5 a day revision B4 - Enzymes Explain the lock and key model. Sketch a graph to show the effect of temperature on enzyme reactions. Explain the lock and key model. Define the terms: Enzyme Active site What is a denatured enzyme and how can it happen? An experiment is carried out using 2 samples of amylase. Sample 1 is first heated to 75C and then cooled to 37C. Sample 2 is cooled to 10C and then heated to 37C. Describe and explain the effect on enzyme activity. @aegilopoides

Sample 2 will work as normal. Cooling does not denature the enzyme. B4 - Enzymes 5 a day revision Graph showing that as temperature increases so does the rate of reaction – up to an optimum. Then rate of reaction decreases quickly. Enzyme: a protein that speeds up a chemical reaction. Active site: region of an enzyme where the substrate joins. A substrate has to be the correct shape to fit into the active site of an enzyme. Denatured means that the shape of the active site has changed – the enzyme will not work. Change in pH or high temperature can cause denaturation. Sample 1 will not work. Heating to 75C will have denatured the enzyme. Sample 2 will work as normal. Cooling does not denature the enzyme. @aegilopoides

5 a day revision B4 - Photosynthesis A B In which part of the cell does photosynthesis take place? State 3 uses of the glucose produced in photosynthesis. What is the balanced symbol equation for photosynthesis? A plant is placed in the dark for 48 hours. A piece of black paper is then placed over part of a leaf as shown. The plant is left in light for 24 hours and then the leaf is tested for the presence of starch. What chemical would you use to test for starch? What colours would be observed at areas A and B, why? Explain why cacti have fewer stomata than other plants. A B @aegilopoides

5 a day revision B4 - Photosynthesis A B Chloroplast Respiration Make chemicals for growth Stored as starch Answer: 6CO2 + 6H2O   C6H12O6 + 6O2 sunlight chlorophyll Iodine A – blue black B – brown A has been in the light, photosynthesis has taken place and some of the glucose produced has been converted to starch. B is in the dark and cannot do this. Any starch present in this area has been converted back to glucose and used. To prevent water loss. A B @aegilopoides

5 a day revision B4 - Respiration Give 3 differences between aerobic and anaerobic respiration . What is respiration? Give the equation for anaerobic respiration in muscles. Sketch a graph to show the changes in sugar and ethanol concentration as yeast grows. Explain the shape of your graph. What is the role of anaerobic respiration in bread making? @aegilopoides

5 a day revision B4 - Respiration The products Aerobic requires oxygen Aerobic is more efficient Aerobic takes place in mitochondria . The chemical reaction that takes place in cells to release energy from glucose. Glucose Lactic Acid (+ Energy) As time increases the amount of sugar will decrease (used up in respiration) and the amount of alcohol will increase (a product). The carbon dioxide that is produced makes the bread rise. @aegilopoides

5 a day revision B4 - Life processes and cell structure What type of cells have a cell wall but no nucleus? Respiration is a characteristic of living organisms. State 4 others. The diagram shows a typical animal cell and typical plant cell. Name X and Y. Name and label another structure found in both cells. Complete the table. What features do plant cells have that animal cells do not? Part of plant cell Function Cell membrane Cell wall Cytoplasm Mitochondrion Nucleus @aegilopoides

Some have chloroplasts B4 - Life processes and cell structure 5 a day revision Bacteria Any 4 from: Movement, reproduction, sensitivity, growth, excretion and nutrition. Cell membrane X = Nucleus Y = cytoplasm Cell membrane Controls passage of substances in/out of cell Cell wall Supports the cell Cytoplasm Enzymes made here and reactions take place here. Mitochondrion Where the reactions in aerobic respiration take place Nucleus Contains DNA- instructions Cell walls Large vacuole Some have chloroplasts @aegilopoides

5 a day revision B4 - Diffusion/Osmosis/Active transport Carbon dioxide and oxygen are exchanged between alveoli and nearby capillaries. Which process is taking place? Compare and contrast diffusion and active transport. Define diffusion. How is osmosis different? Some red blood cells were placed in distilled water and some placed in a concentrated salt solution. Describe the changes that would take place. The 4 cells contain different concentrations of glucose. Draw a series of arrows to show how water will move by osmosis between the cells. 0.1% 10% 2% 5% @aegilopoides

5 a day revision B4 - Diffusion/Osmosis/Active transport Diffusion Diffusion is the movement of molecules from a region of high concentration to a region of low concentration. Osmosis involves only water molecules and requires a semi-permeable membrane Diffusion – molecules from high to low concentration and is passive. Active transport – molecules move from low to high concentration. Energy required. 10% 5% 0.1% 2% RBC placed in distilled water would take in water and eventually burst. RBC placed in salt solution would lose water and shrivel. @aegilopoides