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photosynthesis Flashcards

1
Q

what is chemiosmosis and which molecule does it involve the generation of?

A

movement of hydrogen ions down their electrochemical gradient and helps generate ATP

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2
Q

what moves through ATP synthase?

A

hydrogen ions/protons

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3
Q

how does the electron transport chain work?

A
  • electrons gain energy by absorbing photons
  • they pass from carrier to carrier which each have a lower energy level
  • energy is released as electrons move down the chain
  • the energy is used to pump protons across a membrane against their concentration gradient
  • this creates an electrochemical gradient, maintained by an impermeability to hydrogen ions
  • protons move down channel proteins linked to ATP synthase to resynthesise ATP
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4
Q

how do electrons become excited?

A
  • absorb light energy and pass into an electron transport chain
  • released when chemical bonds are broken
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5
Q

what is a photosynthetic pigment?

A
  • pigments that can absorb certain wavelengths of light
  • used in the light dependent reaction
  • found in the thylakoids
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6
Q

outline the importance of photosynthetic pigments in photosynthesis

A
  • accessory pigments absorb light (photons)
  • they pass the energy to the reaction centre where the electrons are
  • primary pigment becomes oxidised as the excited electrons move to the electron acceptor and down the ETC
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7
Q

is photosynthesis endothermic or exothermic?

A

endothermic

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8
Q

is respiration endothermic or exothermic?

A

exothermic

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9
Q

what is meant by the compensation point?

A

rate of photosynthesis = rate of respiration

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10
Q

what is the structure to function of a chloroplast?

A

stroma - chemical reactions, enzymes etc
granum - SA:V ratio
thylakoid - ATP synthase, ETC

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11
Q

what is a photosystem?

A
  • light harvesting system
  • made of photosynthetic pigments (primary and accessory)
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12
Q

what is the importance of accessory pigments?

A

absorb different wavelengths of light for max light absorption

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13
Q

what do electron acceptors do?

A

pass electrons from the photosystem to the ETC

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14
Q

what are examples of hydrogen carriers?

A
  • NADP
  • FAD
  • NAD
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15
Q

where does the light dependent stage occur?

A

on the thylakoid membrane

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16
Q

what is the function of the light dependent phase?

A

transduce light energy into electrical energy

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17
Q

what are three key stages of the light dependent phase?

A
  • excitation of photosystems by light energy
  • production of ATP via the ETC
  • reduction of NADP and photolysis of water
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18
Q

what are the products of photolysis?

A
  • oxygen molecule
  • electrons
  • protons
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19
Q

what is the importance of photolysis?

A
  • electrons replace the ones lost in photosystem II (PSII)
  • protons reduce NADP
  • oxygen is a byproduct
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20
Q

what is photophosphorylation?

A

use of light energy to make ATP

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21
Q

what are the two types of photophosphorylation?

A

cyclic and non cyclic

22
Q

when does cyclic occur?

A

limited water availability

23
Q

which photosystems does each type of photophosphorylation involve?

A

cyclic - PS1
non cyclic - PS2 and PS1

24
Q

what are the differences in production in the two types of photophosphorylation?

A
  • ATP is produced in both
  • reduced NADP is only produced in non cyclic
25
what are the two stages of photsynthesis?
- light dependent - calvin cycle/light independent
26
what are the three main steps of the calvin cycle?
- carbon fixation - reduction of GP to TP - regeneration of RuBP
27
what happens in carbon fixation?
- rubisco catalyses the attachment of CO2 to 5C RuBP - this results in an unstable compound - it breaks down into 2 lots of 3C compounds called GP - this happens for 3xCO2 so 6GP produced
28
what happens in GP reduction?
- GP converts to TP with NADPH and ATP - oxidation of NADPH transfers a hydrogen atom to GP and ATP provides energy - 6TP produced
29
what happens in the regeneration of RuBP?
- one of 6 TP molecules forms half a glucose (two calvin cycles for one glucose molecule) - remaining 5 recombine to form 3 RuBP (5x3C=3x5C) - requires ATP
30
why does light intensity affect rate?
- excites electrons in photosystems - photolysis of water
31
why is light necessary?
- used to produce ATP for the calvin cycle - produce protons to reduce NADP
32
what happens if light is limited?
- GP increases as NADPH and ATP aren't synthesised - TP and RuBP reduce
33
why does CO2 affect rate?
- source of carbon for carbon fixation in the calvin cycle
34
why is carbon dioxide necessary?
combines with RuBP and enzyme rubisco to generate GP and TP
35
what happens if carbon dioxide is limited?
- reduction in GP and TP production and increase in RuBP as it isn't being used
36
why does temperature affect rate?
controls enzyme based reaction
37
why is heat necessary?
- rubisco is used for carbon fixation - ATP synthase is used to produce ATP
38
what happens if temperature is limited?
all three products decrease as the calvin cycle can't occur
39
why is the dark stage an inaccurate and accurate way to describe the light independent stage?
accurate as no photons are required but inaccurate as it requires products from the light dependent stage
40
what is the name of the primary pigment?
chlorophyll A
41
name some accessory pigments
chlorophyll b, carotenoids, carotene, xanophylls
42
what is the precise location of photosynthetic pigments?
photosystems in the thylakoid membrane
43
outline the processes involved in the production of ATP via chemiosmosis
- occurs in mitochondria - active transport of H+ ions from the cytyosol to the intermembrane space - creates a proton gradient and generates proton motive force - protons move down concentration gradient through ATP synthase - energy powers enzymes to catalyse the synthesis of ATP from ADP and Pi
44
summarise the importance of coenzymes
CoA: transfers acetyl from link to krebs ADP and ATP: - phosphorylation of glucose to form hexose bisphosphate - removes phosphate group from TP in glycolysis NAD: - oxidation of triose phosphate in glycolysis - oxidises pyruvate in link reaction - reduces pyruvate in lactate fermentation and ethanal in alcoholic fermentation
45
what are the uses of TP within the plant?
- regenerate RuBP - form a glucose molecule
46
explain why temperature has a greater effect on the rate of the LDR
- there are more enzyme-controlled reactions - if enzymes denature the calvin cycle can't continue
47
what is the role of chloroplasts in photosynthesis?
- LIR and LDR take place in thylakoid membrane - 2 photosystems containing photosynthetic pigments to absorb light - ETC to move electrons and produce ATP - RuBP as a CO2 acceptor and GP is produced and converted to TP
48
suggest two ways that the ultrastructure of a chloroplast is altered in high temps and explain the effect on photosynthesis
- phospholipid bilayer becomes fluid and unstable so ETC and ATP synthase don't function and LDR cannot continue - damage to chlorophyll reduces LDR
49
what is Q10?
temperature coefficient - effect of raising the temp 10 degrees when measuring rate of reaction
50
what is the rough Q10 of most biological systems?
2-3
51
what is a limiting factor?
the factor that will determine the rate when at lower level

communication, homeostasis and energy (6 decks)

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