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...

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 marks)   ...

The diagram below shows a small part of a human lung as it appears through a microscope.(a) Name the type of blood vessel in which the red blood cell is present.(1 mark)(b) Describe and explain two ways in which the structure of the alveoli, shown in the diagram, enables gas exchange to take place rapidly.(4 marks)(c)...

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...

(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 mass during two...