Bio 178 Lecture 17 Photosynthesis Copyright: J. Elson-Riggins.
Lecture 15 Nov. 1, 2013 Photosynthesis
Transcript of Lecture 15 Nov. 1, 2013 Photosynthesis
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Learning outcomes:
Sequencingenergytransformations
Linkinglight energy to
electrical energy to chemicalenergy
Recognizewhy photosynthesisis notthe reverse of cellularrespiration
Metabolism: PhotosynthesisLecture outline:
Photosynthesis
--light reactions
--synthetic reactions
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glucose
+
high potential energy
low potential energy
oxidation
C-H O-H
High potential energy low potential energy
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glucose
+
high potential energy
low potential energy
Photosynthesis: a whole lot
tougher for the cell
reduction
C-H O-H
High potential energy low potential energy
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1. carbons (source: CO2)
2. Electrons (H ) to make bonds (source: water H2O)
3. Energy (source: sunlight)
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"light reactions" = energy (sunlight ATP and electrons/reducing power
source of low potentialenergy electrons
source of high potential
energy electrons
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synthesis reactions"
(occurs in light and dark)
ordered
disordered
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thylakoid
membranesgrana
(photons)
Visible
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light excites electrons
to outer orbitals ofatoms
low potential energy
high potential energy
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Oneelectron transport chain is used to provide electrons
to make reducing power
=NADPH
electron "hole"
Electron transport chains
grab excited electrons
before they fall back to
original orbital.
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The first electron hole is filled with electrons excited
from a 2nd photosystem using 2ndelectron
transport chain (chain just like mitochondrial chain).
electron "hole" filled
here
NADPH
NAD+
ox
red
chain 1
chain 2
ATP
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Electron transport chain 2 works the same way as in the
mitochondrion: electrochemical gradients and ATP
formation
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The route of electrons: H20 to NADPH (and then
into sugars)
NADPH
NAD+
oxidized
reduced
ATP
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synthesis reactions"
(occurs in light and dark)
Th C l i l CO d i
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The Calvin cycle CO2 made in
respiration now added
to carbons in Calvin
cycle
Melvin Calvin
1961 Nobel Prize
Th C l i l
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The Calvin cycle
electrons, originally inwater, but now in
NADPH = reducing
power, create sugar.
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A re ie of photos nthesis
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A review of photosynthesis
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Photosynthesis: trace atoms from reactants to
products, as we did for respiration
+Genergy
electrons H
You do this trace for the easier pathway:
glycolysis + cellular respiration
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Neil Young
Someone in the audience yells out: "Itall sounds the same!"
Neil Young responds:
"Its all one song!"
Real quotes from the CD "Year of
the Horse" 1997
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C-H O-H
Be certain you can explain what makes a bond (and
participating electrons) high or low potential energy.
Lecture 2 should provide assistance.
Low potential energyHigh potential energy