13) Photosynthesis Flashcards

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1
Q

4 main structures of the chloroplast

A
  • double membrane
  • photosystems I & II
  • thylakoid
  • fluid stroma
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2
Q

what is the function of the double membrane

A
  • contains grana & stroma
  • permeable to CO2, 02, ATP, sugars
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3
Q

what is the function of the photosystems

A
  • provide huge surface area for maximum light absorption
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4
Q

what is the function of the thylakoid related to its structure

A
  • stacked/large sa to increase light absorption
  • membrane (w pigments to absorb light) for light-dependent reaction
  • space for accumulation of H+ = proton gradient
  • green so chlorophyll absorbs red & blue light
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5
Q

what is the function of the fluid stroma

A
  • light-independent reaction/calvin cycle
  • has enzymes (RuBP, NADP)
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6
Q

where is the site of Light Dependent Stage (cyclic/non-cyclic phosphorylation)

A

Thylakoids (grana)

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7
Q

where is the site of Light Independent Stage (calvin cycle)

A

Stroma

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8
Q

where is the precise location of chlorophyll

A

Thylakoid membrane

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9
Q

Explain Non-Cyclic Phosphorylation (LDR)

A
  • Accessory pigments in photosystem II absorbs photons of light.
  • energy passed onto primary pigment & chlorophyll photoactivated.
  • diff wavelengths absorbed.
  • photolysis
  • O2 production
  • energised electrons pass along ETC then to PSI
  • ETC sets up proton gradient = chemiosmosis
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10
Q

Explain Cyclic Phosphorylation (LDR)

A
  • only PSI used
  • light energy absorbed
  • electron excited
  • electron emitted from chlorophyll passed along ETC
  • protons pumped into thylakoid space
  • protons diffuse back to stroma by ATP synthase
  • ATP synthesis
  • electron returns to PSI
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11
Q

How many photosystems are used in cyclic & non-cyclic phosphorylation

A

Cyclic = 1
Non-cyclic = both (2)

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12
Q

What are the products in cyclic & non-cyclic phosphorylation

A

Cyclic = ATP
Non-cyclic = ATP, O2, NADPH

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13
Q

What is the role of NADP reductase

A
  • transfers electrons to NADP
  • to form NADP
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14
Q

Chlorophyll A reflects & absorbs what colours ?

A

absorbs = blue & little violet/orange
reflects = green & little yellow

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15
Q

Chlorophyll B reflects & absorbs what colours ?

A

absorbs = violet & red
reflects = green & yellow

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16
Q

Cartenoids absorb what colours ?

A

colours that chlorophyll cannot absorb.
(can be seen in fall when chlorophyll breaks down)

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17
Q

why do plants appear green?

A

reflection of green light by chlorophyll

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18
Q

Shorter the wavelength, _____ the energy

A

higher

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19
Q

Longer the wavelength, ____ the energy

A

lower

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20
Q

Compare red light with blue light

A
  • lower energy
  • longer wavelength
  • lower frequency
21
Q

What happens to an electron when light strikes it?

A

gets excited and jumps to a higher energy level

22
Q

What are the accessory pigments

A
  • chlorophyll B
  • cartenoids (B carotene & xanthophyll)
23
Q

where is chlorophyll A (primary pigment) found

A

reaction centre

24
Q

Outline the role of accessory pigments in the Light Dependent Stage

A
  • Absorb light/wavelengths not absorbed by primary pigment
  • Passes energy to primary pigment/reaction centre
  • Absorb different wavelengths of light
25
Q

How to calculate Rf value?

A

distance moved by pigment/ distance moved by solvent front

26
Q

Describe the steps of Chromatography (5)

A
  • Place a capillary tube in the pigment, and put one spot on the centre of the line (on chromatograph paper).
  • Repeat this to make the spot concentrated.
  • Place end of the paper into solvent.
  • Mark solvent front after some time.
  • Remove chromatogram before solvent reaches top.
  • Calculate Rf value by measuring distances.
  • Compare with known Rf values to identify the pigment.
27
Q

what are the 3 limiting factors of photosynthesis ?

A
  • light intensity
  • CO2 concentration
  • temperature
28
Q

what is a limiting factor ?

A

the factors that prevents any further increase in the rate of the process

29
Q

when there is no further increase in the rate, what is the limiting factor at the increasing point compared to the straight line

A

increasing point = factor on X axis
straight line = one of the other 2 limiting factors

30
Q

Effect of light intensity

A

At low light intensities :
- decreased photolysis/energy absorbed
- less production of oxygen
- less ATP & glucose
- slower rate

At high light intensities :
- some other factor is limiting photosynthesis

31
Q

Effect of CO2 concentration

A

At low CO2 concentration:
- enzyme used to fix CO2 (Rubisco) not effective
- rate of successful collisions between CO2 molecules & active site of the enzyme is lower
- ATP & high-energy electrons not used as rapidly
- lower oxygen production
- slower rate

At high CO2 concentration:
- some other factor is limiting

32
Q

Effect of temperature

A

At low temps:
- enzymes work slowly

At high temps :
- less production of oxygen/slower photosynthesis
- Rubisco/enzyme decreasingly effective/ denatured
- change in active site = fewer ESCs
- CO2 cannot be fixed
- less ATP produced
- stomata close
- reduction in CO2 uptake
- loss of turger

At intermediate temps:
some other factor is limiting

33
Q

where are accessory pigments found

A

surrounding the reaction centre

34
Q

what is photoactivation

A

excitation of an e- to a higher energy level, causing it to escape a chlorophyll molecule

35
Q

what happens to electrons in cyclic vs non-cyclic phosphorylation

A

cyclic = returns to same photosystem (PSI)
non-cyclic = emitted from PSII absorbed into PSI

36
Q

Explain the Calvin Cycle (light-independent stage)

A
  • NADPH reduces hydrogen to give glycerate 3 phosphate.
  • forming Triose Phosphate
  • fixation of CO2 by Rubisco
  • rubisco catalyses reaction between RuBP and CO2 to give 2 GP.
  • GP to TP uses ATP & NADPH
  • TP –> glucose –> starch
37
Q

Describe the process that produces oxygen during non‑cyclic photophosphorylation

A
  • light absorbed by photosystem II (photoactivation)
  • photolysis
  • water-splitting enzyme
  • water splits into protons, electrons & oxygen
38
Q

Describe how photoactivation of chlorophyll results in the synthesis of ATP in
photophosphorylation

A
  • electrons excited
  • electrons travel along ETC and energy released
  • energy used to pump H+ into thylakoid space
  • creates proton gradient
  • H+ diffuse through ATP synthase to stroma
  • chemiosmosis
39
Q

why might a membrane have many diff coloured pigments to function efficiently ?

A
  • to absorb light energy
  • more wavelengths can be absorbed
  • faster rate of photosynthesis
40
Q

name the process that involves Rubisco in the Calvin Cycle

A

CO2 Fixation

41
Q

what are some molecules produced from Triose Phosphate (TP) & GP molecules

A
  • RuBP
  • hexose (glucose)
  • starch
  • amino acids
  • glycerol/fatty acids
42
Q

why is the Calvin cycle described as a “cycle”

A
  • no start & end point
  • all molecules present all the time
  • RuBP regenerated
43
Q

suggest the imp of glucose/sugars to ecosystems

A
  • oxygen linked to aerobic respiration
  • store of energy/ATP
  • energy flows through food chain/web
44
Q

what is the function of the DNA in chloroplasts

A

make chloroplast proteins

45
Q

function of lipid droplets in chloroplast

A

store products of photosynthesis

46
Q

difference between absorption spectrum & action spectrum

A
  • absorption spectrum = shows how much each wavelength/colour is absorbed
  • action spectrum = shows RATE of photosynthesis for light/wavelengths of colours
47
Q

describe chemiosmosis

A
  • H+ ions move out of stroma into thylakoid space
  • increased H+ concentration in thylakoid space
  • H+ diffuse back into stroma through ATP synthase
48
Q

what is the colour change in DCPIP/Methylene blue when oxidised –> reduced

A

oxidised = blue
reduced = colourless