AQA GCSE (HIGHER) Biology Unit 2- Cells, Tissues and Organs

Part one of the biology unit 2 section, with diagrams and much more :) GOOD LUCK FOR YOUR EXAM :D

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Preview of AQA GCSE (HIGHER) Biology Unit 2- Cells, Tissues and Organs

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Cells, tissues and organs
Animal and Plant cells both have:
A Nucleus- to control the activities of the cell (contains genetic material)
Cytoplasm- where many chemical reactions take place
A Cell Membrane- controls what goes in and out of the cell
Mitochondria- where energy is released from respiration
Ribosomes- where protein synthesis happens
Plant and Algal cells also have:
A Cell Wall- made of cellulose for support
Chloroplasts- that contain chlorophyll (absorb light energy to make food)
for photosynthesis
A Permanent Vacuole- contains cell sap (keeps cell turgid)

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Bacteria and Yeast Cells:
Bacteria Yeast
Very small- can only be seen with a Single celled organism
powerful microscope
Have a cell membrane and wall- surround Have a cell membrane and cell wall and
cytoplasm cytoplasm
No nucleus- contain loose genetic Have a nucleus
Multiply to form colonies- these can be
seen with the naked eye…read more

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Specialised Cells:
Cell Function Adaption
Absorbs light- Full of chloroplasts- absorb
photosynthesis light energy for
Closely packed cells- form a
layer for efficient absorption
of sunlight
Leaf cell
Absorbs water Long 'finger-like' process
and mineral ions with very thin wall- large
from the soil surface area for absorption
Root hair cell
Fertilises an egg Head contains genetic
cell - female information and enzymes-
gamete help penetrate egg
Middle part contains
mitochondria- energy
Sperm cell Tail- allows movement to egg
Contains Thin outer…read more

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If you don't know the cell in the exam:
If a cell has many mitochondria- needs a lot of energy e.g muscle cell or
sperm cell
If a cell has many ribosomes it is making a lot of protein e.g gland cells that
produce enzymes
If a cell has a tail it must be able to move e.g bacteria or sperm cells
If a cell has special structures to detect stimuli is is a receptor e.…read more

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Diffusion: the spreading out of particles in a gas or substance in a
Molecules in gases and liquids move because they have energy.
The net movement depends on the concentration of cells on either side of
the cell membrane.
There will be a net movement from an area of high concentration to an
area of lower concentration.
The difference in concentration- the Concentration Gradient
The bigger the difference in concentration the faster the rate of diffusion.
e.…read more

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Tissues and Organs:
Tissues: a group of cells with a similar function/structure
When multicellular organisms develop their cells differentiate so that
different cells have different functions.
Some animal tissues are:
Muscle tissue- can contract to cause movement
Glandular tissue- produces substances e.…read more

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This is so useful, thank you loads and loads

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