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Flashcards in Intro lecture Deck (29):
1

How to grow better wheat

Enhance mechanisms giving off O2 (photosyn)

2

What is photosynthesis

Capture and use of light energy by organisms

3

What are reaction centres

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

4

Rhodopsin homologues use

Cis/trans retinal isomerisation - proton pumping

5

The two major types of photosynthesis

1. Rhodopsin based 2. Reaction centres

6

How does rhodopsin based photosynthesis work

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

7

Retinal cofactor

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

8

What drives proton pumping in rhodospin homologues

Isomerisation from trans to cis - external reductant needed

9

Photosynthetic RX centre facts

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

10

PSI RC terminal electron acceptor

FeS

11

PSII RC terminal electron acceptor

Quinone

12

When did oxygenic photosynthetic bacteria arise

About 2 billion years ago

13

When did anoxygenic photosynthetic bacteria arise

About 3.2 billion years ago

14

How do green photosynthetic anaerobes work

Use H2S in photosynthesis to generate sulphur

15

Where did oxygenic photosynthesis evolve

Cyanobacteria

16

What are cyanoobacteria

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

17

Where were chloroplasts derived from

Endosymbiosis of cyanobacterium

18

Where do light and carbon reactions take place

Chloroplast

19

How long is a chloroplast

5 micrometres

20

Thylakoid membrane organisation

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

21

What is eukaryotic photosynthesis done by

Endosymbionants

22

How many photons absorbed per chl per second

10 - inefficient

23

Antenna

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

24

How does RC work

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

25

What does light absorption lead to

Photoinduced charge separation

26

Major pigments

Chl a (CH3) and b (CHO)

27

Examples of accessory pigments

Carotenoids, bilins

28

What is the main light harvesting protein in plants

LHC2

29

What are major light harvesting proteins of cyanobacteria

Phycobiliproteins