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Photosynthesis Flashcards

1
Q

Autotroph

A

Carbon source from atmospheric carbon dioxide

Plants, cyanobacteria, algae

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2
Q

Heterotroph

A

Carbon source from organic compounds

Animals, most bacteria

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3
Q

Energy yielding oxidation of glucose

A

C6H12O6 + 6 O2 –> 6 CO2 + 6 H2O + energy

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4
Q

Site of oxidative phosphorylation in eukaryotes

A

Inner mitochondrial membrane

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5
Q

Number of oligomeric assemblies of proteins associated with oxidative phosphorylation, found in the inner mitochondrial membrane

A

5

Complex I, II, III, IV, & V

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6
Q

Complex V in ETC

A

ATP synthase

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7
Q

Site of photosynthesis in eukaryotes

A

Chloroplast

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8
Q

Where is ATP synthesized in mitochondria?

A

Mitochondrial matrix

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9
Q

Where is ATP synthesized in chloroplasts?

A

Stroma

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10
Q

Stroma

A

Outside of thylakoid membrane

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11
Q

Lumen

A

Inside of thylakoid membrane

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12
Q

Light Reactions

A

Generate energy-rich NADPH and ATP at the expense of solar energy

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13
Q

Dark Reactions

A

NADPH and ATP are used to form triodes and more complex compounds (glucose) from CO2 and H2O

Carbon assimilation

Can happen in dark or light

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14
Q

Who is the reducing agent in the given reaction?

CO2 + H2O —light—> (CH2O) + O2

A

H2O is the reducing agent

CO2 is reduced

Gain H = reduced

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15
Q

General Reaction

A

CO2 + 2 H2A —light—> (CH2O) + 2A + H2O

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16
Q

Photoreceptors

A

Light absorbing molecules

Absorb light in the visible region

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17
Q

Energy of Photon

A

E = hv = (hc)/y

v = frequency
c = speed of light (3 x 10e8 m/s)
y (lambda) = wavelength

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18
Q

Principle photoreceptor

A

Chlorophyll

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19
Q

Accessory Pigments in Plants

A

B-carotene
Lutein (xanthophyll)

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20
Q

Antenna Pigments in Cyanobacteria and Red Algae

A

Phycoerythrobilin
Phycocyanobilin

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21
Q

Different fates of excited electrons

A

Produce heat
Fluorescence
Exciton Transfer (resonance energy transfer)
Photooxidation

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22
Q

Antenna chlorophylls in light harvesting centers (LHC) pass the energy randomly, by exciton transfer until it traps by reaction center (RC) chlorophyll

23
Q

Out of many pigments, only chlorophyll molecules associated with RC can transduce light into chemical energy. The other pigment molecules are called ____

A

Antenna molecules

Accessory pigments and other chlorophylls

24
Q

Which of the following is the site of ATP synthesis in chloroplasts?

Outer membrane
Inner membrane
Stroma
Thylakoid membrane
Thylakoid compartment

A

Stroma

ATP synthase is in the thylakoid membrane, but ATP is produced into the stroma

25
Light Harvesting Centers (LHCs)
Transmembrane proteins
26
Functions of Accessory Pigments
1. Harvest light energy and transfer them to nearby chlorophyll similar to the chlorophylls 2. Prevent oxidation of chlorophylls which results in producing free radicals
27
Photosynthetic Reaction Centers (RCs)
Transmembrane protein containing a variety of chromophores
28
How are RCs named?
Based on the wavelength of light they absorb Ex. P870 absorbs light at 870 nm
29
Bacteriopheophytin vs Bacteriochlorophyll
Bacteriopheophytin does not have an Mg in the center
30
Antenna chlorophylls and other accessory pigments...
Absorb light energy, transferring it between molecules until it reaches the RC
31
Reaction Center
Photochemical reaction here converts the energy of a photon into a separation of charge, initiating electron flow
32
Photosynthesis RC: Step 1
Light excites an antenna molecule (chlorophyll or accessory pigment), raising an electron to a higher energy level
33
Photosynthesis RC: Step 2
The excited antenna molecule passes energy to a neighboring chlorophyll molecule (resonance energy transfer), exciting it
34
Photosynthesis RC: Step 3
The energy is transferred to a reaction-center chlorophyll, exciting it
35
Photosynthesis RC: Step 4
The excited reaction-center chlorophyll passes an electron to an electron acceptor
36
Photosynthesis RC: Step 5
The electron hole in the reaction center is filled by an electron from an electron donor
37
Result of Photosynthesis RC
The absorption of a photon has caused separation of charge in the reaction center
38
Bacterial Photosystem I (PSI)
Type I reaction center Present in heliobacteria and green sulfur bacteria
39
Bacterial Photosystem II (PSII)
Type II reaction center Present in purple bacteria and green filamentous bacteria
40
Photosystems in Cyanobacteria
Both PSI and PSII couple in series Cyanobacteria: most abundant class of photosynthetic bacteria
41
Photosystem II
Cyclic Makes proton gradient across membrane to synthesize ATP
42
Photosystem II Reactions Sum
2 photons + 4 H+ (in) ---> 4 H+ (out)
43
Photosystem I
Usually noncyclic Reduces NADP+ to NADPH Green sulfur bacteria: electrons are transferred from H2S or S2O3(2-)
44
When is Photosystem I cyclic?
If more energy is required for biosynthesis reactions (need more ATP) No NADPH is made
45
Most photosynthetic bacteria have one type of reaction center, but cyanobacteria and algae have:
Two photosystems that work in tandem
46
Tandem Photosystems
PSI: Light excites P700 electron (lower reduction potential, donates electrons to higher reduction potential) PSI: P700 becomes electron deficient PSI: NADP+ is reduced to NADPH (noncyclic, needs 2 electrons to reduce) PSII: Light excites P680 electron (lower reduction potential, donates electrons to higher reduction potential) PSII: P680 becomes electron deficient PSII: Proton gradient is formed, electron donated to P700 PSII: P680 accepts electron from H2O --> 1/2 O2
47
ETC Complex IV
1/2 O2 + 2H+ + 2e- ---> H2O Eº' = 0.82 High reduction potential Good oxidizing agent Likes to be reduced
48
In photosynthesis, reverse reaction takes place
H2O ---> 1/2 O2 + 2H+ + 2e- 2 P+(680) + 2 e- ---> 2 P(680) Eº' = higher than O2
49
NADP+ + 2e- + H+ ---> NADPH
Need 2 photons in PSI & PSII (4 total) H2O splitting gives 2 e- to produce 1/2 O2 4 H+ (in cyt b6f) + 2 H+ (water splitting) = 6 H+ increase in lumen ≈ 2 ATP
50
What is produced in the stroma?
ATP NADPH
51
What is produced in the lumen?
H+
52
Most cyanobacteria contain a complex internal network of membranes where ______ are located:
Photosystem complexes
53
Photosystem II of the cyanobacteria Synechococcus elongates
The monomeric form of the complex has two major transmembrane proteins, D1 and D2 Although the two subunits are nearly symmetric, electron flow occurs through only one of the two branches of cofactors (on D1)
54
Water-splitting activity of the oxygen-evolving complex
The sequential absorption of four photons (excitons), each absorption causing the loss of one electron from the Mn center, produces an oxidizing agent that can remove four electrons from two molecules of water, producing O2. The electrons lost from the Mn center pass one at a time to an oxidized Tyr residue in a PSII protein, then to P680+

Advanced Biochem (4 decks)

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