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How Cells Acquire Energy Chapter 6
____________-
– Carbon source is _______________
– Energy source is ___________
_______________
– Get carbon and energy by eating
__________ or _______________
Carbon and Energy Sources
Plants, some bacteria, many protistans
T.E. Englemann’s Experiment
Background – Certain bacterial cells will move
toward places where oxygen concentration is high– Photosynthesis produces oxygen
Hypothesis– Movement of bacteria can be used to determine
optimal light wavelengths for photosynthesis
Method– Algal strand placed on microscope slide and
illuminated by light of varying wavelengths– Oxygen-requiring bacteria placed on same slide
Results • Bacteria congregated where red
and violet wavelengths illuminated alga
ConclusionBacteria moved to most effective light
for photosynthesis
Linked Processes______________
• Energy-storing pathway
• Releases _______• Requires ______
________
_______________• Energy-releasing
pathway• Requires _______• Releases carbon
dioxide
____ + _____ ___ + _____ + _____water carbon
dioxideoxygen glucose water
LIGHT ENERGY
Visible Light • Wavelengths humans perceive as
different ______
• Violet (___ nm) to red (____ nm)
• Longer wavelengths, lower energy
Of the energy that reaches Earth’s surface, about ___ is intercepted by photoautotrophs
shortest longest
Photons• Packets of ______ energy• Photons with most energy travel as ________
wavelength (blue-green light)
• Light-absorbing ________
• Absorb some wavelengths and ________ others
• Color you see are the wavelengths ___ absorbed
Wavelength (nanometers)
chlorophyll b
chlorophyll a
Pigments
Plants contain 4 main pigments • _______________- reflect green- most common• ___________- reflect red/yellow
– Includes xanthophiles and carotenes• ______________- give flowers their colors• __________- in red algae
2 Photosystems and Electron Transporterswater-splitting complex thylakoid
compartment
H2O 2H + 1/2O2
P680
acceptor
P700
acceptor
pool of electron
transporters
stromaPHOTOSYSTEM II
PHOTOSYSTEM I
•In bacteria- pigments are in ____________
•In plants- pigments are in _________ _____________ of chloroplasts
Two _______ of Photosynthesissunlight water uptake carbon dioxide uptake
ATP
ADP + Pi
NADPH
NADP+
glucoseP
oxygen release
2. _______ ______-_______
1. ________________-_________
new water• Pigments absorb ____ energy
• _____split
• ___ and _____ formed
• _______ released
•CO2 converted to _____•Can proceed in the _____•___________ cycle
reaction center (a specialized chlorophyll a molecule)
….but all energy is funneled into ______ _______
Many _______ capture energy…
Then an electron is sent to the ________
1. LIGHT DEPENDENT-REACTIONS
In ET system, ATP is produced
ATP
electron acceptor electron transport system
e–
e–
e–
e–
1. LIGHT DEPENDENT-REACTIONS
photolysis
H2O
NADP+ NADPH
e–
ATP
ATP SYNTHASE
PHOTOSYSTEM IPHOTOSYSTEM II ADP + Pi
e–
In ET system:
• two photosystems: ______ and ______
End result- • _______regenerated• ____ is concentrated inside• _____ made when H+ is moved across membrane
1. LIGHT DEPENDENT-REACTIONS
Calvin- Benson Cycle
CARBON FIXATION
6 CO2 (from the air)
6 6RuBP
PGA
unstable intermediate
6 ADP
6
12
12ATP
ATP
NADPH
10
12PGAL
glucoseP
PGAL2
Pi
12 ADP12 Pi
12NADP+
12
4 Pi
PGAL
CO2 _________
ATP ______
NADPH ________
P-glucose
_______ _______
• The _______ are not only the major route for gas exchange (CO2 in and O2 out), but also for the evaporative loss of _______.
• On hot, dry days plants close the stomata to conserve water, but this causes problems for photosynthesis.
Alternative mechanisms of carbon fixation have evolved in hot, arid climates
•____________- fix ___ (Not CO2)
•But photorespiration can drain away as much as _____ of the carbon fixed by the Calvin cycle
Solution # 1
C3 plants-
CO2
in mesophyll cell, cell carbon fixation
in bundle-sheath cell, carbon fixed again
more CO2in leaf, no photorespiration
CALVIN-BENSONCYCLE
oxaloacetate
__________ ___________
CO2
CALVIN-BENSONCYCLE
In mesophyll cell, stomata open at night; CO2 uptake but no water loss
Stomata close during day; CO2
that accumulated in leaf overnight is used
Solution # 2 Solution # 3
Fix CO2 as other ____________, then use as needed
Fix CO2 as other molecules at _____, then use during ____
e.g. pineapplee.g. sugarcane
Summary of Photosynthesislight
6O212H2O
CALVIN-BENSON CYCLE
C6H12O6
(phosphorylated glucose)
NADPHNADP+ATPADP + Pi
PGA PGAL
RuBP
P
6CO2
end product (e.g. sucrose, starch, cellulose)
LIGHT-DEPENDENT REACTIONS