Photosynthesis

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Exam booklet

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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

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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

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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

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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!!!!!