Photosynthesis 5

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Supramolecular Chemistry, UAF, 2005

PhotosynthesisPhotosynthesis

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PhotosynthesisPhotosynthesis

Where does the energy come from that sustains all life?

The Sun!!Well most of it anyway


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Respiration vs. PhotosynthesisRespiration vs. Photosynthesis

Photosynthesis and respiration as complementary processes in the liing world!

Photosynthesisuses the energy of sunlight to produce sugars and other organic

molecules! "hese molecules in turn sere as food! #espirationis a process that uses

$2and forms %$2from the same car&on atoms that had &een ta'en up as %$2and

conerted into sugars &y photosynthesis! (n respiration, organisms o&tain the energy

that they need to surie! Photosynthesis preceded respiration on the earth for pro&a&ly

&illions of years &efore enough $2was released to create an atmosphere rich in o)ygen!

*"he earth+s atmosphere presently contains 20 $2!-


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Cellular Respiration -vs- PhotosynthesisCellular Respiration -vs- Photosynthesis

Exergonic and endergonicreactions of metabolismExergonic:

C6H12O6+ 6O26CO2+ 6H2O G = -686 cal!mole

Cell"lar res#iration$

Endergonic:

6CO2+ 6H2OC6H12O6+ 6O2G = +686 cal!mole

%&otos'nt&esis$

%ro(ides t&e energ' to r"n cell #rocesses

)llo*s #lants to mae energ' ric& s"gars from

energ' #oor molec"les


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Overview of PhotosynthesisOverview of Photosynthesis

.%$2/ 212$ %.12$./ .$2/ .12$ 3 / .4. 'calmol

6 Photosynthesis, li'e cellular respiration, is a series of redo) reactions7

What is &eing o)idi8ed and what is &eing reduced in the

summari8ing e9uation a&oe?


7/25Supramolecular Chemistry, UAF, 2005

:arly thin'ing; $2released came from the %$2

%$2% / $2

% / 12$%12$

sugar

Water was added to the

car&on to ma'e sugar

an



:)periment @

H218O

CO2CO2

CO2

CO2

CO2

CO2

CO2

H2O

C18O2

C18O2

C18

O2 C18O2C18O2

C18O2C18O2

:)periment @2

1818Oxyen Heavy Oxyen" #sotope $xperi%ent&Oxyen Heavy Oxyen" #sotope $xperi%ent&



1818O #sotope $xperi%entO #sotope $xperi%ent

.%$2/ 212$ %.12$./ .$2/ .12$

%4$2

1ypothesis; (f %$2is &eing o)idi8ed

124$

18O%an you predict where the heay o)ygen will end

up in each case?

.%$2/ 212$ %.12$./ .$2/ .12$

18O



.%$2/ 212$ %.12$./ .$2/ .12$

%4$2

Hypothesis: (f 12$ is &eing o)idi8ed

124$

4$%an you predict where the heay o)ygen will end

up in each case?

.%$2/ 212$ %.12$./ .$2/ .12$

4$

1818O #sotope $xperi%entO #sotope $xperi%ent



.%$2/ 212$ %.12$./ .$2/ .12$

%4$2

124$

4$

.%$2/ 212$ %.12$./ .$2/ .12$

4$

The 'ctual Results!!The 'ctual Results!!

o,,its t&e *ater t&ats being oxidi.ed$



6 CO2 12 H2O/eactants

%rod"cts C6H12O6 6H2O 6O2

Trac(in 'to%s in Photosynthesis&Trac(in 'to%s in Photosynthesis&



)hat *oes this suest a+out photosynthesis,)hat *oes this suest a+out photosynthesis,

6CO2+ 12H2O

C6H12O6+ 6O2+ 6H2O

"he sugars that result from photosynthesis are produced &y adding

the hydrogen ions and electrons from water to car&on dio)ide,



internal leaf structure

chloroplastsouter mem&rane

inner mem&rane

thyla'oid

Plant PhotosynthesisPlant Photosynthesis



The staes of photosynthesis&The staes of photosynthesis&

Light DependentReactions

6$ccurs along the thyla'oid

mem&rane

6this is where 12$ is o)idi8ed!

6chemiosmotic production of

A"P7

6electron carrier *



Light Independent Reactions

6$ccurs in the stroma of the

chloroplast!

6Where %$2is Bfi)edC into

sugars7

The staes of photosynthesis&The staes of photosynthesis&



How plants harness enery fro% sunliht&How plants harness enery fro% sunliht&

%&otos'nt&etic #igments

C&loro#&'lls a 0 t&e main#&otos'nt&etic #igment

C&loro#&'ll b

)ccessor' #igments,,

Carotenoids



Photosynthetic pi%ents are arrane* asPhotosynthetic pi%ents are arrane* asphotosyste%sphotosyste%s



What waelengths of light do

you thin' plants use the least

in photosynthesis?



Photosyste%s use so%e wavelenths of liht +utPhotosyste%s use so%e wavelenths of liht +utreflect others&reflect others&



Dight 1aresting Pigments

#eaction %enter

Photon

Photosyste%Photosyste%

From the Photosystem, e>are passed along an :lectron "ransport

%hain!!

The Photosynthetic Electron Transport Chain (PETC)


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P$TCPhoton

Photosyste%Photosyste%


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Photosynthetic $lectron Transfer Chain P$TC"Photosynthetic $lectron Transfer Chain P$TC"

6 series of electron carriers

which ta'e electrons from

photosystem, and!!

6 ultimately carry electrons to


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Photosyste%sPhotosyste%s

6 :)periments in the E0=s suggested that light photons are

a&sor&ed at 2 different points along the same P:"%!

6 (n fact, there are two Photosystems in operation

Photosynthesis 5

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