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Kelso High School
Biology
Cells
Name…………………….....
Class………..
Keep this booklet safe – you will need it for revision.
1
Cells
Use this table as a checklist for your
revision.
= core
Use the smiley faces to show how well you are coping
= challenge
Understood
and learnt
Level
Need to do
more work
Need to get help
- see my teacher.
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.
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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.
GAS
LIQUID
SOLID
Diffusion in a Gas
Concentration Gradient
Diffusion
___Diffusion___ is the process by which
molecules
move FROM a
region of _higher____ concentration TO a region of ____lower_____
concentration, until the molecules are evenly spaced out.
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Colour the diagram below and add arrows to show the direction in which the molecules move.
LOWER
CONCENTRATION
HIGHER
CONCENTRATION
Diffusion in a Liquid
In a liquid, the molecules diffuse ___from__ a region of HIGHER 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_
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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
energy
GLUCOSE
CARBON
DIOXIDE
+
+
WASTE
MATERIALS
OXYGEN
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Movement Through a Cell Membrane
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
Osmosis is a special case of diffusion which involves ___water___ molecules
diffusing from a region of __higher___ water concentration __to__ a region of lower water
concentration, across a _______selectively___ _______permeable_____
_______membrane_______.
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Osmosis in Animal Cells
selectively permeable
cell membrane
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________ .
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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.
Plant cell in
distilled water
Plant cell in concentrated
(strong) salt solution
Turgid cells give ______support______ to the plant.
If plant cells lose water, the cells become ____flaccid____ and the plant wilts.
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Cell division
The nucleus of a cell controls all the cell’s activities, including cell division.
The nucleus contains chromosomes.
Chromosomes are made up of genes.
Genes are made of DNA .
Genes control the size, shape and function (job)
of the cell.
The process of cell division is also called mitosis .
Mitosis is the way the number of cells is increased in a
plant or animal. This is how we grow and repair damaged
tissues.
Mitosis
When a cell is about to divide, thread-like structures called chromosomes
appear in the nucleus. Each new cell (daughter cell) made by mitosis has a complete copy
of the DNA in the original cell i.e. it is genetically identical to the original cell.
Since the new daughter cells have exactly the same number of chromosomes, the
cells will function normally. The new daughter cells are genetically identical to the
original cell.
The chromosomes are copied before the cell
divides:
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Label the diagram below to show the structure of a cell that is about to divide:
nucleus
chromosome
centriole
Stages of Mitosis
1.
The chromosomes have duplicated. They start to
become visible in the nucleus.
2.
The nuclear membrane breaks down and the centrioles
go to the poles of the cell. The chromosomes are now
visible.
3.
The chromosomes move towards the equator of
the cell. The spindle fibres start to form.
4.
The chromosomes have lined up along the equator and
the spindle fibres have attached to their
centromeres.
5.
The spindle fibres contract, separating the chromatids,
pulling them to opposite poles of the cell.
6.
The cell starts to divide.
7.Two genetically identical daughter cells have formed.
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