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Biology A level > 5.1 Photosynthesis > Flashcards

5.1 Photosynthesis Flashcards

1
Q

Where does the light dependent stage occur?

A

thylakoid membranes

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2
Q

Where does the light independent reaction happen?

A

the stroma

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3
Q

What are the 2 stages of photosynthesis?

A

light dependent reaction
light independent reaction

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4
Q

What is used in the LDR?

A

water and light energy

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5
Q

What is prouced in the LDR?

A

ATP and reduced NADP

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6
Q

What are the 4 stages of the LDR?

A
  1. photolysis of water
  2. photoionisation of chlorophyll
  3. chemiosmosis
  4. production of ATP and reduced NADP
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7
Q

What is photolysis of water?

A

light energy is absorbed by photostem II on the thylakoid membrane and splits water into oxygen, H+ and e-

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8
Q

What is the equation for the photolysis of water?

A

H2O —-> 1/2 O2 + 2e- + 2H+

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9
Q

What happens to the H+ from the photolysis of water?

A

picked up by NADP to form reduced NADP which is used in the LIR

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10
Q

What happens to the e- from photolysis of water?

A

passed along a chain of electron carriers

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11
Q

What happens to the O2 from the photolysis of water?

A

used for resp or diffuses out of the leaf through the stomata

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12
Q

What is the photoionisation of chlorophyll?

A

light energy is absorbed by the chlorophyll and the energy excites electrons, raising their enery levels to leave chlorophyll

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13
Q

What is the energy released from the photoionisation of chlorophyll used for?

A

used to make ATP and reduced NADP in chemiosmosis

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14
Q

What is the LIR also known as?

A

the calvin cycle

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15
Q

What enzyme is involved with the calvin cycle?

A

RuBisCo

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16
Q

Why does temp only affect the calvin cycle not the LDR?

A

the calvin cycle involves enzymes

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17
Q

What does the calvin cycle use up?

A

carbon dioxide
reduced NADP
ATP

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18
Q

What is produced from the LIR?

A

a hexose sugar

19
Q

What is the role of ATP in the calvin cycle?

A

provides energy for reaction

20
Q

What is the use of reduced NADP in the calvin cycle?

A

donates hydrogen (protons) to reduce GP molecules

21
Q

What is oxidation?

A

remove H+

22
Q

What is reduction?

A

add hydrogen

23
Q

Describe the process of the photoionisation of chlorophyll

A

Light energy isabsorbedby chlorophyll

Thisexcites2 electrons carrying them to leave thechlorophylland pass to an electron acceptor

The electrons pass along a series of electron carriers

As they pass theylose energy

This energy is used toproduce ATP from ADP and Pi by chemiosmosis

24
Q

Describe the process of chemiosmosis

A

High energy electrons from thephotoionisationof chlorophyll passes along a series of electron carriers

As they pass they lose energy, which is used to pump protons (H+) from the stroma into the thylakoid space

The protons accumulate producing an electrochemical gradient

As a result the protons are diffuse by facilitated diffusion into the stroma via ATP synthase. This provides the energy to form ATP from ADP and Pi

Protons in the stroma and electrons at the end of the carrier chain combine with NADP to form NADPH

25
Q

Describe the process of the calvin cycle

A

CO2 reacts with RuBP to form 2 molecules of G-3-P - this reaction is catalysed by RuBisCo

G-3-P is reduced to Triose phosphate using energy from ATP and accepting H from reduced NADP

some of the Triose phosphate leaves the cycle to be converted into useful organic substances = glucose/ sucrose

this leaves a 3C compound and a 2C compound = as 1C is removed each cycle
using ATP RuBP is regenerated from these compounds

cycle only produces 1 carbon, so it repeats

26
Q

What is a limiting factor?

A

any factor that reduces the rate of photosynthesis

27
Q

What are the 3 limiting factors of photosynthesis?

A

temp
CO2 conc
light intensity

28
Q

Why is CO2 conc a limiting factor of photosynthesis?

A

it is a reactant in the calvin cycle

29
Q

Why is light intensity a limiting factor of photosynthesis?

A

light energy is needed in the LDR for the photoionisation of chlorophyll and photolysis of water

30
Q

How can each limiting factor be overcome in agriculture techniques?

A

light = artificial lighting
temp = heating greenhouses
CO2 conc = burning fuel

31
Q

How many carbons are in G-3-P?

A

3

32
Q

How many carbons are in RuBP?

A

5

33
Q

How many carbons are in triose phosphate?

A

3

34
Q

What colour is DCPIP when it is oxidised?

A

blue

35
Q

What colour is DCPIP when it is reduced?

A

colourless

36
Q

Describe how you would investigate the effect of light on the rate of deydrogenase activity in chloroplast extracts

A

x4 test tubes
x2 - chloroplast extract, DCPIP, buffer (dark green)
x1 - DCPIP, buffer (blue)
x1 - chloroplast, buffer (light green)

one of the tubes with everything in it is going to be placed in the dark, the other tubes will be plaed under a light
tube with everything under the light will turn a light green colour=DCPIP is reduced and turns blue–> colourless

tube with just chloroplast is used as a colour standard for comparisons of colour
DCPIP tube thats blue is the control for comparison of changes

37
Q

What is DCPIP?

A

an artifical hydrogen acceptor

38
Q

What is the relationship between light intensity and the rate of photosynthesis?

A

at low light intensity = it is the limiting factor
at high light intensity = other factors are limiting the rate of photosyn

39
Q

Describe the relationship between temp and the rate of photosynthesis

A

at low temps = the enzymes work so slowly that photosyn virtually stops = not enough KE
as temp increases so does enzyme activity so the rate also increases
above the optimum temp = enzymes denature and the rate decreases rapidly

40
Q

Describe the relationship between CO2 conc and the rate of photosynthesis

A

low CO2 = it is the limiting factor
high CO2 = other factors limiting the rate

41
Q

What 2 measurements can be taken to determine the rate of photosynthesis while invesigating limiting factors?

A

the change in pH = more acidic –> more photosynthesis
volume of O2 produced

42
Q

Why would increasing the CO2 conc increase the amount of glucose produced?

A

more GP is produced from RuBP
more GP results in more triphosphate
more TP = more glucose

43
Q

Why is there an increase in photosynthesis even when no CO2 is being taken up by the plant?

A

plant uses CO2 from aerobic respiration for photosynthesis

Biology A level (32 decks)

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