Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Hyndland Secondary Credit Material in italics Page 1 09/10/2011 Biology Department 1 Hyndland Secondary Page 2 09/10/2011 INVESTIGATING CELLS INVESTIGATING LIVING CELLS Cell Structure & function All living things are made of cells. Microscopes are used to study the structure of cells. The MAGNIFICATION of a microscope is found by multiplying the strength of the two lenses together: Magnification = eyepiece X objective Stains are coloured solutions used to show up the internal structure of cells more clearly e.g. Iodine stains nuclei yellow. Diagrams of Animal and Plant Cells ANIMAL CELL PLANT CELL Similarities and Difference between Plant & Animal cells FOUND IN BOTH PLANT AND ANIMAL CELLS Structure Nucleus Cytoplasm Description Function Contains chromosomes made of DNA Clear, jelly like substance Controls ALL cell’s activities Site of cell’s chemical reactions e.g. respiration Controls what enters/ leaves the cell Cell Membrane Flexible FOUND IN PLANT CELLS ONLY Cellulose wall Vacuole Chloroplast cell Rigid , made of cellulose Gives cell shape, prevents plant cells bursting when swollen large, membrane bound cavity filled with Provides support, storage sap (watery solution of salts and sugars) contains the green pigment chlorophyll traps light for photosynthesis Credit Material in italics Biology Department 2 Hyndland Secondary Page 3 09/10/2011 WHAT YOU SHOULD NOW KNOW Cells 1- State what are the basic units of all living cells 2- Explain the purpose of staining animal and plant cells 3-State the structure of a typical plant and animal cell and list the differences between them. Credit Material in italics Investigating cells Cells Stains make parts of the cell stand out so that they are easier to see with a microscope Plant and animal cells have in common: 1-Nucleus 2-Cell membrane 3-Cytoplasm In addition, plant cells have: 4- Cell wall (always) 5- A vacuole (most) 6-Chloroplasts (some) Biology Department 3 Hyndland Secondary Page 4 09/10/2011 INVESTIGATING DIFFUSION Diffusion Diffusion is the movement of a substance from a HIGH concentration to a LOWER concentration Diffusion continues until the concentrations are equal. A concentration gradient is a difference in concentration between two areas. Diffusion is said to occur down a concentration gradient. Importance of Diffusion Substance needed by the cell pass INTO the cell by diffusion e.g. oxygen & dissolved food (glucose) Waste substances pass OUT of the cell e.g. carbon dioxide (from respiration), urea (from the breakdown of amino acids) In the body diffusion occurs in the lungs, kidneys and small intestine: Lungs (see S4 notes): oxygen into blood, carbon dioxide out of lungs Kidney: useful substances e.g glucose, amino acids are reabsorbed from the tubule into the blood capillary Small intestine : products of digestion are absorbed into the blood stream. Credit Material in italics Biology Department 4 Hyndland Secondary Page 5 09/10/2011 Cell Membrane The cell membrane controls the passage of materials into & out of the cell It has tiny pores (holes). Small molecules (e.g. glucose, carbon dioxide, urea) can pass through these pores, but larger (e.g. sucrose, starch, proteins) or charged molecules (sodium or potassium ions) cannot. Substances which are not dissolved cannot diffuse through the membrane (e.g. carbon dioxide and oxygen need to dissolve in a layer of mucus before diffusing into the blood from the lung see p). In the leaf a layer of moisture is found on the spongy mesophyll cells into which carbon dioxide diffuses. Osmosis Osmosis is a special case, the diffusion of water across membranes. Osmosis = the movement of water from a higher water concentration (HWC) to a lower water concentration (LWC) across a selectively permeable membrane*. *The cell membrane is a selectively permeable membrane (only small molecules can pass through them) Credit Material in italics Biology Department 5 Hyndland Secondary Page 6 09/10/2011 In the diagram below: Water moves by osmosis from a HWC outside the bag to a LWC Visking tubing (a man made material containing tiny pores). inside the bag Glucose is at a high concentration inside the bag, so diffuses out. Starch is too large to move through the pores in the membrane so stays in the bag. Starch and glucose solution water Osmosis in Plant Cells cytoplasm LIQUID OUTSIDE WATER GAIN or LOSS CHANGE to CELL CELL Water Cell gains water Cell swells Solution equal to cell solution No net gain or loss of water Cell does not change Solution stronger than cell sap Cell loses water Cell shrinks Credit Material in italics Biology Department 6 Hyndland Secondary Page 7 09/10/2011 When plant cells take in water by osmosis, they swell and become TURGID. When plant cells lose water by osmosis they become FLACCID. PLASMOLYSIS occurs when a cell becomes very flaccid. So much water has been lost that the cell membrane shrinks away from the cell wall. This usually starts at the corners The membrane surrounding the vacuole is also selectively permeable and so the vacuole shrinks and expands with osmosis. Osmosis in Animal Cells Animal cells contain weak solutions of salt and sugar and only have a cell membrane. Consequently they BURST if too much pressure is placed on it. Animal cells can gain or lose water by osmosis: Changes in red blood cells due to osmosis Solution outside cell Water gain or loss Change to cell Water Cell gains water Cell swells & bursts Solution weaker than cell solution Cell gains water Cell swells & bursts Solution equal to cell solution No loss/ gain Cell does not change Solution stronger than cell sap Cells loses water Cell shrinks Credit Material in italics Biology Department 7 Hyndland Secondary Page 8 09/10/2011 WHAT YOU SHOULD NOW KNOW Investigating diffusion 4- State what diffusion is It is the movement of a substance from an area of high concentration to an area of low concentration. 5- Give examples of substances which enter Glucose, oxygen, carbon dioxide and water and leave the cell by diffusion 6- (C) Explain the diffusion to organisms importance of Diffusion allows gases to move in and out of cells. In small organisms (e.g. bacteria, amoeba), gases diffuse through the cell membrane. In larger organisms: most cells are not in direct contact with air. Gas exchange takes place through specific organs: e.g. lungs in humans, gills in fish and leaves in plants. 7- Describe the function of cell The cell membrane: controls the passage of membrane substances in and out of the cell. 8- Explain what osmosis is. Osmosis is a special case of diffusion: the molecule which diffuses across the membrane is water 9- Give the name use to describe plants swollen up: turgid cells which have swollen up by osmosis shrunk: plasmolysed and those which have shrunk 10- (C) Explain osmosis in terms of a Osmosis is the movement of water through a selectively selectively permeable membrane and of a permeable membrane (size of membrane holes concentration gradient determines which molecules can go through it) along the concentration gradient, from an area of high water concentration to an area of low water concentration. 11- Explain osmosis in terms of water Osmosis is the movement of water through a concentration of the solution involved. selectively permeable membrane from an area of high water concentration to an area of lower water concentration. Credit Material in italics Biology Department 8 Hyndland Secondary Page 9 09/10/2011 INVESTIGATING ENZYMES Enzymes Within living cells many CHEMICAL REACTIONS occur. However, at body temperature these reaction would be too slow for life to be possible. The reactions are speeded up by enzymes which act as catalysts. CATALYSTS: SPEED UP chemical reactions Remain UNCHANGED during the reaction REPEAT the reaction over and over again Enzymes are CATALYSTS in living cells. Enzymes are made form PROTEIN. They perform two types of reaction: BUILDING UP of small molecules into larger molecules BREAKING DOWN of large molecules into small molecules. Enzymes are needed in cells to: Synthesise useful products Release energy during cell respiration Change poisonous wastes into safer materials Change substances into a form that can be stored or used Reactions of photosynthesis, on which all life depends. SUBSTRATE – the substance on which an enzyme acts PRODUCT – the substance produced by the action of the enzyme enzyme* SUBSTRATE PRODUCT *The enzyme itself is not changed by the chemical reaction Credit Material in italics Biology Department 9 Hyndland Secondary Page 10 09/10/2011 Examples of Enzymes: Name of Enzyme Where found What it Does Test for Activity Degradation reaction (Breaking down reactions) CATALASE In plant and animal Breaks tissues hydrogen down Glowing splint peroxide relights in the gas into OXYGEN and given off WATER AMYLASE In digestive juices STARCH is broken Benedict’s (saliva, pancreatic down juice) reagent into turns orange MALTOSE Synthesis reactions (Building up Reactions) PHOSPHORYLASE In potato tubers Builds special Iodine turns blue reactive glucose black as starch is built (GLUCOSE – 1 – up PHOSPHATE) into STARCH How Enzymes Work Enzymes have a particular shape. On their surface is a groove called the active site (see over). The shape of the active allows the substrate (S) to fit into it exactly, like a key in a lock. When the substrate binds to the active site a chemical reaction occurs. Other molecules, because they have a different shape, cannot fit into the active site. Because of this enzymes can work on only one substrate molecule – they are said to be SPECIFIC. As each enzyme is specific for a single substrate molecule, a different enzyme is required for each chemical reaction. Credit Material in italics Biology Department 10 Hyndland Secondary Page 11 09/10/2011 Effect of Temperature on Enzymes At low temperatures enzymes work slowly – (Their reaction rate is at a MINIMUM) As the temperature increases, they work faster, up to a MAXIMUM RATE. The temperature at which an enzyme works at its maximum rate (not best!) is called the OPTIMUM TEMPERATURE. Any further increase in temperature causes the enzyme protein to be damaged. The enzyme’s shape changes, so the rate decreases again, because the enzyme no longer works. Denaturation of enzymes When an enzyme is unable to work because its shape has changed it is said to be DENATURED. As the temperature rises above the optimum, the enzyme becomes denatured and the activity rapidly decreases to zero. It can non longer work because the shape of the active site no longer fits the shape of the substrate and the substrate can no longer fit in. The effect of pH on enzymes An enzyme will work only in a narrow range of pH. If the conditions become too acid or alkali, the enzyme becomes denatured. The OPTIMUM pH is the pH at which the enzyme has most activity. The optimum pH is different for different enzymes. Pepsin is found in the stomach (acidic) and so has an optimum pH which is acidic. Credit Material in italics Biology Department 11 Hyndland Secondary Page 12 09/10/2011 WHAT YOU SHOULD NOW KNOW 20- Describe a chemical reaction in general terms 21- Explain the meaning of the term “catalyst”. 22- Explain why enzymes are required for the functioning of living cells. 23- State what an enzyme is. 24- Give an example of an enzyme involved in the chemical breakdown of a substance 25- Give an example of an enzyme involved in synthesis (building up) 26- (C) Explain the word “specific” as applied to enzymes and their substrate 27- State what type of molecule enzymes are. 28- Describe the effect of temperature on enzyme activity 29- Describe the effect of a range of pH on the activity of pepsin and catalase 30- (C) Explain the term “optimum” as applied to the activity of enzymes 31-(C) Explain what a control is. Credit Material in italics Investigating enzymes A substrate is chemically altered into a product A catalyst is a substance which speeds up the rate (i.e. the speed) of a chemical reaction without being changed or used up. (i.e. a catalyst is neither a substrate nor a product as it is unaffected by chemical reactions). A large number of chemical reactions takes place in every living cell continuously. These are controlled by enzymes which are catalysts produced by the cells themselves. The cell processes necessary for life would happen too slowly without enzymes. An enzyme is a biological catalyst. C-L-A-P - Catalase: breaks down hydrogen peroxide into water and oxygen - Lipase: breaks down fats into fatty acids and glycerol - Amylase: It breaks down starch into maltose. - Pepsin: breaks down proteins into polypeptides and amino acids. Potato phosphorylase: in potatoes, joins molecules of Glucose-1-phosphate to form starch. Each enzyme only works on one substrate. E.g. Amylase only breaks down starch. Enzymes and substrates have matching shapes like a “lock and key”. Enzymes are proteins. At low temperatures, enzymes do not work effectively (molecules move too slowly). Enzymes increase the rate of reaction (i.e. speed up) most effectively at a temperature called the optimum. Beyond that temperature, an enzyme becomes denaturated, i.e. it is irreversibly damaged Each enzyme has a specific pH, i.e. a pH at which it works most effectively (faster rate of reaction). Enzyme may work at other pH but the rate of the chemical reaction that they control is usually not as fast. Pepsin works most effectively at pH 2.8 (acidic condition found in the stomach). It has a narrow range of pH at which it works well (± 0.5 pH units). Catalase works most effectively at pH 7-9 and has a larger working range of pH than pepsin (± 1 pH units). The conditions at which enzymes work most effectively are called optimum conditions: optimum pH and optimum temperature. A repeat of an experiment to show that the effect 12 Biology Department observed is only due to the factor being investigated (e.g. activity of an enzyme) Hyndland Secondary Page 13 09/10/2011 INVESTIGATING AEROBIC RESPIRATION Need for Energy Living cells are the site of a number of chemical reactions. Together these chemical reactions are called metabolism. Some of these reactions release energy. Living cells need energy for: Cell division e.g. growth & repair Maintaining body temperature (birds & mammals) Movement Chemical reactions e.g. making enzymes, digesting food RESPIRATION is the process by which cells release ENERGY from GLUCOSE. It happens in all living cells (plant & animal) all the time. Aerobic Respiration Oxygen is required for aerobic respiration. Two waste products, water and carbon dioxide are made. Equation for aerobic respiration: GLUCOSE + OXYGEN WATER + CARBON DIOXIDE + ENERGY Reactants waste products useful product The carbon dioxide released can be detected by Turning limewater milky Turning bicarbonate indicator from red to yellow Aerobic respiration occurs in many small steps, each controlled by an enzyme. This allows the energy to be released in small amounts. Credit Material in italics Biology Department 13 Hyndland Secondary Page 14 09/10/2011 The energy in food molecules such as glucose is CHEMICAL ENERGY. Green plants capture LIGHT ENERGY and convert it into chemical energy in photosynthesis (Error! Bookmark not defined.). Animals obtain their food from plants (Error! Bookmark not defined.). The quantity of energy contained in foods can be found by burning a measured mass of food and using the heat energy released to heat a measured volume of water. The energy content of different foods differs: Fats contain TWICE as much energy as proteins or carbohydrates (e.g. glucose & starch) Respirometers A respirometer can be used to measure the rate of respiration The use of respirometers depends on three factors: The volume of oxygen used up is equal to the volume of carbon dioxide produced The carbon dioxide can be absorbed by a chemical (e.g. soda lime, potassium hydroxide) and so the uptake of oxygen is seen as a drop in the volume of air in the respirometer There is no change in the temperature of the apparatus. (changes in temperature cause changes in the volume of gases!) In the apparatus above, the taps are closed at the start of the experiment. As the oxygen is removed the volume of air in the tube decreases and this sucks the coloured liquid up the tube towards the earthworm’s tube. Credit Material in italics Biology Department 14 Hyndland Secondary Page 15 09/10/2011 The control should be a non respiring material (i.e. dead animal or glass beads) and of the same volume as the respiring animal. The syringe is used to return the volume back to its original level. In this way, the volume of oxygen taken in can be measured and if the time taken to produce the change is known, the rate of respiration (oxygen uptake per minute) can be calculated. Energy release During respiration some of the energy is released as heat energy. As a result in a confined space the temperature of the surroundings is raised. The heat can be detected using an air thermometer. The heat released by the respiring animal expands the air in the tube and pushes the coloured liquid. There is no expansion in the control side. Credit Material in italics Biology Department 15 Hyndland Secondary Page 16 31- State three reasons why living cells need energy. 32- Give an example of an energy transformation in a plant and in an animal. 33- State what cells need in order to release the energy from food. 34- Describe aerobic respiration in terms of a word equation 35- State where the carbon dioxide released from food comes from. 36-State what is produced by respiration in addition to carbon dioxide 09/10/2011 Investigating aerobic respiration Cell division, movement (muscle cells), synthesis reactions. Plants: light energy → chemical energy (starch) Animal: chemical energy (fat) → heat energy Cells need oxygen (found in air) to release the energy from food in “aerobic respiration” glucose + oxygen → energy + carbon dioxide + water The carbon dioxide released as a waste product of respiration comes from food. Heat energy and water will be produced by aerobic respiration. 37- (C) State which type of food contains more Fats contain about twice as much energy as energy per gram: proteins, fats, proteins and carbohydrates (sugars, starch) carbohydrates. 38- (C) Explain the importance of the energy Cell metabolism is all the chemical reactions released from food during respiration to (i.e. breakdown as well as synthesis reactions) the metabolism of cells. which take place inside a cell. The energy released from food is needed for many chemical reactions and therefore it is needed for cell metabolism. Credit Material in italics Biology Department 16 Hyndland Secondary Page 17 09/10/2011 PROBLEM SOLVING Percentage Calculations. PERCENTAGE CALCULATIONS 3 Types of percentage calculation can be asked: Percentage change (increase or decrease): To find the change End value—start value Percentage change = X 100 To change to a percentage Start value STEP 1 STEP 2 STEP 3 (use a calculator!!!!!): Find the START Value (in the question) Find the END value (in the question) FIND OUT HOW MUCH IT HAS CHANGED END VALUE – START VALUE STEP 4 - Divide this answer by the START VALUE STEP 5 - Multiply that answer by 100 If the answer is negative the factor has decreased, if it is positive the factor has increased e.g. Calculate the percentage change in blood flow to the skeletal muscles during exercise, if it rises from 10 l/min to 30l /min. Percentage change = 30-10 ÷ 10 X 100 = 20÷10 X 100 = 200% change (increase). Percentage of: To calculate the proportion the subset forms of the total This asks what percentage a subset is of the total Percentage of = Size of subset To change to a percentage X100 Total e.g. What percent of the whole population has blood group AB? Blood Group A B AB O Number 24 45 33 86 Total = 24 + 45 + 33 + 86 = 188 Subset = 33 Percentage = 33 ÷ 188 X 100 = 17.6%% How many, if the percentage is already given: Total X Percentage Number = 100 e.g. If 20% of a class of 40 have blue eyes, how many of the class has blue eyes? Total =40 Number = 40 X 20 ÷ 100 = 800 ÷ 100 = 8 Credit Material in italics Biology Department 17 Hyndland Secondary Page 18 09/10/2011 Ratios A ratio is a way of showing the relationship between two or more values. For example a forest contains two types of deer, Roe deer and Fallow deer. The deer are counted and 360 Roe deer are found, but only 120 Fallow deer are present. To express this as a ratio a number of steps can carried out. each by 120 1. Try to divide the large number by the small number 360 : 120 3:1 this is the simplest whole number ratio. Second example. The head teacher wishes to know the ratio of male staff to female staff in the school. There are 32 male staff and 56 female staff 1. Try to divide the large number by the small number 32: 56 each by 32 1:1.75, not a whole number ratio so move to next step 2. Divide both sides by the largest number which goes in evenly, 32:56 each by 4 8: 14 each by 2 4:7 This is the simplest whole number ratio, the two numbers cannot be divided evenly by the same number! Third example The EU fishery minister suggested that the North Sea contained very little cod, but much more herring. The survey shows that there were 175 cod, and 1,260 herring. What is the ratio of cod: herring. 1. Try to divide the large number by the small number 175 : 1260 each by 175 7.2:1, not a whole number so move to next step 2.Find a number that will divide evenly into both sides (the same number for each side) 175: 1260 each by 5 35:252 can they be divided again? 35:252 5:36 each by 7 This is the simplest whole number ratio, the two numbers cannot be divided evenly by the same number! Credit Material in italics Biology Department 18 Hyndland Secondary Page 19 09/10/2011 Chemical Tests TESTS pH Scale (Acidity/ Alkalinity) The pH Scale gives a measure of how acidic or alkaline a solution is: 1 COLOUR of pH indicator 2 RED 3 4 5 6 7 GREE pH ORANG YELLOW 8 9 10 11 BLUE 12 13 14 PURPLE pH is measured using pH indictor or paper The pH falls (becomes more acidic) when fats are broken down to fatty acids (& glycerol), or protein are broken down (to give amino acids) Carbon Dioxide Carbon dioxide is the gas used up in photosynthesis and produced in aerobic respiration in animals and plants (along with water) and in anaerobic respiration in plants (along with alcohol). In experiments it can be absorbed by soda lime or potassium hydroxide. Carbon dioxide turns limewater milky. Bicarbonate indicator can be used to tell how much carbon dioxide is present Carbon Dioxide Colour of Bicarbonate Indicator Zero Normal (0.03% High Purple Red Yellow Experimental Design In a scientific experiment a test is only fair if only one variable factor has been changed at a time. Examples of variable factors are time, lengths, volumes, weights and concentrations. If more than one is is changed between experiments the test is not fair. A fair test is also a VALID test. Experiments are repeated to make them more RELIABLE or REPRESENTATIVE. To make an experiment more accurate better equipment must be used e.g. a more accurate balance or replace a ruler having centimetre divisions with one having millimetre divisions. Food Tests Food Type Reagent Procedure Positive result Glucose (sugar) Benedict’s Heat with sample at 95°C Turns from blue to orange Starch Iodine Add to sample Turns from orange to blue/ black Protein Biuret Heat with sample Turns from to violet Fats Alcohol and water Shake with sample. Solution goes cloudy Credit Material in italics Biology Department 19 Hyndland Secondary Page 20 09/10/2011 CHARTS Charts/Graphs In Biology two types of chart are used: the BAR chart and the LINE GRAPH Usually a question tells you which to draw. BAR CHART When data concerns the numbers in various groups, then a bar chart is used Number RED 37 40 BLUE 15 35 YELLOW 7 30 WHITE 3 GREEN 24 Number Colour of Flower 25 20 15 10 Germination (%) 0 7 80 10 24 70 20 59 60 30 74 40 37 50 2 Germination (%) Temperature (ºC) GREEN WHITE YELLOW BLUE RED Label; axes names and units (if any) 5 copy the column headings. The first set of 0 information goes on the horizontal axis, the second on the vertical axis. Devise a scale (divide the axis up evenly). Find the highest value in your data. 37 Colour of Flower Count the number of large squares on your vertical axis 8 Divide the highest value by the number of squares, 37/8 = 4.625 round your answer up to the nearest easy* number. i.e. 5 Each large square is worth 5 *easy numbers are usually 1, 2, 5, 10, 50, 100 etc. Draw the bars (you should make each bar the same width and leave a gap between the bars (you won’t lose marks if you don’t) LINE GRAPH Line graphs are used when both sets of data are numbers. A scale must be used on both axes. 50 40 30 20 10 Label axes by copying the column headings (first 1st—horizontal, 2nd column—vertical) 0 Devise scales for both axes 0 10 20 30 40 50 Horizontal 50/10 = Each big box is worth 5 ºC Temperature (ºC) Vertical 74/8 = 9.25, Each big box is worth 10% Plot the points and join with a straight line (Only join 0,0 if that point is in the data) Credit Material in italics Biology Department 20 Hyndland Secondary Page 21 09/10/2011 GLOSSARY Active Site Amylase Atom Catalase Catalyst Cell wall Chloroplast Concentration Concentration Gradient Cytoplasm Denatured Diffusion Distilled water End product(s) Enzyme (Cell) Membrane Molecule Nucleus Optimum conditions Osmosis Pepsin pH Phosphorylase Selectively permeable Solute Solvent Specific Activity Stain Substrate Synthesis Vacuole part of an enzyme molecule to which the substrate attaches an enzyme which speeds up the breakdown of starch the smallest part of an element which can exist chemically an enzyme which speeds up the breakdown of hydrogen peroxide a substance which speeds up a reaction but remains unchanged cellulose layer around the outside of a plant cell structure within a plant cell which contains chlorophyll the number of solute molecules in a specific volume of solvent the difference between two concentration levels the fluid part of a cell permanent damage caused to an enzyme by high temperature movement of molecules from high to low concentration pure water consisting of 100% water molecules compound formed at the end of a reaction chemical found in living cells which acts as a catalyst selectively-permeable layer surrounding the cytoplasm in all cells two or more atoms joined together by chemical bonds control centre of a cell conditions in which an enzyme works most efficiently diffusion of water molecules across a semi- permeable membrane an enzyme which breaks down protein a measure of acidity/alkalinity an enzyme which synthesizes starch allows some molecules to pass through but not others substance which is dissolved in a liquid liquid used to dissolve another substance each enzyme only acts on one substrate coloured dye used to show up cell structure more clearly the molecule on which an enzyme works building up a larger molecule cavity in the cytoplasm of a plant cell