1. Section 1 Introduction to Cells

2. Animal Cell nucleus cell membrane cytoplasm

3. Plant Cell cytoplasm green chloroplast cell wall nucleusvacuole cell membrane

4. The nucleus contains the genetic material of an organism. It controls all the cell’s chemical reactions. It also controls the growth and development of a cell, and so determines the cell’s structure and function. Nucleus nucleus

5. Cells take in many chemicals from their surroundings, and release other chemicals into their surroundings. The cell membrane is a very thin boundary which controls the entry and exit of these materials. Cell membrane

6. There are many chemical reactions happening in all of your cells. These reactions keep the cell alive and allow it to carry out its specific function. Cytoplasm

7. The cell wall is a rigid structure made of a tough mesh of cellulose fibres. It helps to support a plant cell. Cell wall

8. The vacuole is filled with water and pushes out towards the cell wall. This provides support for the plant. Vacuole

9. Plant cells may also contain chloroplasts in the cytoplasm. These contain a chemical called chlorophyll which absorbs light energy for photosynthesis. This allows plant cells to make food. Only the green parts of a plant contain chloroplasts. Chloroplasts

10. StructureFeatureFunction Nucleus Large, usually round structure containing genetic materials Controls all cell activities Cell Membrane Very thin layer surrounds the cytoplasm Controls the passage of substances into and out of the cell Cytoplasm Fluid, jelly-like materialSite of all bio-chemical reactions Cell Wall Outer layer made of basket-like mesh of cellulose fibres Provides plant cells with support Vacuole Fluid-filled sac-like structure in the cytoplasm Stores water and minerals and provides extra support for plant Chloroplasts Disk-like structure containing green chlorophyll Trap light energy for making food by photosynthesis

11. Microscopes Cells are usually too small to be seen with the naked eye Microscopes are used to magnify them Stains (eg. methylene blue or iodine) can be applied to highlight certain cell structures Your teacher will demonstrate how to prepare slides of onion cells and cheek cells, and you will then prepare your own slides and view them under the microscope. You should make labelled drawings of what you see. Include the magnification used.

12. Examining Onion Cells Aim: To observe and draw onion cells using a microscope. Equipment: Glass slide Cover slip Onion skin Iodine stain Microscope Lamp

13. Collect a thin piece of onion skin. Spread the skin on a slide. The skin must not overlap. Stain the cells by adding 2 drops of iodine stain. Place a cover slip over the skin. Use a pencil to lower the cover slip gently so the air is pushed out. Examine the cells under low then medium power. You should be able to see lots of cells arranged like bricks in a wall. Adjust the microscope to a higher power. Draw exactly what you see through the “field of view” using a pencil. Label as many structures as you can see. Return the slide and pack your microscope away carefully. Method:

14. Onion cells in iodine cytoplasm cell wall nucleus

15. Examining Cheek Cells Aim: To make a slide of cheek cells and draw them. Equipment: Glass slide Cover slip Cotton bud Methylene blue stain Microscope and lamp Paper towel

16. Rub the cotton bud over the inside of your cheek to remove some of the cells. Wipe the cotton bud over the surface of a glass slide. Place the cotton bud in disinfectant. Stain the cells with 1 drop of methylene blue stain. Remove some of the stain using paper towel. Use a pencil to lower the cover slip so the air is pushed out. Draw the cells and label the structures. Once you have finished, place the slide and cover slip in disinfectant. Pack away your microscope carefully. Method:

17. Cheek cells in methylene blue cytoplasm cell membrane nucleus

18. Plant Cells Some plant cells have chloroplasts. These disc-like structures contain a green pigment called chlorophyll that traps light so that the plant can make its own food by a process called photosynthesis

19. chloroplasts cell wall

20. Comparison of Cell Types StructurePlant CellAnimal Cell cell wall cell membrane nucleus cytoplasm chloroplasts vacuole

21. Comparison of Cell Types StructurePlant CellAnimal Cell cell wall YesNo cell membrane Yes nucleus Yes cytoplasm Yes chloroplasts YesNo vacuole YesNo

22. Textbook questions Answer q. 1-4 on page 4 in sentences

23. Multicellular Organisms Organisms are usually made up of millions of cells that work together e.g. oak tree or human These are called multicellular organisms

24. Unicellular Organisms But there are also organisms that are made up of just one single cell These are called unicellular organisms and are very small e.g. Amoeba

25. Different types of cells Microbes : a word used to describe a microscopic unicellular organism such as bacteria and fungi.

26. Microbes Some microbes are harmful and can cause disease. Others can be useful e.g. helping to make useful products in biotechnology industries. An example of a useful fungus is penicillium, which produces the chemical penicillin, an antibiotic.

27. Cells & Biotechnology Yeast cells are important to biotechnology because under the right conditions they can convert sugars into alcohol and carbon dioxide – this process is called fermentation yeast sugarcarbon dioxide and alcohol

28. Yeast Is a unicellular fungus. It cannot photosynthesise, it has no chloroplasts. It needs a food source e.g. sugar. It can respire anaerobically ( in the absence of oxygen). It is widely used in the brewing and baking industries. It reproduces by ‘budding’. Yeast cells can reproduce rapidly if they have a source of food and a suitable temperature.

29. 30 mins 1 hour 1 hour 30 mins 2 hours 2 hours 30 mins

30. Yeast dividing calculation One yeast cell is placed in a sugar solution. It divides to form 2 cells in 30 minutes. How many yeast cells will there be after 12 hours? How to work it out 12 hours = 24 divisions Number doubles each division

31. 1.2 2.4 3.8 4.16 5.32 6.64 7.128 8.256 9.512 10.1024 11.2048 12.4096 13.8192 14.16384 15.32768 16.65536 17.131072 18.262144 19.524288 20.1048576 21.2097152 22.4194304 23.8388608 24.16777216 Answer = 16,777,216 yeast cells

32. Looking at microbes Yeast is a very useful microbe, it is a fungi. Looking at yeast… Collect the following: Microscope, slide, 1 drop of yeast, cover slip. Prepare a yeast cell slide.  View the yeast cells at low and high power. Look for cells that are budding.

33. Looking at yeast cells

34. Applications of Fermentation by Yeast Brewing Industries Alternative Fuel Industries e.g. Gasohol (alcohol mixed with petrol) Bread-making Industries

35. Yeast and alcohol Yeast can make alcohol when it has a source of sugar. This is called alcoholic fermentation and is used in the brewing industries to make wine and beer.

36. Yeast and alternative fuels Yeast can be added to sugar to make alcohol. Alcohol is flammable and can be used as fuel. However, it must first be mixed with petrol. This forms an alternative fuel called gasohol. alcohol (made by yeast) + petrol = gasohol

37. Yeast and breadmaking Yeast is added to flour, water and a little sugar (to feed the yeast!). The dough is then left for about and hour in a warm place. During this time the yeast produce carbon dioxide and a little alcohol. The carbon dioxide gas causes the dough to rise. It is then put in an oven to bake. This kills the yeast and evaporates off the alcohol.

38. Yeast and breadmaking 1.Label two beakers A and B. 2.Add 3 spoons of flour and half a spoon of sugar to each beaker. 3.Add yeast suspension to beaker A and mix with a stirring rod to make a dough. 4.Add water to beaker B and stir to form a dough. 5.Transfer the doughs to two measuring cylinders and transfer the labels A and B onto them. 6.Leave in a warm place for 30 minutes. 7.Look at the height of the dough in each cylinder.

39. Yeast and breadmaking Results Complete the results table. Conclusion: What effect does yeast have in breadmaking?

40. Antibiotic Production using other fungi Alexander Fleming Video clip

41. Antibiotic Production Antibiotics are antibacterial chemicals produced by microbes such as fungi. They prevent the growth and may cause the death of other microbes. Antibiotics do not work against viruses so cannot be used to treat the cold or the flu. Many bacteria are now resistant to antibiotics. Video clip

42. Penicillium colony bacterial colony bacteria cannot grow near the Penicillium

43. Antibiotic multidisc Clear zone around arm shows that the bacteria is killed by the antibiotic. This would be a good antibiotic to give the patient. A disc with several antibiotics on the ‘arms’ can be used to find out which is the most effective antibiotic to treat an illness. This is used in labs where swabs from patients are sent for checking.

44. Resistant bacteria In the above example, the bacteria S.Albus is not killed by the antibiotic V. We say that the bacteria is resistant to the antibiotic. In the above example, the bacteria M.Luteus is killed by antibiotic V. We say that the bacteria is sensitive to the antibiotic.

45. Resistant bacteria If a bacteria is not killed by an antibiotic we say that the bacteria is resistant to the antibiotic. If a bacteria is killed by an antibiotic we say that the bacteria is sensitive to the antibiotic. An antibiotic multidisc can show which antibiotic is best to treat each bacteria.

46. The use of bacteria Bacteria can be used to produce -Yoghurt -Biogas (another alternative fuel)

47. Yoghurt Making During the souring of milk, bacteria growing in the milk will feed on the milk sugar (lactose) and break it down to lactic acid. This process is called lactic acid fermentation Lactic acid makes milk curdle. The manufacture of yoghurt depends on the curdling of milk Lactose Lactic Acid bacteria

48. Investigating Microbes… True or False…True or False… 1.Microbes are all harmful and can cause disease 2.Fungi can be used in yoghurt making 3.Bacteria can be killed by antibiotics 4.Yeast make their own food through the process of photosynthesis 5.Some bacteria are resistant to antibiotics 6.Fungi carry out fermentation 7.Fermentation releases oxygen 8.Yeast use glucose as an energy source for respiration 9.Gasohol is petrol mixed with alcohol 10.Antibiotics are produced by fungi

49. Diffusion Diffusion is the movement of molecules in a liquid or gas from high to low concentration until they are evenly spread out Diffusion clip – BBC learning zone

50. Cells and diffusion The entry and exit of substances in and out of cells is called diffusion. This happens across the cell membrane. Animal cells take in glucose and oxygen by diffusion. Carbon dioxide and waste materials leave animal cells by diffusion.

51. Cells & Osmosis Water also enters and leaves cells by a similar process called osmosis. Osmosis is the special diffusion of water from high water concentration to low water concentration through a selectively permeable membrane.

52. Selectively Permeable Membranes Pores in the membrane are small, only small molecules such as glucose, oxygen and carbon dioxide can get through. Large molecules such as starch cannot pass through. Selectively permeable membranes allow certain molecules to pass through but not others. nucleus selectively permeable membrane cytoplasm

53. Selectively Permeable Membranes Cell membranes are described as selectively permeable. This means that they allow small molecules like oxygen and water to pass through them freely. This is because the membrane has tiny holes in it called pores that make it permeable. Large molecules like starch are unable to pass through.

54. Visking tubing Visking tubing is a selectively permeable material that can be used to show the effect of osmosis on cells. The visking tubing behaves like a cell membrane, and we can use it to make model cells. Your teacher will show you how to use it.

55. Osmosis experiment A B Visking tubing bag 10% sugar solution water Boiling tube

56. Results AB Mass of bag and contents at start (g) Mass of bag and contents after 20 minutes (g) Difference in mass (g)

57. Conclusion Bag A increased/decreased in mass. This was because water moved in/out by osmosis. Bag B increased/decreased in mass. This was because water moved in/out by osmosis. Water always moves from ________ water concentration to ______ water concentration.

58. Answer the following questions in sentences 1.Why was the visking tubing bag dried in a paper towel before being weighed? 2.Why was visking tubing used in this experiment? What property does it have that makes it a good model cell? 3.What would happen to an onion cell placed in pure water? 4.What would happen to a cheek cell placed in 10% sucrose solution?

59. Concentration Gradient high ground gradient (slope) low ground ball ball rolls down gradient ball stops

60. Concentration Gradient Like the ball on the slope, water always moves down a gradient from high to low Solutions are made up of a solute dissolved in a solvent e.g. sugar dissolved in water Concentrations of the mass of solute are written in percentages e.g. 1 % sugar solution contain 1% sugar and 99% water.

61. Concentration Gradient The difference in concentration of two solutions is called a concentration gradient water molecule sugar molecule

62. Concentration Gradient Water moves down a concentration gradient by osmosis from high to lower water concentration. The water will stop moving when the two concentrations are equal.

63. Osmotic Effect On Cells Water concentrations If we think about solutions in terms of their water concentrations, it is easier to recognise which direction water molecules will flow in. A dilute sugar solution will have a high concentration of water, whereas a concentrated sugar solution will have a lower water concentration

64. Dilute Sugar Solution Concentrated Sugar Solution Low water concentration High sugar concentration High water concentration Low sugar concentration

65. Solutions in the body fall into one of three categories: Hypotonic – Where the solution has a higher water concentration than the cell. Isotonic – Where the solution and the cell have an equal water concentration. Hypertonic – Where the solution has a lower water concentration than the cell. Water Concentrations

66. In a hypotonic solution, the water will move from the solution into the cell. In an isotonic solution the water concentration will stay the same. In a hypertonic solution the water will move from the cell into solution.

67. Water Concentrations Hypotonic Solution H 2 O concentration > A hypotonic solution has a higher water concentration than the water concentration within the cell, so water enters by osmosis. cell Direction of water movement

68. Water Concentrations Hypertonic Solution cell H 2 O concentration < A hypertonic solution has a lower water concentration than the water concentration within the cell, so water leaves the cell by osmosis.

69. Water Concentrations cell H 2 O concentration = Isotonic Solution An isotonic solution has a water concentration that is equal to the water concentration within the cell, so there is no gain or loss of water by osmosis.

70. Osmosis in potato tissue

71. Plant Cells and Osmosis Hypotonic solution : more water outside of the cell than inside, therefore water will move into the cell by osmosis. This causes the cell to swell and become turgid Hypertonic solution: more water inside the cell than outside, therefore water will move out of the cell by osmosis. This causes the cell to become softer or flaccid

72. Animal Cells & Osmosis The effects of osmosis on animals cells are totally different to plant cells because animals cell structures are different Animals cells do not have: Cell walls Vacuoles

73. Animal Cells & Osmosis Red blood cells (RBCs) float in a solution called plasma which is isotonic RBCs in isotonic plasma do not change size because the water has no concentration gradient to follow RBCs in hypotonic and hypertonic plasma will change because there is a concentration gradient for water to follow

74. Normal RBC RBC in hypertonic solution RBC in isotonic solution RBC in hypotonic solution Cell loses water and shrinks No net osmosis, cell stays the same Cell takes in water, swells and eventually bursts