.1 Cells and Cell Structures
Summary
All living things are made up of cells. The structures of different types of cells are related to
their functions. To get into or out of cells, dissolved substances have to cross the cell
membranes.
Cells
Cells are the smallest unit of life.
All living things are made of cells.…read more

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AQA GCSE Biology ­ Unit 2 summary notes
Mitochondria where most energy is released in respiration.
Ribosomes where protein synthesis occurs.
Cell wall ­ made of cellulose and strengthens plant cells.
Chloroplasts absorb light energy to make food in plant cells.
Permanent vacuole filled with cell sap in plant cells.
Yeast
Yeast is a singlecelled organism.
The cells have a nucleus, cytoplasm and a membrane surrounded by a cell wall.
Bacteria
Bacterium is a singlecelled organism.…read more

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AQA GCSE Biology ­ Unit 2 summary notes
Cells may be specialised to carry out a particular function.
Examples:
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 eg water.
Solute and solvent molecules move around randomly.
Solutes can move into and out of cells by diffusion.…read more

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AQA GCSE Biology ­ Unit 2 summary notes
B2.1 Tissues, Organs and Organ Systems
Summary
The cells of multicellular organisms may differentiate and become adapted for specific
functions. Tissues are aggregations of similar cells organs are aggregations of tissues
performing specific physiological functions. Organs are organised into organ systems, which
work together to form organisms.
Multicellular organisms
Large multicellular organisms develop systems for exchanging materials.
During the development of a multicellular organism, cells differentiate so that they can
perform different functions.…read more

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AQA GCSE Biology ­ Unit 2 summary notes
Plant organs
Plant organs include stems, roots and leaves.
Examples of plant tissues include:
epidermal tissues, which cover the plant
mesophyll, which carries out photosynthesis
xylem and phloem, which transport substances around the plant.…read more

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AQA GCSE Biology ­ Unit 2 summary notes
B2.3 Photosynthesis
Summary
Green plants and algae use light energy to make their own food. They obtain the raw materials
they need to make this food from the air and the soil. The conditions in which plants are grown
can be changed to promote growth.…read more

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AQA GCSE Biology ­ Unit 2 summary notes
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 rate as fewer molecules will be available for the reaction.
3) Light intensity
A shortage of light means there is less energy to power the reaction.…read more

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