Cell Structure. Cell Structure

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1 Cell Structure All living things are made of cells. Biology is the study of living things therefore, understanding cells and how they work is very important in this subject. Some of the key words you will need to use during this section are: Magnification, nucleus, plasma membrane, cytoplasm, cell wall, mitochondria, ribosomes, chloroplast, vacuole, function, specialised, fungus, bacterium, plasmid, structure, compare, contrast, unicellular, multicellular. Learning Outcomes You will be able to: label the different parts of a microscope use a microscope safely to study cells calculate the magnification of a microscope label the different parts of animal, plant, bacterial, fungal cells and viruses. describe the function of the different parts of the cells compare and contrast the different cells research the relationship between structure and function of specialised cells Cell Structure Cells are the basic unit of all living organisms. There are different types of cells: animal, plant, fungal, bacteria and viruses. Cells contain different parts called organelles. Each organelle has a particular function. Different types of cells contain different organelles. 1 P a g e

2 Microscopes The total magnification of a microscope can be calculated by multiplying the strength of the eyepiece lens with the strength of the objective lens. Total magnification = eyepiece lens x objective lens Don t forget the units when calculating total magnification.e.g. If the eyepiece lens is x10 and the objective lens is x40, the total magnification is x400. Learning Activity 1 1. Stick in handout number 1 and label the diagram of the microscope. 2. Stick in handout number 2 and complete the magnification tasks. Pass your work to the person sitting next to you and let them check your work. 2 P a g e

3 Stains are used in preparation of microscope slides to make cell structures (such as the nucleus, cytoplasm and cell membrane) more clearly visible Animal Cells You do not need to know the functions of all the organelles in an animal cell at this stage. However, you do need to learn the following: nucleus, cytoplasm, cell membrane (or plasma membrane), ribosome and mitochondria. A typical animal cell has the common structures shown in the diagram above. These include: Cell Membrane: The cell membrane contains the contents of the cell and provides a barrier to control what enters and leaves the cell. The cell membrane is often described as selectively permeable as it allows some but not all substances to pass across it. You will learn more about the cell membrane later. Nucleus: The nucleus controls everything that takes place in the cell. It is where DNA is stored within the cell. DNA contains a genetic code which is translated into proteins. All the chemical reactions that take place in cells are controlled by these proteins. You will learn more about how this happens later. Mitochondria: Mitochondria are the power houses of cells. They are found within the cytoplasm of the cell and they are the site of the majority of the chemical reactions involved in respiration. Respiration is a process where 3 P a g e

4 chemical energy is released from food molecules. We will learn more about respiration later. Ribosomes: Ribosomes are tiny structures also found within the cytoplasm. Ribosomes are the sites of protein production (synthesis) in cells. You will learn more about protein synthesis later. Plant Cells You have already learnt the functions of some of the structures which are also found in animal cells (nucleus, cell membrane, ribosomes and mitochondria). However, there are some structures that are only found in plant cells. You need to learn the function of these organelles (specialised subunit within a cell): Cell Wall: Plant cell membranes are surrounded by a wall which is made of cellulose fibres. Plant cell walls provide structure to the cell and to the plant. The cell wall allows the cell to fill with water without bursting. Plant cell walls are fully permeable. Chloroplasts: As well as mitochondria, plant cells also contain chloroplasts. The chloroplast is the site of Photosynthesis in the cell. This is where energy from sunlight along with carbon dioxide and water are used by the plant to produce sugar. We will learn more about photosynthesis later. Chloroplasts contain a green pigment called chlorophyll. Chlorophyll gives leaves their green colour and absorbs light that is used in the process of photosynthesis. Vacuole: Plant cells have a large central vacuole which fills with fluid, or sap, which helps provide structure to the cell and the plant. 4 P a g e

5 The cell wall is outside the cell membrane. Chlorophyll is the pigment found inside chloroplasts, don t get them mixed up! Learning Activity 2 1. Collect handout number 3 (animal and plant cell) and complete the labelling of the cell. 2. Copy and complete the following table using the information above: Cell Structure In plant or animal cell or both Function site of protein synthesis controls cell division and cell chemistry controls the movement of materials into and out of cells site of photosynthesis site of aerobic stages of respiration supports the cell site of chemical reactions Carry out Practical 1 (Observing Cells Under The Microscope) Collect the handout for observing cells under the microscope. Using the success criteria below, you are going to develop the skill of producing a scientific drawing. 5 P a g e

6 Success Criteria for Scientific Drawing Drawing done on blank paper Drawing done with sharp pencil Firm clear lines (no sketching) No shading/colour used (stipples allowed) Only relevant and easily seen details are included Large drawing (1/2 the page at least) Labels are neatly printed Labels all located to the right of the drawing Labels listed in an even column Label lines are parallel and done with a ruler Label lines do not cross Name and date located in top right corner Appropriate title located at the top Title underlined Total magnification located in bottom right Many students think that all animal cells look the same and all plant cells look the same. THIS IS NOT THE CASE. Cells are specialised and come in all shapes and sizes to suit their function. Make sure you learn a couple of examples of specialised cells. Research Task Below are just a few examples of specialised cells. You are going to research 2 or 3 different cells. 6 P a g e

7 Success Criteria 1. My work includes at least one plant cell and one animal cell. 2. I have described the role of the different cells and why they are important 3. I have linked the role/function of the cell to its structure. 4. I have included a labelled diagram of all the cells. 5. I have referenced the books and websites I got my information from 6. I have not just copied and pasted the work. Once you have completed your piece of work, use to success criteria to self and then peer assess your work before getting feedback from your teacher. As well as animal and plant cells there are also micro-organisms. The 3 main classes are fungi, bacteria and viruses. Fungi Mushrooms and toadstools are fungi, but these are made of lots of cells, so they are not microbes. Yeasts are single-celled fungi, so they are microbes. Fungi are usually the biggest type of microbe. If there is just one of them, we call it a fungus. Yeast is a single-celled fungus. Penicillium is a multicellular filamentous fungus. Fungal cells do not contain chlorophyll and therefore cannot make their own food they have to be supplied with food in the form of sugar. Except for yeasts which are unicellular, the bodies of fungi are constructed of units called 7 P a g e

8 hyphae. Hyphae are minute threads composed of cell walls (made of chitin) surrounding a plasma membrane and cytoplasm. The cytoplasm contains many organelles including mitochondria, nucleus, ER and ribosomes. Bacteria Bacteria are usually smaller than fungi. If there is just one of them, we call it a bacterium. Bacteria have many different shapes. Some have 'tails' (called flagella) that let them swim. Bacterial cells are different from plant and animal cells as they do not contain a membrane bound nucleus or mitochondria but they do have a circular bacterial chromosome and they have ribosomes. Some bacterial cells contain an extra ring of DNA called a plasmid. Bacterial cells are enclosed in a membrane, a cell wall and a capsule and some have flagella for movement. Virus Viruses are the smallest type of microbe. As a virus can only reproduce inside a cell, some people are not convinced that viruses are really living things. 8 P a g e

9 Learning Activity 3 1. Collect handout number 4 and stick in the diagrams of the virus as well as the fungi and bacterial cell. 2. Label the different parts of the cells. 3. Use the information you have just read to copy and complete the table below. Type of cell Animal Cell wall Cell organelles present ( )or absent (x) Cell Nucleus Chloroplasts Ribosomes Mitochondria membrane Plant Bacteria Fungi Challenge task Make 3-D model/poster of an animal and a plant cell. Success Criteria 1. Show the differences between animal and plant cells 2. Organelles are labelled accurately 3. The function of the organelles is described 4. Research is done into the relative sizes of the different organelles and this is taken into account in the model 5. The differences between the model and the real cell are highlighted Peer Assessment Get another group to assess your completed work. They will give 2 positive comments and one thing that could have been improved. Use the above success criteria to evaluate the piece of work. 9 P a g e

10 Teacher Assessment Show your work to your teacher and allow them to check your understanding. Check your UNDERSTANDING 1. Use an analogy to describe a cell and the roles of the different organelles found within the cell. 2. In your opinion, what are the 3 most important organelles within a cell? Why? 3. Would life be better if we were made of plant cells? Explain. Success Criteria Read over the following success criteria and evaluate your own learning. Your teacher may want to have a conversation with you about your progress. Skills I can draw a scientific drawing I can use a microscope effectively and safely. I can calculate the magnification of a microscope. I am able to reference sources when researching Knowledge and Understanding I can explain what the different parts of a cell do I can compare and contrast the different types of cell I can explain the link between the structure and function of a specialised cell. Have a conversation with the person next to you, explain what each of the following keywords mean. Take it in turns. Magnification, nucleus, plasma membrane, cytoplasm, cell wall, mitochondria, ribosomes, chloroplast, vacuole, function, specialised, fungus, bacterium, plasmid, structure, compare, contrast, unicellular, multicellular. 10 P a g e

11 Didbook is a tool for reflecting on your learning. It is important that you think carefully about your learning, have a clear idea about what you have achieved, what you haven t yet achieved, future goals, next steps to make sure you keep improving and identifying strategies you are going to use to improve your learning. Think carefully and answer the following questions: 1. What skills have you developed over the past few lessons? How do you know and how could you prove it to someone? 2. What areas have you found difficult? What strategies are you going to use to overcome these problems? 11 P a g e

12 Choice Extension Task Task Choose at least 2 of the following activities to complete. 1 Make a model of a specialised cell and explain how it's structure suits it's function. 2 Honey I Shrunk the Kids - Write a story describing a journey through a plant cell. Describe what you see, hear and feel. 3 Write a set of instructions for an idiot on how to use a microscope. 4 5 Use the microscope to look at some ready made slides and carry out some scientific drawings of what you see. Research the scientist Robert Hooke. Produce a piece of work to teach someone else about the man and his work. 6 Make a quiz to test your friend's knowledge on cells. 7 Write down 10 facts about cells that amaze your teacher! 8 Research cells that are able to move. Explain how and why they move. How long do cells live for and what happens to them when they die? Produce a piece 9 of work to answer these questions. 10 Make a cake that when cut open shows the different structures in a cell. 12 P a g e