Photosynthesis: Light Dependent Reaction

Question 1

Location

Answer 1

thylakoid membranes/grana

Question 2

Photolysis of water - equation

Answer 2

H₂O -> 1/2O₂ + 2e⁻ + 2H⁺

Question 3

Photolysis of water - steps

Answer 3

• The H+ is picked up by NADP to form NADPH and is used in the LIR
• The e- are passed along a chain of electron carrier proteins
• The oxygen is used for respiration or diffuses out the leaf through the stomata
• O2 not used in photosynthesis - technically a waste product

Question 4

Photoionisation of chlorophyll - steps

Answer 4

• Light energy is absorbed by the chlorophyll
• Light energy excites electrons, raising up a level and leaving the chlorophyll
• Chlorophyll has been ionised by light
• Some energy from released electrons is used to produce ATP and NADPH in chemiosmosis

Question 5

Chemiosmosis

Answer 5

• Electrons released from photoionisation of chlorophyll are picked u and move along a series of proteins embedded in the thylakoid membrane
• As electrons move along they release energy - some energy is used to actively transport protons across chloroplast membranes into the thylakoid lumen
• Electrochemical gradient is created: high conc. H+ in thylakoid lumen
• facilitated diffusion occurs using ATP synthase - leads to ATP production
• Protons combine with NADP -> NADPH, also picks up electron at the end of the ETC