Autotrophs at work
So that heterotrophs
Can work
Light reactions
Power the dark reactions
And the rest of terrestrial
Life.
Carbon dioxide Levels are on the rise?!
0
N=5
-20
20
N=16
-40
N=20
N=16
N=22
Testing Conditions
at
he
W
an
s
So
y
be
ss
ra
G
C
or
n
Pl
an
ts
-60
N
o
Change iin
CO2 ppm
m/min/gra
am of see
ed
Measuring
g a Plant's Ability
y to Remove CO2 from the Air
per gram of seed planted
Stromal surface of thylakoid membrane
Calvin cycle (dark
Reactions)
Synthesize Hexose
sugars
From Carbon
dioxide
And water.
water
Anatomy of a chloroplast (~1 to 100/cell)
ATP and
NADPH
production
Sugar production
Stage 1 : Carbon Fixing!!!
Using Ribulose 1,5 bisphosphate carboxylase/oxidase
AKA Rubisco
Following Carbon in CO2
A “Pulse-Chase” experiment
Melvin Calvin’s experiments
Rubisco
The most
Abundant
Enzyme
On the
Planet!!!
Important active site
Amino acid
Lysine
y
201
Must bind another
CO2 to form a
“carbamate”
This allow Mg ion
To coordinate in
The active site!
This is not the
CO2 that is going
To be fixed.
Mg is important…without it, no
Catalysis
Catalysis.
This is the
CO2 to be
Fixed.
2 useful products
The desired
Products.
Here are the reactions
With the Mg ion
removed…just to see
Them better.
“Wasteful” photorespiration. This occurs when O2
andd not
o CO2 eenters
e s thee active
c ve site.
s e.
1 useful 3-PG
1 “wasteful”
Phosphoglycolate
Dealingg with
The problem
Requires
Peroxisome
And wastes
A CO2
C b !
Carbon!
Lose a CO2
The way things are supposed
To happen
Using 2 3-PGs to make hexose
Sugars.
Starch and sucrose
Useable forms
Of carbohydrates
Starch in chloroplast
Sucrose in the
Cytoplasm.
Key component
Thioredoxin
Controls enzymes
In sugar production
C4 plants “store” Carbon dioxide, spatially
CAM plants temporal storage
Temperature selection for “photorespiration”
photorespiration