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SNAB biology hoe > 5A Photosynthesis > Flashcards

5A Photosynthesis Flashcards

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1
Q

explain relationship between STRUCTURE and FUNCTION of granum in photosynthesis

A
  1. thylakoid membrane -> big s.a so absorbs as much light energy as possible
  2. thylakoid membrane -> contains lots of ATPsynthase = PRODUCES ATP in light DEP. reaction
  3. thylakoid membrane -> contain photosynthetic pigments
    eg. CHLOROPHYLL (attached to proteins) to absorb light

x2 membrane chloroplasts also keeps reactants for p/s close to react

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2
Q

describe how starch is formed FROM PRODUCTS of light indep. stage

A
  1. 2 GALP molecules make GLUCOSE
  2. glucose joined together by GLYCOSIDIC BONDS -> make AMYLOSE and AMYLOPECTIN by CONDENSATION REACTIONS
  3. amylose + amylopectin = STARCH
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3
Q

where does light DEPENDENT stage take place?

A

thylakoids of chloroplasts

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4
Q

where does light INDEPENDENT stage take place?

A

stroma of chloroplasts

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5
Q

how does light DEP. reaction generate ATP?

A
  1. light energy excites e- in chlorophyll -> as they leave PS1 they are replaced by e- from PHOTOLYSIS OF H₂O
  2. e- pass down electron transfer chain of e- carriers
    -> lose energy down E.T.C …
  3. … allows chemiosmosis to occur
  4. H⁺ ions actively pumped from a low conc. in
    stroma-> high conc. in the thylakoid = conc. grad. across thylakoid membrane
  5. ATPsynthase allows H⁺ ions thylakoid->stroma
  6. movement of H⁺ causes ATPsynthase to generate ATP
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6
Q

in light INDEP. stage

A
  • 3 ADP + Pi made from ATP
  • 2 NADP made from NADPH
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7
Q

ADP -> ATP

A

phosphorylation

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8
Q

ATP -> ADP

A

hydrolysis

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9
Q

ATP

A

adenosine triphosphate

phosphorolated nucleotide

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10
Q

metabolism

A

chemical processes that occur within a living organism in order to maintain life

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11
Q

outline the overall reaction of photosynthesis

IMPORTANT!!!

A
  1. in light dependent stage -> light energy breaks strong covalent bonds in H₂O
  2. O₂ released into atm
  3. in light indep stage (Calvin cycle) fixation with CO₂ enables H₂ to be stored as glucose a respiratory fuel
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12
Q

describe the light dependent stage of photosynthesis

non-cyclic phosphorylation

A
  1. light energy absorbed by PSII and excites e- in chlorophyll
  2. e- move along E.T.C
  3. photolysis of water
    H₂O -> 2H⁺ + 2e⁻ + ½ O₂
  4. e- made replace those lost in PSI
  5. energy lost by e- down E.T.C used to make ATP
  6. e- transferred to NADP + H⁺(from stroma) -> ↓ NADP
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13
Q

how do excited e- generate ATP?

A
  1. excited e- lose energy down E.T.C
  2. this energy is used to transport H⁺ into thylakoids
  3. so thylakoid has higher conc of H⁺ than stroma
  4. forms H⁺ gradient across membrane
  5. H⁺ move down conc grad into stroma via ATPsynthase
  6. (chemiosmosis) - energy from this movement causes
    ADP + Pi -> ATP
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14
Q

chemiosmosis

A

process where movement of H⁺ ions across a membrane generates ATP

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15
Q

how is energy stored in ATP?

A

stored as chemical energy in the phosphate bond

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16
Q

what enzyme catalyses the phosphorylation of ADP?

A

ATPsynthase

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17
Q

how does ATP supply energy?

IMPORTANT!!!

A
  • diffuses to part of cell that needs energy …
  • … where it is broken down via hydrolysis into ADP and inorganic Pi …
  • … causing chemical energy release from Pi bond and used by cell
  • ATPase catalyses this reaction
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18
Q

what enzyme catalyses hydrolysis / the breakdown of ATP to ADP?

A

ATPase

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19
Q

what happens after ATP is broken down into ADP and inorganic phosphate?

A

they are RECYCLED and process starts again

20
Q

coenzyme

A

molecule that aids function of enzyme

21
Q

how do coenzymes work?

A

transfer chemical group from one molecule to another

22
Q

what is the coenzyme used in photosynthesis?

A

NADP -> tranfers H₂ from one molecule to another
-> so can red. (give H₂) or ox. (take H₂) a molecule

23
Q

what is the function of the double membrane in chloroplasts?

A

keeps reactants for p/s close to reaction sites

24
Q

what are photosynthetic pigments?

A

coloured substances that absorb light energy needed for photosynthesis

25
Q

at what wavelength does PSI absorb light best?

A

700nm

26
Q

at what wavelength does PSII absorb light best?

A

680nm

27
Q

structure and function of stroma

A
  • contains all enzymes, sugars and organic acids
  • required for light independent reaction of p/s
  • contains oil droplets -> store non-carbohydrate organic material
28
Q

what happens at the thylakoid membranes in the light dependent reaction of p/s?

A
  • light energy absorbed by photosynthetic pigments (eg. chlorophyll) in photosystems …
  • … and converted to chemical energy
29
Q

what does NADPH transfer to light independent reaction?

A

H₂

30
Q

what happens to H₂O in light dependent reaction?

A

ox. to O₂

31
Q

what does the calvin cycle rely on?

A

products of light dependent reaction

32
Q

what is ATP and NADPH from the light dependent reaction used for in the Calvin cycle?

A

3ATP used supply energy to catalyse GP->GALP and GALP->RuBP (regeneration of RuBP)

2NADPH used to catalyse GP->GP

33
Q

cyclic phosphorylation

understand this

A
  • only uses PSI
  • e- from chlorophyll are NOT passed onto NADP -> are passed back to PSI via e- carriers
  • e- are recycled and repeatedly flow through PSI
  • only produces small amount of ATP
34
Q

what is stage 1 of the Calvin cycle called?

A

carbon fixation

35
Q

describe the process of carbon fixation in the Calvin cycle

A
  1. CO₂ enters leaf through stomata and diffuses into stroma of chloroplast
  2. here it is combined with RuBP , catalysed by RUBISCO
  3. this gives an unstable 6C compound which immediately splits into 2 3C compunds called GP
36
Q

what is stage 2 of the Calvin cycle called?

A

reduction of GP

37
Q

describe the process of reduction of GP in the Calvin cycle

A
  1. hydrolysis of ATP from light dep. reaction provides energy to turn GP -> GALP (3C)
  2. this reaction requires H⁺ (come from NADPH from light dep.)
    NADPH is recycled to NADP
  3. 1/6 GALP is converted into useful organic compounds
    rest continues in Calvin cycle to regenerate RuBP

check if its 1/6

38
Q

what is stage 3 of the Calvin cycle called?

A

regeneration of RuBP

39
Q

describe the process of regeneration of RuBP in the Calvin cycle

A
  1. 2 GALP molecules used to make hexose sugar BUT 5/6 GALP used to regenerate RuBP
  2. regenerating RuBP uses rest of ATP from light dep. reaction
40
Q

what organic substances can be made from products of the Calvin cycle?

products being GP and GALP

A
  • CARBS -> simple sugars eg. glucose
    -> polysaccharides eg. starch and cellulose (join hexose sugars)
  • LIPIDS made using …
    -> glycerol made from GALP
    -> fatty acids made from GP
  • A.A -> some made from GP
  • NUCLEIC ACIDS -> sugar in RNA (ribose) made using GALP

go into more detail for how lipids and nucleic acids made in diff flashcards -> for 3 marks

41
Q

why is the production of simple sugars eg. glucose from products of the Calvin cycle essential for an organism?

A
  • glucose is used in respiration …
  • … which provides energy needed for biological processes
42
Q

what is the role of e- in PS1?

A
  • generate ATP in chemiosmosis
    -> movement of H⁺ down conc grad via ATPsynthase
  • reduce NADP in photophosphorylation
  • produce O₂ in photolysis of H₂O
43
Q

design an experiment to investigate photosynthesis using isolated chloroplasts

A

(Hill reaction)

  1. using pestle + mortar, grind 5g chopped spinach leaves with 10cm³ cold (0.5M) sucrose sol
  2. strain this liquid (funnel + muslin cloth) into cool centrifuge tube + centrifuge for 10 mins high speed
  3. pipette liquid from top of centrifuge and discard -> now have pellet
  4. add 2cm³ cold sucrose sol + 20cm³ cold pH 7 phosphate buffer sol + mix
  5. add 5cm³ chloroplast / buffer sol to 2 test tubes (A + B)
  6. add 10cm³ DCPIP each -> leave A under bench lamp (well lit) -> wrap B in tin foil (no light)
  7. observe A until DCPIP decolourises -> pop A + B sols in cuvettes + use colorimeter to compare % absorbance

NOTE: control = test tube only containing DCPIP + cilled isolation sol (NO CHLOROPLASTS) -> proves DCPIP colour doesn’t just deteriorate over time!!!

44
Q

explain how DCPIP can be used to investigate p/s

A

hill reaction depends on e- released in light-dep stage being picked up by DCPIP (e- acceptor)

  • so DCPIP takes the place of NADP so allows photolysis to continue even when all NADP used up
  • DCPIP decolourises when it has accepted e- (been reduced) -> so can see that light-dep stage happened!!!
45
Q

suggest why sucrose sol is used in hill reaction

A

to prevent H₂O being drawn from chloroplasts by osmosis

46
Q

describe how triglycerides are made using products of the Calvin cycle

(3 marks)

A
  • GALP used to produce glycerol…
  • which is used for building lipid molecules eg. phospholipids, triglycerides
  • GP used to produce fatty acids

-> triglyceride = 1 glycerol + 3 fatty acids joined by condensation reactions

SNAB biology hoe (15 decks)

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