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A Level Biology > Photosynthesis > Flashcards

Photosynthesis Flashcards

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1
Q

What is light harvesting?

A
  • absorption of light energy by accessory pigments and the passing of the energy to the reaction centre chlorophyll a molecule
  • the chlorophyll a molecule uses the energy to excite e-s - drives light dependent reactions
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2
Q

light harvesting complexes are part of ?

A

a photosystem

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3
Q

humans are ?

A

heterotophs

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4
Q

plants are ?

A

(photo)autotrophs

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5
Q

autotrophs are?

A
  • can synthesise complex organic molecules from simple substances in their surroundings
  • using energy from light or inorganic chemical reactions
  • can ‘fix’ carbon
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6
Q

how do autotrophs fix carbon?

A

• inorganic form (CO2) ➡ organic (proteins, carbs, lipids)

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7
Q

heterotrophs?

A

cannot fix carbon, have to obtain C from complex organic molecules in other organisms, consuming them

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8
Q

autotrophs convert light energy into

A

chemical energy

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9
Q

Phys eq?

A

6CO2 + 6H2O ➡ (light energy) C6H12O6 + 6O2

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10
Q

resp eq?

A

C6H12O6 + 6O2 ➡ (ATP coming off arrow) 6CO2 + 6H2O

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11
Q

Another type of autotroph?

A
  • chemoautotroph

* obtain light energy from chemicals

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12
Q

leaves must be able to?

A
  1. contain chlorophyll and other photosynthetic pigments
  2. take out O2 and in CO2
  3. steady water supply
  4. make carbs and transport them
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13
Q

what is the reaction centre pigment molecule?

A

chlorophyll a - 2 types though

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14
Q

2 sets of reactions in phys?

A
  1. light dependent

2. light independent

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15
Q

LDR can only occur if?

A

pigments that can absorb certain wavelengths of light are present

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16
Q

why is light needed in LDRs?

A
  • photolysis - splitting H2O ➡ H2 + O

* provide chemical energy (ATP) for the reduction of CO2 to C6H12O6 in LID

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17
Q

What are photosynthetic pigments?

A
  • coloured molecules that absorb specific wavelengths of light (colours)
  • pick up specific colours not others
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18
Q

what happens to the wavelengths of light that are not absorbed?

A
  • wavelengths not absorbed are either reflected or transmitted through
  • we only see unabsorbed wavelengths
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19
Q

2 major photosynthetic pigments in plants?

A
  • chlorophyll a
  • chlorophyll b
  • chlorophyll a absorbs slightly longer wavelengths of light than b
  • this can be plotted on a graph called an absorption spectrum
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20
Q

In all photosynthesising plants there is?

A

chlorophyll a

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21
Q

accessory pigments?

A
  • e.g. carotenoids (carotene) which absorb more blue/ green light than chl
  • accessory bc there to help chl
  • pick up wavelengths of light that would otherwise be missed and pass the energy onto chl
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22
Q

% error equation?

A

uncertainty / measurement x100

x2 if 2 measurements taken

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23
Q

to get total % error?

A

add them together

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24
Q

to decrease percentage error?

A
  • use longer TLC paper

* take photo and zoom in ➡more accurate measurement ➡ reduced uncertainty

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25
Q

uncertainty is ?

A

half of resolution

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26
Q

chloroplast structure?

A
  • lamella
  • starch grain
  • envelope
  • DNA loop
  • lipid droplet
  • 70s ribosomes
  • thylakoid
  • granum
  • stroma
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27
Q

lamella?

A

paired membranes (the disks in the cell)

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28
Q

granum?

A

• flattened stack of thylakoids

  • hold pigments and enzymes for phys
  • increase SA:V for max light absorption
  • site of chemiosmosis
  • grana = plural
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29
Q

thylakoid?

A

membrane bound sac studded w phys pigments & e-s carriers

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30
Q

stroma?

A
  • would be cytoplasm if was cell

* 2 phospholipid membrane system runs thru the stroma - this is the site of LDRs

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31
Q

size and shape of chloroplast?

A
  • biconcave disk

* 3-10 micrometer

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32
Q

2 variations of the reaction centre (chl a )

A

• P700
• P680
refers to wavelength of light best absorbed

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33
Q

access pigms are pigments other than ?

A

chl a

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34
Q

LDR summary?

A

H2O (+light energy) ➡ O2

takes place in the thylakoid membrane

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35
Q

LDR and LID reactions are linked by?

A

ADP reversible arrow ATP

OxNADP to redNADP and back

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36
Q

LID reaction summary?

A

CO2 ➡ Calvin cycle ➡ glucose

stroma

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37
Q

NADP?

A
  • coenzyme

* acts as hydrogen carrier

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38
Q

The Z scheme?

A
  • H2O -> H2 +O2 - splitting = photolysis
  • ATP produced in photophosphorylation
  • and redNADP
  • ATP and redNADP passed onto the LID stages
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39
Q

How is redNADP formed?

A
  • red= gain of e-

- H2O -> 2H+ + 2e- + 1/2O2

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40
Q

Photophosphorylation?

A
  • ADP -> ATP
  • can be cyclic or non cyclic
  • 1 photosystem involved
41
Q

Cyclic photophosphorylation?

A
  • generates ATP but not redNADP
  • photons passed on by acc. pigments to P700
  • an e- in the chl a is excited to a higher energy level and is emitted from the chl a
  • picked up by an e- carrier
  • passed back to P700 via a chain of e- carriers
  • As it is passed along, enough energy is released to phosphorylate ADP
42
Q

only ? is involved in CP?

A

PS1

43
Q

non-cyclic photophosphorylation?

A
  • e-s emitted and move to P700
  • now P680 has a + charge
  • light absorbed by both photosystems
  • excited e-s are emitted by both PS
  • both now have + charge
  • At PSII e- picked up by e- acceptor
  • passed along by e- carriers where it is absorbed by PSII reaction centre
  • as the e- are passed along, enough energy is released to ADP-> ATP
44
Q

non-cyclic photophosphorylation 2

A
  • e- in PSII are replaced by the photolysis of H2O
  • PSII has a H2O splitting enzyme
  • H2O -> 2H+ + 2e- + 1/2O2
  • H+ combine with e- from PSI and NADP to give NADPH2 (redNADP)

both NADP and ATP pass onto LIR to make glucose

45
Q

⭐ cannot make redNADP using…

A

cyclic phosphorylation

46
Q

ATP synthase is a.k.a as

A

ATPase

47
Q

how does photophosphorylation work?

A
  • using chemiosmosis
48
Q

Chemiosmosis?

A
  • movement of high energy e- down ETC
  • energy from e- used to AT H+ across thylakoid membrane
  • formation of H+ gradient
  • Facilitated diffusion of H+ through ATP synthase
  • production of ATP using energy from the movement of H+
  • for every 3H+ that go through, 1 ATP made
49
Q

LIR?

A

Calvin Cycle

50
Q

LIR background?

A
  • occurs in the stroma
  • takes place regardless of whether light is present or not
  • basically the reduction of CO2 using redNADP and ATP from LD
51
Q

How many turns of the calvin cycle are needed to make a hexose sugar?

A
  • 1 C entered every turn

- so 6 turns needed

52
Q

calvin cycle fixes

A

C

53
Q

stages of Calvin Cycle?

A
  1. CO2 combines with RuBP (5C) forming ustable 6C intermediate
  2. intermediate breaks up into 2 mols of GP (3C)
  3. GP + redNADP + ATP -> TP (+Pi, ADP, oxNADP)
  4. some TP converted through a sugar shuffle into RuBP
    - some released from cycle to condense, some makes hexose sugars, some converted to acetyl coA
54
Q

RuBISCO is the enzyme that?

A

converts RuBP + CO2 into 2GP

55
Q

Factors affecting rate of phys?

A
  • light intensity
  • CO2 conc
  • Temp
56
Q

limiting factor?

A
  • factor that is in the shortest supply
  • if another factor increases, no difference because the limiting factor is the one that is actually affecting the rate of phys
57
Q

whichever factor is the most limiting is

A

in the shortest supply and and is the limiting factor

58
Q

Why is temp imp for LIDs?

A
  • KE needed for enzymes (Rubisco)
59
Q

When you increase the limiting factor, why does the graph eventually plateau off?

A

another factor becomes limiting

60
Q

CO2 conc in air?

A

0.04%

61
Q

Q10 ?

A
  • should be 2 for biological systems

- but is not for LDRs as not controlled by enzymes

62
Q

Why is temp more complicated as a LF?

A
  1. LDRs not directly affected by temp bc they’re noy enzyme catalysed reactions that occur in solution like LIR. So Q10 not around 2
  2. At higher T and lower CO2 conc, O2 can act as a competitive inhibitor for rubisco, slows the rate of phys
63
Q

LF: water stress?

A
  • when water in short supply, stomata close to reduce water loss
  • CO2 entry decreases so the rate of LIR decreases
  • water availability is not considered a LF bc for water to become limiting, water potential of the cells will have become so low that stomata will have already closed stopping phys
64
Q

light intensity and distance are ?

A
  • inverse square law
  • LI = 1/d^2
  • the light intensity becomes 1/4 when distance x2
65
Q

problems with LI PAG?

A
  • determining colour = subjective ➡ use colorimeter
  • only did once = repeatability unclear
  • light from other lamps - true LI is different
  • diff sizes = diff SA = less diffusion distance
66
Q

where do autotrophs get CO2 ?

A
  • air, respiration of heterotrophs

- H2O: respiration of plant cells, from soil

67
Q

where does glucose go from autotrophs?

A
  • resp

- biosynthesis of other molecules by plant cells which can be used as a food source by heterotrophs

68
Q

where does O2 go from autotrophs?

A
  • resp of plant cells

- excreted into atmosphere if in excess, can be used for resp by heterotrophs

69
Q

where does glucose come from for resp of autotrophs?

A
  • phys

- or storage molecules e.g. starch

70
Q

where does O2 come from for resp of autotrophs?

A

phys or atmosphere

71
Q

where does CO2 go from autotrophs in resp?

A
  • air, via stomata

- used in phys

72
Q

where does water go from autotrophs in resp?

A

air as water vapour or phys

73
Q

where do heterotrophs get glucose from for resp?

A
  • eating food

- storage molecules like glycogen in muscle and liver tissue

74
Q

where do heterotrophs O2 from for resp?

A

air

75
Q

how do heterotrophs get rid of CO2?

A

air

76
Q

how do heterotrophs get rid of H2O?

A

urine (Excreted) or enters cell’s cytoplasm, TF, blood

77
Q

the long thing on diagrams between grana is?

A

lamella

78
Q

CP only involves ?

A

PS1 not PSII

79
Q

Lollipop experiment aim?

A
  • to discover the order of compounds synthesised after CO2 is fixed
80
Q

What was the lollipop?

A

a thin flask containing algae - apparatus looked like a lollipop

81
Q

Lollipop experiment: how was C14 used?

A
  • algae were exposed to C14O for short lengths of time
  • this fixed the C14 onto more compounds, the longer the exposure
  • C14 is radioactive so shows up on chromatograph - location can be detected
82
Q

Lollipop experiment: why was ethanol boiled?

A

kill algae to stop them phys

83
Q

Lollipop experiment: how were the compounds separated from the algae?

A

2D chromatography: w 2 diff solvents

84
Q

Lollipop experiment: how were the compounds containing C14 identified?

A
  • used autoradiography

- where compounds containing C14 appeared as dark smudges

85
Q

in the membrane of the thylakoid,

A

LDR happening

86
Q

Why are thylakoids stacked into grana?

A
  • inc SA of the membrane containing proteins needed for LDRs

- more membrane = more proteins = more LDRs

87
Q

compensation point on LF graph?

A

• part where the line crosses the x axis

resp rate = phys rate

88
Q

at very low LI

A
  • graph goes below x axis for CO2 uptake

* resp> phys rate so CO2 being produced not used

89
Q

Why is keeping a greenhouse warm in the winter a bad idea?

A

LI is the LF not temp so it would be a waste of energy and plant may start respiring more, the plant would be using up the fuel more than it was making it

90
Q

Q10 equation?

A

Q10 = R2/ R1 (^10/ temp change)

91
Q

R1 and R2?

A 
R1 = rate before the temp rise
R2 = rate after T rise
92
Q

What happens to [TP], [GP] and [RuBP] in high LI conditions?

A
  • At high LI, ATP and redNAD are in plentiful supply from the LDRs
  • so all conversions can happen at an equal rate
  • so levels remain constant
93
Q

What happens to [TP] in low LI?

A
  • needs ATP and redNAD from LDR which are not occuring

* so levels fall

94
Q

What happens to [RuBP] in low LI?

A
  • At low LI, ATP and redNADP are now not being provided by the LDR
  • GP to TP slows and stops
  • but TP to AA and lipids continues
  • tp TO RuBP stops so levels decline
95
Q

What happens to [GP] in low LI?

A

• RuBP -> GP continues so GP levels rise

96
Q

When LI rises again?

A
  • ATP and redNADP available again
  • GP to TP can happen again so GP levels fall back down and TP levels rise
  • TP to RuBP can happen again to RuBP levels rise
97
Q

at low LI the conc of only ? rises

A

GP

98
Q

TP can also go on to make?

A

hexose sugar

A Level Biology (28 decks)

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