3.1 Cells and cell function

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3.1 Cells and cell function

In this section:

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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.

Features and functions of a cell

The table below shows the function of specifi c 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

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.

Key terms

Unit 3: See pages 72–73 for more about DNA and chromosomes.

nucleus mitocondria cell membrane

cytoplasm chloroplast containing a green

substance called chlorophyll cell membrane

cell wall nucleus

cytoplasm

vacuole filled with cell sap

(a) Typical plant cell. (b) Typical animal cell.

Activity A

List the similarities and differences between plant and animal cells.

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Unit 3 Biology and our environment

Activity B

Give three examples of tissues and where they are found in the body.

did you know?

Stem cells are cells which are

undifferentiated. They have the ability to grow into any type of specialised cell under the right conditions.

Grading tip

You need to use your knowledge of cells to help you to complete <P1.

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Functional skills

You can use your researching skills in ICT and reading in books to search for more information about cells and their function.

1 Which part of a cell controls the activities of the cell and what

does it contain?

2 Research further into cell structure and variation between cells

using the Internet and books. Make notes on your findings.

Assessment activity 3.1

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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) (c) (d) (e) (f) (g) female

nucleus

cytoplasm red blood cell (no nucleus) cilla white blood cell (no nucleus) nucleus cytoplasm male nucleus tail cell membrane nucleus nucleus nucleus nucleus

nucleus cell wall

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

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 •

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, •

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BTEC Level 2 First Applied Science

Unit 3

Biology and our environment

© Pearson Education Ltd 2010. Copyright permitted for purchasing institution only. This material is not copyright free.

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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

HSW 3 11

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

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BTEC Level 2 First Applied Science

Unit 3

Biology and our environment

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

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BTEC Level 2 First Applied

Unit 3

Biology and our environment

© Pearson Education Ltd 2010. Copyright permitted for purchasing institution only. This material is not copyright free.

1

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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BTEC Level 2 First Applied Science

Unit 3 Biology and our environment

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

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.

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.

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BTEC Level 2 First Applied Science

Unit 3 Biology and our environment

© Pearson Education Ltd 2010. Copyright permitted for purchasing institution only. This material is not copyright free.

1

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.

SK2

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BTEC Level 2 First Applied Science

Unit 3 Biology and our environment

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 0.1mm wide and you looked through a microscope with a total magnification of ×40, the cell would look 4mm 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 0.2mm and you could see 6 divisions then the field of view would be 1.2mm 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.

Figure

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