light dependent reaction

Question 1

define photolysis

Answer 1

light energy is absorbed by chlorophyll and splits water into oxygen H+ and e-

H2O —-> 1/2 O2 + 2e- + 2H+

Question 2

define photoionization of chlorophyll

Answer 2

light energy is absorbed the the chlorophyll and this energy results in electrons becoming excited and moving up an energy level allowing them to leave the chlorophyll molecule

Question 3

define chemiosmotic theory

Answer 3

electrons that gained energy and left the chlorophyll molecule move along electron carriers in the thylakoid membrane

Question 4

define oxidation in terms of electrons and hydrogen

Answer 4

loss of electrons
loss of hydrogen

Question 5

define reduction in terms of electrons and hydrogen

Answer 5

gain of electrons
gain of hydrogen

Question 6

explain the light dependent stage of photosynthesis

Answer 6

• photoionisation
  chlorophyll molecule absorbs light energy and a pair of electrons are raised up an energy level. These pair of electrons leave the chlorophyll leaving the chlorophyll molecule ionised
• excited electrons are passed from electron carrier to electron carrier in a series of redox reactions. these electron carriers are located in the thylakoid membrane. each electron carrier is a lower energy level than the other so the electrons lose energy
• this energy is then used to pump hydrogen ions into the space of the thylakoid
• Hydrogen ions move from the high concentration inside the thylakoid to the lower
  concentration in the stroma, through ATP synthase
  ATP synthase combines ADP and Pi to form ATP
• hydrogen ions pass through ATP synthase and are taken up along with electrons by NADP to form NADPH
• photolysis
  splitting water with light provides electrons to replace those lost from chlorophyll during photo ionisation

Question 7

explain how chloroplasts are adapted to carry out light dependent reaction

Answer 7

thylakoid membranes - large SA for chlorophyll electron carriers and for enzymes to attach

proteins in grana - hold chlorophyll in precise place for max absorption of light

ATP synthase in thylakoid membrane - ATP production