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This is a platform where you can post your doubts related to your O-level and Alevel past papers. The board is bound to be GCSE or IGCSE.

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BIOLOGY MARCH 2020 PAPER 12 Q1: The diagram shows an eyepiece graticule and cell viewed through a microscope. When the eyepiece graticule was calibrated at this magnification, the whole length of the graticule shown covered 12 divisions of a stage micrometer scale. There were 100 divisions in 10 mm of the stage micrometer.  What is the actual length of the cell?  A 2.5µm  B 3.6µm  C 360µm  D 3 mm ANSWER C In this question, you need to make use of the data given in the question. To begin with, find the magnitude of one division of the stage micrometer. If 100 divisions occupy 10mm, then 1 division of the stage micrometer would be ((1*10))/100) = 0.1mm. Since 100 divisions of a graticule covered 12 divisions of a stage micrometer, then 100 divisions would be equal to 12*0.1mm = 1.2mm. Therefore, 1 division of an eyepiece graticule would be equal to 0.012mm. In the picture shown above, the cell covers 29 divisions of a graticule, so the length of the cell is 29*0.0...
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WINTER 2019 VARIANT 12 Q1: A student calibrated the scale on an eyepiece graticule in the eyepiece lens of a light microscope. The student was given a stage micrometer scale to use. The divisions on the stage micrometer scale were 0.1 mm apart. Which data must the student collect in order to calibrate the eyepiece graticule?  1 magnification of the eyepiece lens of the microscope  2 number of divisions of the stage micrometer scale seen in one field of view of the microscope  3 number of divisions of the eyepiece graticule scale equivalent to each division of the stage micrometer      scale  A 1 and 3  B 2 and 3  C 2 only  D 3 only In this question, magnification of the eyepiece lens of the microscope is of no help to the calibration of the eyepiece graticule since it is the objective lens for which the eyepiece graticule has to be calibrated seperately. The eyepiece magnification is usually fixed Also, it is the eyepiece divisions that...
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  NOVEMBER 2019 PAPER 4 Q10a Describe the features of ATP that make it suitable for its role as the universal energy currency of cells. (6) For this part of the question you need to list the features of ATP in a comprehensive manner. You should begin writing by saying the ATP as a molecule is small and water soluble and thus have a rapid rate of intracellular diffusion. It serves as the link between the energy yielding and energy- requiring reactions. It possesses energy rich bonds which can be easily hydrolysed to release about 30.5 kJ of energy per mole of bonds hydrolysed. Its rapid turnover allows it to be easily reformed when needed.
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