AS

#84 Question 7

Beetroot cells contain a red pigment that cannot normally escape from the cells through the cell surface membrane. A student carried out an investigation into the effect of temperature on the permeability of the cell surface membrane of beetroot cells. She measured permeability by using a colorimeter to measure the absorbance of green light by …

#83 Question 6

The diagram below shows pressure changes in the left atrium and left ventricle ofthe heart and the aorta during the cardiac cycle. (a) Calculate how many heart beats there will be in one minute. (2 marks) (b) (i) On the diagram, indicate the point at which the semilunar valves in the aorta snap shut. (1 …

#81 Question 4

The diagrams below show five molecules found in living organisms. (a) Give the letter of one molecule that fits each of these descriptions. You can use each letter once, more than once or not at all.    (i) the form in which carbohydrates are transported through phloem tissue in plants (1 mark)    (ii) the …

#80 Question 3

(a) The diagrams show a cell in various stages ofthe mitotic cell cycle. Name the stage represented by each diagram, and arrange them in the correct sequence. (b) Describe the role of spindle microtubules in mitosis. (3 marks) (c) The graph below shows the changes in the mass of DNA per cell and total cell …

#79 Question 2

The diagram shows the bacterium Mycobacterium tuberculosis, which causes tuberculosis (TB). (a) M. tuberculosis is taken up by macrophages and multiplies inside them. Suggest how this strategy could help to protect M. tuberculosis from the immune response by B cells. (3 marks) (b) In an experiment to investigate how M tuberculosis avoids destruction by macrophages, …