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Biology > 5.2.1 Photosynthesis > Flashcards

5.2.1 Photosynthesis Flashcards

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1
Q

photosystem

A

chlorophyll and other pigments arranged in complexes with proteins such as lipids and enzymes
- contains a reaction center

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2
Q

what does the reaction center of photosystem contain?

A

chlorophyll A

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3
Q

what does the primary photosynhetic pigment do?

A

abdsorbs light energy at particular wavelength for light dependant reaction

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4
Q

what does action spectrum show ?

A

rate of photosynthesis at different wavelengths of light

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5
Q

what is chemiosmosis ?

A

movement of H+ ions through ATP synthase producing a proton motive force to form ATP from ADP and Pi

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6
Q

what molecule is the final electron acceptor

A

NADP

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7
Q

what molecule is dehydrogenated in non cyclic photophosphorylation

A

water

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8
Q

where does photolysis of water occur

A

inside the thylakoid

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9
Q

where does atp synthase occur

A

in the stroma

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10
Q

what molecule is hydrogenated in non cyclic photophosphorylation

A

NADP

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11
Q

which wavelenth of light does the chlorophyll absorb in photosystem 2

A

680nm

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12
Q

which wavelenth of light does the chlorophyll absorb in photosystem 1

A

700nm

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13
Q

where do protons for chemiosmois come from

A

from the photolysis of water

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14
Q

why is it called phosphorylation

A

your in light adding a phosphate group to make ATP

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15
Q

what is phosphorylated

A

ADP

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16
Q

products of non-cyclic photophosphorylation

A

ATP
NADPH
O2

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17
Q

general name of pigment complexes in non-cyclic photophosphorolyation

A

photosystems

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18
Q

why is the pH of the thylakoid lumen lower than that of the stroma

A

the thylakoid contains a higher concentration of H+ ions than to the stroma so more acidic= lower pH

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19
Q

what is the function of the pH gradient in the non-cyclic photophosphorylation

A

forms electrochemical gradient so chemiosmosis occurs so H+ ions move down concentration gradient through the ATP synthase to produce the protein motive force to make ATP

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20
Q

explanation of cyclic photophosphorylation

A

light energy is absorbed by photosystem 1
chlorophyll a releases an electron
shifts to electron carrier and eventually back to PS1 to replace e-
helps keep electrochemical gradient
H+ then move down conc gradient through the ATP synthase to produce ATP by chemiosmosis from ADP and Pi

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21
Q

products of cyclic photophosphorylation

A

ATP

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22
Q

what is the purpose of cyclic phosphorylation

A

to produce more ATP so there’s enough for calvin cycle

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23
Q

how are electrons raised to higher energy levels or excited

A

electrons present in pigment molecules such as chlorophyll are excited by absorbing light from the sun
- high energy electrons are released when chemical bonds are broken in respiratory substrate molecules

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24
Q

what are excited electrons passed into

A

electron transport chain and used to generate a proton gradient

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25
Q

what makes up an electron transport chain

A

series of electron carriers

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26
Q

what do pigment molecules do

A

absorb specific wavelengths of light and reflect others

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27
Q

what causes different colour and shades of leaves

A

due to the different combinations of pigments

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28
Q

where does the light independant reaction occur

A

in stroma

29
Q

what impact does greater light intensity have on photophosphorylation ?

A

increase

30
Q

what impact does greater light intensity have on ATP and NADPH production

A

increase

31
Q

what impact does greater light intensity have on GP levels

A

remain the same or could increase

32
Q

what impact does greater light intensity have on TP levels

A

increase

33
Q

what impact does greater light intensity have on RuBP levels

A

increase

34
Q

what impact does greater light intensity have on rate of photosynthesis overall

A

increase

35
Q

what impact does lower light intensity have on photophosphorylation

A

decrease

36
Q

what impact does lower light intensity have on ATP and NADPH production

A

decrease

37
Q

what impact does lower light intensity have on GP levels

A

increase as can’t turn GP into TP

38
Q

what impact does lower light intensity have on TP levels

A

decrease

39
Q

what impact does lower light intensity have on RuBP levels

A

decrease or stays the same

40
Q

what impact does lower light intensity have on rate of photosynthesis overall

A

decrease

41
Q

what might limit the carbon dioxide concentration that can be taken in through the stomata

A

if increase transpiration - windy conditions cause stomata to close so CO2 won’t be taken in

42
Q

what might limit the photosynthetic rate at high temperatures

A

enzyme denatures
transpiration rate

43
Q

photorespiration

A

oxygen competes with CO2 for the active site of rubisco leading to a decrease in the fixation of CO2

44
Q

what impact does a higher carbon dioxide concentration have on carbon fixation

A

increases

45
Q

what impact does a higher carbon dioxide concentration have on GP levels

A

increase

46
Q

what impact does a higher carbon dioxide concentration have on TP levels

A

could increase but would need more ATP and NADH

47
Q

what impact does a higher carbon dioxide concentration have on RuBP levels

A

stay same or increase

48
Q

what impact does a higher carbon dioxide concentration have on overall rate of photosynthesis

A

increase

49
Q

what impact does a lower carbon dioxide concentration have on carbon fixation

A

decrease

50
Q

what impact does a lower carbon dioxide concentration have on GP levels

A

decrease

51
Q

what impact does a lower carbon dioxide concentration have on TP levels

A

decrease

52
Q

what impact does a lower carbon dioxide concentration have on RuBP levels

A

increase as will accumulate

53
Q

what impact does a lower carbon dioxide concentration have on overall rate of photosynthesis

A

decrease

54
Q

why might enzymes and proteins be affected by high temperature

A

enzyme active site denatures

55
Q

why is a problem if plants don’t do photosynthesis

A

can’t produce TP

56
Q

what is a compensation point

A

rate of respiration and rate of photosynthesis are equal

57
Q

what is DCPIP

A

blue indicator that accepts electrons

58
Q

what can DCPIP replace in the light dependant reaction

A

NADP

59
Q

if DCPIP replaces NADP what happens

A

DCPIP turns from blue to colourless

60
Q

explain how pairs of electrons move from chlorophyll to electron carrier system during part of the light-dependant reaction

A

chlorophyll a absorbs light energy and causes e- to be excited out and be accepted by electron carrier

61
Q

how are electrons lost from chlorophyll replaced

A

photolysis of water occurs
the H2O absorbs light and breaks down into O2 and H then the H splits into H+ and e-

62
Q

explain how ATP is synthased when electrons pass through the atp synthase

A

electrons pass through and cause an electrochemical gradient so H+ ions move through the ATP synthase by chemiosmosis down a concentration gradient across the thylakoid membrane and causes a proton motive force
the ADP and Pi joinn to form ATP

63
Q

name the enzyme responsible for fixing CO2 in the light-independant stage

A

Rubisco

64
Q

what is light intensity measured in

A

Lux

65
Q

what is photorespiration

A

rubisco can bind to either O2 or CO2
in high temp O2 levels increase so O2 outcompetes the CO2 so less carbon fixation occurs

66
Q

why are high temperatures a problem for C3 plants

A

abobe 25 degrees photorespiration exceeds photosynthesis as oxygenese activity of rubisco increases more than carboxylase activty
so reduces rate of photosynthesis
can also denature proteins
also stomata may close due to high water loss so less CO2 enters plant

67
Q

why aren’t C4 plants affected as much by high temperatures

A

rubsico is only in the bundle sheath so CO2 from atmosphere binds to PEP carboxylase instead and then CO2 released from their is passed to rubisco

68
Q
A

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