Photosynthesis

Question 1

Describe the light dependant reaction

Answer 1

•Chlorophyll absorbs light energy
•Excited electrons to higher energy level
•Electrons lost from chlorophyll
•Electrons pass down electron transfer chain by a series of redox reactions
•Energy released is used to pump protons (H+) across thylakoid membrane, into thylakoid, forming proton electrochemical gradient
•Protons diffuse down electrochemical gradient, though ATP synthase, catalysing ADP +Pi&raquo_space;> ATP
•Light splits 2H2O»> 4H+ + 4e- + O2
•e- replace electrons in chlorophyll
•H+ and NADP act as an electron acceptor for electron at end of ETC forming NADPH

Question 2

Describe the light independent reaction

Answer 2

•Rubisco catalyses CO2 combining with RUBP
•Splits into 2xGP
•GP is reduced using NADPH to triose phosphate
•This uses energy from ATP
•Triose phosphate can be converted into glucose , organic substances
•Most triose phosphate is conver back into RUBP