Transcript Photosynthesis Acquiring Energy From Light

Photosynthesis
Acquiring Energy From Light
What is Photosynthesis? Click me
•Photosynthesis is a two stage process by which Light,
Water and Carbon dioxide are used to make high energy
compounds Glucose (carbohydrates).
PHOTOSYNTHESIS:
Chemical equation:
Reactants (needed)
12H2O +6CO2
Simplified:
6H2O + 6CO2


Products (what is produced)
C6H12O6 + 6O2 + 6H2O
[C6H12O6] + 6O2
sunlight energy-
Light energy
SUN
H20
Light
Chemical energy
ATP, NADPH
Light- Dependent Reactions
(photophosphorylation)
ATP,
NADPH
CO2
“chemical energy”
SUGARS
(C6H1206)
Light- Independent Reactions
(Calvin Cycle)
O2
“chemical energy”
C6H12 O6
Figure 8-7 Photosynthesis: An Overview
6H2O + 6CO2 ---sunlight energy-- C6H12O6 + 6O2
Light
6H
2O
Light
CO2
6CO2
NADPH+
NADP+
ADP
+P
ADP+P
LightDependent
Reactions
Light
Dependent
Reactions
3O2
Calvin
Cycle
LightATP
ATP
NADPH
NADPH
Independent
Reactions
Calvin Cycle
Sugars
C6H12O6
Chloroplast
Chloroplast
Where Do These Reactions Take
Place?
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Chloroplast
Occurs in the chloroplast of plant
and other autotrophs
Thylakoid
membranes
Photosynthesis starts in the (thylakoid membrane
system) of the chloroplasts
Light Dependent Reaction
The Making of Chemical Energy: PHOTOPHOSPHORYLATION
Light energy is used to split water molecules (PHOTO)
6 Water molecules are split into atoms of Hydrogen and atoms of
Oxygen
Step 1-photolysis (click me)
6 H2O
12 H and 6 O2
Oxygen (O2) is by product in this reaction
Step 2-phosphorylation
H+ (hydrogen ions) from water are used to generate
“Chemical energy” in the form of ATP and NADPH
ADP  ATP
NADP+ + HNADPH
Figure 8-10 Light-Dependent Reactions
Section 8-3
Chloroplast
Photosystem II
Hydrogen
Ion Movement
ATP synthase
Inner
Thylakoid
Space
The products of the light
dependent reaction:
Oxygen, ATP
Thylakoid
Membrane
Stroma
Electron
Transport Chain
Photosystem I
ATP Formation
The Role of Chlorophyll
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• Light trapping pigment Chlorophyll is required for photosynthesis
• Chlorophyll absorbs all light energy EXCEPT GREEN, green
wavelengths are reflected, this is why leaves are perceived as green in
color.
• Fall colors of leaves result from the absence of chlorophyll and the
presence of other pigments which reflect their respective colors
• Ex. Carotene (reflects orange and red wavelengths of light).
Figure 8-5 Chlorophyll Light Absorption
Section 8-2
Absorption of Light by
Chlorophyll a and Chlorophyll b
Chlorophyll b
Chlorophyll a
V
B
G
YO
R
Light Independent reactions
(Calvin Cycle)
LIGHT INDEPENDENT REACTIONS:
Also known as “Calvin cycle” and "Carbon Fixation "
-does not depend on sunlight for energy and proceeds in
the absence of sunlight
The energy made in the light dependent reaction in the
form of (ATP, NADP+H) reaction are “spent” to convert
carbon compounds found in the plant cells into sugars
like (glucose) C6H12O6 a carbohydrate end product.
Video 5
CARBON FIXATION
The first step involves CO2 (carbon dioxide) combining
with RUBP- a 5 carbon compound found in plants
CO2 Enters the Cycle
Energy Input
ChloropIast
5-Carbon
Molecules
Regenerated
6-Carbon Sugar
Produced
Sugars and other compounds
The Light-Independent Reactions
“Carbon Fixation”
Step 1) Carbon dioxide from the air is combined with a 5carbon sugar RuBP (Ribulose biphosphate)
3 CO2 + 3 RuBP------> 6 PGA (each cycle)
This forms a 6-carbon molecule PGA (Phosphoglycerate)
Step 2) 12 ATP are "spent" to convert PGA to PGAL a 3carbon molecule and 12 H (hydrogen) are added to the
molecule
6 PGA + [Chemical Energy] 12 PGAL =Phosphoglyeraldehyde
[12 ATP12 ADP]
“spending energy”
[12 NADP+H 12 NADP]
Step 3) 6 additional ATP are "spent" to convert PGAL into sugar
and recycle RuBP
PGAL + PGAL--------> C6H12O6 + RuBP
[6 ATP---> 6ADP] “energy spent”
Summary:
18 ATP made in the light dependent reactions
are "spent" in the light independent reaction to
make one molecule of PGAL
Two cycles of the Calvin Cycle = 2PGAL
Total cost is 36 ATP+2PGAL=1glucose (sugar)
Concept Map
Section 8-3
Photosynthesis
includes
Lightdependent
reactions
H2O
Calvin cycle
use
take place in
Energy from
sunlight
Thylakoid
membranes
to produce
ATP
NADPH
O2
takes place in
Stroma
uses
CO2
ATP
NADPH
of
to produce
Chloroplasts
High-energy
sugars