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Biology 12 > Photosynthesis > Flashcards

Photosynthesis Flashcards

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1
Q

Mitochondria vs Chloroplast

A
  • both have thier own set of DNA
  • double membranes
  • stroma liquid like the mitochondrial matrix
  • ATP Synthase
  • ETC
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2
Q

Stomata

A

the openings in leaves where gases enter the leaf

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3
Q

Stroma

A

the inner matrix of the chloroplast.

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4
Q

Photolysis

A

the separation of molecules by the action of light

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5
Q

Photosynthesis Equation

A

6CO2+ 6H2O -> C6H12O6 + 6O2

Net products of reaction

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6
Q

What reactions are endergonic or exergonic?

A

Endergonic = light dependent

Exergonic = light independent

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7
Q

Photosynthesis

A
  • capturing of light to convert low energy CO2 to synthesize high energy glucose
  • low energy water is made in respiration, in photosynthesis this splits and the electrons make CO2 high energy
  • solar energy provides ‘power’ for reaction
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8
Q

Chlorophyll

A

a molecule with chemical properties that allow for absorbing light energy, electrons go to higher energy levels and are oxidized

  • organized in array of photosystems
  • reaction centre chlorophyll a
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9
Q

Chloroplast

A
  • organelle with double membrane, contains stacks of thylakoid disk found in cytoplasm
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10
Q

Structures in chloroplast

A

thylakoid disk > granum > grana > chlorophyll

(ETC embedded in grana membrane)

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11
Q

Water in Photosynthesis

A

water is not a limiting factor, 99% is evaporated from xylem trnasport

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12
Q

Electromagnetic Spectrum

A
  • transfer of energy through waves from visible light section
  • blue, red and violet boos electrons to higher orbitals
  • blue has short wavelength, high energy
  • red has long wavelength, low energy
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13
Q

Pigment

A

chemical structure that allows photons to boost to different levels

  • needs alternating double bonds
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14
Q

Photosystem

A

contains many copies of molecules that excite molecules using energy from light

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15
Q

Adaption of Plant: SA for light capture

A
  • Palisade mesophyll has many chloroplst in cytoplasm
  • Palisade mesophyll in tight columns top layer
  • folded thylakoid disk in chloroplast
  • spongy mesophyll contain cholorplast
  • thylakoid disk stacked in grana
  • photosystem embeded in membrane of thylakoid
  • photosystem contain a variety of pigment molecules, broad range of wavelength absorbed
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16
Q

Adaption of Plant: Rate of Reaction (CO2)

A
  • shape of leaf is broad, flat and thin
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17
Q

What maximizes reactions?

A

More CO2 and light captured

(more glucose with blue light because higher energy wavelength)

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18
Q

What happens when electrons drop down energy levels?

A

amount of energy will be the same or some will be given off as heat

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19
Q

Retention factor

A

amount that component of mixture trails, depends on chemical structure

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20
Q

Light Dependent Reactions (9)

A
  1. Photolysis of Water
  2. Photosystem II
  3. PQ mobile electron carrier
  4. B6-F Complex Enzyme
  5. PC electron carrier
  6. Photosystem I
  7. Ferredoxin
  8. NADP Reductase Enzyme
  9. ATP Synthase Enzyme
  • products are used for calvin cycle
  • make ATP and NADPH
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21
Q

Photolysis of Water

A
  • water goes throguh water splitting enzyme in Photosystem II and O2 diffuses out
  • Hydrogen adds to gradient in thylakoid lumen but is then reduced in photosystem II
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22
Q

Photosystem II

A
  • has antenna complex that funnels energy to Chlorophyll a to get to the reaction centre as it is the only one that oxidizes
  • electrons boosted then transferred
  • electrons lost replaced by oxidized water
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23
Q

PQ electron carrier

A
  • transfer electrons in redox reactions from Photosystem II to B6-F complex
  • heat released when transferred
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24
Q

B6-F Complex Enzyme

A
  • received electrons used to provide energy for complex to pump protons into lumen, creating electrochemical gradient
25
Q

PC protein

A

transfer electrons from B6-F to Photosystem I

26
Q

Photosystem I

A
  • also getting hit by photons that are excited
  • Photosystem I electrons replaced by Photosystem II electrons
27
Q

Ferredoxin

A

passes electrons to NADP Reductase

28
Q

NADP Reductase Enzyme

A

reduce NADP+ to NADPH

29
Q

ATP Synthase Enzyme

A
  • uses proton gradient to synthesize ATP by chemiosmosis
  • ATP produced in stroma
30
Q

Non- cyclic phosphorolation

A

goes through both photosystems, regular ETC

31
Q

Cyclic Phosphorolation

A
  • produces no NADPH
  • goes from ferrodoxin to PQ, no Photosystem II
  • in photosynthetic bacteria
  • happens if more ATP is needed
32
Q

cLight Independent Cycle

A
  • uses ATP and NADP from ETC
  • starting reactant is CO2
  • 6 turns = 1 glucose (2 G3P)
  • for 6 turns, 18 ATP and 12 NADPH used
  • in stroma of chloroplast

Calvin Cycle

  1. Carbon Fixation
  2. Reduction
  3. Regeneration of RuBP
33
Q

Carbon Fixation

A
  • 3CO2 enters 1 at a time and binds to enzyme RuBISCO
  • fixes from gas state to solid
  • RuBISCO takes 3 molecules RuBP and forms a short lived intermediate, splitting in half forming 6-3PG
  • 6, 3 carbon molecules
34
Q

Reduction

A
  • substrates are gaining electrons from 6 ATP
  • extra phosphate by phosphorolation added on giving us 3-carbon BPG acid
  • G3P then formed by NADPH oxidized (reduced NADP+)
  • phosphate leaves (1 from each BPG)
  • given 1 - G3P sugar aldehyde
35
Q

Regeneration of RuBP

A
  • need to lose some carbons to go back to original #
  • G3P leaves as a product, leaving 5 G3P
  • regeneration in multiple steps
  • 2 phosphate leaves and 3 more ATP used
36
Q

unboiled chloroplast, no light

A
  • light could not be emitted through the foil cover that reflects most visible light
  • no photons for Photosystem 1 and Photosystem 2 to absorb to continue through the electron transport chain.
  • As a result, ATP and NADPH could not be used as reactants for the light independent reactions for the Calvin cycle in order to produce sugars.
  • since there were no photons of light, DPIP could not be reduced from ferredoxin due to the lack of electrons and the colour did not turn colorless
37
Q

unboiled chloroplast, light

A
  • photons of light were emitted andthe right conditions were met to carry out both reactions
  • Light is absorbed by the chlorophyll inside the chloroplast and into the photosystems, the electron transport chain in the thylakoid disk carry out reactions producing ATP and NADPH
  • as more electrons readily available, electrons from ferredoxin are able to reduce DPIP, changing its color from blue to colorless, which increases light transmittance.
  • the rate of the reactionwas increasing
38
Q

boiled chloroplast, light

A
  • there was enough light but enzymes in the boiled chloroplast were denatured due to the increase in temperature, losing their overall shape, function and efficiency as it had surpassed its optimal temperature range.
  • the reduction of DPIP was prevented as there were no electrons to reduce it since electrons were not passed through the early enzymes of the light dependent reaction such as Photosystem 2 and B6-F Complex enzyme because of the denaturing, DPIP could not accept excited electrons from ferredoxin
39
Q

no chloroplast, light

A
  • negative control
  • no change in the transmittance of light as there was no leaf pigments to absorb the light
  • DPIP was not reduced and the colour of the remained constant
40
Q

What happens when you have no light?

A
  • no light reaching the leaf so only respiration could happen

A byproduct of respiration is CO2, so a lot of CO2 was produced but not consumed due to the lack of light in the tube

  • The rate of respiration is greater than the rate of photosynthesis, so there will be a net release of carbon dioxide from the plant
41
Q

Two Control Variables

A

Temperature:

- different temperatures cause for different rate of reactions

  • The greater the temperature, the more photosynthesis occurs because of greater collisions and better fit as enzymes are more flexible due to induced fit

Intensity of the light:

  • if it is increased, photosynthesis will be increased initially as more photons are hitting photosystems at a higher rate, going through the Electron Transport Chain, overall yielding more glucose through the Calvin cycle
  • this will eventually decrease when the light is so intense the amount of oxidation happening to chlorophyll is damaging
42
Q

Why are most plants green?

A

Most plants are green because they contain an abundance of pigment molecule called chlorophyll, the primary photosynthetic pigment. Plants contain chlorophyll a and b, differing slightly in composition. Chlorophyll absorbs light in the red (long wavelength) and the blue (short wavelength) regions of the visible light spectrum as they contain the highest energy, making them the most energetically favorable. Green light is not absorbed by chlorophyll but reflected, making the plant appear green.

43
Q

What molecule absorbs green light?

A

Carotenoids are another key group of pigments that absorb violet and blue-green light. In photosynthesis, carotenoids help capture light, but they also have an important role in getting rid of excess light energy. Carotenoids in chloroplasts help absorb excess energy preventing damage to photosynthetic molecules and dissipate it as heat.

44
Q

The light dependent reactions synthesize ATP, NADPH and O2 using the following processes:

a) oxidation only
b) reduction only
c) oxidation and reduction
d) oxidation, reduction and electrolysis

A

a) oxidation only
b) reduction only

c) oxidation and reduction

d) oxidation, reduction and electrolysis

45
Q

In Photosystem I, light-energized electrons are replaced by:

a) oxygen
b) oxidation of NADPH
c) water
d) reduction of NADPH
e) electrons from photosystem II

A

a) oxygen
b) oxidation of NADPH
c) water
d) reduction of NADPH

e) electrons from photosystem II

46
Q

Many plant species are capable of shortcutting photosystem I to produce more ATP by passing electrons back to:

a) ATP Synthase
b) NADP+
c) Photosystem II
d) B6-F complex
e) NADP reductase

A

a) ATP Synthase
b) NADP+
c) Photosystem II

d) B6-F complex

e) NADP reductase

47
Q

What is the role of RuBISCO is the Calvin Cycle?

a) the regeneration of RuBP
b) the conversion of G3P into glucose
c) the formation of G3P
d) the production of O2 from CO2
e) the incorporation of CO2 into RuBP

A

a) the regeneration of RuBP
b) the conversion of G3P into glucose
c) the formation of G3P
d) the production of O2 from CO2

e) the incorporation of CO2 into RuBP

48
Q

Environmental Factor: Temperature

A
  • denaturing or photorespiration
49
Q

Environmental Factor: Light Intensity

A

initially increase, but too much causes photooxidation

50
Q

CO2 concentration

A
  • limiting reagent/factor
  • substrate and enzyme concentration saturation
  • O2 is a competitive inhibitor
51
Q

Photorespiration

A
  • when there is water loss, stomata closes causing CO2 decrease and O2 increase
  • RuBISCO fixes both, but it prefers CO2 and O2 is more abundant
  • if carbon is not fixed, less glucose and photosynthesis forming awaste product
  • costs 25-30% of plant energy
52
Q

Photooxidation

A

when the light is so intense that it is damaging to chlorophyll oxidation

53
Q

Where is chloroplasts most abundant?

A

mesophyll cells

54
Q

C3 Plants

A

regular photosynthesis, fixes CO2 into 3Carbon 3PG in mesophyll cells

55
Q

How to limit photorespiration

A
  1. Driught adapted limit water loss (in C3)
    - sheltering of stomates indentation to not expose to wind and limit water loss
    - more layers of epidermal for insulation, waxy cuticles
    - tricomb hair structure prevent water from leaving and provides local humidity
  2. Concentrate CO2, so O2 can not compete
    - C4 and CAM plants
56
Q

C4 Plants

A
  • fixes CO2 and produces a 4 carbon molecule
  • happens in mesophyll and bundle sheat cells
  • spatially separating carbon fixation and calvin cycle
  • first carbon fixation is catalyzed by PEP carboxylase so Co2 can be stored by PEP, producing 4C acid
  • 4C is rearranged and loses a carbon with O2 from non-cyclic phosphorolation to form CO2, leaving behind pyruvate 3C
57
Q

CAM Plants

A
  • in mesophyll, temporal separation
  • C4 at night and calvin cycle during the day
  • stomata open at nigt, malate stored in vacule
  • malate pumped out of vacule for the day
  • desert plants
58
Q

photophosphorolation

A

production of ATP in chloroplasts

Biology 12 (5 decks)

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