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Molecular Basis of Life > Photosynthesis > Flashcards

Photosynthesis Flashcards

1
Q

Define photosynthesis

A

A metabolic pathway that converts light energy into chemical energy for synthesis of carbohydrate

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2
Q

What is the cytosol of the chloroplast called and give 2 suspensions

A

Stroma - free ribosomes and starch granules

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3
Q

What makes up the envelope of the chloroplast

A

Inner and outer membrane
Intermembrane space

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4
Q

How is the main structure in chloroplasts arranged

A

Thylakoid membranes form thylakoids - they stack forming grana

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5
Q

Where is the chlorophyll stored

A

In the thylakoid membranes

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6
Q

How long are chloroplasts

A

7micrometers

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7
Q

Where are the chloroplasts found in leaves

A

In the mesophyll

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8
Q

Where does visible light range in the electromagnetic spectrum

A

380nm - 750nm

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9
Q

What are substances that absorb visible light called

A

Pigments

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10
Q

What light works best for chlorophyll a in terms of photosynthesis

A

Violet-blue and red

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11
Q

What colour is chlorophyll a and b (what type of pigment is b)

A

a - Blue green
b - Olive green + accessory

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12
Q

What is the role of carotenoids

A

Dissipate light that would damage the chlorophyll

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13
Q

What happens when light is shone on an isolated chlorophyll molecule (3)

A

Molecule moves from a ground state to unstable excited state
Falling back to ground state gives off heat and photons
This causes molecule to fluoresce

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14
Q

When chlorophyll is not isolated and light is shone - what happens to the photons and heat given off

A

It is converted into chemical energy

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15
Q

what are photosystems made up of (RCC + LHC)

A

Reaction centre complex
Light harvesting complex

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16
Q

What does the reaction centre complex contain

A

a pair of chlorophyll a molecules

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17
Q

What makes up the light harvesting complexes

A

Pigments bound to proteins

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18
Q

Outline the general process of photons ending up as electrons with the primary electron acceptor

A

Pigments in LHC absorb photon and pass electron between pigments - electron is then transferred to special chlorophyll a molecules which then pass it to primary electron acceptor

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19
Q

What are the products of the linear flow of electrons in the light dependent cycle

A

ATP, NADPH and O2

20
Q

What are the chlorophyll a molecules in the reaction complex centre in PSII called

A

P680

21
Q

How does P680 become reduced after transferring its electron to the primary electron acceptor

A

P680+ oxidises H2O to form O2

22
Q

What complex makes up the ETC from PSII to PSI

A

Cytochrome complex

23
Q

What does the passing down of the electrons in the ETC cause

A

A release of energy which drives the creation of a proton gradient across the thylakoid membrane

24
Q

What are the chlorophyll a molecules in the reaction complex centre in PSI called

A

P700

25
Q

How does P700 become reduced after transferring its electron to the primary electron acceptor

A

P700+ accepts electron passed down the ETC from PSII

26
Q

Where do the electrons from PSII’s go

A

Down a secondary ETC to ferredoxin (Fd)

27
Q

Once the electrons reach Fd in the second ETC what do they do

A

Reduce NADP+ to NADPH

28
Q

What PS does the cyclic electron flow involve and what is produced

A

PSI and ATP

29
Q

What is the advantage of cyclic electron flow

A

Photoprotection

30
Q

Outline the cyclic electron flow - starting with Fd - what is produced

A

Electrons cycle back from Fd to the PSI reaction complex centre via the ETC producing ATP

31
Q

What is the general function of the Calvin cycle

A

To reduce CO2 to sugar using ATP and NADPH

32
Q

How many turns of the Calvin cycle is needed to form a glucose molecule

A

6

33
Q

What are the 3 general stages in the Calvin cycle

A

Carbon fixation
Reduction
Regeneration

34
Q

What is the first and immediate second step in the Calvin cycle - enzyme?

A

CO2 is joined to ribulose bisphosphate to form an unstable 6C sugar catalysed by RuBISCO
6C intermediate splits into 2 molecules of 3-phosphoglycerate

35
Q

How is ATP used in the 1st step of the 2 step reduction process of the Calvin cycle

A

ATP converted to ADP and each 3-phosphoglycerate becomes 1,3-bisphosphoglycerate

36
Q

What is the second step in the reduction stage of the Calvin cycle

A

NADPH reduces 1,3-bisphosphoglycerate to G3P

37
Q

If 6 G3Ps are produced how many leave the Calvin cycle and what happens to them

A

1 - forms glucose and other organic compounds

38
Q

What is regenerated during the regeneration step of the Calvin cycle and what is formed as a biproduct

A

5 G3Ps become ribulose bisphosphate
3 molecules of ADP

39
Q

What is the advantage of photorespiration

A

Oxygen - oxidative damage

40
Q

Why would a plant carry out photorespiration

A

Hot and dry conditions so stomata have to remain closed to retain water

41
Q

How does the Calvin cycle differ in photorespiration

A

RuBISCO adds RuBP to oxygen instead of CO2 which forms a 2C compound

42
Q

What is carbon fixed to in C4 plants

A

A C4 compound

43
Q

What enzyme is used instead of RuBISCO in C4 plants - why is it advantageous

A

PEP carboxylase - has a high affinity for CO2 even in low CO2 conditions

44
Q

2 unique anatomical leaf features in C4 plants

A

Bundle sheath cells and Mesophyll cells

45
Q

What is the type of separation in CAM plants in comparison to C4 plants

A

C4 - structural / spatial separation
CAM - Temporal separation

46
Q

What does the build up of acids do in CAM plants

A

They release CO2 to use in the Calvin cycle during the day when stomata are closed

Molecular Basis of Life (16 decks)

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