Transcript You Light Up My Life

How Cells Acquire Energy
Chapter 6
Carbon and Energy Sources
____________-
Plants, some bacteria, many protistans
– Carbon source is _______________
– Energy source is ___________
_______________
– Get carbon and energy by eating
__________ or _______________
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
Conclusion
Bacteria moved to most effective light
for photosynthesis
Linked Processes
______________
• Energy-storing
pathway
• Releases _______
• Requires ______
________
_______________
• Energy-releasing
pathway
• Requires _______
• Releases carbon
dioxide
LIGHT ENERGY
____ + _____
water
carbon
dioxide
___ + _____ + _____
oxygen
glucose
water
Visible Light
• Wavelengths humans perceive as
different ______
• Violet (___ nm) to red (____ nm)
• Longer wavelengths, lower energy
shortest
longest
Of the energy that reaches Earth’s surface, about
___ is intercepted by photoautotrophs
Photons
• Packets of ______ energy
• Photons with most energy travel as ________
wavelength (blue-green light)
Pigments
• Light-absorbing ________
• Absorb some wavelengths
and ________ others
• Color you see are the
wavelengths ___
absorbed
chlorophyll a
chlorophyll b
Wavelength (nanometers)
Plants contain 4 main pigments
• _______________- reflect green- most
common
• ___________- reflect red/yellow
– Includes xanthophiles and carotenes
• ______________- give flowers their colors
• __________- in red algae
•In bacteria- pigments are in ____________
•In plants- pigments are in _________
_____________ of chloroplasts
2 Photosystems and Electron Transporters
water-splitting complex
H2O
thylakoid
compartment
2H + 1/2O2
P680
P700
acceptor
acceptor
PHOTOSYSTEM II
pool of
electron
transporters
stroma
PHOTOSYSTEM I
Two _______ of Photosynthesis
sunlight
water uptake
carbon dioxide uptake
ATP
1. ________
_________________
ADP + Pi
2. _______
_____________
NADPH
NADP+
P
• Pigments absorb ____ energy
oxygen release
• _____split
• ___ and _____ formed
• _______ released
glucose
•CO2 converted tonew
_____
water
•Can proceed in the _____
•___________ cycle
1. LIGHT DEPENDENT-REACTIONS
Many _______
capture energy…
….but all energy is
funneled into ______
_______
reaction center
(a specialized chlorophyll a molecule)
Then an electron is sent to the ________
1. LIGHT DEPENDENT-REACTIONS
In ET system, ATP is produced
electron acceptor
e–
electron
transport
system
e–
e–
ATP
e–
In ET system:
1. LIGHT DEPENDENT-REACTIONS
• two photosystems: ______ and ______
H2O
photolysis
e–
e–
NADP+
PHOTOSYSTEM II
PHOTOSYSTEM I
ATP SYNTHASE
NADPH
ADP
+ Pi
End result• _______regenerated
• ____ is concentrated inside
• _____ made when H+ is moved across membrane
ATP
6
CalvinBenson Cycle
CO2
ATP
NADPH
_________
______
________
CO2 (from the air)
CARBON
FIXATION
6
6
RuBP unstable intermediate
12
PGA
6 ADP
6
12 ATP
ATP
12 NADPH
4 Pi
P-glucose
12 ADP
12 Pi
12NADP+
10
PGAL
12
PGAL
2
PGAL
_______
_______
Pi
P
glucose
Alternative mechanisms of carbon fixation
have evolved in hot, arid climates
• 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.
Solution # 1
C3 plants-
•____________- fix ___ (Not CO2)
•But photorespiration can drain away as much as
_____ of the carbon fixed by the Calvin cycle
Solution # 2
Solution # 3
__________
CO2
___________
e.g. pineapple
e.g. sugarcane
CO2
In mesophyll cell,
stomata open at
night; CO2 uptake
but no water loss
in mesophyll cell,
oxaloacetate
cell carbon fixation
CALVINBENSON
CYCLE
in bundle-sheath
cell, carbon fixed
again
more CO2in leaf, no
photorespiration
Fix CO2 as other
____________, then
use as needed
CALVINBENSON
CYCLE
Stomata close
during day; CO2
that accumulated
in leaf overnight
is used
Fix CO2 as other
molecules at _____,
then use during ____
Summary of Photosynthesis
light
12H2O
LIGHT-DEPENDENT
REACTIONS
2
ADP + ATP
Pi
6CO2
6O
NADP+ NADPH
PGA CALVIN- PGAL
BENSON
CYCLE
RuBP
P
C6H12O
6
(phosphorylated
glucose)
end product (e.g. sucrose, starch, cellulose)