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ocr biology > 5.5 photosynthesis > Flashcards

5.5 photosynthesis Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

how is energy stored?

A

in glucose

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2
Q

where do animals take glucose from?

A

eating plants or other animals

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3
Q

where do plants take glucose from?

A

make it in photosynthesis

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4
Q

whats the photosynthesis equation?

A

6(CO2) + 6(H2O) = C6H1206 + 6(O2)

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5
Q

define respiration

A

cell releasing energy from glucose

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6
Q

what are the 2 types of respiration

A

anaerobic

aerobic

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7
Q

aerobic respiration equation

A

C6H12O6 + 6(O2) = 6(CO2) + 6(H2O)

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8
Q

which are the coenzymes used in photosynthesis?

A

NADP -transfers oxygen from one molecule to another (reduce/oxidise molecule)

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9
Q

coenzymes used in respiration

A

NAD/FAD -transfers hydrogen from one molecule to another (reduce/oxidise molecule)
coenzyme A - transfers acetate between molecules

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10
Q

chloroplast

A
  • flattened structure in plant cells
  • Double membrane
  • inside contains thylakoid membrane stacked up into structures called grana linked together by bits of thylakoids, lamellae
  • contain photosynthetic pigments
  • contain stroma
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11
Q

which are the 3 photosynthetic pigments?

A

chlorophyll a
chlorophyll b
carotene

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12
Q

what are photosynthetic pigments?

A

coloured substances that absorb light energy

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13
Q

where are photosynthetic pigments found

A

chloroplast, thylakoids membrane attached to proteins

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14
Q

proteins + pigments =

A

photosystem

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15
Q

what does a photosystem contain?

A

2 types of photosynthetic pigments

  • PRIMARY
  • ACCESSORY
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16
Q

what is the role of primary photosynthetic pigment?

A

is the reaction centre

where electrons are excited in the light dependent reaction

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17
Q

what is the role of accessory photosynthetic pigment?

A

make up light-harvesting system, surrounds reaction centre and transfer light energy to them to excite electrons

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18
Q

how many photosystem are used to capture light energy?

A

2

  • PI absorbs best at wavelength 700nm
  • PII absorbs best at wavelength 680nm
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19
Q

what is stroma?

A

gel-like substances

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20
Q

where is stroma found?

A

surrounding thylakoids

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21
Q

what does stroma contain?

A
  • enzymes
  • sugars
  • organic acids
  • DNA (often circular), there can be multiple copies
  • carbohydrates not used straight away (produced in photosynthesis) stored in starch grains
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22
Q

how many stages does photosynthesis have?

A

2

  • light dependent reaction
  • light independent reaction
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23
Q

where does LDR occur?

A

thylakoids membranes

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24
Q

describe LDR

A
  • light energy absorbed by photosynthetic pigments in photosystem
  • converted into chemical energy
  • energy used to:
    1. add an inorganic phosphate to ADP –> ATP (phosphorylation)
    2. reduce NADP to form reduced NADP
    3. split water into protons, electrons and oxygen (photolysis)
  • H2O oxidises to O2
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25
Q

where does LIR occur?

A

stroma

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26
Q

describe LIR

A
  • doesn’t use light energy directly but relies on products

- ADP & reduced NADP supply energy and hydrogen to make glucose from CO2

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27
Q

experiment - to separate photosynthetic pigments

A

thin layer chromatography

28
Q

two phases of thin layer chromatography

A
  • mobile phase (liquid solvent)

- stationery phase (chromatography plate)

29
Q

process of thin layer chromatography

A
  1. grind leaves + anhydrous sodium sulfate + propanone = liquid
  2. liquid + petroleum ether - test tube, shake - 2 layers, top one is pigments
  3. top layer + anhydrous sodium sulfate - test tube
  4. pencil line - bottom of chromatography plate, concentrates spot of liquid (several drops, dry) point of origin
  5. plate in beaker with a solvent (line little above)
    different pigments move at different rates, they will separate
  6. when solvent nearly reached the top take out and mark solvent front and separated pigments (coloured spots)
  7. calculate Rf values
30
Q

Rf formule

A

distance travelled by spot / distance travelled by solvent

31
Q

which are the two types of phosphorylation?

A
  • non cyclic

- cyclic

32
Q

how are photosystems linked in non cyclic phosphorylation?

A 
electron carriers (proteins)
form electron transpost chain
33
Q

describe non cyclic phosphorylation

A
    • light energy absorber by PSII
      - electrons in chlorophyll are exited, move along electron transport chain
    • electrons must be replaced
      - light energy splits water into protons and oxygen
      H2O -> 2H+ + 1\2O2
    • excited electrons lose energy in electron transport chain
      - is used to transport protons in thylakoids via membrane proteins (proton pump)
      - higher concentration of protons in thylakoids
      - protons move down into stroma via an enzyme ( ATP synthase)
      - energy from this movement combines ADP and inorganic phosphate to form ATP
  4. light energy absorbed by PSI, excites electrons at a even higher energy level
    - electrons transferred to NADP with a proton from the stroma to form reduced NADP.
34
Q

what are protons

A

h ions

35
Q

describe cyclic phosphorylation

A

only uses PSI

-electrons from chlorophyll are passed back to PSI via electron carries (recycled)

36
Q

what does cyclic phosphorylation produce?

A

small amount of ATP

-no O2 or NADP

37
Q

how is light independent reaction also called

A

Calvin cycle

38
Q

where does Calvin cycle take place

A

in stroma

39
Q

what does Calvin cycle need

A

ATP and protons

40
Q

describe Calvin cycle

A
  1. co2 enters stoma through stomata
    - is combined with ribulose bisphosphate (RuBP), a 5C compound
    - this gives an unstable 6c compound
    - quickly breaks down into 2 molecules of 3c compound, glycerate 3 phosphate (GP)
    - ribulose bisphosphate carboxylase (RuBisCO) catalyses reaction between co2 & RuBP
  2. ATP (from LDR) gives energy to turn GP into a different 3c compound, triose phosphate (TP)
    - this requires also h ions from red NADP (from LDR) recycled to NADP
    - TP converted into useful substances , 5 every 6 are used to regenerate RuBP, where the rest of ATP (from LDR) is used.
41
Q

how many turns of Calvin cycle to form an hexose sugar?

why?

A

6

two triose phosphate are needed to form an expose. sugar

42
Q

how many molecules of triose phosphate are produced in 3 turns of Calvin cycle?

A

6

43
Q

how many molecules of triose phosphate are used to regenerate RuBP every 6 molecules

A

5

44
Q

what do 6 turns of Calvin cycle need

A

18 ATP
12 reduced NADP
froml LDR

45
Q

what are triose phosphate and glycerate 3 phosphate converted into?

A
  1. carbohydrates- hexose sugers, join 2 TP e.g. glucose
    - larger carbohydrates (starch, cellulose) join hexose sugars in different ways
  2. lipids
    - TP synthesises glycerol
    - GP fatty acids
  3. some amino acids made from GP
46
Q

why is important to maintain an optimum temperature during photosynthesis?

A

enzymes are involved
under 10 C inactive
above 40C denature

47
Q

what happens in photosynthesis if temperature is too high?

A
  1. -stomata close to safe water
    - less carbon dioxide enters
    - photosynthesis slow
  2. -thylakoid membrane can be damaged
    - rate of LDR decreases because less sites are available for electron transfer
  3. membrane around chloroplast damaged enzymes needed in Calvin cycle are released into the cell
    - reduce rate of LIR
  4. -chlorophyll damaged
    - reduce amount of pigment that can absorb light energy
    - rate of LDR slows
48
Q

which are the limiting factors in photosynthesis

A

-light intensity (wavelength)
-co2
-temperature
(water)

49
Q

how does wavelength affect photosynthesis?

A
  • higher intensity of light provides more energy
  • only certain wavelength are used in photosynthesis, photosynthetic pigments only absorbs red and blue light (green is reflected)
50
Q

how does carbon dioxide affect photosynthesis?

A
  • makes up 0.04% of gases in atmosphere
  • increased to 0.4% : higher rate of photosynthesis
  • any higher stomata close.
51
Q

how do limiting factors of photosynthesis interact ?

A

all need to be at the optimum level to have quicker photosynthesis
-if one is too low it will be limited

52
Q

whats usually the limiting factor in sunny windless places?

A

co2

53
Q

whats the limiting factor of photosynthesis at night?

A

light intensity

54
Q

define metabolic pathway

A

a series of small reactions controlled by enzymes e.g. respiration and photosynthesis

55
Q

phosphorylation

A

adding a phosphate to a molecule

56
Q

photophosphorylation

A

adding a phosphate to a molecule using light

57
Q

photolysis

A

splitting of a molecule using light energy

58
Q

hydrolisis

A

splitting of a molecule using water

59
Q

decarboxylation

A

removal of carbon dioxide from a molecule

60
Q

dehydrogenation

A

removal of hydrogen from a molecule

61
Q

redox reactions

A

reaction that involve oxidation and reduction

62
Q

reduction

A

gained an electron, may have gained hydrogen or lost oxygen

63
Q

oxidation

A

lost an electron, may have lost hydrogen or gained oxygen

oxidation of a molecule always involves reduction of another molecule

64
Q

how does light intensity affect tp gp and rubp levels?

A

short supply of LDR products (ATP and red NADP)
conversion of GP into TP and RuBP is slow
GP levels rise
TP and RuBP levels fall

65
Q

how does temperature affect TP GP RuBP?

A

All reaction in Calvin cycle are catalysed byenzymes
reactions are slower
levels of GP TP RuBP fall

66
Q

how does carbon dioxide concentrations affect GP TP RuBP levels?

A

conversion of RuBP into GP slower
level of RuBP rise
level of GP and TP fall

67
Q

investigating rate of photosynthesis using pondweed

A
  1. pondweed + water in a test tube connected to a capillary tube connected to a syringe
  2. source of white light placed at a set distance
  3. let photosynthesise for a set amount of time , oxygen is collected in the capillary tube
  4. syringe move oxygen up along side a ruler, length is measured
  5. variables (time temp.) must be controlled
  6. repeated, average
  7. repeat at different distances

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