Bio 2010_autotrophic Nutrition Notes

7/21/2019 Bio 2010_autotrophic Nutrition Notes

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The Chemistry of

Photosynthesis


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Learners Outcomes

Describe the full process of photosynthesis with

reference to the full equation for photosynthesis.

Describe the light-dependent reaction of photosynthesisas involving only water and light, and producing oxygengas and the energy molecules ATP and NADPH (in

simple terms).

Describe the light-independent reaction ofphotosynthesis as involving the products of the light-

dependent reaction (ATP and NADPH) converting

carbon dioxide to glucose (in simple terms).


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Learners Outcome

Explain that ATP is an energy carrier in cellsbecause it has high-energy phosphate bonds that

release energy when broken.

Show that the rate of photosynthesis is dependent

on various factors

Explain the effect of changes in temperature, lightintensity, wavelength, carbon dioxide and oxygen

concentration on the rate of photosynthesis.


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Where does

photosynthesishappen?


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!"#$%%&&&'()*#+,-./0'1,2%#!,3,45/%1!+,-,#+643'!32+


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!"#$%%&&&'()*#+,-./0'1,2%#!,3,45/%1!+,-,#+643'!32+89:;


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The chloroplast is the main site for photosynthesis


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Thylakoids- where light reaction of

photosynthesis occurs

Stroma- where light independent

reaction occurs


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EFG

=)C 6/C D+H) +.0!3 6D4,-D)C D5 1!+,-,#!5++


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Photosynthesis occurs in 2 stages

Light dependent stage

Light independent stage


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Light dependent reaction

!12 H2O + 12NADP + 18ADP + 18Pi+ light and

chlorophyll

+

6 O2+ 12 NADPH + 18 ATP


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Light reaction

!Occurs in thylakoids

!Chlorophyll molecule captures light energy

!Excited electron causes water to split into

hydrogen and oxygen

!High energy molecules - ATPand NADPH

produced


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P700

P680

Photon hits, excited

electrons picked up by

reaction center

PS II splits water into !O2

and 2 electrons. These

electrons replaces those

going to PSI.

ATP produced as protons

move thru ATP synthetase

complexes

Meanwhile, photons hit

P700 complex and excited

electrons are picked up by

ETC of PSI.

PSI ETC produces NADPH

and H+


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What is ATP?

Adenosine Triphosphate

High energy molecule

Energy found in the bondsbetween the phosphate ionsand adenosine

Bond broken = energyreleased

Bond formed = energy

required

2


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The Calvin Cycle (Dark Reactions)

!A.k.a light-independent reactions

!Occurs in stroma.

! 12NADPH + 18ATP + 6CO2=> Glucose +

12NADP++ 18ADP + 18Pi +O2

!Fixes CO2to produce glucose.


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Factors Affecting Photosynthesis

!Carbon dioxide concentration

!Water

!Light intensity

!Chlorophyll levels


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Graph of Rate of Photosynthesis against Light

Intensity

!As light intensity increases, rate

of photosynthesis increases.

! There is a limit to the maximum

rate (saturation point).

!At the saturation point, the rate

of photosynthesis cannot

increase due to the presence of

a limiting factor.

!

Only by increasing the limitingfactor can the rate increase.

Rate of

Photosynthesis

Light Intensity


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Observe how a change in the CO2concentration

affects the graphs


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Practice Time!

!Draw a graph of rate of photosynthesis against

light intensity.

!Label this graph as one showing the graph attemperature T.

!Now draw on the same axes another graph, but

this time at temperature T+10.


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Photosynthesis and Temperature

!Did it look like this?

!Note the circled regions of A and B.

!Do you know the significance of the trendsshown at A and B?


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Factors affecting

photosynthesis


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Uses of Glucose

Triose phosphates and glucose are used as a material to

build most other biomolecules (these are products from

photosynthesis)

Disaccharides

Cellulose

Starch

Amino acids

Lipids


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Bio 2010_autotrophic Nutrition Notes

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