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B11- PHOTOSYNTHESIS > 11.2- THE LIGHT-DEPENDENT REACTION > Flashcards

11.2- THE LIGHT-DEPENDENT REACTION Flashcards

1
Q

What does LDR of photosynthesis involve?

A

capture of light

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2
Q

What is the light captured from LDR used for? (2)

A

to add an inorganic phosphate (Pi) molecule to ADP, thereby making ATP

split water into H+ ions (protons) + OH- ions
as splitting caused by light, known as photolysis

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3
Q

What is oxidation?

A

when substance gains oxygen or loses hydrogen

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4
Q

What is reduction?

A

when substance loses oxygen or gains hydrogen

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5
Q

In practice, what is oxidation and reduction?

A

oxidation- lose of electrons

reduction- gains electrons

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6
Q

What is done to energy due to oxidation?

A

energy given out

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7
Q

What is done to energy due to reduction?

A

energy taken in

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8
Q

What happens to a pair of electron when a chlorophyll molecule absorbs light energy?

A

boosts energy of a pair of electrons within chlorophyll molecule, raising them to higher energy level

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9
Q

When a chlorophyll molecule absorbs light energy and it boosts the energy of a pair of electrons within the chlorophyll molecule, what is the electrons said to be in?

A

said to be in excited state

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10
Q

As the pair of electrons from the chlorophyll molecule become so excited, what happens?

A

they leave chlorophyll molecule altogether

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11
Q

As the pair of electrons become so excited and leave the chlorophyll molecule altogether, what happens to the chlorophyll molecule?

A

chlorophyll molecule becomes ionised + so process called photoionisation

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12
Q

What happens to the electrons that leave the chlorophyll molecules?

A

taken up by molecule called electron carrier

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13
Q

Is the chlorophyll molecule oxidised or reduced as it has lost a pair of electrons?

A

oxidised

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14
Q

Is the electron carrier oxidised or reduced as it has gained electrons?

A

reduced

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15
Q

What do the electrons do as they have left the chlorophyll molecule and have been taken up by the electron carrier?

A

electrons now passed along number of electron carriers in series of oxidation-reduction reactions

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16
Q

What do the electron carriers form and where?

A

form transfer chain that’s located in membranes of thylakoids

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17
Q

What position is each new electron carrier than the previous one?

A

at slightly lower energy level than previous one, and so electrons lose energy at each stage

18
Q

What is some of the lost energy from the electrons as it passes down the electron transfer chain used for?

A

used to combine inorganic phosphate molecules with ADP molecule to make ATP

19
Q

By which theory can the precise mechanism by which ATP is produced be explained by?

A

chemiosmotic theory

20
Q

What is each thylakoid and what is pumped into it? #1 chemiosmotic theory

A

each thylakoid is an enclosed chamber into which protons (H+) pumped from stroma using protein carriers in thylakoid membrane called proton pumps

21
Q

Where does the energy to pump protons from the stroma using protein carriers in the thylakoid membrane called proton pumps come from? #2 chemiosmotic theory

A

energy to drive process comes from electrons released when water molecules split by light- photolysis of water

22
Q

What does the photolysis of water also produce, other than electrons #3 chemiosmotic theory

A

protons which further increase their conc. inside thylakoid space

23
Q

What does the protons from the photolysis of water increasing their conc. inside the thylakoid space do? #4 chemiosmotic theory

A

creates + maintains conc. gradient of protons across thylakoid membrane with high conc. inside thylakoid space + low conc. in stroma

24
Q

Where can the protons cross through? #5 chemiosmotic theory

A

protons can cross thylakoid membrane through ATP synthase channel proteins- rest of membrane permeable to protons
these channels form small granules on membrane surface so also known as stalked granules

25
Q

What do the protons do to the ATP synthase as they pass through them? #6 chemiosmotic theory

A

cause change to structure of enzyme which then catalyses combination of ADP with inorganic phosphate to form ATP

26
Q

When light strikes the chlorophyll molecule and it loses electrons, what is it short of?

A

short of electrons

27
Q

After the chlorophyll molecule has lost electrons has been lost, what must be done for it to continue absorbing light energy?

A

these electrons must be replaced

28
Q

How are the replacement electrons for the chlorophyll molecules provided?

A

from water molecules that are split using light energy

29
Q

Equation for photolysis of water

A

2H20 -> 4H+ + 4e- + O2

30
Q

When the protons from the photolysis of water pass through the ATP synthase channels what happens to them after?

A

taken up by electron carrier called NADP

31
Q

What happens when the NADP take up the protons?

A

become reduced

32
Q

What is the main product of LDR and what happens to it?

A

reduced NADP and it enters LIR taking with it the electrons from chlorophyll molecules

33
Q

Why is the reduced NADP important?

A

as it’s a further potential source of chemical energy to the plant

34
Q

What happens to the oxygen by-product from the photolysis of water?

A

either used in respiration or diiffuses out of leaf as waste product of photosynthesis

35
Q

Where does LDR happen?

A

in thylakoids of chloroplasts

36
Q

What are the thylakoids?

A

disc-like structures that are stacked together in groups called grana

37
Q

How are chloroplasts structurally adapted to their function of capturing sunlight + carrying out LDR? (4)

A

thylakoid membranes provide large SA

network of proteins in grana

granal membranes have ATP synthase channels within them

chloroplasts contain both DNA + ribosomes

38
Q

How is the thylakoid membranes providing a large SA an adaptation for chloroplasts?

A

large SA for attachment of chlorophyll, electron carriers and enzymes that carry out LDR

39
Q

How is a network of proteins in the grana an adaptation for chloroplasts?

A

network of proteins in grana hold chlorophyll in very precise manner that allows maximum absorption of light

40
Q

How is the granal membranes having ATP synthase channels within them chloroplasts an adaptation for chloroplasts?

A

they catalyse production on ATP

also selectively permeable which allows establishment of a proton gradient

41
Q

How is the chloroplasts containing both DNA + ribosomes an adaptation for chloroplasts?

A

so they can quickly + easily manufacture some of the proteins involved in the LDR

B11- PHOTOSYNTHESIS (3 decks)

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