Lecture 4-Chloroplast

Question 1

How often do plants replenish atmospheric content of oxygen

Answer 1

every 2000-3000 years

Question 2

Three steps of photosynth

Answer 2

photochemistry, electron transfer and production of NADPH and ATP
incorporation of CO2 into carb and production of O2

Question 3

Pigments

Answer 3

transfer radiant energy to chemical bonds, many double bonds that interact with photons

Question 4

Enzymes

Answer 4

transfer chemical energy

Question 5

Light reactions driven by photons entering chloroplast

Answer 5

2h2o>o2+4h+
3ADP+3Pi>3ATP
2NADP+ +2H+>2NADPH

Question 6

Chloroplast double membrane

Answer 6

no PS, allows passage of small compounds, water, some proteins

Question 7

Stroma

Answer 7

liquid, dark reactions

site of ATP and NADPH accumulation

Question 8

Thylakoid membrane

Answer 8

light reactions

Question 9

Thylakoid space

Answer 9

light reactions

Question 10

Thylakoids

Answer 10

site of photosystems 1 and 2

Question 11

3 Light absorbing compounds

Answer 11

chlorophylls (a and B)
Cartenoids
Phycobilins (red algae and cyanobacteria which have a and c but no b)

Question 12

Interaction between photons and double bonds of pigments depends on

Answer 12

molecular structure
length of carbon chain
number of d.b in chain
structures at end of chain

Question 13

Primary electron acceptor

Answer 13

2 chla coupled to protein, chla without magneisum

Question 14

Trap chlorophyll

Answer 14

chla and protein

Question 15

P680chl a/protein complex

Answer 15

680 nm (red light)

Question 16

P700 chl a/protein complex

Answer 16

700nm (far red light, people cannot see)

Question 17

Resting P680

Answer 17

powerful oxidant, readily accepts electron.

readily splits water, releasing protons and oxygen

Question 18

excited P680

Answer 18

excited by photons from chl a reactive centre, electrons torn from water are boosted to a higher state and passed along to another compound (pheophytin). falls back to unexcited state, cycle begins again

Question 19

Non-cyclic photophosphorylation

Answer 19

excited P680 passes e to pheophytin in Photosystem II. Pheophytin passes e to quinone.
Quinone gives to cytochrome b6/f
Passed to PSI, chla passes energy to P700.
boosted to excited state by photons. e donated to PSI which forms NADPH.
ATP and NADPH in equal amounts. O2 is byproduct

Question 20

PSII

Answer 20

electron transport chain that releases energy in form of a proton. Proton enters thylakoid space, joining protons split of H2O, resulting in proton gradient that drives ATP synthase

Question 21

PSI

Answer 21

harvests light, different absorption spectrum.

Question 22

NADPH

Answer 22

electron carrier for biosynthetic reactions

Question 23

Purpose of having 2 PS

Answer 23

one creates pool of protons to drive ATP formation

one creates pool of energy rich NADPH

Question 24

Cyclic photophosphorylation

Answer 24

ATP production uncoupled from NADPH (more ATP can be produced than NADPH)
e recycling
PSII passes e to PSI, gets excited and passes e to ferredoxin which passes e back to cyb6/f, releasing proton, forming only ATP

Question 25

Photophosphorylation

Answer 25

creation of ATP using proton gradient that is light dependent