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3.1 Cells and cell function
In this section:
P1
How you are made
Cells that make up the body can be compared to bricks that make up a
house. In the very same way all life that exists on Earth is made up from
cells. Cells are very small so you will need a microscope to see them.
Key terms
Tissue – a group of similar cells acting
together to perform a particular
function.
Epithelial cells – one of several cells
arranged in one or more layers that form
part of a lining or covering of the body.
Unit 3: See pages 72–73 for more
about DNA and chromosomes.
Activity A
List the similarities and differences
between plant and animal cells.
Features and functions of a cell
The table below shows the function of specific features that make up
animal and plant cells. Some of these features are common to animal
cells and plant cells but others are unique to plant cells.
Cell feature
Function
In animal cell?
In plant cell?
Cell
membrane
Partially permeable so allows
the movement of substances
into and out of the cell
Yes
Yes
Nucleus
Contains DNA arranged in
chromosomes
Controls the activities of the
cell, e.g. maintenance, repair
and growth
Yes
Yes
Cytoplasm
Jelly-like substance
Where chemical reactions of
the cell occur
Yes
Yes
Cell wall
Made from cellulose
Prevents the cell from
bursting and gives the cell
shape
No
Yes
Vacuole
Contains cell sap
No
Yes
Chloroplast
Contains chlorophyll
Where glucose is made in
photosynthesis
No
Yes
Mitochondrion
Releases energy for the cell
Yes
Yes
chloroplast containing a green
substance called chlorophyll
cell membrane
nucleus
cell wall
cell membrane
mitocondria
cytoplasm
nucleus
vacuole filled with cell sap
cytoplasm
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(a) Typical plant cell.
(b) Typical animal cell.
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Unit 3 Biology and our environment
Specialised cells – cells with a difference
As cells develop, they can become specialised to perform specific
functions. This is called differentiation. Some examples of specialised
cells can be seen below:
(a)
(b)
female
nucleus
cytoplasm
cell
membrane
(c)
red blood cell
(no nucleus)
(d)
cilla
(e)
(f)
nucleus
(g)
nucleus
cell wall
nucleus
cytoplasm
male white
nucleus
nucleus blood cell
tail
(no nucleus)
nucleus
nucleus
Specialised cells: (a) egg and sperm, (b) blood cells, (c) ciliated epithelial cell, (d) muscle cell, (e) nerve cell, (f) root hair cell,
(g) onion cell.
Tissues
Did you know?
Tissues are made up from a group of cells which have a similar structure
and do the same job in the body. Some examples of tissues in the
body are:
• nervous tissue found in the nervous system
Stem cells are cells which are
undifferentiated. They have the ability
to grow into any type of specialised
cell under the right conditions.
• epithelial tissue found in the skin and linings of the inside of
the body – different epithelial cells perform different functions,
e.g. secretion or absorption; some cells have tiny hairs (cilia)
• muscular tissue, which makes up the muscles involved in movement,
in the heart or which also line the insides of the body.
Activity B
Grading tip
Give three examples of tissues and where they are found in
the body.
You need to use your knowledge
of cells to help you to complete <P1.
P1
Assessment activity 3.1
P1
1 Which part of a cell controls the activities of the cell and what
does it contain? P1
2 Research further into cell structure and variation between cells
using the Internet and books. Make notes on your findings. P1
Functional skills
You can use your researching skills in
ICT and reading in books to search
for more information about cells and
their function.
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BTEC Level 2 First Applied Science
Unit 3 Biology and our environment
3.1 Cells and cell function: Lesson plan
Duration
60 mins
Working towards
P1
Student book pages
70–71
Subject specialism
Biology
Lesson resources
Learning Outcomes
● Interactive whiteboard, Internet connection, computer
and data projector.
● Microscopes, slides, lamps, cover slips, iodine
solution, methylene blue stain (to prepare slides of
cheek cells), disinfectant and safety glasses.
● Prepared slides of specialised cells.
● List of the specialised cells.
● A3 paper and pens.
● Prepared PowerPoint presentation for plenary activity.
● SK1, SK2 and SK3.
Interactive activities and hotlinks
Drag and drop activity on cell labelling in
an animal cell
Drag and drop activity on cell labelling in a plant cell
Video on the inner life of a cell
ActiveTeach 3.1
All learners will be able to …
● Recognise the structure of typical plant and animal cells.
Most learners will be able to…
● Appreciate the diversity of cells and understand that cells
are specialised, and work together to form tissues.
Some learners will be able to…
● Understand how specialisations of cells in particular tissues
help them to fulfil their role.
Suggested starter activity (10 mins)
Show ‘Inner life of a cell’ video to learners to introduce the topic and as a basis for discussion.
Suggested main activities (40 mins)
Looking at Cells Observation of plant, animal and specialised cells using a microscope. (AS1 and TT1)
Suggested plenary activity (10 mins)
Use PowerPoint to gradually reveal a picture of a specialised cell or a particular tissue (prepare by obscuring a
background image with boxes – remove one per slide). Play in teams. Individual learners race to name each
picture. Their team then provides a description of how the cell is specialised.
Stretch and support
Ensure learners work in mixed-ability groups of three during the practical activity. Less able learners can present the
information from research as a series of ‘job advertisements’, which includes structure and function of specialised cells
(e.g. starting with ‘Epithelial cell wanted…’); more able learners could produce an information leaflet on specialised cells,
focusing on the role of each tissue as a whole.
Functional Skills
ICT – research
information using a
variety of websites and
present findings
English – write up the
findings of their research
PLTS
Self-managers
Team workers
Keywords
cell, tissue, epithelial
cell, permeable,
cellulose, sap,
chlorophyll,
photosynthesis,
differentiation
Links to
other
subjects
Unit 6 – Health applications of life science
Unit 10 – The living body
Unit 12 – Growing plants for food
Unit 14 – Science in medicine
Unit 20 – Biotechnology procedures and applications
HSW
3
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BTEC Level 2 First Applied Science
Unit 3 Biology and our environment
AS1
Looking at cells
You are a technician working in a university cell biology department. The labels have fallen off
some slides of cells. You have a list of the cells on the slides but you don’t know which is which.
Aim
Prepare slides of onion cells. Using your onion slides and the cheek slides supplied draw the two
types of cell. Use the drawings to help you identify the mystery slides as animal cells or plant
cells. Then look at how the mystery cells are specialised to decide what the cells are and what
their role is.
Before you start
You will need:
● microscope and lamp
● iodine solution
● microscope slide
● prepared slide of cheek cells
● cover slip
● prepared slides of specialised cells
● piece of onion
● tweezers and/or mounted needle
● beaker of disinfectant
● safety glasses
Safety
Please dispose of the cheek cell slides in the disinfectant provided. Be careful when cutting
onion and using tweezers or the mounted needle. Wear safety glasses.
What you need to do
1
Peel a thin layer from the inside of one layer of the onion and place it on the slide. Cut a
small piece and pull it out flat. Dispose of the rest. Add one drop of iodine solution. Use your
mounted needle to place a cover slip on top of the slide.
2
Put your slide on the microscope and look at it under low power. Use the focusing knob to
focus it, and move up to medium power. Make a quick drawing of one of the cells. Label the
drawing. Then look at the cheek cell slides, and draw and label one of the cells.
Using the evidence
1
Look at each slide of specialised cells. Complete a copy of the table below. Use the list of
cells you’ve been given to help you complete the last column.
2
For each cell try to explain why it has its particular specialisations and how they relate to its
role or function within a living thing.
Slide
number
Animal or
plant cells
Differences to onion cells
Differences to cheek cells
What type of cells do you think
are on the slide?
Extension
Choose one of the cells to research. Create an entry for a Facebook profile for your chosen type
of cell, focusing on describing the cell’s role and specialisations.
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BTEC Level 2 First Applied
Unit 3 Biology and our environment
TT1
Looking at cells
Aim
Learners prepare and draw slides of onion cells and cheek cells. They identify the features of animal and plant
cells and gain an understanding of cell specialisation and how the structure of cells relates to their function.
Equipment
● microscope and lamp
● iodine solution and beaker of disinfectant
● microscope slide and cover slip
● prepared slides of specialised cells
● onions divided into scale leaves
● tweezers and/or mounted needle
● prepared slides of cheek cells (use methylene
blue stain and a cotton bud)
● safety glasses
● beaker of disinfectant
Safety notes
Check local regulations on using cheek cells. Learners may be able to make them themselves but this activity
assumes you will pre-prepare some cheek cell slides. Learners should dispose of the cheek cell slides in
disinfectant. Warn them to be careful if cutting onion and using tweezers or the mounted needle. Learners
should wear safety glasses.
Running the activity
1
Before the lesson prepare slides of cheek cells, staining them with methylene blue. Because different
schools may have different sets of prepared slides of cells you can choose which ones you use, but cells
with obvious specialisations are most appropriate. Label the slides 1, 2, 3 etc. and give learners a list of
what they are (but without telling them which is which).
2
You will need to demonstrate to learners how to make an onion cell slide and how to set up and focus the
microscope. Ensure you discuss the importance of focusing so the distance between slide and objective
lens increases, and emphasise how to move between objective lenses (Skills sheets 1, 2 and 3 will be
useful). Support learners in identifying differences between the specialised cells and the ‘template’ onion
and cheek cells.
Expected outcomes
All learners should be able to draw an onion cell and cheek cell and label them. Most learners will be able to
identify similarities and differences between the prepared slides of specialised cells, the onion cells and cheek
cells, and identify cells appropriately as plant or animal. Some learners will be able to relate the differences to
the potential function of the cell.
Links to other units within BTEC
Cell structure and specialisations links to Units 6, 10 and 12, and to aspects of health and safety.
Other resources
Skills sheets 1 (Using a microscope), 2 (Magnification) and 3 (Microscope magnification).
PLTS and Functional Skills
TW and SM.
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Unit 3 Biology and our environment
SK1
BTEC Level 2 First Applied Science
Using a microscope
Microscopes are very delicate pieces of equipment. They are easy to break and expensive to
mend! You must be very careful when using one. Make sure you can carry it around properly
and never touch the glass of the lenses.
Looking at your slides
Take care! If
you hit the thin
glass slides when
you focus the
microscope they
will break.
Never use a
microscope
where the Sun’s
rays could reflect
off the mirror.
Looking
closer
•
To look at cells in more detail you need to use a higher magnification. Turn the lenses until
the middle lens is pointing down at the stage.
•
Turn the fine focusing knob to get a clear picture.
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Unit 3 Biology and our environment
SK2
BTEC Level 2 First Applied Science
Magnification
A magnifying glass makes small things look larger. It magnifies things. The magnifying glass in
the picture makes things look twice as large. A one penny coin is 2 cm across, so through the
magnifying glass it will look 4 cm across.
The magnification is 'times 2'. We write this as ×2. Magnifying by 2 is the same as multiplying the
size by 2.
2 cm × 2 = 4 cm
Microscopes work in the same way. They magnify things more than a magnifying glass does.
How well you can see things through a microscope depends on how large it makes them look.
This depends on the magnification of the microscope lenses.
1
Look closely at the eyepiece lens or the objective lens. You should be able to see a number
like ×10 on it. This is the magnification it gives. A magnification of ×10 means the lens
makes things look 10 times larger.
2
Look again at both lenses and write down the magnification of each lens. They may be
different.
3
Now multiply the two numbers together. For example:
The number 40 is the total magnification of the microscope’s lenses. You can write it as ×40.
The objective lens makes things 4 times larger and then the eyepiece lens makes them 10 times
larger again, making 40 times larger in total.
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Unit 3 Biology and our environment
SK3
BTEC Level 2 First Applied Science
Microscope magnification
A microscope makes small things look much larger. It magnifies things. How well you can see
things through a microscope depends on how large it makes them look. This depends on the
magnification of the microscope lenses.
1
Look closely at the eyepiece lens or the objective lens. You should be able to see a number
like ×10 on it. This is the magnification it gives. A magnification of ×10 means it makes
things look 10 times larger.
2
Look again at both lenses and write down the magnification of each lens. They may be
different.
3
Now multiply the two numbers together. For example:
The number 40 is the total magnification of the microscope’s lenses. You can write it as ×40.
The objective lens makes things 4 times larger and then the eyepiece lens makes them 10
times larger again, making 40 times larger in total.
4
Look again at the objective lens. This can usually be changed to give different
magnifications. Often there are three lenses.
A microscope may have three objective lenses: ×4, ×10 and ×40. With an eyepiece lens of
×10 you get a total magnification of ×40, ×100 and ×400.
5
If a cell was 0.1 mm wide and you looked through a microscope with a total magnification of
×40, the cell would look 4 mm wide through the microscope.
6
It is possible to measure the size of objects under the microscope by measuring the size of
the field of view. This is the diameter of what you can see at a particular magnification.
Place a slide with a scale on it (like a tiny ruler) under the microscope and focus on it. Count
up how many divisions you can see. This is how wide the field of view is.
If each division was equal to 0.2 mm and you could see 6 divisions then the field of view
would be 1.2 mm wide.
Remember: The field of view is different at different magnifications. The more you magnify
something, the less of it you can see in the same area.
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