Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Membranes > Photosynthesis > Flashcards

Photosynthesis Flashcards

1
Q

What is the chemical equation for photosynthesis?

A

6CO2 + 6H2O —> C6H12O6 + 6O2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does light driven electron transport chains generate?

A
  • ATP
  • NADPH
  • both needed to reduce CO2 to sugar
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the two different types of photosynthesis?

A 
Anoxygenic
- electron donor is H2S (SO42-)
- better e- donor
- need only one photosystem to reduce NADP+
Oxygenic
- electron donor is H2O (O2) 
- bad e- donor
- needs 2 photosystems in series to reduce NADP+
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why are chlorophylls good at absorbing light?

A
  • high extinction coefficient
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where is the gap in chlorophyll?

A

Huge absorbance gap where visible light is, hence why it does not absorb green and instead reflects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How does an organism that has chlorophyll fill the gap?

A

organism uses other pigments to fill the gap

  • pigments phycocyanin and phycoerythrin in the 500-600nm wavelength region
  • pigment carotenoids use for 400-500nm region
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens when chlorophyls absorb light?

A
  • becomes excited

- shifts redox potential to more negative value

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What can bacteriochlorophylls do that normal chlorophylls cannot do?

A
  • absorb in the infrared
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the structure of the Phycobilin pigment?

A
  • linear tetrapyrrole
  • no Mg
  • light harvesting complexes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the two functions of Carotenoids?

A
  • protection from photooxidation

- light harvesting: not perfect but do fill gap

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What happens once light is absorbed by a pigment?

A
  • energy transfer from electron to the chlorophyll in the photosystem
  • works better if the two electrons are closer together (<0.5nm)
    (get 100% quantum yield)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How can you prevent fluorescence from happening?

A
  • having a faster energy transfer than competing reactions

- photon emitted doesn’t have a longer wavelength than the photon absorbed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Name different energy transfer mechanisms from fastest to slowest?

A

fastest - delocalised exciton coupling
fast - resonance transfer (resonance between dipoles)
slowest - inductive resonance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the overall organisations of the light harvesting complexes?

A
  1. reaction centre in the middle containing light harvesting complex 1
    - 2 chlorophylls
  2. light harvesting complexes surround the reaction centre
    - have multiple chlorophylls that orientate themselves in each light harvesting complex to absorb the most energy and get a fast transfer
    - energy transferred onto the reaction centre
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the different photosynthetic organism groups that undergo photosynthesis?

A 
anoxygenic phototrophs
- purple bacteria (proteobacteria) have photosystem 2
- green bacteria have photosystem 1
oxygenic phototrophs
- cyanobacteria have both photosystems
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the characteristics of the purple bacteria?

A
  • use photosystem 2
  • have chlorophyll A
  • Thylakoid membrane
  • Calvin-Benson cycle for CO2 fixation
  • has reverse electron transfer
17
Q

What are the two types of purple bacteria (Proteobacteria)?

A 
Purple sulphur bacteria 
- H2S and S as electron donor
Purple non-sulphur bacteria
- alpha-proteobacteria
- names begin with Rhodo
- can use a wide range of fermentation products as electron donors
- can grow anaerobically
18
Q

How does the photosystem 2 work in purple bacteria?

A
  • special pair exist in the reaction centre
  • 2 bacteria chlorophylls
  • they absorb a photon or get it passed on by light harvesting complexes
  • one of the chlorophyll will get oxidised once excited
  • donates an e- to another chlorophyll
  • this passes on the e- to bacteriopheophytin
  • passed e- to quinone
  • passes e- to a quinone pool in the membrane
  • there is a symmetry present between 2 branches
19
Q

What is the chlorophyll in the special pair in photosystem 2?

A
  • P870
20
Q

What happens when pigment P870 gets excited? Redox explanation

A

redox potential shifts from +500 to -900

  • it then gets oxidised (loses electron) passing it onto bacteriopheophytin and Quinones
  • quinone is at +100 mV so 1V is lost v quickly so that electron flows at one direction
  • can be passed from the Cytbc1 complex
  • then passes onto now oxidised chlorophyll
  • cycle can happen and it can get reduced again back to -900
21
Q

What does the cyclic electron transfer produce?

A

PMF that can be used to make ATP

22
Q

How is NADPH created during cyclic electron transfer?

A
  • do a reverse electron transfer
  • use NADH dehydrogenase
  • put 4 protons in to the cell to transfer electron from UQ to NADH
  • redox potential of NADH and NADPH is similar, but NADPH is less
  • moves electron from NADH to NADPH using transhydrogenase
23
Q

Why is an external electron donor needed in photosystem 2?

A
  • to replenish the electrons given to NADH by UQ when trying to make NADPH
  • electron donors can be H2S, H2, Succinate2-
24
Q

What are the two types of green bacteria?

A

green sulphur bacteria
- uses H2S and S as an electron donor
- have chlorosomes (light harvesting organelles)
- using reductive TCA cycle for CO2 fixation
chloroflexus
- filamentus bacteria
- can glide across surfaces
- found in hot springs
- 3-hydroxypropionate cycle for CO2 fixation

25
Q

What are chlorosomes?

A

vesicles that touch the membranes

  • stuffed fill with bacteria chlorophylls
  • able to grow at very low light intensities
26
Q

How does the photosystem 1 work in chloroplast?

A
  • special pair exist in the reaction centre
  • 2 chlorophylls
  • they absorb a photon or get it passed on by light harvesting complexes
  • one of the chlorophyll will get oxidised once excited
  • donates an e- to another chlorophyll
  • this passes on the e- to phylloquinone
  • passed e- to quinone
  • passes e- to iron sulfur complexes
  • e- end up in the level of ferredoxin
  • there is a symmetry present between 2 branches (only go down one path)
27
Q

What is the chlorophyll in the special pair in photosystem 1?

A

P840

28
Q

What happens when pigment P840 gets excited? Redox explanation

A

redox potential shifts from +300 to -1200

  • it then gets oxidised (loses electron) passing through FeS clusters and Quinones, ending up at Ferredoxin
  • can be passed to the Cytbc1 complex
  • goes back to the chlorophyll at +300 to P840
  • cycle can happen and it can get reduced again back to -1200
29
Q

Why is no reversed electron transfer needed in photosystem 1?

A

Because Ferredoxin is at the same level of NADPH and therefore electrons can be passed easier
- Ferredoxin can be used directly to reduce CO2

30
Q

What are the characters of cyanobacteria?

A
  • have chlorophyll a
  • use H2O as electron source, generating Oxygen
  • uses both photosystems to create a Z system
  • uses Calvin-Benson cycle for CO2 fixation
31
Q

What are physcobilisomes?

A

light-harvesting complexes in cyanobacteria and red algae

32
Q

What is the difference between the individual photosystems and the Z system?

A
  • redox potential of photosystem 2 (P680) is red not infrared and is more positive (+1000) than the redox potential of water (+880)
  • can take electrons from water via the Mn4 cluster
  • needs 2 photons
33
Q

What happens when pigment P680 gets excited in Z-scheme? Redox explanation

A

In PSII:
redox potential shifts from +1000 to -700
- it then gets oxidised (loses electron) passing through Pheo and PQ, ending up at Ferredoxin
In PSI:
end up with electrons to reduce ferredoxin
- from that they can reduce NADPH
- e- goes to water and then PQ and can be passed to the Cytbf complex
- cycle can happen and it can get then go to P700 in PSI.

34
Q

Why is no reversed electron transfer needed in Z-scheme?

A
  • using 2 photosystems, can shift redox potential to use h2o as an electron donor and ends up with NADPH
35
Q

How is ATP made?

A

Through cyclic e- transfer in PSI

  • protomotive force made by e- going from Ferredoxin to PQ then Cytbf
  • used to make ATP

Membranes (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions