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B2 Exam Revision Plant cells vs. Animal cells Both types of cell have these: 1) Nucleus This controls the cell 2) Cytoplasm This is the jelly like substance where chemical reaction take place 3) Cell membrane Controls what goes in and out of the cell 4) Mitochondria Energy is released here by respiration Only plant cells have these: 5) Cell wall Gives support to the cell 6) Large vacuole Large space filled with cell sap 7) Chloroplasts Where photosynthesis takes place Food Production + Yeast • Yeast is a single celled organism which can respire both aerobically and an anaerobically • Aerobic respiration produces CO2 and water and is used to make bread rise • Anaerobic respiration produces CO2 and ethanol, the process is known as fermentation • This is used in the production of beer, wine and other alcoholic drinks Complete this definition of Diffusion using the key words: Partially permeable Diffusion Concentration Gradient Random movement Particles Diffusion is the _______ __________ of ______ from where there are lots of particles ( high __________) to where there are less particles. We say the particles diffuse down a concentration _________. In cells, the cell membrane has small holes that allow small particles through, but not large molecules. We call this membrane ________ ________. The bigger the difference in concentration, the faster the rate of ________. Food Production + Bacteria • Bacteria are used to make cheese abd yoghurt • Yoghurt is formed when bacteria act on lactose (sugar in the milk), producing lactic acid and changing the texture and taste of the milk • Different type of bacteria is added for cheese, making much more lactic acid is made and it is thicker (curds) • This is cooled and left in moulds to set and then more bacteria is added to give different flavours Photosynthesis - The equation 1. What factors are needed to make glucose? 2. What products are made by photosynthesis? Limiting factors • If you alter the levels of light, carbon dioxide or change the temperature the rate of photosynthesis will change! What happens to the glucose? Enzymes • Enzymes are biological catalysts, they increase the rate of reactions. • Enzymes are protein molecules made up of long chains of amino acids. • When enzymes are denatured the active site changes shape. What happens at the active site? In the same way that a key fits into a lock, so a substrate is thought to fit into an enzyme’s active site. The enzyme is the lock, and the reactant is the key. ↔ + enzyme + reactant ↔ ↔ enzyme-reactant complex + ↔ enzyme + products Factors affecting enzymes If the temperature and pH changes sufficiently beyond an enzyme’s optimum, the shape of the enzyme irreversibly changes. This affects the shape of the active site and means that the enzyme will no longer work. When this happens the enzyme is denatured. heat pH normal denatured Aerobic Respiration Oxygen + Glucose Carbon Dioxide + Water Energy + + Amylase Protease Lipase Bile Hydrochloric acid Where are the enzymes found? Enzymes of digestion Chromosomes, Genes and Alleles 3. …………….. 2. ………....... b B 5. ……………. (b) 1. ………….. 4. ……………… Nucleus, Gene, Chromosome, Allele, Cell Gregor Mendel (The Pea Plant Man) Why was his work not spread quickly? • He was not a famous scientist – nobody knew about him at the time. • His job as abbot stopped him giving lectures at universities. • He published his work in an obscure journal that few people read. • Biologists at the time did not think mathematics had anything to do with Biology. Disease • Some disorders are inherited • Huntington’s disease is caused by a dominant allele of a gene and can be inherited from only one parent • Cystic fibrosis is caused by a recessive allele of a gene and so must be inherited from both parents Cystic Fibrosis • The treatment involves chest physiotherapy. • They are very prone to chest infections and malnutrition. • The mucus encourages the growth of pathogenic microbes that cause infection and cause long term lung damage. Effect of Exercise • Energy from respiration used to make muscles contract • When this happens, you need more respiration to take place (ie more O2 + glucose, quicker CO2 release) • Causes increased heart/breathing rate • Arteries dilate more blood for muscles increases oxygen/glucose supply CO2 is removed quicker Anaerobic Respiration • Your everyday muscle movements are made possible by AEROBIC respiration • If heart rate is increased, blood cant supply O2 quick enough • Anaerobic respiration doesn’t involve O2 and is less efficient • Glucose Lactic Acid (+ energy) • Lactic acid needs to be got rid of (by reacting with O2 to form CO2 + water) = OXYGEN DEBT PHEW! •Good Luck