Photosynthesis – biochemistry

  • explain that energy transferred as ATP and reduced NADP from the light dependent stage is used during the light independent stage (Calvin cycle) of photosynthesis to produce complex organic molecules
  • state the sites of the light dependent and the light independent stages in the chloroplast
  • describe the role of chloroplast pigments (chlorophyll a, chlorophyll b, carotene and xanthophyll) in light absorption in the grana
  • interpret absorption and action spectra of chloroplast pigments use chromatography to separate and identify chloroplast pigments and carry out an investigation to compare the chloroplast pigments in different plants (reference should be made to Rf values in identification)
  • describe the light dependent stage as the photoactivation of chlorophyll resulting in the photolysis of water and the transfer of energy to ATP and reduced NADP (cyclic and non-cyclic photophosphorylation should be described in outline only)
  • outline the three main stages of the Calvin cycle:
    • fixation of carbon dioxide by combination with ribulose bisphosphate (RuBP), a 5C compound, to yield two molecules of GP (PGA), a 3C compound
    • the reduction of GP to triose phosphate (TP) involving ATP and reduced NADP
    • the regeneration of ribulose bisphosphate (RuBP) using ATP
  • describe, in outline, the conversion of Calvin cycle intermediates to carbohydrates, lipids and amino acids and their uses in the plant cell
  • explain the term limiting factor in relation to photosynthesis b) explain the effects of changes in light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis
  • explain how an understanding of limiting factors is used to increase crop yields in protected environments, such as glasshouses