Kelso High School
Biology
Cells
Name……………………..... Class………..
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Cells
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Level / You need to be able to…… // State that cells are the basic units of living things
/ Explain the purpose of staining cells
/ Describe the similarities and differences between plant and animal cells
/ Explain the function of each cell structure
/ State that a substance can diffuse from an area of
high concentration to a region of lower concentration,
until the molecules are evenly spread out
/ Explain the importance of diffusion to organisms
/ Give examples of substances that can enter and leave
the cell by diffusion e.g. dissolved food (glucose),
oxygen, carbon dioxide and water
/ State that the cell membrane controls the
passage of substances into and out of the cell
/ Explain that ‘osmosis” is a special case of diffusion of water through a selectively permeable membrane
/ Explain the effects of osmosis in plant and animal
cells when placed in distilled water or strong salt solution
/ Describe the appearance of turgid and flaccid plant cells
Date of ‘Cells’ End of Unit Assessment:
………………………………….
Remember, in addition to testing your knowledge the assessment will include
problem solving questions, e.g. graph drawing, calculations, etc.
Diffusion
Solids, liquids and gases are made up of molecules.
In gases the molecules move around quickly and in liquids they move more slowly. In solids the molecules are packed closely together, so are not as free to move around. Therefore diffusion happens quickly in gases, more slowly in liquids and very, very slowly in a solid.
Diffusion in a Gas
Concentration Gradient
___Diffusion___ is the process by which water molecules move FROM a
region of _high____ concentration TO a region of ____low_____
concentration, until the molecules are evenly spaced out.
Colour the diagram below and add arrows to show the direction in which the molecules move.
LOW HIGH
CONCENTRATION CONCENTRATION
Diffusion in a Liquid
In a liquid, the molecules diffuse ___from__ a region of HIGH concentration __to__ a
region of LOWER concentration, until they are evenly spaced out. Diffusion is __slower___
in a liquid than in a gas.
water
purple permanganate molecule
Examples of diffusion are:
1._perfume moving through a room ______
2._a drop of food colouring moving through still water_
Diffusion in simple cells
Cells are constantly using up oxygen and producing carbon dioxide. These gases pass into
and out of the cell through the cell membrane.
Diffusion is important to cells because oxygen and ____glucose____ enter cells by
___diffusion____________and are needed by the cell to produce ___energy__
during aerobic respiration.
Carbon dioxide and _waste ______materials_____ are poisonous and
_____diffuse______out of the cell through the __cell___________membrane______.
Aerobic Respiration
Movement Through a Cell Membrane
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The cell membranes surrounding living cells do not allow all substances to pass through
them. Some molecules are ___too______large_____ to pass through the membrane.
Membranes that allow ___small___ molecules (like glucose) to pass through
them, but not __larger____ molecules (like sucrose), are said to be selectively
___permeable______.
The cell membrane __controls___ the passage of substances into and out of the cell.
Osmosis is a special case of diffusion which involves ___water___ molecules
diffusing from a region of __high___ water concentration __to__ a region of lower water
concentration, across a ______selectively______permeable_____
______membrane______.
Osmosis in Animal Cells
If an animal cell is placed in distilled water, there will be a higher concentration of water
outside the cell than inside. Water will _____enter_____ the cell by ___osmosis___ .
As a result, the cell will swell and __burst______.
If a red blood cell is placed in ______concentrated (strong)______salt____
______solution______, the cell will ___lose_____ water by osmosis and will
_____shrivel______.
Osmosis in Plant Cells
Plant cells have two selectively permeable membranes.
Plant cells also have a cell wall that gives the cell support and prevents it from bursting when placed in distilled water.
Turgid cells give ______support______to the plant.
If plant cells lose water, the cells become ____flaccid____ and the plant wilts.
[End of topic]
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