Photosynthesis 3
Today s topics:
• 
• 
• 
Review Light
reactions and Calvin
Cycle
Photorespiration and
the C-4 pathway
Light
Reactions
(energy
capture)
Start Cell Cycle and
Mitosis
Dark
Reactions
Oct 19, 2016
(energy utilization)
1
H 2O
CO2
LIGHT
NADP+
ADP
Light
Dependent
Reactions
Produce
LIGHT
REACTOR
RUBISCO is
Light enzyme
the
that fixes
carbon dioxide
CALVIN
CYCLE
H 2O
ATP
NADPH
STROMA
(Low H+ concentration)
LIGHT
REACTIONS
[CH2O] (sugar)
Photosystem II
Cytochrome
complex
O2
Photosystem I
NADP+
reductase
2 H+
To power
The
Calvin
Cycle
Phase 1:
Carbon
1: Carbon
fixation
fixation
Input
3 (Entering one
CO2 at a time)
CALVIN
CYCLE
ATP
NADPH
O2
Light
NADPH
And
ATP
CO2
NADP+
ADP
Fd
3
Rubisco
[CH2O] (sugar)
3 P
3 P
P
Short-lived
intermediate
P
Ribulose bisphosphate
(RuBP)
NADP+ + 2H+
P
6
3-Phosphoglycerate
6
Pq
Pc
1⁄
2
3
6 P
ATP
6 NADPH
2 H+
Phase 3:
Regeneration
6 NADP+
6 P
5
6
P
Glyceraldehyde-3-phosphate
(G3P)
ADP
1
H+
3
2:
Reduction
Phase 2:
Reduction
P
G3P
(a sugar)
Output
ATP
P
i
P
G3P
ATP
synthase
Thylakoid
membrane
P
1,3-Bisphosphoglycerate
O2
+2 H+
To
Calvin
cycle
STROMA
(Low H+ concentration)
CALVIN
CYCLE
3 ADP
2
H 2O
1
THYLAKOID SPACE
(High H+ concentration)
ATP
6 ADP
NADPH + H+
Glucose and
other organic
compounds
4
3-C Acid -COOH
5 sec
Calvin
Cycle
Melvin Calvin
Rubisco
3-C Sugar
-C=O
H
30 sec
Do Not Memorize!
5
6
1
Photorespiration
Glycolysis
Oxygen is a competing substrate for Rubisco
CO2
3 C Acid
3 C Acid
5 Carbons
Rubisco
2 C Acid
3 C Acid
Do Not Memorize!
O2
8
Solutions to the Oxygen Problem:
C4 Pathway
•  Division of Labor between Cells
•  C4 leaf Anatomy
•  Keep O2 and Rubisco separated
e.g. Corn
•  Rubisco (yellow
green) only in
bundle sheath
cells
9
CAM Plants
C4 pathway
PEP carboxylase
CO
CO
2
2
Oxaloacetate (4 C)
PEP (3 C)
NADPH
used
ADP
Malate (4 C)
ATP
Oxaloacetate (4 C)
NADPH
regenerated
In Mesophyll Cell
•  Produce
NADPH & ATP
•  Capture CO2
Pyruate (3 C)
CO2
Cyclic
e- flow
Little O2
In Bundle Sheath
Cell
•  Produce Sugar
(Calvin Cycle)
CALVIN
CYCLE
Sugar
10
NIGHT
•  CO2 Fixation PEP carboxylase
•  Accumulate malate in vacuole
•  Get energy from sugar oxidation
(NADH and ATP)
DAY
•  light reactions
•  mostly cyclic e- flow to produce
ATP (low O2)
•  decarboxylate malate to yield
CO2 and NADPH
•  Use C3 Calvin Cycle to
produce sugars and starch
12
Vein
11
2
Mitosis and the Cell Cycle
Compare C4 and CAM
Pineapple
Sugarcane
Sunlight
Powers
Both
phases
CO2
Mesophyll Cell
CO2
Organic acid
Organic acid
Night
Bundle-sheath cell
Spatial
separation
Sugar
Oxidation
Powers
One
Phase
Day
CALVIN
CYCLE
Temporal
separation
CALVIN
CYCLE
Sugar
.
Sugar
C4
13
CAM
14
Overview of Mitosis
G2 of Interphase
Chromatin
(duplicated)
Prophase
Early mitotic
spindle
Metaphase
Centromere
Prometaphase:
Nuclear envelope
breaks down.
Chromosomes
Prophase:
attach to spindle
Chromosomes begin to condense.
15
Spindle starts to form
Chromosome, consisting
of two sister chromatids
DNA replication during
Interphase
Overview of Mitosis
Prometaphase
Mitosis figure from your book
Anaphase
Metaphase
plate
Spindle
Centrosome at
one spindle pole
Metaphase:
Chromosomes align in
center of cell
Telophase and Cytokinesis
Cleavage
furrow
Daughter
chromosomes
Anaphase:
Sister chromatids separate
Telophase:
Complete set of
chromosomes
at each pole
16
Mitosis figure from your book
3
In-Text Art, Chapter 7, p. 135
Figure 7.5 The Phases of the
Eukaryotic Cell Cycle
Figure 7.7 Cytokinesis Differs
in Animal and Plant Cells
Cell Cycle
4