C1.3 Photosynthesis

Question 1

photosynthesis

Answer 1

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

Question 2

glucose formed in photosynthesis can be stored as

Answer 2

temporarily stored as starch

Question 3

photosynthesis in relation to the atmosphere

Answer 3

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

Question 4

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

Answer 4

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

Question 5

photolysis

Answer 5

light energy used to split water

Question 6

what is light

Answer 6

a form of electromagnetic radiation produced by the sun

Question 7

what is the result of photolysis

Answer 7

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

Question 8

what is the hydrogen atoms and ATP from photolysis used for

Answer 8

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

Question 9

what else carries out photosynthesis instead of plants

Answer 9

algae and cyanobacteria contain photosynthetic pigments, producing glucose and oxygen

Question 10

cyanobacteria

Answer 10

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

Question 11

red and green algaie

Answer 11

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

Question 12

purpose of chromatography in photosynthesis

Answer 12

ideal technique for separating biologically active molecules

Question 13

what are chromatograms run on

Answer 13

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

Question 14

absorption spectrum of pigments are obtained by

Answer 14

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

Question 15

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

Answer 15

the chemical structure of the chlorophyll molecule

Question 16

how is light energy transformed to chemical energy

Answer 16

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

Question 17

action spectrum

Answer 17

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

Question 18

limiting factor for photosynthesis

Answer 18

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

Question 19

effect of carbon dioxide concetnration on photosynthesis

Answer 19

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

Question 20

effect of light intensity concentration on photosynthesis

Answer 20

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

Question 21

effect of temperature on photosynthesis

Answer 21

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

Question 22

what is FACE

Answer 22

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

Question 23

the two stages of photosynthesis are

Answer 23

light dependent reactions and light independent reactions

Question 24

light dependent reactions

Answer 24

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

Question 25

photophosphorylation

Answer 25

ATP being generated from ADP and Pw

Question 26

where do light dependent reactions occur

Answer 26

in the grana of chloroplast

Question 27

light independent reactions

Answer 27

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

Question 28

where do light independent reactions occur

Answer 28

in the stroma of the chloroplasts

Question 29

photosystems and where are they located

Answer 29

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

Question 30

what does each photosystem contain

Answer 30

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

Question 31

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

Answer 31

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

Question 32

what happens when light energy reaches a reaction centre

Answer 32

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

Question 33

LHC proteins

Answer 33

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

Question 34

what do the different types of pigments enable

Answer 34

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

Question 35

purpose of different pigments

Answer 35

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

Question 36

where do the photosystems electrons come from

Answer 36

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

Question 37

generation of oxygen by the photolysis of water in photosystems

Answer 37

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

Question 38

ATP production by chemiosmosis in thylakoids

Answer 38

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

Question 39

Reduction of NADP by Photosystem 1

Answer 39

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

Question 40

non cyclic photphosphorylation

Answer 40

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

Question 41

cyclic photophosphorylation

Answer 41

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

Question 42

what is the calvin cycle

Answer 42

the light independent reactions

Question 43

carbon fixation by rubisco

Answer 43

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

Question 44

synthesis of triose phosphate

Answer 44

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

Question 45

regeneration of Ribulose Biphosphate

Answer 45

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

Question 46

synthesis of carbon compounds

Answer 46

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

Question 47

interdependence of the light dependent and independent reactions

Answer 47

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

Question 48

what happens to photosynthesis reactions if there is no light

Answer 48

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

Question 49

what does carbon dioxide act as in photosynthesis

Answer 49

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

Question 50

what happens with the removal of hydrogen carbonate in photosynthesis?

Answer 50

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

Question 51

what happens with the removal of carbon dioxide in photosynthesis?

Answer 51

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