3.1 Cells and cell function

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1 BTEC s own resources 3.1 Cells and cell function In this section: P1 How you are made 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. 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 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 Unit 3: See pages for more about DNA and chromosomes. Nucleus Contains DNA arranged in chromosomes Controls the activities of the cell, e.g. maintenance, repair and growth Activity A Cytoplasm Jelly-like substance Where chemical reactions of the cell occur List the similarities and differences between plant and animal cells. Cell wall Made from cellulose Prevents the cell from bursting and gives the cell shape No Vacuole Contains cell sap No Chloroplast Contains chlorophyll Where glucose is made in photosynthesis No Mitochondrion Releases energy for the cell chloroplast containing a green substance called chlorophyll cell membrane cell wall cytoplasm vacuole filled with cell sap cell membrane mitocondria cytoplasm 70 (a) Typical plant cell. (b) Typical animal cell.

2 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) cytoplasm red blood cell cilla (no ) female cell membrane cell wall cytoplasm male tail white blood cell (no ) 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, in the heart or which also line the insides of 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. Activity B Give three examples of tissues and where they are found in the body. Assessment activity 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 P1 Grading tip You need to use your knowledge of cells to help you to complete <P1. 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. 71

3 3.1 Cells and cell function: Lesson plan Duration 60 mins Working towards P1 Student book pages Subject specialism Biology Lesson resources 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 Suggested starter activity (10 mins) Learning Outcomes 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. 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 Unit 20 Biotechnology procedures and applications

4 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 microscope slide cover slip piece of onion beaker of disinfectant iodine solution prepared slide of cheek cells prepared slides of specialised cells tweezers and/or mounted needle 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.

5 BTEC Level 2 First Applied 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 microscope slide and cover slip onions divided into scale leaves tweezers and/or mounted needle safety glasses iodine solution and beaker of disinfectant prepared slides of specialised cells prepared slides of cheek cells (use methylene blue stain and a cotton bud) 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.

6 SK1 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. Visit today for more free materials and to save up to 15% on your next order. Pearson Education Ltd Copyright permitted for purchasing institution only. This material is not copyright free. 1

7 SK2 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. Visit today for more free materials and to save up to 15% on your next order.

8 SK3 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 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. Visit today for more free materials and to save up to 15% on your next order.