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bioenergetics > photosynthesis > Flashcards

photosynthesis Flashcards

1
Q

vwhat are the structures present in the chloroplast?

A
  • chloroplast envelope
  • thylakoids
  • stroma
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2
Q

what is the structure of the chloroplast envelope?

A
  • it is bounded by a double membrane
  • both outer and inner membrane form smooth continuous boundaries
  • the outer membrane is selectively permeable
  • the inner membrane is highly permeable due to increased numbers of transporters
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3
Q

what are the functions of the chloroplast envelope?

A
  • it separates the organelle from the cell
  • allows for compartmentalisation
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4
Q

what is the structure of the thylakoids?

A
  • is a network of flattened discs
  • are usually stacked to form grana
  • contains the thylakoid space inside it
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5
Q

what are the functions of the thylakoids?

A
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6
Q

what is the structure of the stroma?

A
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7
Q

what are the functions of the stroma?

A
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8
Q

where are chloroplasts typically found?

A
  • palisade mesophyll cells
  • spongy mesophyll cells
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9
Q

what is the definition of absorption spectrum?

A
  • it is the graph of light energy absorbed for each photosynthetic pigment at each wavelength
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10
Q

what is the only wavelength of light not absorbed?

A
  • green light!
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11
Q

what are the 2 wavelenghts of light that bring about high rate of photosynthesis?

A
  • blue light
  • red light
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12
Q

what is the definition of action spectrum?

A
  • it is the graph of the rate of photosynthesis occuring at each wavelength of light
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13
Q

explain the significance of an absorption spectrum. [2]

A
  • the absorption spectrum is the graph of the amount of light energy absorbed by each pigment at each wavelenght of light [1]
  • comparing it with the action spectrum, it shows the photosynthetic pigments responsible for the absorption of light energy in photosynthesis [1]
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14
Q

comment on the relationship between the absorption and action spectra. [3]

A
  • as the amount of light absorped by (pigments) increases, the rate of photosynthesis also increases [1]
  • signifying that there is a close similarity between the absorption and action spectra [1]
  • {QF} [1]
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15
Q

where does the light reaction occur?

A
  • across the thylakoid membranes of chloroplasts, with the chlorophyll facing outwards for photon absorption
  • includes the grana and intergranal lamellae!!
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16
Q

what are the requirements for non-cyclic photophosphorylation?

A
  • light energy
  • NADP+
  • H2O
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17
Q

what are the products formed from non-cyclic photophosphorylation?

A
  • ATP → for the Calvin Cycle
  • NADPH → for the Calvin Cycle
  • O2 → by-product
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18
Q

what are the requirements for cyclic photophosphorylation?

A
  • light energy
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19
Q

what are the products formed from cyclic photophosphorylation?

A
  • ATP → for Calvin Cycle
20
Q

where are photosynthetic pigments found in?

A
  • photosystems which are embedded in the thylakoid membrane
21
Q

what are the 2 types of photosystems embedded in the thylakoid membrane?

A
  • PSI: P700 reaction center
  • PSII: P680 reaction center
22
Q

what is the significance of the number in the reaction center?

A
  • the number represents the wavelength of light energy which the pair of special chlorophyll a best absorbs

* P700, SCA best absorbes 700nm
* P680, SCA best absorbes 680 nm

SCA → special chlorophyll a

23
Q

what does each photosystem consists of?

A
  • a light harvesting complex (LHC)
  • a reaction centre (RC) surrounded by LHC
24
Q

what does the LHC consist of?

A
  • accessory pigments which absorb light energy from 400nm to 700nm, and transfer the energy to the RC
25
Q

what does the RC consist of?

A
  • special chlorophyll a, whose electrons are displaced during photoactivation
26
Q

when does non-cyclic photophosphorylation occur?

A
  • ALL THE TIME when light energy is present
27
Q

what is the 1st step in non-cyclic photophosphorylation?

A
  • light harvesting
28
Q

what are the steps involved in light harvesting?

A
  1. light of appropriate wavelengths strikes the photosynthetic pigments in the Light Harvesting Complex (LHC) of Photosystem II (PSII) & Photosystem I (PSI)
  2. light energy is absorbed by the LHC, and passed to neighbouring pigments
  3. until it reaches the pair of special chlorophyll a in the Reaction Centre (RC) of PSII & PSI

X is either I or II

29
Q

what is the second step in non-cyclic photophosphorylation?

A
  • photoactivation of the pair of special chlorophyll a
30
Q

what are the steps involved in the photoactivation of the pair of special chlorophyll a?

A
  1. an electron is displaced from the pair of special chlorophyll a in the RC of PSII & PSI respectively,
  2. as it is excited due to the photoactivation of special chlorophyll a, which occurs simultaneously in both PSII & PSI
  3. the displaced electron is accepted by a primary electron acceptor
31
Q

what is the 3rd step in non-cyclic photophosphorylation?

A
  • photolysis of water
32
Q

where does photolysis of water occur?

A
  • thylakoid space
33
Q

why is photolysis of water necessary?

A
  • photolysis of water occurs to replenish displaced electrons from RC of PS II
  • it also allows for the accumulation of H+ in the thylakoid space, which is crucial for ATP synthesis
34
Q

what is the by-product released during the photolysis of water?

A
  • oxygen
35
Q

what is the fourth step in non-cyclic photophosrylation?

A
  • flow of electrons down the first electron transport chain (ETC), and second ETC
36
Q

what are the steps involved in the flow of electrons down the 1st ETC & 2nd ETC?

A
  1. the displaced electron from PSII is passed down electron carriers of decreasing energy levels in the ETC from PSII to PSI
  2. while the displaced electron from PSI is passed down electron carriers of the 2nd ETC
37
Q

where are the electron carriers of decreasing energy levels found in?

A
  • the thylakoid membrane
38
Q

why does photolysis of water not occur for PSI?

A
  • the electron that is passed down electron carriers of the 1st ETC between PSII and PSI will reach the pair of special chlorophyll a in the RC of PSI,
  • replenishing the displaced electron in RC of PSI
39
Q

what is the fifth step in non-cyclic photophosphorylation?

A
  • pumping of H+ from the stroma into the thylakoid space
40
Q

what are the steps involved in pumping H+ from the stroma into the thylakoid space?

A
  1. energy released from the flow of electrons down electron carriers of decreasing energy levels of the 1st ETC & 2nd ETC is used to pump H+ from the stroma into the thylakoid space,
  2. creating a steep proton gradient
41
Q

why does the diffusion of H+ from the stroma into the thylakoid space require energy?

A
  • H+ will be moving against the concentration gradient, as the [H+] in the thylakoid space is greater than that in the stroma
42
Q

how does the thylakoid membrane prevent H+ from diffusing into the stroma?

A
  • the thylakoid membrane is impermeable to H+ due to the hydrophobic core of the phospholipid bilayer
43
Q

what is the sixth step in non-cyclic photophosphorylation?

A
  • NADPH synthesis
44
Q

what are the steps involved in NADPH synthesis?

A
  1. the electron that is pased down electron carriers in the 2nd ETC is accepted by the final electron acceptor, NADP+,
  2. to form NADPH,
  3. catalysed by NADP+ reductase, an enzyme
45
Q

what is the last step in non-cyclic photophosphorylation?

A
  • ATP synthesis, via ATP synthase
46
Q

what are the steps involved in ATP synthesis via ATP synthase?

A
  1. diffusion of H+ from the thylakoid space into the stroma,
  2. through the hydrophilic channel of ATP synthase down the concentration gradient,
  3. releases energy
  4. which is coupled to ATP synthesis, catalysed by ATP synthase
47
Q

describe the process of non-cyclic photophosphorylation [7]

A

bioenergetics (2 decks)

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