Photosynthesis 1 ! Exam booklet 2 3 4567 8 9 10 11 12 13 14 !
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Transcript of Photosynthesis 1 ! Exam booklet 2 3 4567 8 9 10 11 12 13 14 !
Photosynthesis
1 !
Exam booklet
2 3 4 5 6 78 9 1011121314!
Water is split into oxygenAnd hydrogen/ hydrogen ionsLight energy raises electrons to higher energy levelElectrons received by photosystem II
ATPProvides energy
Reduced NADP/ NADPHReduces GP/ passes H to GP
Electrons in chlorophyll/ photosystems are raised to higher energy level by lightElectrons pass along transfer chain
The energy is used to make ATP from ADP and PiElectrons (and H+) reduce NADPH+come from photolysis
They are used in the light independent stage/ Calvin cycleTo convert GP to TP
The reduced NADP supplies hydrogen atomsThe ATP supplies energy
Reduced by electronsFrom photolysis / chlorophyll
RuBP reacts with carbon dioxide to form 2 molecules of GP
Less is used to combine with carbon dioxide /Less used to form GP
Carbon dioxide is used in photosynthesis /Will allow detection of products
ATP and reduced NADP are not producedGP is not being used to form RuBP
Used in respiration/ formation of starch/ cellulose
Original / 100% reading – light meter reading
Oxygen produced / change in oxygen concentration in unit time
Oxygen is produced in light dependent reactionLight energy absorbed by chlorophyll/ excites electronsElectrons leave the chlorophyllPhotolysis of water occursElectrons replaced in chlorophyll
Red light leads to more photosynthesis / more oxygen produced with red light (compared to green light)
More red light absorbed (by chlorophyll)(Most) green light reflectedBacteria need oxygen to respire
Water is split using light energyIt provides electrons/ hydrogen ionsReplaces the electrons lost by chlorophyllProvides hydrogen ions for ATP production
It binds to chlorophyll moleculesPrevents the release/ absorption of electronsStops the movement of electrons down the first transport chainSo the breakdown of water reduces
Less ATP producedFor the Calvin cycle/ light independent reactionSo less sugar produced for respirationRate of reaction becomes greater than the rate of photosynthesis
Reduced NADP/ NADPH
2
Less GP formed
So less TP
Less RuBP regenerated/ made
Less CO2 taken up
High levels of oxygen reduce the rate of photosynthesis, effect greater at higher temperaturesHigher concentration means more effective competitor/ more RuBP reacts with oxygen
ATPReduced NADP / NADPH
O2 produced / CO2 taken up
To ensure a high rate of photosynthesis/ so that neither factor is limiting
More photosynthesis when the dark period increased from 3 to 17ms
Even though amount of light is the same
Products made in the light dependent system have been used up (in 17ms)
Few/no trees already presentSpecies X has high rate of photosynthesis at high light intensitiesSpecies X trees grow fastest at high light intensities X will outcompete Y/Z
Species X trees will provide shade / reduce light intensity
Species Z grows best/ more photosynthesis in low light intensity
High concentration of CO2 at night/ darknessNo photosynthesis in dark/ light required for light dependent stage
Plants respire [all the time]
In the light there is a net uptake of CO2 by plants/ rate of photosynthesis is higher than rate of respiration
Decrease in CO2 concentration with height
At ground level less light/ less photosynthesis
Carbon dioxide combines with ribulose bisphosphate/ RuBP
To produce two molecules of glycerate 3-phosphate/ GP
GP is reduced to TPWhich requires reduced NADP/NADPHAnd energy from ATP
242 = 5761 576 = 0.0017 0.001
7
Radius/ diameter of the capillary tube
Bubble in CO2
Add(dissolved) hydrogen carbonate
Oxygen used in respiration
Oxygen would dissolve in the water
Oxygen may leak from the apparatus
May remain as bubble in leaf air spaces
Nitrogen present in the air in the leaf/Will leave leaf with the oxygen/May come out of solutionLevel higher than expected/
normal/ in atmospherePlant is respiring/ produces CO2
CO2 has been added to the water/ present in excessComes out of solution
Intensity:less/lower light intensity in
deep waterpigments can absorb what
light there isWavelength:
not all wavelengths of light can penetrate/ mainly short wavelengths/ mostly blue light penetrates
pigments can absorb these wavelengths
Light intensity
Some other factor is now limiting the ratee.g. carbon dioxide concentration or temperature
1
Rate increases when temperature increases from 15OC to 25OCRate increases when carbon dioxide concentration increases from 0.04% to 0.4%
Enzymes will (start to) denatureE.g. rubiscoActive site will change shape Less photolysisLess ATP producedNamed step in Calvin cycle affected
Increased rate of transpirationStomata will closeLess carbon dioxide taken in
Less reflection of lightMore light absorbedMore wavelengths of light absorbedMore ATP / reduced NADP producedTemperature of leaf will increaseEnzymes work more eff ectivelyReduces limiting eff ect of light intensity / temperature
As a controlTo show that light is producing the effect
Cut discs the same sizeTo give same surface area
Cut discs from same/similar part of leafTo give same amount of chloroplasts
Carry out at same temperatureTemperature affects enzyme action/structure
Carry out repeatsTo calculate means/identify anomalous results
Place lamp same distance from tubesTo give same light intensity
Use filters of same thicknessTo give same light intensity
Carry out in darkened roomTo ensure only one wavelength of light
Give CO2 in excessSo that CO2 is not a limiting factor
Use same volume/concentration of indicatorSo that colour changes can be compared
Put heat sink between lamp and tubesTo minimise temperature changes
Chlorophyll a
Chlorophyll reflects/does not absorb green lightLittle/no photosynthesis/light dependent reaction
Little/no photolysis/ splitting of waterLittle/no CO2 taken up
Some CO2 produced in respirationCO2 increases acidity/ lowers pH
Photosynthesis is controlled by enzymes
Optimum temperature can be controlled withheaters/ ventilation/air conditioningCO2 can be increased by
burning gas/paraffin CO2 will not be a limiting factor/ Calvin cyclewill increase
Obtaining individual organelles
Chlorophyll aChlorophyll bCarotene
XanthophyllFucoxanthin
From waterWater is split in photolysisLinked to photosystem 2
Reduced NADP/ NADPH
Chloroplasts retain biochemical activityPrevent activity of (lysosome) enzymesPrevent membrane/protein damageBuffer keeps pH constantNo (net) water movement/ osmosisSo no change in volume/ turgidity of chloroplasts
bluegreen
Boiled suspension:enzymes denaturedchange in tertiary
structure/ active siteno photolysisno hydrogen releasedDCPIP remains blue/
oxidisedphotosystems damaged by
heat
The End!!!!!