Intro lecture

Question 1

How to grow better wheat

Answer 1

Enhance mechanisms giving off O2 (photosyn)

Question 2

What is photosynthesis

Answer 2

Capture and use of light energy by organisms

Question 3

What are reaction centres

Answer 3

Chlorophyll based, electron transfer, photochemistry, oxygenic and anoxygenic versions

Question 4

Rhodopsin homologues use

Answer 4

Cis/trans retinal isomerisation - proton pumping

Question 5

The two major types of photosynthesis

Answer 5

1. Rhodopsin based 2. Reaction centres

Question 6

How does rhodopsin based photosynthesis work

Answer 6

Uses photons of light to pump protons across membrane - generates protonmotive force used to drive ATP synthesis but not enough for organism to grow as doesn’t fix carbon

Question 7

Retinal cofactor

Answer 7

Covalent Schiff base to Lys216 - 7 TM helix protein homologous to GPCR

Question 8

What drives proton pumping in rhodospin homologues

Answer 8

Isomerisation from trans to cis - external reductant needed

Question 9

Photosynthetic RX centre facts

Answer 9

All derived from common ancestor, membrane proteins, dimers, core of 5 TM helices, bind Chl, do photochemistry, donor oxidised, acceptor reduced, has other cofactors

Question 10

PSI RC terminal electron acceptor

Answer 10

FeS

Question 11

PSII RC terminal electron acceptor

Answer 11

Quinone

Question 12

When did oxygenic photosynthetic bacteria arise

Answer 12

About 2 billion years ago

Question 13

When did anoxygenic photosynthetic bacteria arise

Answer 13

About 3.2 billion years ago

Question 14

How do green photosynthetic anaerobes work

Answer 14

Use H2S in photosynthesis to generate sulphur

Question 15

Where did oxygenic photosynthesis evolve

Answer 15

Cyanobacteria

Question 16

What are cyanoobacteria

Answer 16

Oxygenic phototrophs - internal membranes (thylakoid membranes) contains membrane protein complexes of the light RX

Question 17

Where were chloroplasts derived from

Answer 17

Endosymbiosis of cyanobacterium

Question 18

Where do light and carbon reactions take place

Answer 18

Chloroplast

Question 19

How long is a chloroplast

Answer 19

5 micrometres

Question 20

Thylakoid membrane organisation

Answer 20

PSI and ATP synthase located in stromal lamellae. PSII found in granal regions. Cytb6f found evenly distributed throughout membrane

Question 21

What is eukaryotic photosynthesis done by

Answer 21

Endosymbionants

Question 22

How many photons absorbed per chl per second

Answer 22

10 - inefficient

Question 23

Antenna

Answer 23

Couple thousands of pigments to single RC so RC is excited many times per second

Question 24

How does RC work

Answer 24

1. Absorb photon - antenna pigment becomes excited
2. Exciton can jump around antenna
3. Small upward energy jumps possible but mainly downward
4. Exciton diffuses around antenna but ends up in RC

Question 25

What does light absorption lead to

Answer 25

Photoinduced charge separation

Question 26

Major pigments

Answer 26

Chl a (CH3) and b (CHO)

Question 27

Examples of accessory pigments

Answer 27

Carotenoids, bilins

Question 28

What is the main light harvesting protein in plants

Answer 28

LHC2

Question 29

What are major light harvesting proteins of cyanobacteria

Answer 29

Phycobiliproteins