Photosynthesis
Photosynthesis tests the light-dependent reaction, the Calvin cycle, limiting factors, pigments and practical investigations. Expect questions on chloroplast structure, ATP and reduced NADP, carbon fixation and chromatography.
Light-dependent reaction
Occurs on thylakoid membranes. Light excites chlorophyll electrons; photolysis of water produces oxygen, protons and electrons. Electron transport generates ATP and reduces NADP. ATP and reduced NADP pass to the stroma.
Calvin cycle
Occurs in the stroma. Rubisco fixes carbon dioxide to ribulose bisphosphate (RuBP), forming two glycerate 3-phosphate molecules. ATP and reduced NADP reduce GP to triose phosphate; some triose phosphate regenerates RuBP and some forms glucose and other products. Light intensity, carbon dioxide concentration and temperature can limit the rate.
Worked example
In paper chromatography, a pigment travels 4.2 cm and the solvent front travels 6.0 cm. Rf = 4.2 / 6.0 = 0.70. Rf values help identify pigments because each pigment has a characteristic ratio under the same conditions.
Traps
Oxygen comes from water, not carbon dioxide. NADP is reduced in the light reaction; NAD is used in respiration. A limiting factor is the one in shortest supply. Do not say ATP is used to fix carbon dioxide directly.