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SBI4UN 2023-2024 > Photosynthesis > Flashcards

Photosynthesis Flashcards

anatomy, light reactions, dark reactions, factors, types of photosynthesis

1
Q

what is photosynthesis

A

chemical rxns where light energy is converted into chemical energy

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2
Q

what is the chemical rxn for photosynthesis

A

6CO2 + 6H2O –(RuBisCo)-> C6H12O6 + 6O2

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3
Q

leaves: purpose & structure

A

purpose: photosynthetic organs
- contains CHLOROPLASTS (site of photosynthesis)
structure: maximizes SA for gas exchange and photosynthesis

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4
Q

Mesophyll

A

air spaces between layers of cells, packed with chlorophyll

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5
Q

Stomata

A

pores that open/close to allow co2 to leave (diffusion) and control water loss (osmosis)

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6
Q

transpiration

A

loss of water out of stomata during gas exchange while photosynthesizing and respiring

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7
Q

how do plants combat transpiration

A

many plants use tiny needle-like leaves instead to minimize sa and water loss

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8
Q

where does photosynthesis occur

A

chloroplast

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9
Q

explain Z-scheme

A
  1. h2o is split by Z-PROTIEN into H+, O2, e-
    - o2 leaves as waste via stomata
  2. P2 chloroplast is hit by LIGHT (photons) –> excites e- –> excited e- caught by PQ (initial e- acceptor)
  3. PQ e- goes thru ETC to make ATP
  4. moving e- in ETC releases energy that pumps H+ from stoma to LUMEN, creating conc grad
  5. H+ moves along conc grad through ATP SYNTHASE to create ATP -> goes to CALVIN CYCLE
  6. e- goes to P1 and is hit by light AGAIN –> caught by NADP+ REDUCTASE –> creates NADPH –> goes to CALVIN CYCLE
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10
Q

what are photosystems

A

clusters of pigment embedded in the thylakoid membrane to absorb light
- P1/P700
-P2/P680

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11
Q

what is the anatomy of CHLOROPHYLL

A

PORPHORIN RING:
- Mg central
- absorbs light energy and transfers e-

PHYTOL TAIL:
- hydrocarbon tail = nonpolar = INSIDE membrane
- ANCHORS pigment into membrane

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12
Q

what is the purpose of WATER in photosynthesis

A
  • provides e- for z-scheme
  • e- donor
  • without water, z-scheme would never occur –> calvin cycle would never occur (no ATP/NADPH created) and no sugar or more atp would be made
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13
Q

Stroma

A

interior space, where calvin cycle takes place

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14
Q

thylakoid

A

sacs

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15
Q

grana

A

stacks

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16
Q

lamellae

A

connects thylakoid and grana

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17
Q

chlorophyll

A

embedded in thylakoid membrane
- absorbs energy to begin photosynthesis
- green

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18
Q

explain what happens in a photosystem when hit by a light using a labelled diagram

A

picture
- light hits photosystem –> chloroplast –> granum -> thylakoid membrane –> photosystem –> chlorophyll
- photons excite e- –> e- transfers energy from pigment to pigment until it reaches RXN CENTRE

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19
Q

where does z-scheme take place

A

thylakoid membrane

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20
Q

accessory pigments

A

pigments that allow for MOST amount of energy to be absorbed at any given time

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21
Q

cyclic e- flow

A
  • cycle: starts and ends at same spot
  • begins at P1
  • instead of going to FNR (NADP+ reductase), cycle back to Fd and go to PQ , re-enter ETC to create MORE ATP
22
Q

non-cyclic e- flow

A
  • z-protein splits h2o
  • e- used to replenish P2
  • O2 waste
  • starts and ends at DIFF spots
23
Q

what are the reactants and products of light reactions

A

reactants: H2O, NADP+, ADP + Pi
products: O2, NADPH, ATP

24
Q

what are the 3 phases of calvin cycle

A
  1. carbon fixation
  2. reducation
  3. regeneration of RuBP
25
Q

what happens in carbon fixation (dark rxns)

A
  • co2 enters from air
  • 3co2 (2c) binds to 3 RuBP (5C) to create 6 unstable 6C
  • 6C unstable break into 2 3C (3-PG)
26
Q

why are leaves green

A

chlorophyll absorbs blue and red light and reflects green light which hits our eyes

27
Q

what colors of light are best for photosynthesis

A

purple/blue, red

28
Q

what does a rxn centre contain

A

pigments to absorb light (chlorophyll)

29
Q

lumen

A

thylakoid space
- gel like substance

30
Q

what happens in reduction phase (dark rxns)

A

-atp donates a PO4 to each 3-PG made in carbon fixaton
- 3-PG -> 1,3-BPG
- 1,3-BPG reduced by NADPH
- loses PO4, gains H+, becomes G3P
-G3P goes onto regenerate

31
Q

what is the purpose of RuBisCo

A

catalyzes fixation of atmosphere CO2 into 3-PG in carbon fixatoin

32
Q

why does a leaf have so much rubisco

A

rubisco works VERY slowly

33
Q

what happens in Regeneration of RuBP phase? (dark rxns)

A
  • G3P gets PO4 from ATP to produce RuBP
  • RuBP reactivates Calvin Cycle
34
Q

what is the fate of the lone G3P in calvin cycle?

A
  • made into glucose by various enzymes which can then be converted into cellulose, starch, fructose or used in cell respiration
35
Q

explain the steps of calvin cycle using chemical equations

A
  1. 3CO2 + 3RuBP -(RuBisCO)-> 6 3-PG
  2. 6 3-PG + 6 ATP –> (6 ADP + Pi) + 6 1,3 -BPG
  3. 6 1,3 - BPG + 6 NADPH –> 6 NADP + 6 G3P (one leaves to become sugar)
  4. 5 G3P + 3 ATP –> 3 RuBP + (3ADP + Pi)
36
Q

what are the reactants and products of calvin cycle

A

reactants: 6CO2, 6 NADPH, 6 ATP
products: sugar, 6 NADP+, 6 ADP +Pi

37
Q

what are the 3 factors that affect photosynthetic rate

A
  1. [CO2}
  2. light intensity
  3. temperature
38
Q

what is photorespiration

A

when rubisco reacts with o2 instead of co2 under high light/heat
- inc temp = inc ek= inc collisions = inc mistakes = decreased R.O.P

39
Q

light intensity vs R.O.P

A
  • light acts as SUBSTRATE
    • supplies e-
  • enzymes: P1/2, ETC, NADP+ REDUCATSE
  • when inc [substrate] eventually point of saturation will be reached
  • e- can only move so fast in photosystem, process takes time
40
Q

temperature vs R.O.P

A
  • inc temp = inc collisions (can’t hoffs rule)
  • inc temp = inc ek = co2 moves too fast for rubisco to bind too
  • rubsico becomes inaffective, grabbing o2 instead of co2 (photorespiration)
  • dec co2 intake = dec photosynthetic activity
  • their is an OPTIMAL temp at 23c, denaturation DOESNT occur here
41
Q

[CO2] vs R.O.P

A

RuBisCO is saturated with co2 = point of saturation reached
- active sites are all occupied with substrate

42
Q

Water Use Efficiency

A

maximize co2 intake while minimizing h2o loss
- rate of photosynthesis to rate of transpiration

43
Q

Adaptive Value

A

all the combined influences of characteristics that affect the fitness of an individual/population
- added ability to cope with environment

44
Q

How to the events of calvin cycle depend on light reactions

A

light reactions create the NADPH and ATP needed in calvin cycle
- in calvin cycle, ATP phosphorylates 3 -PG to create 1,3 - BPG and NADPH reduces 1,3 -BPG to make G3P

45
Q

what are the 3 types of photosynthesis

A
  1. C3
  2. C4
  3. CAM
46
Q

C3 photosynthesis
- adaptive value(s)
- how
- who

A

a.v: more efficient under avg water, light, temp, moisture

how: uses RuBisCO to collect CO2 during the DAY and undergo photosynthesis

who: most plants

47
Q

what difficulties are there in c3 photosynthesis

A

when temp inc
1. transpiration happens and plants are less efficient in z-scheme
- stomata opens, h2o lost, less e- to feul z-scheme)
2. photorespiration happens
- rubsico grabs o2 instead of co2

48
Q

c4 photosynthesis
- adaptive value(s)
- how
- who

A

av 1: photosynthesizes fater under high heat/light conditions

how: PEP CARBOXYLASE collects co2 during the day and hand delivers it to rubsico, elimination photorespiration threat
- PEP carboxylase adds co2 to PEP to form oxaloacetate/malate (plants preform krebs too)

av 2: better water use efficiency

how: PEP carboxylase is faster at pulling co2 in than rubsico so stomata doesnt need to be open for as long and not as much h2o is lost

who: desert summer plants, grasses, sugar canes, weeds

49
Q

CAM photosynthesis
- adaptive value(s)
- how
- who

A

Av: better W.U.E & CAM-idling

how: PEP Carboxylase collects CO2 during NIGHT as oxaloacetate/malate, stomata closes during day when photosynthesis occurs to avoid transpiration
- during day, co2 delivered to rubsico to make sugar via calvin cycle
- oxaloacetate/malate sent to calvin
- stomata can be kept closed at all times and can use co2 from cell resp to photosynthesize and o2 from photosynthesis for respiration

who: plants in very hot temperatures (cactus, pineapples)

50
Q

why do CAM plants grow slower than C3 plants when both placed in ideal growing conditions

A

cam plants exist in extremely dry/hot/humid environments so they’ve adapted to it by closing their stomata during the day to avoid transpiration and closing it during the night where PEP Carboxylase grabs co2 instead of rubisco and stores it as oxaloacetate/malate
- stomata closed = no h2o loss = no co2 entry
- less co2 = dec r.o.p = grows slower

SBI4UN 2023-2024 (16 decks)

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