Photosynthesis
Pigments of Photosynthesis
Pigments are molecules that absorb specific
wavelengths (energies) of light and reflect all
others.
• Chlorophyll is the main molecule in charge of
capturing the energy from sunlight.
Absorption of Light by
Chlorophyll a and Chlorophyll b
Chlorophyll b
Chlorophyll a
V
B
G
YO
•Chlorophyll a absorbs …………….. light best.
•Chlorophyll b absorbs ……………. light best.
•Why do plants look green?
•THEY RELFECT GREEN LIGHT!!!
R
Chloroplast Structure
NADP+ – Electron Carrier Molecule
• Electron Carrier Molecules
– Compound that can accept a pair of high energy
electrons and transfer them, along with most of
their energy to another molecule
– One way the sunlight can be trapped in a chemical
form and use it to build glucose for the plant cell
– Example:
• NADP+ = accepts and holds 2 high energy electrons along
with a hydrogen ion (H+)
• When NADP+ accepts 2 electrons and a H+ it becomes
NADPH
Chemical Energy and ATP
• ATP
– Adenosine triphosphate
– Compound that cells use to
store and release energy
– Made of adenine, 5-carbon
sugar (ribose), and 3 phosphate
groups
• ADP
– Adenosine diphosphate
– Made of adenine, 5-carbon
sugar (ribose), and
2 phosphate groups
Chemical Energy and ATP
Photosynthesis:
Step 1 – Light-Dependent Reaction
• Sunlight is used toFigure
split water
into hydrogen (H)
8-7 Photosynthesis: An
andSection
oxygen
(O).
8-3
• The Oxygen is released to the atmosphere.
• Also produces NADPH and ATP for the next step!
HO
CO
• Takes place inLight
Thylakoids.
Chlo
2
2
Chloroplast
NADP+
ADP + P
LightDependent
Reactions
Calvin
Cycle
ATP
NADPH
O2
Sugars
Photosynthesis:
Step 2 – Light-Independent Reaction
• This step is also called the Calvin Cycle or Light Independent
Reaction because it does not need light.
• CO2 combines with the hydrogen (H) released during step 1 to
form C6H12O6 (glucose)
Figure 8-7 Photosynthesis: A
• The NADPH and ATP made in Light Dependent Rxn provides
the energy to make Lt. Independent Rxn work.
Section 8-3
•
Takes place in stroma.
Light
CO2
C
Chloroplast
NADP+
ADP + P
LightDependent
Reactions
Calvin
Cycle
ATP
NADPH
O2
Sugars
H2 O
Light
Chloroplast
CO2
NADP+
ADP + P
LightDependent
Reactions
Calvin
Cycle
ATP
NADPH
O2
Sugars
What affects the rate of photosynthesis?
• Amount of :
- sunlight
- CO2
- H2O
- temperature
• All the reactions of photosynthesis are
controlled by enzymes. Temperatures above
or below the optimum temperature will slow
down the chemical reactions.