Photosynthesis
 What is it?
 Who does it?
 Where does it take place?
 How is it done?
 Why do it?
What is it?

 Complex process by which plants use light energy to make
food molecules (glucose, C6H12O6) from carbon dioxide and
water (CO2) + H20)
Two Steps
light reaction
dark reaction
Who does it?
 Autotrophs-producers
 Ex. Plants, algae, photosynthetic bacteria
Where is it done?
Leaf
Green tissue in the interior of
the leaf =mesophyll
chloroplast
Grana:
stack of
thylakoids
Thylakoids: disc
like membrane sac,
where the light
reaction occurs
Stroma: thick fluid
like cytoplasm,
where the dark
Dark reaction: (aka Calvin Cycle, Carbon Cycle)
reaction takes place Does not require light
How is it done?
Summary:
Section 8-3
light
What goes in?
What comes out?
H20
CO2
Chloroplast
NADP+
ADP + P
Calvin
Cycle
LightDependent
Reactions
(Stroma)
(Grana)
ATP
H+
e-
O2
Chloroplast
NADPH
sugar (Glucose)
Video 2
Photosynthesis
 Click the image to play the video segment.
Concept Map
Section 8-3
Photosynthesis
includes
Lightdependent
reactions
use
Light
H2O
Calvin cycle
Thylakoid
Membranes/grana
to produce
ATP
NADPH
takes place in
take place in
O2
Stroma
CO2
uses
ATP/NADPH
of
to produce
Chloroplasts
High-energy
sugars
Process of Photosynthesis
 1st Stage: Light Dependent Reaction
 Requires light
 Occurs in thylakoid membrane/grana
 Water is split
 Oxygen is given off/released out of chlorophyll
 ATP and NADPH produced
 Extra energy from e- hit by light in chlorophyll
molecule is used to attach 3rd Phosphate to ADP to
form ATP.
Video 3
Light-Dependent Reactions, Part 1
 Click the image to play the video segment.
Process of Photosynthesis cont.
 2nd stage: Light Independent Reaction (Calvin cycle)
 No light energy
 Occurs in the stroma
 Uses CO2 and energy from ATP + NADPH (from 1st
stage) in a series of complex reactions to form
glucose and other nutrients the plant needs.
 Used energy given off: ADP, NADP +
ATP
Section 8-1
Adenine
Ribose
3 Phosphate groups
Figure 8-3 Comparison of ADP and
ATP to a Battery
Section 8-1
ADP
ATP
Energy
Adenosine diphosphate (ADP) + Phosphate
Partially
charged
battery
Energy
Adenosine triphosphate (ATP)
Fully
charged
battery
Light Reaction
Section 8-3
Photosystem II
Hydrogen
Ion Movement
Chloroplast
Inner
Thylakoid
Space
ATP synthase
Goes in:
Sunlight (photon)
Water
NADP+, ADP
Thylakoid
Membrane
Stroma
Electron
Transport Chain
Photosystem I
ATP Formation
Goes out:
ATP
NADPH
O2
Photosystem:
•Pigment molecules
•Reaction centers
•e- acceptors
Video 4
Light-Dependent Reactions, Part 2
 Click the image to play the video segment.
Figure 8-11 Calvin Cycle
Dark Reactions
(Calvin Cycle/Carbon Cycle)
Section 8-3
CO2 Enters the Cycle
Energy Input
ATP and NADPH
come from light
reaction
Goes in:
CO2
ATP
NADPH
5-Carbon
Molecules
Regenerated
6-Carbon Sugar
Produced
Sugars and other compounds
Goes out:
Sugar
NADP+,
ADP
Video 5
Calvin Cycle
 Click the image to play the video segment.
Why do it?
Glucose
other organic
compounds
cellular
respiration
starch
cellulose
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