AP ? Of the Day

1.
2.
3.
4.
Which of the following has the least
amount of stored energy per molecule?
ATP
Pyruvic Acid
NADH
CO2
Think about their relationships

An ATP molecule contains less energy than an NADH
because 1 NADH supports the synthesis of 3 ATP during
electron transport.

NADH contains less free energy than pyruvate, because
the oxidation of pyruvate
produces 4 NADH (plus 1 FADH2 and 1 ATP).

Carbon dioxide contains the lowest amount of free
energy in this list,
because it has only 1 carbon atom, and the others all
have more than 1.
Today…
Notes on the Calvin Cycle
 Finish POGIL
 Pre-lab, design your experiment for
Friday/Monday

Photosynthesis II
Dark Reactions
or more appropriately,
Light Independent Rxns.
AKA – Calvin Cycle.
I love science.
Recap. . .
H2O + CO2 + Light  glucose + O2
 Light reactions  thylakoid membrane
 Produce ATP & NADPH
 What for?
 To power Calvin Cycle
 How produce ATP?
 chemiosmosis

Light Independent Rxn
Calvin Cycle
Where?
 Stroma
 Use ATP & NADPH from light reactions
 What is left in the equation?
 CO2
 Purpose: produce glucose

Calvin Cycle



Carbon Fixation
 Add 3CO2 to 3
RuBP (5C)
molecules  6
PGA (3C)
Reverse of
glycolysis
 Add 6 ATP & 6
NADPH reduce
PGA into 6 G3P
(3C) (G3P)
molecules
 1 G3P molecule
leaves 
glucose
Reform RuBP
 Change G3P 
RuBP by adding
3 ATP
 G3P (3C) 
RuBP (5C)
(starts cycle)
Photorespiration
In the presence of O2, Rubisco (enzyme)
releases CO2
 Undoes the Calvin cycle
 20% of fixed carbon is lost to
photorespiration
 As temp increases more photorespiration
occurs
 C3 vs C4 vs CAM

C4 Photosynthesis
Use PEP carboxylase instead of Rubisco
 NO PHOTORESPIRATION
 C4 molecule is modified & releases a CO2
 This CO2 is captured by Rubisco  Calvin
cycle
 Adaptation for plants in warmer climates

C4 Pathway




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C4 photosynthesis in
mesophyll cells
Calvin Cycle in bundle
sheath cells
Creates high local levels
of CO2 for rubisco in the
Calvin cycle
Oxaloacetate maltate
 bundle sheath cell
Releases a CO2  Calvin
cycle (pyruvate)
CAM Pathway

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
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Crassulacean Acid
Succulent plants
Stomata open at night &
closed in day
Reverse of most plants
Fix CO2 using C4
pathway
Fixed & stored at night 
decarboxylized during
day
High CO2 drives the
Calvin cycle & reduces
photorespiration
Comparison of C4 & CAM
Photosynthesis