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Biology 8. Metabolism, Cell Respiration and Photosynthesis > 8.3 Photosynthesis > Flashcards

8.3 Photosynthesis Flashcards

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1
Q

What is part of photosynthesis called that uses light directly?

A

light dependent

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2
Q

What is part of photosynthesis called that does not use light directly?

A

light independent

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3
Q

What are light independent reactions dependent on?

A

can work in dark but only shortly, need substances produced by light dependent reactions

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4
Q

what does the inner membrane of a chloroplast enclose?

A

third system of interconnected membranes called thyla koid membranes

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5
Q

What are thylakoid membranes?

A

third system of interconnected membranes enclosed by inner membrane of chloroplast

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6
Q

What is within thylakoid?

A

compartment called thylakoid space

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7
Q

What are the products of light dependent reactions

A

light energy converted into chemical energy in form of ATP and reduced NADP

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8
Q

What do ATP and NADP serve as for light independent reactions?

A

energy sources

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9
Q

What is a stroma

A

compartment which inner membrane of the chloroplast encloses; protein rich with enzymes to use for calvin cycle (light independent reactions)

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10
Q

What is the calvin cycle?

A

anabolic pathway for light independent reactions that require endergonic reactions so that ATP is hydrolised and reduced NADP is oxidized

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11
Q

What are photosystems?

A

chlorohyll and accessory pigments grouped together in large light harvesting arrays (contain chlorophyll)

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12
Q

Where are photosystems located?

A

in thylakoids, an arranment of membranes inside chloroplast

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13
Q

What do photosystems I and II have?

A

light harvesting arrays (with chlorophyll), reaction centres and many chlorophyll molecules that absorb light energy

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14
Q

What happens when chlorophylls in the reaction centre absorb energy?

A

when energy is absorbed from photon of light an electron within molecule gets excited. which makes chlorophyll photoactivated

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15
Q

How can a chlorophyll get photoactivated?

A

chlorophyll absorbs energy from photon of light, electron gets excited

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16
Q

What is a special property of chlorophylls in the reaction centre?

A

can donate excited electrons to electron acceptor

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17
Q

What is the electron acceptor of photosystem II called?

A

plastoquinon

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18
Q

What does plastoquinon do?

A

collects to excited electrons from photosystem II, then moved to another position in the membrane

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19
Q

Describe a property of plastoquinone

A

Hydrophobic; has no fixed position but remains within mmbrane

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20
Q

what does the absorption of two photons of light cause?

A

produces one reduced plastoquinone, where chlorophyll at reaction centre lost 2 electrons to plastoquinone

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21
Q

Can photosystem II repeat the process of producing a new plastoquinone?

A

Yes it can repeat the process and produce a second reduced plastoquinone

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22
Q

What does photo phosphorylation produce?

A

ATP using energy from light

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23
Q

Who carries out phosphorylation?

A

thylakoids

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24
Q

What does a thylakoid membrane include?

A

photosystem II; chain of electron carriers; photosystem I; ATP synthase

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25
Q

How are electrons carried from reaction centre of photosystem II to chain of electron carriers?

A

reduced plaetoquinone is needed

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26
Q

What happens once plastoquinone transfers its electrons?

A

electrons are passed from carrier to carrier in chain

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27
Q

What happens when electrons pass through the electron carrier chain?

A

energy is released from excited electrons from photosystem II which provides protein pumps to pump H+ across thylakoid membrane the lumen of the thylakoid; concentration gradient developed;

28
Q

How is a concentration gradient created across the thylakoid membrane?

A

excited electrons from photosystem II is passed along electron carrier chain (cytochrome complex) which releases energy that actively transports H+ across membrane into lumen; photolysis also increases H+ concentration

29
Q

How is ATP generated in thylakoids?

A

High concentration of H+ in thylakoid space is reduced by passing them through the enzyme ATP synthase; energy is released through the passive transport of H+ (down concentration gradient) synthesizes ATP from ADP +Pi

30
Q

What is the process called when H+ passes through ATP synthase from high concentration to low, to convert ADP to ATP

A

chemiosis

31
Q

What is the production of ATP in chlorophylls calld?

A

photophosphorylation

32
Q

What occurs when electrons reach end of carrier chain?

A

passed to plastocynanin to be passed to photosystem I

33
Q

How does photoactivation work in photosystem I?

A

chlorophyll molecules within photsystem I absorb light energy to pass it the two chlorophyll in the reaction centre which re-excites the electrons (raise to higher level)

34
Q

Why does a second photoactivation need to happen at photosystem I?

A

much of the energy has been lost from electrons (move down in energy level) and needs re charge

35
Q

What happens to electrons after photosystem I?

A

passed to ferredoxin which becomes reduced ferredoxin to reduce NADP, to form NADP.

36
Q

What is plastocynanin?

A

a water-soluble electron acceptor in the fluid inside the thylakoids

37
Q

What happens when NADP runs out in a chloroplast?

A

electrons return to the electron transport chain that links the photosystems, rather than being passad to NADP

38
Q

What is ferredoxin?

A

protein in fluid outside the thylakoid

39
Q

What is cycling photosphorylaiton?

A

flow of electrons along chain to allow more ATP production

40
Q

Where does carbon fixation occur in plants and algae?

A

light independent reactions, in the stroma

41
Q

How does photosystem 1 replace its loss electrons?

A

with electrons emitted by phosphosystem II and passed along electron carriers

42
Q

Which photosystem can absorb more light to produce more excited electrons?

A

Photosystem I

43
Q

Where does calvin cycle occur in the chloroplast?

A

stroma

44
Q

Does CO2 react with a 2 carbon compound (calvin cycle)?

A

No. reacts with 5 carbon compound known as RuBP

45
Q

What is produced from Co2 and RuBP?

A

two molecules of glycerate 3-phosphate

46
Q

What does the stroma contain large amounts for for the calvin cycle?

A

rubisco (maximizes carbon fixation)

47
Q

What is the ratio of hydrogen and oxygen in sugars?

A

2:1

48
Q

Whats needs to be added to glycerate 3-phosphate to become a carbohydrate?

A

Hydrogen because RuBP when converted to glycerate 3-phosphate has reduced amount of oxygen

49
Q

What is needed to add hydrogen to glycerate 3-phosphate?

A

ATP and reduced NADP (NADPH) produced from light dependent reactions; ATP provides energy for reaction; NADPH provides hydrogen atoms

50
Q

What is the first carbohydrate of light independent reactions?

A

triose phosphate

51
Q

What happens if triose phosphates are combined?

A

can form hexose phosphate; hexose can condense to starch

52
Q

Why cannot all triose phosphate produced be converted to starch or hexose phosphate?

A

supplies of RuBP would run out; triose phosphate must be regenerated to RuBP

53
Q

What is important rule for calvin cyle to continue indefinitely?

A

as much RuBP must be produced as consumed

54
Q

What occurs in the last phase of the calvin cycle?

A

series of enzyme catalyzed reactions convert triose phosphate into RuBP

55
Q

How many molecules of RuBP would be produced with 5 molecules of triose phosphate?

A

3 molecules of RuBp

56
Q

For every six molecules of triose phosphate formed in light independent, how many must be converted to RuBP?

A

five

57
Q

What structual features do all chloroplasts share?

A

double membrane forming outer chloroplast envelope; extensive system of internal membrane called thylakoid; small fluid filled spaces inside the thylakoids; colourless fluid called stroma (contains enzymes); stacks of thylakoid called grana

58
Q

If a chloroplast has been photosynthesizing rapidly, what could be seen in chloroplast?

A

starch grains or lipid droplet

59
Q

function of granum

A

a stack of thylakoids for absorption of photons of light

60
Q

function of thylakoid space

A

with a very small volume steep concentration gradient builds up after relatively few absorbed photons

61
Q

function of stroma

A

containing all the enzymes of calvin cycle; lots of rubisco; naked DNA and 70S ribosomes (synthesis for protein possible)

62
Q

function of chloroplast envelope

A

creates a compartment in which enzymes and other components photosynthesis is concentrated

63
Q

function of starch grain

A

storage of carbohydrate produced by photosynthesis until it is exported from chloroplast

64
Q

function of thylakoid membrane

A

provide large surface area for light absorbing photosystems; site for electron flow; generation of proton gradient and chemiosmosis

65
Q

Draw Diagram of chloroplast

A

thylakoid membrane; thylakoid; thylakoid space; grana; stroma; 70S ribosome and naked DNA; starch grain; lipid droplets; chloroplast envelopes (inner/outer)

66
Q

How does photolysis occur at photosystem II?

A

After electrons have been transferred to the plastoquinone (becomes reduced), the chlorophyll becomes strong oxidizing agent (wants to get reduced); polerizes water and splits it; into H+ and O2

Biology 8. Metabolism, Cell Respiration and Photosynthesis (5 decks)

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