AQA Biology WELL SOLVED. Practical Techniques

AQA Biology WELL SOLVED. Practical TechniquesDescribe how the length of a cell could be estimated with an optical microscope - ANSWERMeasure length with an eyepiece graticle; calibrate with a stage micrometer Describe the method used to find the mean number of capillaries per mm2 in a thin section cut from sample of heart muscle - ANSWERMeasure diameter of field of view and calculate area; Using stage micrometer and eyepiece graticle; Count the number of capillaries in large number of fields of view and calculate the mean; Select fields of view randomly Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells hen using an optical microscope - ANSWERAdd a drop of water to a glass slide; Obtain thin section of plant tissue and place on slide; Stain with potassium iodide; Lower cover slip using mounted needle Explain why an electron microscope shows more detail of cell structure than a light microscope - ANSWERElectron microscope has higher resolution; electron beams have a shorter wavelength Give two processes which occur during interphase that enable cell division to occur - ANSWERDNA replication; Increase in volume of cell; Increase in number of organelles; ATP synthesis / respiration Starting with some lettuce, describe how you would obtain a sample of undamaged chloroplasts. Use your knowledge of cell fractionation and ultracentrifugation to answer this question - ANSWERChop up / blend; Cold; Buffer; Isotonic / same water potential; Filter and centrifuge filtrate; Centrifuge supernatant; At a higher speed; Chloroplasts in second pellet