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biology - module 5 > Photosynthesis > Flashcards

Photosynthesis Flashcards

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AP® Biology flashcards
1
Q

compare photosynthesis + aerobic respiration + anaerobic respiration

where it occurs

energy

conversion of energy

anabolic or catabolic

overall equation

how ATP is produced

coenzyme used

A
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2
Q

describe how ATP is synthesised

A

electrons excited

pass through electron transport train

energy released

+ used to pump protons across membrane

creates conc gradient

protons diffuse back through membrane down conc - CHEMIOSMOSIS

diffuse via hydrophilic transmembrane channels linked to ATP synthase

flow of protons provide energy needed to make ATP from ADP + Pi

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3
Q

what is chemiosmosis

A

Diffusion of protons from region of high concentration to region of low concentration

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4
Q

what does chemiosmosis result in

A

Movement of protons down gradient released energy used in attaching phosphate ion to ADP forming ATP

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5
Q

how are electrons excited

A

Electrons present in pigment molecules – chlorophyll – are excited by absorbing light

High energy electrons released when chemical bonds are broken in respiratory substrate molecules

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6
Q

what is the electron transport chain

A

Made up of electron carriers – progressively lower energy levels

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7
Q

how large are chloroplasts

A

2 – 10 micrometres in diameter

larger than mitochondria

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8
Q

describe the structure of chloroplasts

A

Surrounded by double membrane

Have cytosol-like fluid – stroma

Has separate system of membranes

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9
Q

describe the double membrane

A

Outer – permeable to ions / small molecules

Inner – has transport proteins

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10
Q

what is in the stroma

A

Carbon dioxide / sugars / enzymes

Has 70s ribosomes + loop of DNA + starch grains

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11
Q

describe the separate membrane system

A

has flattened fluid-filled sacks = thylakoids

Thylakoid membrane – has pigments / enzymes / electron carriers

Thylakoids stack to form grana

Grana connected by membranous channels – lamellae

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12
Q

what is the purpose of lamellae

A

Ensure sacs are connected but distanced from each other

Membrane of grana – large SA

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13
Q

how is the stroma adapted for photosynthesis

A

Gel-like fluid

Enzymes for light-independent reactions

Surrounds grana and membranes

Facilitates rapid transport of products from light-dependent stage

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14
Q

how is the grana adapted to photosynthesis

A

Stacks of thylakoids

Large surface area

Presence of many photosystems

Maximizes light absorption

More membrane space for electron carriers and ATP synthase enzymes

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15
Q

how are the ribosomes adapted for photosynthesis

A

Present in chloroplast

Allows translation of proteins coded by cpDNA

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16
Q

how is the inner membrane adapted for photosynthesis

A

Selective transport proteins

Control flow of molecules between stroma and cytosol

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17
Q

what are the two types of pigments

A

chlorophylls

carotenoids

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18
Q

what are the two types of chlorophyll

A

chlorophyll a

chlorophyll b

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19
Q

what are the two types of carotenoids

A

beta carotene

xanthophyll

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20
Q

what are the colours of the chlorophyll pigments

A

chlorophyll a - yellow-green

chlorophyll b - blue-green

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21
Q

what are the colours of the carotenoids pigments

A

beta carotene - orange

xanthophyll - yellow

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22
Q

what wavelengths do chlorophyll absorb + reflect

A

absorb wavelengths in blue-violet + red regions

reflect green light

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23
Q

what wavelengths do carotenoids absorb

A

absorb wavelength’s in blue-violet regions

24
Q

what is a photosystem

A

??

Light harvesting system + reaction centre

25
Q

what is the role of a photosystem

A

to absorb / harvest light energy + transfer energy quickly to reaction centre

26
Q

where are the photosystems found

A

In the membrane of thylakoids

27
Q

what are the two photosystems

A

Photosystem 1 (P700)

Photosystem 2 (P680)

28
Q

what is the max absorption of photosystem 1

A

700nm

29
Q

what is the max absorption of photosystem 2

A

680nm

30
Q

what are the two stages of photosynthesis

A

light dependant

light independant - calvin cycle

31
Q

what happens overall in the light dependant stage

A

Energy from sunlight absorbed + used to form ATP

Hydrogen from water used to reduce coenzyme NADP to reduced NADP

32
Q

where does the light dependant stage occur

A

Thylakoid membrane

33
Q

what process does the light dependant stage occur via

A

noncyclic or cyclic photophosphorylation

34
Q

describe non cyclic photophosphorylation

A

Light absorbed by PS2

PS2 has oxygen evolving complex – water splitting enzyme

Breaks down water - photolysis = H2O → 2H+ + 2e- + ½O2

Photon collides with chlorophyll a + excites an electron in a Mg atom (photoionisation)

As electrons leave PS2 – replaced by electrons from photolysis

excited electrons pass down electron transport chain

H+ transported to stroma by ATP synthase

Chemiosmosis + photophosphorylation

Electron passes from electron transfer chain to PS1

Electrons excited at PS1 in Mg atom - photoionisation

New electron goes through electron carrier 2

+ replaced by electron coming from electron carrier 1 (PS2)

Electrons combine with H+ and NADP to get reduced NADP (NADPH

35
Q

describe chemiosmosis again

A

As high energy electrons move through carriers – energy released

Energy used to pump protons across membrane from stroma to thylakoid lumen= making conc gradient

Gradient maintained from permeability of membrane to hydrogen ions

NOW - only way protons move back through membrane DOWN conc gradient is through membrane channels linked to ATP synthase

Facilitated diffusion of protons provides energy used to make ATP from ADP + Pi

36
Q

what are the end products of non cyclic photophosphorylation

A

Used water

Produced oxygen as a biproduct

Produced NADPH + ATP

37
Q

describe cyclic photophosphorylation

A

Only involves PS1

Times of stress

Rather than end result of NADPH – electron passed back to PS2 from PS1

Re-enters electron transfer chain

Keep pumping H+ into thylakoids = produce more ATP

NO reduced NADPH produced

38
Q

state the difference between cyclic + non cyclic photophosphorylation

A

?

39
Q

where does the light independant stage occur

A

stroma

40
Q

describe the calvin cycle

A

Carbon dioxide enters intercellular spaces in spongy mesophyll via diffusion through stomata

Diffuses into stroma of chloroplasts

Combined with ribulose biphosphate (RuBP)

Carbon dioxide is now fixed – incorporated into organic molecule

Six carbon unstable intermediate produced

Breaks down – 2 three carbon glycerate 3-phosphate (GP) molecules

Each GP reduced into another 3 carbon – triose phosphate (TP)

Uses hydrogen from NADPH + energy from ATP

TP – carbohydrate + majority recycled to regenerate RuBP

Regeneration uses ATP

41
Q

draw out the calvin cycle

A
42
Q

what is the fixation of carbon dioxide

A

Combining with ribulose biphosphate (RuBP

43
Q

what is RuBP

A

5 carbon sugar

ribulose biphosphate

44
Q

what is the fixation of carbon dioxide catalysed by

A

Catalysed by ribulose biphosphate carboxylase (RuBisCO)

45
Q

whats bad aboutn RuBisCo

A

Carbon dioxide is now fixed – incorporated into organic molecule

46
Q

what needs to happen in the calvin cycle for 1 glucose molecule to be made

A

six carbon dioxide molecules have to enter

6 full turns of the cycle

make 12 TP molecules – 2 of which will be removed to make the glucose molecule

10 TP molecules recycled to make 6 RuBP

47
Q

what are the uses of TP

A

Can condense to form hexose phosphate – used to produce starch / sucrose / cellulose

Can be converted into glycerol

Used to make amino acids

48
Q

state the factors effecting rate of photosynthesis

A

light intensity

carbon dioxide conc

temperature

49
Q

how does light intensity effect rate of photosynthesis

A

Rate of photosynthesis increases as light intensity increases

Greater light more energy supplied to plant

Faster light dependant stage can occur

Produces more ATP + NADH for Calvin cycle

50
Q

state the relationship between decreasing light intensity and the conc of NADH / GP / TP / RuBP

A

Decrease light intensity = decreases conc of TP + RuBP

BUT slight increase in GP

51
Q

how does decreasing light intensity effect conc of NADH / GP / TP / RuBP

A

Decrease light intensity = decrease in TP + RuBP BUT slight increase in GP

Less light – light dependant stops + doesn’t form any more products (ATP + NADH)

GP builds up as it is not converted to TP

Lack of TP – RuBP wont form

Overtime fixation of carbon dioxide will stop + GP conc will plateau

52
Q

how does carbon dioxide conc increase rate of photosynthesis

A

rate of photosynthesis increases as carbon dioxide concentration increases

More carbon dioxide.. more combined with RuBP + faster

Faster Calvin cycle + faster rate of photosynthesis

53
Q

state the relationship between decreasing carbon dioxide conc and the conc of NADH / GP / TP / RuBP

A

Low conc of carbon dioxide – decrease in conc of GP + TP but increase in RuBP

54
Q

how does decreasing carbon dioxide conc effect conc of NADH / GP / TP / RuBP

A

Low conc of carbon dioxide – decrease in conc of GP + TP but increase in RuBP

RuBP accepts carbon dioxide so when there is a lack it remains unfixed + builds up

Prevents TP + GP from forming

55
Q

why doesnt temp have a significant effect on the light dependant stage

A

driven by light energy rather than kinetic energy

56
Q

how does increasing temp effect rate of photosynthesis

A

Increasing temp – cause stomata to close – carbon dioxide cant be fixed + slow rate down

Light dependant reaction relied on proton gradient forming across thylakoid membrane = membrane permeability influenced by extreme temp

57
Q
A

biology - module 5 (8 decks)

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