chapter 10 photosynthesis -...
TRANSCRIPT
The summary equation of photosynthesis including the
source and fate of the reactants and products.
How leaf and chloroplast anatomy relates to
photosynthesis.
How photosystems convert solar energy to chemical
energy.
How linear electron flow in the light reactions results in
the formation of ATP, NADPH, and O2.
How chemiosmosis generates ATP in the light reactions.
How the Calvin Cycle uses the energy molecules of the
light reactions to produce G3P.
The metabolic adaptations of C4 and CAM plants to arid,
dry regions.
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Chloroplasts
• _________________
• _________________
fluid-filled interior
• _________________
• _________________
Thylakoid membrane contains
• chlorophyll molecules
• electron transport chain
• ATP synthase
H+ gradient built up within
thylakoid sac
H+H+
H+
H+
H+H+
H+H+
H+H+
H+
outer membrane inner membrane
thylakoidgranum
stroma
thylakoid
chloroplast
ATP
Plants and other autotrophs are
producers of biosphere
____________________: use light E to
make organic molecules
____________________: consume organic
molecules from other organisms for E
and carbon
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Sites of Photosynthesis
• _______________: chloroplasts mainly found in these cells of leaf
• ____________: pores in leaf (CO2 enter/O2 exits)
• ____________: green pigment in _____________ membranes of chloroplasts
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6CO2 + 6H2O + Light Energy C6H12O6 + 6O2
____________ Reaction:
_______ is split ___ transferred with H+ to ____ sugar
Remember: OILRIG
Oxidation: lose e-
Reduction: gain e-
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Reactants:
Products:
6 CO2 12 H2O
C6H12O6 6 H2O 6 O2
Evidence that chloroplasts split water molecules
enabled researchers to track atoms through
photosynthesis (C.B. van Niel)
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Nature of sunlight
Light = Energy = ______________ radiation
__________ wavelength (λ): ____________ E
Visible light - detected by human eye
Light: reflected, transmitted or absorbed
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_______________________ like in cellular respiration
• proteins in organelle membrane
• __________________
______________
• proton (H+)
gradient across
inner membrane find the double membrane!
• ATP synthase
enzyme
H+H+
H+H+
H+H+
H+H+
H+H+
H+
H+H+
H+H+
H+H+
H+H+
H+H+
H+ATP
thylakoidchloroplast
Mitochondria transfer chemical energy from food molecules
into chemical energy of ATP
use electron carrier ___________
ETC of Respiration
generate H2O
ETC of Photosynthesis Chloroplasts transform light energy
into chemical energy of ATP
use electron carrier ___________
generate O2
moves the electrons
runs the pump
pumps the protons
builds the gradient
drives the flow of protons
through ATP synthase
bonds Pi to ADP
generates the ATP
… that evolution built
sunlight breakdown of C6H12O6
respirationphotosynthesis
H+
ADP + Pi
H+H+
H+
H+ H+
H+H+
H+
ATP
Chlorophylls & other pigments
• embedded in thylakoid membrane
• arranged in a “photosystem” collection of molecules
• structure-function relationship
How does thismolecular structurefit its function?
Pigments absorb different λ of light
chlorophyll – absorb violet-blue/red light,
reflect green
chlorophyll ___ (blue-green): light reaction,
converts solar to chemical E
chlorophyll ___ (yellow-green): conveys E to
chlorophyll a
_______________ (yellow, orange): photoprotection,
broaden color spectrum for photosynthesis
Types: xanthophyll (yellow) & carotenes (orange)
_______________ (red, purple, blue):
photoprotection, antioxidants19
1. Which color/wavelength of light provides the MOST energy to plants?
2. Why do most pigments have greater absorbance of shorter wavelengths of light
vs. longer wavelengths?
3. Why would a plant not have pigments to capture ALL wavelengths of light?
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4. Why do most plants appear green?
5. If a plant contained mostly carotenoids, what color would you expect
them to appear?
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Action Spectrum: plots rate of photosynthesis vs. wavelength
(absorption of chlorophylls a, b, & carotenoids combined)
Engelmann: used bacteria to measure rate of photosynthesis in algae; established action spectrum
Which wavelengths of light are most effective in driving photosynthesis?
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Photosystems of photosynthesis
• 2 photosystems in thylakoid membrane– collections of chlorophyll molecules
– act as light-gathering molecules
– _________________• __________________
• P680 = absorbs 680nm wavelength red light
– _________________• __________________
• P700 = absorbs 700nm wavelength red light
reaction
center
antenna
pigments
Summary:
1. Light energy splits ______ to _____
releasing high energy electrons (e-)
2. Movement of e- used to generate ______
3. Electrons end up on NADP+, reducing it
to ________________
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Two routes for electron flow:
A. __________ (noncyclic) electron flow
B. __________ electron flow
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1. Chlorophyll excited by light absorption
2. E passed to reaction center of
_______________(protein + chlorophyll __)
3. e- captured by _________________________
• Redox reaction e- transfer
• e- prevented from losing E (drop to
ground state)
4. ______is split to replace e- ___ formed
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5. e- passed to __________________ via ___
6. E transfer pumps ___ to thylakoid space
7. _____ produced by ___________________
8. e- moves from PS I’s primary electron
acceptor to 2nd ETC
9. NADP+ reduced to NADPH
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Proton motive force generated by:
(1) H+ from water
(2) H+ pumped across by cytochrome
(3) Removal of H+ from stroma when NADP+ is reduced
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Occurs in the ____________
Uses ____, ________, _______
Produces 3-C sugar ________
(glyceraldehyde-3-phosphate)
Three phases:
1. ___________ fixation
2. Reduction
3. Regeneration of _____ (CO2 acceptor)
38
Phase 1: 3 CO2 + ________ (5-C sugar ribulose bisphosphate)• Catalyzed by enzyme ______________ (RuBPcarboxylase)
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Alternative mechanisms of carbon fixation have evolved in hot, arid climates
Problem for C3 plants
• Hot or dry days
– _________________________________
– _______________
• gain H2O = stomates open
• lose H2O = stomates close
– adaptation to living on land, but…
creates PROBLEMS! 42
When stomates close…
xylem
(water)
phloem
(sugars)
H2OO2 CO2
CO2
O2
• Closed stomates lead to…
– ______build up from light reactions
– ______is depleted in Calvin cycle
• causes problems in Calvin Cycle
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Photorespiration
• Metabolic pathway which:
– Uses _____ & produces _____
– Uses ATP
– No ____________ production (rubisco binds ______ breakdown of RuBP)
• Occurs on hot, dry bright days when stomata close (conserve H2O)
• Why? Early atmosphere: low O2, high CO2?
Alternative mechanisms of carbon fixation have evolved in hot, arid climates
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Evolutionary Adaptations
1. Problem with C3 Plants:
– CO2 fixed to 3-C compound in Calvin cycle
– Ex. Rice, wheat, soybeans
– Hot, dry days:
» partially close stomata, _____CO2
» ____ Photorespiration
» ____photosynthetic output (no sugars made)
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Evolutionary Adaptations
2. C4 Plants:
– CO2 fixed to 4-C compound
– Ex. corn, sugarcane, grass
– Hot, dry days stomata close
– 2 cell types = ____________ & _________________cells
» mesophyll : _______________________fixes CO2 (4-C), pump CO2 to bundle sheath
» bundle sheath: CO2 used in Calvin cycle
– 2 stages of photosynthesis are _________________ separated
– ____photorespiration, ____sugar production
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3. CAM Plants:
• Crassulacean acid metabolism (CAM)
• NIGHT: stomata open CO2 enters converts to
________________, stored in ________________ cells
• DAY: stomata _______ light reactions supply ATP,
NADPH; CO2 released from organic acids for
Calvin cycle
• Ex. cacti, pineapples, succulent (H2O-storing)
plants
• 2 stages of photosynthesis are ___________________
separated
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C3 C4 CAM
C fixation &
Calvin together
C fixation &
Calvin in different
______
C fixation &
Calvin at different
_________
Rubisco PEP carboxylase Organic acid
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Photosynthesis
Light
Reaction
Light
ENERGY
______
split
organic
molecules
____
released
____
regenerate
________
photophosphorylation
ATP_____________
energized
electrons
Calvin
Cycle
________
______
fixed to
RuBP
C3
phosphorylated
and reduced
G3P
________
& other
carbs
stored in in which
involves both
Reduce
NADP+ to
using
in process
called
to form
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RESPIRATION PHOTOSYNTHESIS
Plants + Animals
Needs O2 and food
Produces CO2, H2O and
ATP, NADH
Occurs in mitochondria
membrane & matrix
Oxidative phosphorylation
Proton gradient across
membrane
Plants
Needs CO2, H2O, sunlight
Produces glucose, O2 and
ATP, NADPH
Occurs in chloroplast
thylakoid membrane &
stroma
Photorespiration
Proton gradient across
membrane
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