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BIO HL > C1.3 Photosynthesis > Flashcards

C1.3 Photosynthesis Flashcards

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1
Q

photosynthesis

A

energy of sunlight used to produce glucose from carbon dioxide and water. oxygen as waste product

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2
Q

glucose formed in photosynthesis can be stored as

A

temporarily stored as starch

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3
Q

photosynthesis in relation to the atmosphere

A

maintains its composition.
only natural process that releases oxygen into the atmosphere

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4
Q

why is it improtant that oxygen from plants is converted into ozone in the atomsphere

A

to protect life from UV light that reachs earth from the sun and cause mutations in nucleic acids

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5
Q

photolysis

A

light energy used to split water

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6
Q

what is light

A

a form of electromagnetic radiation produced by the sun

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7
Q

what is the result of photolysis

A

releases oxygen and allows hydrogen atoms to be retained on hydrogen acceptor molecules
ATP is also generated from ADP and P, using energy from light

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8
Q

what is the hydrogen atoms and ATP from photolysis used for

A

the hydrogen is carried to a series of reactions that result in the formation of glucose

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9
Q

what else carries out photosynthesis instead of plants

A

algae and cyanobacteria contain photosynthetic pigments, producing glucose and oxygen

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10
Q

cyanobacteria

A

the first organisms on earth to produce oxygen, 2.8 billion years ago
have accessory pigments called phycobilin and transfers energy from this to chlorophyll a

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11
Q

red and green algaie

A

developed 1.5 bn years ago
red has same pigments as cyanobacteria, deriving color from phycoerythrin
green algae have chloroplasts contained chlorophyll a and b which is why theyre green

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12
Q

purpose of chromatography in photosynthesis

A

ideal technique for separating biologically active molecules

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13
Q

what are chromatograms run on

A

adsorbent paper, powdered solid or on a thin film of dried solid

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14
Q

absorption spectrum of pigments are obtained by

A

measuring their absorption of colours. results are then plotted as a graph showing the amount of light absorbed over the wavelength range

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15
Q

what causes absorption of energy of blue and red light in chlorophyll

A

the chemical structure of the chlorophyll molecule

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16
Q

how is light energy transformed to chemical energy

A

absorption of light excites electrons. accessory pigment transfer excited electrons to chlorophyll a which leads to a series of reactions ultimately forming glucose

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17
Q

action spectrum

A

action spectrum of chlorophyll is the wavelength of light that are used in photosynthesis

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18
Q

limiting factor for photosynthesis

A

an environmental factor that when in short supply, affects rate of photosynthesis

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19
Q

effect of carbon dioxide concetnration on photosynthesis

A

shows positive correlation, suggesting it is the limiting factor.
at much higher concetration it reaches a plateau meaning another factor is limiting

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20
Q

effect of light intensity concentration on photosynthesis

A

positive correlation, showing its limiting factor
reaches plateau, suggesting other factor is limiting

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21
Q

effect of temperature on photosynthesis

A

at low temperature there is correlation
at high temperature, rate of photosynthesis abruptly drops and falls. there is clear optimum temperature for photosynthesis
due to enzymes controlling photosynthesis

22
Q

what is FACE

A

free air carbon dioxide enrichment experiments
investigate effects of carbon dioxide enrichment on trees
used to try to predict the effects of increasing global warming

23
Q

the two stages of photosynthesis are

A

light dependent reactions and light independent reactions

24
Q

light dependent reactions

A

photolysis
hydrogen removed and retained by NADP/hydrogen acceptor
ATP generated from ADP and P, using light energy
oxygen given off as waste product

25
Q

photophosphorylation

A

ATP being generated from ADP and Pw

26
Q

where do light dependent reactions occur

A

in the grana of chloroplast

27
Q

light independent reactions

A

glucose synthesized using carbon dioxide
products of light dependent reactions are used in glucose production
requires a continous supply of products from light dependent but does not directly involeve light energy

28
Q

where do light independent reactions occur

A

in the stroma of the chloroplasts

29
Q

photosystems and where are they located

A

arrays of pigment molecules that can generate and emit excited electrons.
located in thylakoid membranes of grana and occur in cyanobacteria and chloroplasts

30
Q

what does each photosystem contain

A

several hundred chlorophyll molecules
accessory pigments and proteins/light harvesting complements
all harvest light energy of different wavelengths and funnel energy to single chlorophyll molecule of the photosystem, known as reaction core. chlorophyll is then photoactivated

31
Q

what are the two types of photosystems present in the thylakoid membrane of the grana

A

photosystem 1 activates with wavelength 700 nm, called P700
photosystem 2 activates with wavelength 680 nm, called P680

32
Q

what happens when light energy reaches a reaction centre

A

ground state electrons in the reaction centre are raised to an excited state by the energy recieved
means high energy electrons are releases and these electrons bring about the biochemical changes of the light dependent reaction
spaces vacated by high energy electrons are continously refilled by ground state electrons

33
Q

LHC proteins

A

consist of enzymes which catalyse formation of ATP and catalyse conversion of hydrogencarrier to reduced carrier
also consist of electron carrier molecules

34
Q

what do the different types of pigments enable

A

enables light energy to excite electrons in a controlled way and direct these electrons along electron transport chains

35
Q

purpose of different pigments

A

allows plants to harvest light from a range of different wavelengths, increasing flow of electrons to the reaction centre

36
Q

where do the photosystems electrons come from

A

PS 1 electrons come from PS 2
PS 2 electrons come from splitting water molecules

37
Q

generation of oxygen by the photolysis of water in photosystems

A

excited electrons from photosystem 2 are accepted and passed along a chain of electron carriers
as a result of energy transfers, excitation levels of the electrons fall back to ground state and they fill vacancies in reaction centre of ps 1
vacancies are then filled in ps 2 by electrons from the water systems
2 is a ctalyst that splits the water molecule, triggering release of hydrogen and oxygen atoms, and ground state electrons
from the split water molcule, oxygen is cretes and hydrogen ions used in reduction of NADP

38
Q

ATP production by chemiosmosis in thylakoids

A

in grana, synthesis of ATP is coupled to electron transport via movement of protons by chemiosmosis
hydrogen ions trapped within the thylakoid space activates rotary mechanism of ATP synthase moving down gradient
ATP is synthesized
as excited electrons pass from PS 2 along electron transport chain, some of energy causes pumping of hydrogen ions/protons from matrix into thylakoid.
Protons accumulate, causing pH to drop which results in proton gradient, sustaining synthesis of ATP.
protons pass down gradeient though ATP synthase resulting in ATP

39
Q

Reduction of NADP by Photosystem 1

A

excited electron from photosystem 1 are passed two at a time to NADP, reduced to form NADPH + H
electrons released by ps 1 are transferred back to 1 instead of moving into the NADP. This movement of electrons result in formation of ATP molecules
electrons cycle repeatedly through ps 1 and the first portion of the electron transport chain but do not pass through 2, NADPH is not formed and water is not requred
The ADP and NADP diffuse back into the grana for resuse in light dependent reactions
sequence of reactions, repeated again and again, the light dependent reaction are formed

40
Q

non cyclic photphosphorylation

A

in the reduction of NADP by photosystem 1, pathway from 2 to 1 is linear, with electrons being accepted by NADP

41
Q

cyclic photophosphorylation

A

because electrons move in a cyclin manner, production of ATP is known as

42
Q

what is the calvin cycle

A

the light independent reactions

43
Q

carbon fixation by rubisco

A

carbon dioxide is combined with an acceptor molecule in the presence of a special enzyme rubisco in the stroma
high concentrations of it are requird because it works slowly and not effective at low carbon dioxide concentration
ribulose biphosphate is a 5 carbon sugar and carbon dioxide is added to it in a process known as fixation.
after theyve combined it splits into 2 molecules of glycerate 3 phosphate

44
Q

synthesis of triose phosphate

A

glycerate 3 phosphate is immediately reduced to triose phosphate using NADH and ATP
reduced NAD supplies the hydrogen to reduce glycerate 3 phosphate and ATP supplies the necessary energy
is the reduction step

45
Q

regeneration of Ribulose Biphosphate

A

triose phosphate is metabolised to produce the molecule that first reacts with carbon dioxide. regeneration of acceptor step
5 molecules of triose phosphate are converted to three molecules of RuBP allowing calvin cycle to continue
remaining triose phosphate can be used to synthesize other products including glucose. each run of the cycle generates two molecules of triose phosphate, three turns are needed to produce 6 molecuels.
this allows 5 to be converted to RuBP and one to be used in the formation of other molecules

46
Q

synthesis of carbon compounds

A

metabolism of the green plant is sustained by the products of photosynthesis
synthesis of carbohydrates, amino acids and other carbon compounds uses the products of the calvin cycle and mineral nutrients
product synthesis steps

47
Q

interdependence of the light dependent and independent reactions

A

light dependent reactions provide the NADPH and ATP, which in turn provides the electrons and energy needed to produce carbohydrates in the light independent reactions

48
Q

what happens to photosynthesis reactions if there is no light

A

lack of light stops light dependent reactions and thus, NADPH and ATP are not produced which stops the light dependent reactions

49
Q

what does carbon dioxide act as in photosynthesis

A

a terminal electron acceptor at the end of reactions and a proton acceptor at the beginning of reactions

50
Q

what happens with the removal of hydrogen carbonate in photosynthesis?

A

slows electron transfer through the electron acceptors in ps 2 since it is bound to proteins, which are needed for the activity of the electron transport chain

51
Q

what happens with the removal of carbon dioxide in photosynthesis?

A

depletion of carbon dioxide not only causes cessation of carbon dioxide fixation but also a strong decrease in the activity of ps 2

52
Q
A

BIO HL (23 decks)

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