This document summarizes key concepts about investigating cells using microscopes and the process of diffusion and osmosis. It describes the major parts of light microscopes and how to properly use one. It explains that diffusion is the passive movement of molecules from an area of high concentration to low concentration. Osmosis is a type of diffusion where water moves through a selectively permeable membrane from high to low concentration. The document compares how animal and plant cells are affected by osmosis, becoming turgid when gaining water and plasmolyzed when losing water.

1. INVESTIGATING CELLS

2. This unit is divided into five sub-topics. Investigating……… Diffusion Living cells Cell division

3. Enzymes And Aerobic respiration

4. SUB-TOPIC A... Investigating living cells

5. Overview In the same way that there are different kinds of cells inside you, different organisms have different types of cells. Trees have different cells than you and so do monkeys. Each of those cells is different in some way.

6. What Is a Microscope? Name derived from Greek words: micro meaning “small” and scope “to see” Used to see details invisible to the naked eye A valuable tool for the biologist Research in cell biology Medical diagnoses and tests Observation of microbes

7. What Is a Microscope? Light microscope.Transmitted light passes through a specimen on a glass slide, through two or more magnifying lenses (ocular lens & objective lens), and appears as an enlarged image.

8. What Are the Major Parts of the Light Compound Microscope? Eyepiece lens Body tube Coarse adjustment Fine adjustment Revolving nosepiece Objective lenses Stage Stage clips Base

9. What Are the Major Parts of a Light Microscope? Eyepiece (ocular) lens - magnifies image Body tube – directs light through scope Nosepiece – contains objective lenses and switches from high to low power Arm – handle to carry microscope Stage – platform used to mount microscope slide

10. What Are the Major Parts of a Light Microscope? Mechanical stage adjustment knobs – moves slide across stage to view different areas of specimen Objective lenses – high & low power, magnifies image Coarse adjustment knob – rough focusing Fine adjustment knob – fine focusing

11. How do you use a microscope? -rules for microscope use Use two hands to carry the microscope Lens paper only to clean lenses Always begin with low power Fine focus only when using high power Return scope to assigned place with low power in place, and cord neatly wrapped.

12. How do you use a microscope? -focusing hints Turn revolving nosepiece to low power Place slide with cover slip on stage and center specimen Use adjustment to bring slide and stage as close together as possible

13. How do you use a microscope? -focusing hints (cont.) Look into eyepiece and move stage with coarse adjustment until specimen comes into view For high power viewing: follow above steps and then rotate nosepiece to high power objective.

14. What Are Some Characteristics of Microscope Viewing? Magnification. The power of magnification is marked on each lens. For example: ocular = 10x, low power = 10x, high power = 45x. Note: scopes will vary.The total magnification is determined by multiplying the power of the ocular lens times the power of a single objective lens. For example: under low power (10x)(10x) = 100x. Therefore, your object appears 100 times greater than natural size.

15. Eyepiece Lens X Objective Lens = Total Magnification

16. Low Power = 4 x Medium Power = 10 x High Power = 40 x Objective Lenses

17. Vocabulary Review Magnification – enlargement of image Resolution – clarity of image Transmitted light – light that passes through a specimen Reflected light – light that bounces off a specimen Now lets have a look at some cell stuff !!!!

18. Cells Tissues Organs Systems Organisms

19. Animal cells Complex organisms like you are made up of many different kinds of cells. Nucleus controls what the cell does. Contains the DNA (with genes) Cytoplasm is where all the chemical reactions take place. Cell membrane holds the cell together and controls what goes in and out of the cell.

20. Plant cell Plant cells are very special as they can trap sunlight and store the energy as “plant food” Nucleus controls what the cell does. Contains the DNA Cytoplasm is where all the chemical reactions take place. Cell membrane holds the cell together and controls what goes in and out of the cell Chloroplasts containing chlorophyll for photosynthesis Vacuole containing cell sap, a solution of sugar and salts. Ridged cell wall made of cellulose, gives support for the cell

21. The design of a cell is a clue to its function. This group of four cells are very thin. This would allow small molecules to pass through them So what do you think this cell is specialised for. These cells are specialised for lining blood capillaries. If you look carefully you can usually work out what the cell speciality is.

22. Can you work out what this cell’s function is? The obvious feature is the hairs. Hairs on cell usually indicate that its function is for moving something. This cell is specialised for moving egg cells inside the female reproductive systems.

23. Comparing animal cell and plant cells Both cells have:- A nucleus Cytoplasm Cell membrane But only plant cells have:- A cell wall A vacuole Chloroplasts Remember there are lots of different kinds of animal and plant cells but all of them have the above features

24. 6 7 8 9 A white blood cell B gland cell C sperm cell D capillary wall cell The drawings show four kinds of cell that are found in the human body. Match up their names.

25. The drawings show four kinds of cell that are found in the human body. A B C D 10. Which kind of cell is specialised for ingesting microbes? 11 . Which kind of cell is specialised for communicating with many other cells? 12. Which kind of cell is specialised for moving egg cells inside the female reproductive system? 13. Which kind of cell is specialised for moving oxygen around the body?

26. Sub topic B Investigating Diffusion

27. What is Diffusion ???? Molecules in a liquid and a gas move about freely all the time Molecules move from areas where they are numerous to areas where there aren’t so many of them So… Diffusion is… The movement of a substance from an area Of high concentration to one of Low concentration

28. So Which things can diffuse? Dissolved foods(eg. Amino-acids, glucose,fatty acids) Oxygen Carbon Dioxide Water Diffusion is important because it is the process By which USEFUL molecules enter the body Cells and waste products are REMOVED

29. Diffusion of liquids

30. DIFFUSION Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural kinetic energy.

31. Diffusion of Bromine

32. Diffusion of Bromine

33. Diffusion through a membrane Cell membrane Inside cell Outside cell

34. Diffusion through a membrane Cell membrane Inside cell Outside cell diffusion

35. Diffusion through a membrane Cell membrane Inside cell Outside cell EQUILIBRIUM

36. Diffusion The raw materials and end products of respiration get INTO and OUT of cells by DIFFUSION DIFFUSION is the movement of molecules from an area of HIGH concentration to an area of LOW concentration until EVENLY SPREAD Examples : O 2 and Glucose move from high conc in blood to low conc in cells (where they get used in respiration) CO 2 moves from high conc in cells (where it is produced in respiration) to low conc in blood

37. An example of diffusion…in YOU Oxygen moves from HIGH concentration(in the AIR) to a LOWER concentration(in the Blood) The CELL MEMBRANEs control this movement into and out of the cell It is said to move DOWN A CONCENTRATION GRADIENT

38. Osmosis : The net movement of water molecules along a concentration gradient from an area of high water concentration (HWC) to an area of low water concentration (LWC) through a selectively permeable membrane . Osmosis is just a special case of DIFFUSION

39. More on Membranes… PERMEABLE means “allows anything to pass through” Membranes allow small molecules to pass through (like water) … but prevent larger molecules from passing through This is called SELECTIVELY PERMEABLE

40. Passing water… Pure water has the highest water concentration possible As more salt/sugar is dissolved,the water concentration DECREASES A concentration gradient may be caused REMEMBER: Osmosis is the movement of water Molecules from high to low concentration DOWN A CONCENTRATION GRADIENT

41. Osmosis in animal cells Animal cells are surrounded by only ? …… .. A MEMBRANE If too much water enters by OSMOSIS,what will happen ? …… they will swell up and BURST If too much water leaves by OSMOSIS,what will happen ? …… they will shrivel up

42. Osmosis in ANIMAL CELLS In Pure water In STRONG Sugar solution WEAK sugar/salt solution INSIDE animal cell Cell swells & ... BURSTS ! WEAK sugar/salt solution INSIDE animal cell Cell shrinks : PLASMOLYSED

43. Osmosis in Red Blood Cells Shrunken RBC Normal RBC

44. The Role of a Contractile Vacuole in an Amoeba

45. Osmosis in Plant cells Plant cells have a strong cell wall outside the membrane This all prevents them swelling up too much They become STIFF and HARD ( like a FOOTBALL) … .we call this TURGID If they lose water they become LIMP AND FLOPPY (like a ball with no air in it) Because the membrane has shrunk away from the cell wall We call this a PLASMOLYSED cell

46. Osmosis in PLANT CELLS In Pure water In STRONG Sugar solution WEAK sugar/salt solution INSIDE potato cell Cell swells : TURGID WEAK sugar/salt solution INSIDE potato cell Cell shrinks : PLASMOLYSED

47. Osmosis in Plant Cells Normal Red Onion Cells Plasmolysed Red Onion Cells

48. Important Terms Turgid - the term used to describe a plant cell which has swollen due to entry of water by osmosis. Plasmolysed - the term used to describe a plant cell whose contents have shrunk due to loss of water by osmosis.

49. Hypotonic (HWC) - a region of lower water concentration (to the surroundings) Hypertonic (LWC) - a region of higher water concentration. Isotonic - a region where there are equal water concentrations on either side of a membrane. Some Important Terms

50. Effects of osmosis on cells a. Isotonic - “same strength” b. Hypotonic - “below strength” c. Hypertonic - “above strength” These all refer to concentration of solute molecules Isotonic solution Hypotonic solution Hypertonic solution

51. Osmosis Osmosis is a special type of diffusion Osmosis is the movement of WATER from where it is in high concentration to where it is in low concentration across a selectively permeable membrane (cell membrane) During OSMOSIS , water can either leave or enter a cell depending on the STRENGTH of solution surrounding it ( be careful here!) REMEMBER : All cells contain a weak salt/sugar solution.

53. Sub-topic C Investigating Cell Division

54. All cells of plants and animals grow to a certain size and then divide. The size of the plants and animal varies, not so much in the cell size, but in the number of cells the organism has.

55. Human has about 100 trillion cells (100,000,000,000,000 or 10 14 )

56. Why are there no giant cells ( since there are giant animals) Largest cell in humans is the sciatic nerve in leg -approximately 2 meters long. If a cell becomes too big, its surface area would be too small to allow food or oxygen to enter or waste products to leave.

57. Why Cells Divide Cell size is limited Cells cannot keep growing indefinitely Replacement of damaged cells Growth - embryo Sexual reproduction - meiosis

58. Cell Cycle and Mitosis Before a cell divides it must copy DNA Genes are found on chromosomes Chroma - colored body Soma - body First noticed when staining cells To look at under microscope Only visible sometimes Chromatin - combo of DNA & protein

59. Mitosis is a process of cell division that increases the number of body cells in an individual organism. Mitosis ensures genetic continuity. The genetic materials in the parent duplicate and then divide into two identical sets. After this the cytoplasm divides as well.

60. 1879 Walter Flemming used red dye to observe cell structures during mitosis, it killed the cells and so he had to take pictures at each stage in order to come up with a pictorial model of mitosis.

61. Same as animals except: -plants develop a cell plate ( wall) between daughter cells. Mitosis in Plants

62. Sexual Reproduction Each parent contributes genes to the offspring. each offspring has a different set of inherited traits from the parents different also than any other members of its own species. Gives offspring a better chance of surviving in a changing environment.

63. Involves specialized haploid reproductive cells called gametes female - egg , male - sperm When male and female gametes unite, a fertilized egg, or zygote , is formed. The zygote can develop into a complete mature organism. The cell division in sexual reproduction is called meiosis .

64. Chromosome: is the structure in the nucleus that contains hereditary material.

66. One chromosome Unduplicated (unreplicated) Replicated chromosome Consists of 2 sister chromatids Exact copies of each other Connected by a Centro mere Cell division separates chromatids Each new cell gets one copy of each chromosome

68. Duplicated Chromosome

69. Mitosis Mitosis is the process by which new body cell are produced for: Growth Replacing damaged or old cells. This is a complex process requiring different stages

70. 2 daughter cells identical to original Parent cell Chromosomes are copied and double in number Chromosomes now split

71. Mitosis All daughter cells contain the same genetic information from the original parent cell from which it was copied. Every different type cell in your body contains the same genes, but only some act to make the cells specialise – e.g. into nerve or muscle tissue.

72. Mitosis – bone cell slides 2 4 5 Parent cell Chromosomes copied Copies separating 2 daughter cells Cells split

73. Plants Apical Meristem

74. Rat – epithelial cells

76. 21 trisomy – Downs Syndrome Can you see the extra 21 st chromosome? Is this person male or female?

77. Cancer Cell cycle control system Enzymes in cell control when and where cells divide Malfunction in system means cells divide at inappropriate times and places Benign tumor - abnormal mass of essentially normal cells Stay at original site, don’t move Cancer uncontrolled cell division

78. Cancer Problem not only uncontrolled division Metastisis Cancer cells can move to other sites New tumor at that site Three treatments Surgery to remove tumor Radiation Chemotherapy Last two aimed at controlling division

80. Cancer treatments Radiation Disrupts cell division Most actively dividing cells are tumor Can damage normal cells- ovaries / testes Chemotherapy Some disrupt cell division Taxo l freezes spindle Vinblastine prevents spindle formation

81. Sub-Topic D... Investigating Enzymes What they do and how they do it !

82. What are Enzymes ? Living things work at fairly low temperatures They need many chemical reactions to keep them alive So… where do enzymes fit in ? They are “BIOLOGICAL CATALYSTS” Where are they found ? In ALL LIVING CELLS A catalyst is a substance which speeds Up a reaction but is unchanged by it !

83. Enzymes Enzymes are biological catalysts. They help the reactions that occur in our bodies by controlling the rate of reaction. Yeast is an example of an enzyme. It is used to help a process called fermentation: The alcohol from this process is used in making drinks and the carbon dioxide can be used to make bread rise. Enzymes work best in certain conditions: Enzymes are denatured beyond 40 O C Sugar Alcohol + carbon dioxide Enzyme activity Temp pH pH 40 0 C Could be protease (found in the stomach) Could be amylase (found in the intestine)

84. Enzymes - Where can we find them? Meat tenderisers Washing powders Err, but you just said that they were In all living cells didn't you ?

85. Enzymes – Where can we find them in us? One place is in our digestive system! Digestive enzymes are made and work here to help us digest our food To allow them to do this – the digestive system provides an environment suited to the needs of each enzyme.

86. Enzymes – What happens when we eat cake? Firstly - What food groups does cake contain? Fats (i.e., Butter) Protein (i.e., Egg) Carbohydrate (i.e., Starch) Water Vitamins Minerals … And don’t forget the CHOCOLATE !

87. A bit about chemical reactions.. They either involve the BREAKDOWN of big molecules into smaller ones Or they BUILD UP smaller molecules into bigger ones This is called a SYNTHESIS reaction Without enzymes,the chemical reactions In living cells would be far too slow To keep life going ! !

88. More reaction facts… An example of a BREAKDOWN reaction.. The enzyme,AMYLASE breaks down STARCH into MALTOSE An example of a SYNTHESIS reaction... The enzyme PHOSPHORYLASE builds up glucose(-1 phosphate) into STARCH. BUT REMEMBER,EACH ENZYME CAN ONLY CATALYSE ONE REACTION.

89. Enzymes – How they work! Enzymes Big Molecule of Protein (for example) Lots of Smaller Amino-acids

90. What’s this ‘one reaction’ stuff all about then ? The substance on which an enzyme acts is called the SUBSTRATE The reaction happens when the ENZYME molecule and the SUBSTRATE molecule are fitted together Each ENZYME has to be shaped EXACTLY to suit its own substrate So a DIFFERENT ENZYME is needed for every SUBSTRATE We can summarise this by saying that Enzymes are SPECIFIC...

91. We call this the lock-key hypothesis!!

92. Enzymes – What happens when we eat cake? Mouth Stomach Small Intestine Large Intestine & anus Chewing Alkaline Carbohydrates Mixing Acidic Protein Absorbing Alkaline Protein Fats Carbohydrates Squeezing & Absorbing Water Removal of waste

93. Enzymes – What happens to the food we eat? Poo Growth & Energy

94. ENZYMES ARE... Made of protein So they are DENATURED at high temperatures (above about 50 oC ) Their rate of activity increases with temp. up to a maximum,then falls to zero as the enzyme is denatured Also affected by pH (each enzyme has its own range of pH in which it will work i.e Pepsin only works between pH 1 - 4 Where do we find Pepsin in the body ?

95. Enzymes in living cells Enzymes are PROTEINS which are present in ALL LIVING CELLS. They act as biological CATALYSTS by SPEEDING UP chemical reactions without being used up itself. Why do we need enzymes ? most cells work at relatively low temperatures and their chemical reactions ( e.g. respiration, digestion, photosynthesis ) would be too slow to sustain life without the help of enzymes !

96. Specificity Remember…‘Lock & Key’ hypothesis!

97. Temperature & Enzyme Activity All enzymes are made of PROTEIN so are DENATURED at high temperatures (above about 50°C) .. think boiled eggs !! The rate of enzyme activity increases with temperature up to a maximum ( OPTIMUM TEMP .) then falls to zero as the enzyme is denatured.

98. pH & Enzyme Activity pH also affects the rate of enzyme activity. Each enzyme has its own range of pH in which it will work. Examples : the enzyme PEPSIN only works between (pH 1-4) pH 1 - pH 4 (acidic) the enzyme CATALASE only works between (pH 8-11) pH 7 - pH 11 (alkaline) Optimum = "the best” ... The enzyme is working at its very fastest

99. Uses of enzymes 1) Enzymes are used in washing powders to help digest food stains. Biological washing powders will only work on 40 0 C or lower. 2) Enzymes are used in baby foods to “pre-digest” the proteins. 3) Enzymes are used to convert starch into sugar which can then be used in food. 4) Conversion of glucose into fructose – glucose and fructose are “isomers” (they have the same chemical formula), but fructose is sweeter. Daz

100. And finally... ‘ Optimum’ is a useful word which means ‘best’ So we call the TEMPERATURE and the pH which makes an ENZYME work at its very fastest, the OPTIMUM for that enzyme.

101. SUB-TOPIC E... Investigating Aerobic Respiration

102. Respiration Respiration is not just breathing in and out. Respiration takes place in all plant and animal cells for 24 hours a day. Respiration is the process of converting glucose into energy. It takes place in all plant and animal cells. There are two types of respiration: Aerobic respiration Anaerobic respiration

103. Aerobic Respiration Aerobic means using oxygen (with air) and it is the most efficient method of energy production Word equation Glucose + Oxygen = Carbon dioxide + Water + Energy Symbol equation C 6 H 12 O 6 + 6O 2 = 6CO 2 + 6H 2 O + Energy

104. O 2 + Glucose ----> CO 2 + H 2 O + ENERGY AEROBIC RESPIRATION Vital chemical reaction going on in all living cells all the time Process converts the CHEMICAL energy in the food we eat into other forms of useful energy - heat, movement, cell reactions Raw Materials for respiration are OXYGEN and GLUCOSE We get these by breathing in O 2 ( LUNGS ) and consuming animals & plants for food. ENZYMES : speed up all cellular reactions. Digest large insoluble molecules of food into small, soluble molecules that can pass through cell membranes Raw materials and end products of respiration get into and out of cells by DIFFUSION & OSMOSIS The CIRCULATORY SYSTEM ( heart, blood vessels ) transports the raw materials & end products around the body to all cells. We need to move and co-ordinate our senses to find food to eat … EYES, EARS, NERVOUS CONTROL & THE BRAIN, REFLEXES

105. Aerobic Respiration Cellular process which releases ENERGY from food Living things need this energy to GROW , MOVE & REPRODUCE All foods contain energy but CARBOHYDRATES (glucose) are our main source O 2 + Glucose ----> CO 2 + H 2 O + ENERGY Use a RESPIROMETER to measure the RATE of respiration.

106. Getting energy from food

107. Getting energy from food -The Equation + Glucose Oxygen Carbon Dioxide Water Energy + +

108. Where do we get the raw materials from? - Glucose Eating and digesting Carbohydrates How much energy in the food we eat? Fats contain twice as much energy per gram as either Carbohydrates or proteins

109. Where do we get the raw materials from? - Oxygen Breathing Gaseous exchange in the lungs and

110. How do we remove the waste products? Carbon Dioxide via Breathing Water via urine and breathing and Heat energy may also be released from cells during respiration

111. The concept of metabolism Metabolism = all the chemical reactions taken place inside the living organisms Metabolic reactions produce different life processes, e.g. photosynthesis respiration movement growth reproduction

112. Control of metabolism Metabolic reactions can be controlled and speeded up by enzymes metabolic reactions would be too slow to occur if no enzymes are present!

113. Remember… Energy is important as the heat produced enables ENZYMES to work more quickly Some reactions need energy to get them started (ACTIVATION ENERGY) Some reactions need energy to keep them going GOOD LUCK WITH YOUR TEST !!!!