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A Level Biology Paper 2 > Photosynthesis > Flashcards

Photosynthesis Flashcards

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1
Q

Photosynthesis word equation

A

Carbon dioxide + water = Glucose + Oxygen

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2
Q

Photosynthesis balanced equation

A

6CO2 + 6H2O = C6H12O6 + 6H2O

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3
Q

Explain some uses of ATP

A

Provides energy for active transport/muscle contraction/protein synthesis

Phosphorylation to bind to enzymes or substrates and either lower activation energy or alter the tertiary structure to make molecules more reactive

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4
Q

Why is ATP useful

A

Releases small manageable packets of energy so less wasted as heat

Immediate energy source so makes energy available rapidly

Phosphorylates compounds ro make them more reactive or lower activation energy

Can be rapidly resynthesised so cycle is continuous

Large so doesn’t diffuse out of cell

Insoluble so doesn’t affect water potential

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5
Q

What is NADP

A

Nicotinamide Adenine Dinucleotide Phosphate

Essential molecule acting as a hydrogen acceptor becoming reduced to form NADPH

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6
Q

OILRIG

A

Oxidation
Is
Loss (of electrons/hydrogen)(gain of oxygen)

Reduction
Is
Gain (of electrons/hydrogen)(loss of oxygen)

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7
Q

What is photosynthesis

A

Process in which plants absorb a range of different wavelengths of light energy and converts it into chemical potential energy

Simple inorganic molecules converted into organic molecules

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8
Q

Explain the function of chloroplast and list its features

A

The site of photosynthesis to convert wavelengths of energy to chemical energy

Double membrane
Thylakoids
Starch grains
Stroma
Grana (plural)
Lamella
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9
Q

Function of double membrane in chloroplast

A

Inner and outer membrane for support

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10
Q

Function of thylakoid

A

One of a collection of flatterned membrane bound stacks found in chloroplast containing chlorophyll
Used in LDR

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11
Q

Function of grana

A

Stacks of thylakoids
Plural = grana
Single = granum
Provide a large surface area for the attachment of photosynthetic pigments

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12
Q

Function of starch grains

A

Stores starch as energy store of plants

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13
Q

Stroma function

A

Where the LIR occurs
Converts carbon dioxide and water into organic molecules
Contains enzymes needed for photosynthesis. DNA and RNA

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14
Q

Where does the LDR occur

A

Thylakoid membrane of chloroplast

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15
Q

Where does the LIR occur

A

In the stroma of chloroplast

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16
Q

Define photoionisation

A

Of chlorophyll
Light energy is absorbed by chlorophyll molecules embedded in thylakoid membrane
Exciting it’s electrons and raising them to higher energy levels
Chlorophyll is oxidised

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17
Q

Describe photolysis

A

Of water
Splitting of water molecules by light energy
Providing the low energy electrons to replace those lost from chlorophyll during ohotoionisation
2H2O split by photolysis into 4e-, 4H+ and O2

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18
Q

Describe photophosphorylation

A

Energised electrons from chlorophyll then lose energy as they pass through the Electron Transport Chain
This energy activates a proton pump to build and electrochemical gradient
Used by ATP synthase to make ATP from ADP and Pi

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19
Q

Describe the Light Dependant Reaction

A

Chlorophyll absorbs light energy via photoionisation
Exciting electrons so they’re removed from chlorophyll
Electrons move along Electron Transport Chain, releasing energy via a series of REDOX reactions
Energy used to create the electrochemical gradient so H+ ions can diffuse through ATP synthase (photophosphorylation)
Providing energy to join ADP and Pi via ATP synthase to form ATP
Photolysis of water produces (2H2O—>4e-, 4H+, O2)
Electrons lost from chlorophyll replaced
NADP reduced by electrons and hydrogen

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20
Q

Describe the Light Independant Reaction

A 
Carbon dioxide combines with RuBP
Catalysed by the enzyme rubisco
Producing 2 GP
GP reduced to triose phosphate
Using reduced NADP
Using energy from ATP
Triose phosphate converted to glucose, amino acids and lipids
Triose phosphate regenerated into RuBP
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21
Q

Why isn’t ATP from the LDR a plants only source of ATP

A

Plants don’t photosynthesise in the dark
Not all parts of a plant photosynthesise (roots, bark) but still need ATP
Plants require more ATP than they produce in LDR
ATP used in active transport

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22
Q

Describe the effects of herbicides on the Electron Transport Chain

A 
Reduced transfer of protons across the thylakoid membrane
Reduced electrochemical gradient
So less ATP is produced
Less reduced NADP produced
So light independant reaction slows
Less GP reduced into triose phosphate
23
Q

Why is pencil used in chromatography

A

Ink would mix with pigments
Origin would be in a different place with pen
Pencil is insoluble so origin still visible in same place

24
Q

Why can some photosynthesising organisms fluoresce?

A

If the electrin transport chain is not present/blocked
Excited electrons cannot lose energy via it
So energy released as light/heat

25
Q

In chromatography, what is the method to separate pigments after pigment solution applied to origin

A

Level off solvent below the origin

Remove before solvent reaches top of chromatography paper

26
Q

What is the rf value

A

Retention Factor
A value/ratio used to compare and help identify compounds
Always less than 1

Distance traveled by pigment/distance traveled by solvent

27
Q

Advantage of different pigments in leaves

A

Absorb different wavelengths of light e.g different intensities

28
Q

Explain the role of water in the light dependant reaction

A

Photolysis to break down water (2H2O–>4e-,4H+,O2)
Replaces electrons removed from the chlorophyll during photoionisation
The H+ and e- also used to reduce NADP and O2

29
Q

What are the 3 stages of the Calvin cycle

A

Fixation
Reduction
Regeneration

30
Q

Explain the first stage of the Calvin cycle

A

Fixation

5C RuBP acts as a carbon acceptor
CO2 combines with RuBP, catalysed by rubisco
Producing 2 GP

31
Q

Explain the second stage of the Calvin cycle

A

Reduction

GP is reduced to triose phosphate
Requiring NADPH from the LDR
Providing the reducing power
And the energy from ATP
Some triose phosphate is converted into useful organic compounds
(Glucose, carbohydrates, amino acids)
32
Q

Explain the third stage of the Calvin cycle

A

Regeneration

Most triose phosphate is used to regenerate RuBP (5/6)
1/6 is used to make glucose

33
Q

Suggest and explain why most triose phosphate is converted back into RuBP

A

RuBP needs to be replaced because its a continuous cycle and allows the light independant reaction to continue in the stroma
2 triose phosphate needed to synthesise Glucose, leaving 10 from 6 cycles to regenerate 5 RuBP using ATP
Each RuBP is involved in fixing 1 CO2 to make GP, catalysed by rubisco
GP is reduced to make triose phosphate

34
Q

What is the result of 6 cycles of the LIR

A

6 cycles => 36 carbon

6 Carbon for Glucose (1x)
30 Carbon for RuBP (5x)

35
Q

How is the chloroplast adapted to maximise the rate of photosynthesis in the stroma

A

Large surface area: More chlorophyll, more LDR, more photoionisation to release more electrons and create an electrochemical gradient and more photophosphorylation to make ATP and NADPH so more LIR

36
Q

List and rank the factors affecting photosynthesis from most to least affect

A

Light intensity/wavelength of light
Carbon dioxide concentration
Temperature

37
Q

When is photosynthesis at its highest rate

A

When all the factors are at their optimum level

Temperature, light intensity, carbon dioxide concentration

38
Q

Why is carbon dioxide concentration different at different heights

A

Decrease in carbon dioxide with increase in height

At ground level fewer leaves/less photosynthesis/less light/more respiring organisms/more carbon dioxide lower

39
Q

Why is the concentration of carbon dioxide different at different times over 24 hours

A

Night:
Higher carbon dioxide concentration
Less photosynthesis due to less light
Aerobic respiration occurs in the dark, producing carbon dioxide and increasing the concentration

Light:
Lower carbon dioxide concentration
Net uptake of carbon dioxide is greater than what is produced
Rate of photosynthesis > rate of aerobic respiration
More photosynthesis in daylight

40
Q

How can you manipulate factors for maximum productivity

A

Commercial glass house to manipulate factors for increased yield or productivity

41
Q

How can you manipulate light intensity for maximum productivity using a commercial glass house

A

Artificial light to increase intensity to optimum levels

Blinds to shade plants if light intensity is very high since very high light intensity may damage chlorophyll (protein)

42
Q

How can carbon dioxide concentration be manipulated in a commercial glass house to increase productivity

A

Burning fossil fules (paraffin heater)

Pumping CO2 into glass house (e.g. from the atmosphere also helps to reduce global warming)

43
Q

How can carbon dioxide concentration be manipulated in a commercial glass house to increase productivity

A

Burning fossil fules (paraffin heater)

Pumping CO2 into glass house (e.g. from the atmosphere also helps to reduce global warming)

44
Q

How can temperature be manipulated in a commercial glass house to increase productivity

A

Heaters can be used to raise temperature to optimum levels

Can be used at night to prevent temperatures falling to levels where plants may be damaged

45
Q

What is chromatography

A

A process that separates molecules because of their different solubility in selected solvent
Solvent carries substance across the paper and leaves a chromatogram which can be analysed to detect the presence of molon ecules

46
Q

What stages can occur without ATP

A

Fixation (not reduction or regeneration)

47
Q

What stages can occur without NADP

A

Fixation and regeneration (not reduction)

48
Q

Role of chlorophyll in photosynthesis

A

Absorb photons of light with the correct wavelength

Convert it into chemical energy

49
Q

How is light converted into chemical energy in LDR

A

An excited Electron from chlorophyll is raised to a higher energy level
And moves along the Electron Transport Chain
Releasing energy along the way
Creating an electrochemical gradient

LDR produces ATP and NADPH which can be used in the LIR to convert CO2 and water into organic compounds

50
Q

What happens to the amount of GP as carbon dioxide concentration lowers

A

Less RuBP is used for fixation
Less GP is made
Any GP is reduced to triose phosphate, further decreasing the amount of GP
Also means less regeneration of RuBP so the amount of GP reduces

51
Q

What is GP

What is RuBP

A

Glycerate Phosphate

Ribulose Bisphosphate

52
Q

What is GP

What is RuBP

A

Glycerate Phosphate

Ribulose Bisphosphate

53
Q

What is NADPH

A

A reducing agent, meaning it can donate hydrogen ions to other molecules during REDOX reactions

As it loses H+ NADPH is oxidised to NADP (NADP reduced)

A Level Biology Paper 2 (16 decks)

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