4.1.1 Cell structure The specification mentions a range of specialised cells and offers opportunities to use a microscope again later on in the course. Spec ref. Summary of the specification content Learning outcomes What most students should be able to do Suggested timing (hours) Opportunities to develop Scientific Communication skills Opportunities to develop and apply practical and enquiry skills Self/peer assessment opportunities and resources Reference to past questions that indicate success 4.1.1.2 Animal and plant cells Section 4.2.1 Principles of organisation, is covered at KS3 so the content be recapped now, rather than later in the course. Most animal cells have a nucleus, cytoplasm, membrane, mitochondria and ribosomes. Plant and algal cells also have a cell wall and often have chloroplasts and a permanent vacuole. Functions of the organelles. Required practical: Microscopy Label diagrams of animal and plant cells. Describe the function of the main organelles. Prepare slides of plant and animal cells and describe the procedure. Correctly use a microscope to observe cells under different magnifications. Describe the order of size of: cell, nucleus, chromosome and gene. 2 Recap cell structure from KS3 by drawing an animal and a plant cell on mini white boards. Class to vote on which are the best and why. Display diagrams of a and animal cell – students spot the difference between the two. Label diagrams of plant and animal cells. Complete a card sort to match the organelle to the function. Construct a table to compare animal to plant cells. Include organelles and processes that they carry out (eg respiration, photosynthesis and protein synthesis). Prepare slides and observe using a microscope. Watch video clips on plant and animal structures. Prepare slides of onion epidermis, rhubarb epidermis, cheek cells, spirogyra, moss etc. Observe under a microscope. Model plant and animal cells. Observation activity materials: microscopes slides coverslips tiles forceps mounted needles cotton buds iodine solution methylene blue onion rhubarb spirogyra moss. National Stem Centre – Cells and organ systems Video clips:
Use a light microscope to observe, draw and label a selection of plant and animal cells. A magnification scale must be included. Make a plant or animal cell model. 4.1.1.3 4.1.1.4 Cell specialisation Cell differentiation Cells differentiate to form different types of cells. Animal cells differentiate at an early stage, whereas many plant cells can differentiate throughout life. Differentiation is the generation of specialised cells which acquire different organelles to enable them to carry out specific functions. Explain the need for differentiation in a multicellular organism. Describe the differences between differentiation in plants and in animals. Explain how specialised cells are adapted for their function. 1 Write a job description for a newspaper for each type of specialised cell (xylem, sperm cell, red blood cell etc), eg: ‘Sperm cell wanted – must be a strong swimmer…’ This could be done using ICT. Watch video clips showing specialised plant and animal cells. What am I? Describe the key features of different specialised cells – students guess the cell type. Observe prepared slides of specialised cells under the microscope, or use bioviewers. Observe root hair under a microscope in sprouting mung beans. Observation activity materials: microscopes slides coverslips sprouting mung beans prepared slides bioviewers slide strips. Video clip:
Cells may be specialised to carry out a particular function. 4.1.2.3 Stem Topic can be delivered after Cell differentiation. Alternatively, you may want to create a separate section about biotechnology where stem cell research, and genetic engineering could be taught together. Stem cells are unspecialised cells that can differentiate to form many different types of cells. Stem cells from human embryos and adult bone marrow can be cloned and made to differentiate into different cells, eg nerve cells. Define the term ‘stem cell’. Describe where stem cells can be found in animals and plants. Describe in simple terms how nerve cells genetically identical to a patient could be obtained. Describe how stem cells could be used to help treat some medical conditions. Evaluate risks and benefits, as well as the social and ethical issues concerning the use of stem cells from embryos in medical research and treatments. 1 Watch a video clip showing cell differentiation in plants and animals. Watch the stem cell story at Europe’s stem cell website. Tell the story of Christopher Reeve (show photos of Superman or watch the Superman trailer) and get students to suggest how stem cells could be used to treat other people with paralysis. Provide a circus of different stem cell related articles which cover current uses, potential uses as well as pros and cons. Students circulate to complete a summary table on uses, pros and cons. Use of models. National Institute of Health – Teachers TV:
are smaller than eukaryotic cells and have a cell wall, membrane and cytoplasm, but do not have a nucleus. Their genetic material is a single loop of DNA or several small rings of DNA called plasmids in the cytoplasm. Construct a table to compare the structure of plant, animal and bacterial cells. Use Teachit interactive resources about cells of animals, plants and bacteria. 4.1.1.5 Microscopy An electron microscope has a much higher magnification and resolution than a light microscope, so it can be used to study cells in much finer detail and show organelles. Describe the differences in magnification and resolution of light and electron microscopes. Explain how electron microscopy has increased understanding of organelles. Calculate the magnification of a light microscope. Carry out calculations using the formula: 1 Use a variety of resources to research the differences between a light microscope and an electron microscope. Use online materials to make a display of cell images from a light microscope and from an electron microscope. Write a newspaper article entitled: ‘Microscope…..the best invention ever!’ where students explain the significance of the microscope and discuss what the world would be like if microscopes were never invented. Use online and printed materials to calculate the real sizes of cells and structures. Limited to the differences in magnification and resolution. Extension work Use a microscope with graticule to measure cells and calculate their real size. Observation activity materials: microscope graticule prepared slides calculator.
Rearrange the equation to calculate size or magnification. Convert values for the units: cm, mm, µm and nm. Calculate the real size of microscope images, and convert units as appropriate. Rearrange the equation to calculate a different unknown. 4.1.2 Cell division This section of the specification contains some difficult concepts, which you may want to teach later in the course. Spec ref. Summary of the specification content Learning outcomes What most students should be able to do Suggested timing (hours) Opportunities to develop Scientific Communication skills Opportunities to develop and apply practical and enquiry skills Self/peer assessment opportunities and resources Reference to past questions that indicate success 4.1.2.1 Chromosomes Chromosomes are found in the nucleus. They are made of DNA. Each chromosome carries a large number of genes. Describe what a chromosome is and where chromosomes are found in the cell. 0.5 Draw and label diagrams showing cell, nucleus, chromosome and gene. Consider the scale of these structures. Observe images of human karyotypes as seen under the microscope and arranged into pairs. Students could attempt Observe chromosomes using bioviewers or prepared slides. Observation activity materials: microscopes prepared slides bioviewers. National Human Genome Research Institute:
In body cells chromosomes are found in pairs. to arrange chromosome images into pairs. This be extended to show karyotypes of males, females, Down syndrome and Turner syndrome. Discuss the differences and suggest what the possible reasons and consequences of these differences are. Research on chromosome abnormalities. 4.1.2.2 Mitosis and the cell cycle This topic could be left until later and taught with Asexual reproduction in 4.6.1. Mitosis occurs during growth or to produce replacement cells. During mitosis: copies of the genetic material separate the cell then divides once to form two Describe simply how and why body cells divide by. Knowledge and understanding of the stages in mitosis are not required. Draw simple diagrams to describe mitosis. Draw a simple diagram to describe the cell cycle in terms of: cell growth, when the number of organelles increases replication of chromosomes, so the genetic material is doubled 1 Watch video clip showing mitosis. Discuss how organisms grow and relate this to cell division. Observe mitosis in cells. Role play the process of mitosis or use plasticine, pipe cleaners, beads etc to make a simple model. Draw simple diagrams to describe the cell cycle and mitosis. Use bioviewers or root tip squashes to show chromosomes and mitosis. Model mitosis. Video clip: (first part of Mitosis and meiosis) Observation activity materials: bioviewers microscopes slides coverslips root tips. Nuffield Foundation-
genetically identical cells. Mitosis forms part of the cell cycle. separation of the chromosomes: division of the nucleus division of the cell to form two identical cells. Activity: What would happen if…? Eg: ….DNA did not replicate? …..chromosomes did not line up down the middle? …..organelles did not replicate? Investigating mitosis in allium root tip squash Animation: 4.1.3 Transport in cells Spec ref. Summary of the specification content Learning outcomes What most students should be able to do Suggested timing (hours) Opportunities to develop Scientific Communication skills Opportunities to develop and apply practical and enquiry skills Self/peer assessment opportunities and resources Reference to past questions that indicate success 4.1.3.1 Diffusion Substances can move into and out of cells across membranes by diffusion. Define the term ‘diffusion’. Explain how temperature, concentration gradient and surface area affect the rate of diffusion. 2 Observe and suggest explanations: Time how long it is before students can smell a perfume placed in a corner of the room. Choose investigations as appropriate: potassium permanganate in beaker of water; potassium Demo materials: strong perfume concentrated NH4OH concentrated HCl
Definition of diffusion and factors affecting rate. Oxygen, carbon dioxide and urea passes through cell membranes by diffusion. Single celled organisms have a bigger surface area to volume ratio than multicellular organisms, so transfer sufficient substances across their surface. Multicellular organisms require specialised organ systems to exchange sufficient substances. Factors affecting the effectiveness of an exchange surface. Give examples of substances that diffuse into and out of cells. Calculate and compare surface area: volume ratios. Explain how the small intestine and lungs in mammals, and roots and leaves in plants, are adapted for exchange of substances. Describe and explain how an exchange surface is made more effective. Is the rate of diffusion different for different gases? Use concentrated ammonium hydroxide and hydrochloric acid in a large glass tube. Does temperature affect the rate of diffusion? Fresh beetroot placed in iced water and warm water. Record observations and suggest explanations. Watch a video or computer simulation of diffusion on BBC or McGraw-Hill website. Role play diffusion in gases and liquids at different temperatures and concentrations. Observe micrographs of exchange surfaces in plants and animals. Make drawings and relate structure to function. Produce a mind map to summarise diffusion and exchange surfaces. permanganate on agar investigate diffusion of different acids and alkalis through agar investigate rate of diffusion of glucose through cellulose tubing use digital microscope to observe diffusion of particles in milk or yogurt solution. diffusion. Observe slides or micrographs of villi, alveoli, root hair cells and leaves. Calculate surface area: volume ratios for different objects or using data about organisms. gloves mask forceps cotton wool long glass tube with strips of damp litmus along length beetroot beakers kettle ice two gas jars of NO2 two empty gas jars. Optional demo materials: beaker of water pot perm crystals straw forceps agar in test tube or
may move across cell membranes by osmosis. Osmosis is the movement of water from a dilute solution to a more concentrated solution through a partially permeable membrane. Required Practical: Osmosis Investigate the effect of a range of concentrations of salt or sugar solutions on the mass of plant tissue. Apply knowledge of osmosis to unfamiliar situations and make predictions. the capillary tube rises during the lesson. Explain the movement of molecules as a special type of diffusion through a partially permeable membrane. Predict and explain what will happen to cellulose tubing bags filled with water or sugar solution, placed in beakers of water or sugar solution. Observe and explain the effects of and concentrated salt solution on cells of onion/ beetroot/ rhubarb. Use a model to show osmosis or get students to make a model. Watch a computer simulation of osmosis in plant and animal cells. Watch a video clip of osmosis in blood cells. Investigate the effect of water and concentrated salt solution on onion/ beetroot/ rhubarb cells. osmosis. attached to capillary tube held in clamp, beaker of water. 2) Four beakers (two of water and two of sugar solution); four cellulose sausages (two of water and two of sugar solution). Observation activity materials: living plant cells: onion/ beetroot/ rhubarb microscopes slides coverslips water concentrated solution pipettes