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Big Yerp > Unit 5 - Photosynthesis > Flashcards

Unit 5 - Photosynthesis Flashcards

1
Q

Define autotrophs

A
  • An organism that makes their own food from inorganic molecules using (chemical/ light) energy
  • Producers in an ecosystem
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2
Q

Define Chemosynthesis

A

Making food using chemical energy

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3
Q

Photoautotrophs

A

Organisms that photosynthesise using sunlight

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4
Q

When do plants photosynthesise and repsire

A
  • photosynthesise only in sufficent light levels
  • respire continuously
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5
Q

Compensation point

A

The rate of photosynthesis is equal to the rate of respiration
No net loss or gain of mass (carbs)
CO2 uptake in Ps = CO2 production is R

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6
Q

Compensation period

A

Time it takes to reach the compensation point

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7
Q

Photosystems

A

Particles attached to thylakoid membranes

Contain photosynthetic pigments which carry out the absorption of light in two distinct chlorophyll complexes

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8
Q

characteristics of Photosystem I (PSI)

A

Funnel-shaped
Absorption wavelength is 700 nm
Found in intergranal lamellae

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9
Q

Photosystem II (PSII)

photsystem 2

A

Funnel-shaped
Absorption wavelength is 680 nm
Found on the grana

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10
Q

Chlorophyll a

A

Reflects blue-green
Primary pigments
Found at reaction centre of both photosystems
2 forms absorb light at wavelength 680 (PSII) and 700nm (PSI) - red light
Can also absorb some blue (400nm)

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11
Q

Chlorophyll b

A

Reflects yellow - green
An accessory pigment
Absorbs light wavelengths 400-500nm (blue) and 640 (red)

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12
Q

Accessory pigments

A

Carotenoids
Xanthophyll
Chlorophyll b

Pass emitted electrons to the primary pigments which are then emitted (light harvesting pigments)
This drives photosynthesis

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13
Q

Carotenoids

A 
Reflect yellow
Absorb blue (400-500nm)
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14
Q

Xanthophyll

A

Reflects yellow

Absorbs blue/green (375-550)

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15
Q

Absorption spectrum

A

Results of the colorimeter test plotted on a graph

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16
Q

Action spectrum

A

Combined absorption spectra of pigments

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17
Q

Structure of chlorophyll molecule

A

Porphyrin head - hydrophilic, flat head lies parallel to thylakoid membrane for maximum absorption
Lipid soluble tail - hydrophobic, lies in thylakoid membrane
Side chains - determines which wavelengths are absorbed

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18
Q

How are electrons excited and how do they go back to normal

A

Chlorophyll pigments absorb light, electrons enter an ‘excited state’
This is unstable and electrons return to ‘ground state’
Lost excitation energy gets trapped during photosynthesis

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19
Q

Chlorophyll excitement equation

A

chlorophyll –> chlorophyll^+ + e^-

Reduced —-> oxidised + excited elctron

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20
Q

Chloroplast membrane

A

Both inner and outer membrane

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21
Q

Integranal lamellae

A

Extension of thylakoid membrane

Acts as skeleton

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22
Q

Intermembrane space

A

Space between membranes (10-20nm)

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23
Q

Granum

A

Stack of thylakoids

Plural grana

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24
Q

Stroma

A

Contains enzymes needed for photosynthesis, DNA and ribosomes

25
Q

Thylakoids

A

Where the green pigment is found

Site of light absorption and ATP synthesis

26
Q

Chromatogrophy table

A

Pigment
Distance travelled by compound
Distance travelled by solvent
Rf value

27
Q

explain how to carry out paper chromatogrophy to seperate pigments

A
  • Dissolve pigments in solvent (propan-2-ol)
  • Allow the solvent to move up the chromatography paper and seperate the pigments
  • Diff pigments would move at diff speeds up the paper
  • Calculate Rf values
28
Q

Why do plants contain a mixture of diff pigments

A

Light is made up of many diff wavelengths

To allow plants to absorb maximum light for photosynthesis

29
Q

Photophosrylation

A

Production of ATP in the presence of light from ADP and Pi

30
Q

ATP

A

Adenosine tri-phosphate

Formed from inorganic phosphate and ADP during photophosphorylation

31
Q

NADP

A

Co.enzyme reduced to NADPH by the addn. of protons and electrons at the end of the light dependent stage

32
Q

Photolysis

A

2H2O —> 4 H+ and 4 e- and O2
H+ and e- used in photophosphorylation
O2 used in respiration and/or released

33
Q

Non cyclic photophosphorylation

A

Involves PSII and PSI

Produces ATP, oxygen and reduced NADP

34
Q

Cyclic photophosphophorylation

A

Involves PSI

Produces ATP in smaller amounts. No photolysis involved so no protons or oxygen produced

35
Q

Process of cyclic photophosphorylation

A
  • Light hits a chlorophyll molecule in PSI and electrons rise to higher energy level & leaves
  • e- is passed along electron transport chain and energy is released in small amounts to pump H^+ into the thylakoids disc
  • Builds up conc. gradient
  • Diffuse back via chemiosmosis
  • Movement provides energy to combine ADP and Pi
36
Q

Non-cyclic vs cyclic photophsophophorylation

A
  • non-cyclic produces ATP, oxygen and Red. NADP while cyclic produces ATP only
  • non-cylic uses photosystems 1 and 2 while cyclic only uses 1
37
Q

Role of chlorophyll in photolysis

A

It is the lost electrons from photolysis that go to the chlorophyll after absorbing light
Causes more water to dissociate

38
Q

How is energy of light converted into chemical energy in the LDR

A

Electrons excited
Use of electrons carriers
Production of ATP

39
Q

Calvin cycle

A

6 CO2 (+ RuBisCO) —> 12 GP (+ 12 ATP) —> 1,3 biphosphate (+12 NADPH) —> 12 TP —> 10 TP (5 ATP) —> 6 RuBP

40
Q

Light Independent Stage

A

Only happens during the day as it needs continuous supply of products from LDR (ATP/ NAPDH)

41
Q

Where does the CO2 needed in LIS come from

A

CO2 from respiration and other organisms (people) enter leaf through stomata
Diffuses to palisade layer then into cells then into stroma

42
Q

Reactions in LIS

A

Carbon fixation
Reduction
Regeneration

43
Q

Carbon fixation in LIS

A

CO2 combines w/ a CO2 acceptor (RuBP)
Reaction is ctalysed by RuBisCO
By accepting carboxylate group RuBP forms an unstable intermediate 6C compounds that immediately breaks down into GP compounds
CO2 is now fixed

44
Q

Reduction in LIS

A

ATP reacts w/ GP to form 1,3 biphosphate which is reduced using H from NADPH into TP

45
Q

Regeneration in LIS

A

10/12 TP molecules are rearranged into 6 RuBP using phosphate groups from ATP.
Remaining 2 TP are products and can be used to synthesise organic compounds

46
Q

Use of triose phosphate

A

2 TP can be used to synthesise glucose
Glucose can then be converted into sucrose, starch and cellulose (or used immediately in respiration)
Synthesis of fatty acids, glycerol and amino acids
Regeneration of RuBP

47
Q

Factors affecting photosynthesis

A

Light Intensity
CO2 conc.
Temp
Water stress

48
Q

Light intensity as a factor of photosynthesis

A

Provides power to produce ATP and NADPH
Light allows stomata to open, enabling gas exchange
Transpiration occurs, allowing water from the roots

49
Q

Molecules from Calvin Cycle in bright light

A

RuBP - high
TP - high
GP - low

50
Q

Molecules from Calvin Cycle in dim light

A

RuBP - low
TP - low so RuBP cannot be regenerated
GP - high as cannot be reduced to TP

51
Q

CO2 conc. as a factor of photosynthesis

A

CO2 levels in the atm. and aquatic habitats usually high enough to not become a limiting factor

52
Q

Molecules from Calvin Cycle in high CO2

A

TP - High
RuBP - low
GP - high

53
Q

molecules from Calvin Cycle in low CO2

A

RuBP - High as nothing for to acccept so it accumulates
GP - low as cannot be made
TP - low; cannot be made

54
Q

Temp as factor of photosynthesis

A

25 - 30 degrees: rate increases
30 - 45 degrees: O2 more successfully competes w/ CO2 for active site of RuBisCO
> 45 degrees: Enzymes denature

55
Q

Calvin cycle as temp increases

A

CO2 not accepted by RuBP (denaturing/ O2 filling binding sites)
Less GP therefore less TP
RuBP initially accumulates but doesn’t regenerate due to lack of RuBP

56
Q

Non - cyclic photophosphorylation

A

Light is absorbed by PS2, e- in primary pigment raised to a higher energy level until it leaves PS
Travels down etc releasing energy to pump H+ into thylakoid space
Photolysis of H2O replaces e- lost from reaction centre in PS2
Light absorbed by PS1, excites e-, accepted by NADP and combines w/ excess H+ from ATP synthase
Protons accumulate in thylakoid space, membrane impermeable to H+ so diffuse down channels associated w/ ATP synthase

57
Q

Measuring the rate of photosynthesis

A

Use a photosynthometer, measures volume of O2 produced
Use NaHCO3 as source of extra carbon
Change temp, CO2 conc. (by adding NaHCO3 to aerated water), LI (moving lamp)
Allow apparatus to equilibrate for 5 mins

58
Q

Chemiosmosis

A

Uses an electrochemical gradient

Moving down a conc.gradient using a proton motive force

59
Q

How many times does the Calvin cycle need to occur to produce 1 glucose molecule

A

6

Big Yerp (42 decks)

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