Catalyst

Could humans survive without plants? Why, if at all, are
plants important?
Cell Parts: Chloroplast

Photosynthesis: occurs only in plants (not animals!)

6CO2
+
6H2O
(carbon dioxide)
(water)
absorb
through leaves
from roots
+
light
(energy)
C6H12O6

+
(glucose sugar)
from sun stored in plant; for plant
use or animal use with
cellular respiration
Image Source: http://upload.wikimedia.org/wikipedia/commons/1/11/Chloroplast-new.jpg
6O2
(oxygen)
released
from leaves

Chloroplast: capture light energy; make food energy
Cell Parts: Chloroplast

Thylakoid: flattened discs containing chlorophyll

Granum (pl. Grana): stack of thylakoids

Stroma: fluid inside chloroplast (similar to a cell’s cytoplasm)

Lamella: links thylakoids in grana together

Lumen: inside of the thylakoid
Image Source: http://upload.wikimedia.org/wikipedia/commons/1/11/Chloroplast-new.jpg
Cell Parts: Chloroplast


Chlorophyll: pigment in chloroplasts that absorbs light
Review:Visible Light Spectrum
Violet Indigo Blue Green Yellow Orange Red
“VIB G YOR” (or “ROY G BIV”)
Cell Parts: Chloroplast

The color you see is the color that is reflected
Reflects: RED
R
O
Y
G
Absorbs: OTHER COLORS
B
I
V

We See: RED
Chlorophyll reflects green; absorbs ROYBIV!
Light energy the plant uses!!!!
Cell Parts: Chloroplast


Phase I: Light-Dependent Reactions
Phase 2: Light-Independent Reactions / Calvin Cycle
Image Source: bioweb.uwlax.edu
Cell Parts: Chloroplast

Phase 1: Light-Dependent Reactions


Occurs at thylakoid membrane (Lumen Stroma)
Requires light (dependent)
Cell Parts: Chloroplast

Phase I: Light-Dependent Reactions
Another e- carrier
(like NAD+, FAD)
STROMA
Light
H+
H+
NADP+
Light
4H+
NADPH
e-
ATP
ADP
P
Photosystem II
e-
Thylakoid
Membrane
Ferrodoxin
Photosystem I
H+
H2
O
e-
2H+
½O
2
H+
H+
H+
H+
LUMEN
ATP Synthase
(enzyme/protein)
Cell Parts: Chloroplast

Phase 1: Light-Dependent Reactions

Another e- carrier
(like NAD+, FAD)
Mini-Steps:
1.
Photosystem II absorbs light energy to spilt
STROMA
water into: oxygen, H+s in lumen, & activated
Light
H
H
NADP+
+
+
Light
4
H
+
e- that enters the ETC.
e
-
2.
Electron Transport Chain – e-s move through
Photosystem II
Photosystem I absorbs light energy and reenergizes e-, which moves to ferrodoxin
ADP
P
membrane to pump H+s into lumen.
3.
A
TP
NADPH
e
-
Ferrodoxin
Thylakoid
Membrane
Photosystem I
(protein) to form NADPH.
4.
H+s
accumulate in lumen to create a gradient
e
+
H
+
H
+
thylakoid membrane through ATP Synthase,
ADP is converted into ATP.
+
H
2H
ATP Synthesis – As H+s move across
H
+
H2
O
-
(high [H+] in lumen, low [H+] in stroma).
5.
H
+
½
O2
Chemiosmosis
LUMEN
ATP Synthase
(enzyme/protein)
Cell Parts: Chloroplast

Phase 2: Calvin Cycle / Light-Independent Reactions



In stroma
Doesn’t directly require light energy (independent)
ATP & NADPH = energy, but not stable  converted to glucose sugar.
Cell Parts: Chloroplast

Phase 2: Calvin Cycle
6
6
CO2
(3-phosphoglyceric
acid)
ribulose 1,5-bisphosphate
C
C
C
C
C
12
3-PGA
C
C
6 ADP
6 ATP
6
Transported from
chloroplast to make glucose,
fructose, starch, etc.
(carbohydrates / sugars)
C
C
C
C
12 ATP
Calvin Cycle
ribulose 5-phosphate
12 ADP
C
12 NADPH
Rubisco
2
12 NADP+
G3P
12
C
C
C
C
C
G3P
C
C
(glyceraldehyde
3-phosphate)
Cell Parts: Chloroplast

Phase 2: Calvin Cycle

Mini-Steps:
1.
2.
3.
4.
Carbon Fixation: Carbon dioxide
joins a five-carbon molecule to make
twice as many three-carbon
molecules.
ATP & NADPH turn 3-PGA into
G3P (a high energy molecule). ATP
supplies phosphate groups; NADPH
supplies H+s and e-s.
Two G3P molecules leave to make
glucose & other carbohydrates.
Rubisco (enzyme/protein) converts
remaining ten G3P molecules into
five-carbon molecules to be used in
carbon fixation.
6
6
CO2
(3-phosphoglyceric
acid)
ribulose 1,5-bisphosphate
C
C
C
C
C
12
3-PGA
C
C
6 ADP
6 ATP
6
C
C
C
C
12 ATP
Calvin Cycle
ribulose 5-phosphate
C
12 ADP
C
12 NADPH
Rubisco
2
12 NADP+
G3P
12
C
C
G3P
(glyceraldehyde 3phosphate)
C
C
C
C
Cell Parts: Chloroplast

Phase I: Light-Dependent Reactions
water: H+s, oxygen, &

e-.

Photosystem II uses light to split

ETC: e- pumps H+s into lumen.

Photosystem I re-energizes e- with light: forms NADPH.

H+s in lumen create a concentration gradient.

H+s move across thylakoid membrane through ATP Synthase:
converts ADP into ATP
Phase 2: Light-Independent Reactions /
Calvin Cycle

CO2 molecules join with 5-carbon
molecules to make 3-PGA molecules.

NADPH and ATP from Light-Dependent
Reactions turn 3-PGA into G3P.

Two G3P molecules leave the Calvin Cycle
to form glucose & other carbohydrates.

Remaining G3P molecules converted by
Rubisco into 5-carbon molecules that
restart the cycle.
Image Source: bioweb.uwlax.edu