1. Photosynthesis

2. What is photosynthesis?
• Photo = light
• Synthesis = the making of something by combining
separate components
• Photosynthesis is the process of converting light energy
into chemical energy that is store in carbohydrates and
other organic molecules
• A process that is carried out by photosynthetic autotrophs
such as plants, protists (i.e. algae), and some bacteria
• Occurs in the chloroplasts

3. The location and structure of chloroplasts
LEAF CROSS SECTION MESOPHYLL CELL
LEAF
Chloroplast
Mesophyll
CHLOROPLAST Intermembrane space
Outer
membrane
Inner
membrane
Thylakoid
compartmentThylakoidStroma
Granum
StromaGrana

4. What are the reactants & Products?
The goal is to know when and how each reactant is used during the process of
photosynthesis

5. What are the two stages of photosynthesis?

6. • The Calvin cycle makes
sugar from carbon
dioxide
– ATP generated by the light
reactions provides the energy
for sugar synthesis
– The NADPH produced by the
light reactions provides the
electrons for the reduction of
carbon dioxide to glucose
Light
Chloroplast
Light
reactions
Calvin
cycle
NADP+
ADP
+ P
The light reactions
convert solar energy
to chemical energy
• Produce ATP & NADPH
AN OVERVIEW OF PHOTOSYNTHESIS

7. Structure & Function of
a photosystem
Components of a photosystem:
•Light harvesting complex = pigment
molecules attached to proteins
•Reaction Center Complex = proteins
that contain a special pair of
chlorophyll a molecules
What happens in a photosystem:
1.Chlorophyll pigment absorbs
light
2.Energy transferred from
pigment to pigment
3.Energy reaches reaction center
where special chlorophyll a uses
the energy to launch an e- to a
higher energy level
4. primary e- acceptor captures
e-
Study this figure of How a photosystem harvests light
Thylakoidmembrane
Photon
Photosystem STROMA
Light-
harvesting
complexes
Reaction-
center
complex
Primary
electron
acceptor
Transfer
of energy
Special pair of
chlorophyll a
molecules
Pigment
molecules
THYLAKOID SPACE
(INTERIOR OF THYLAKOID)
e−

8. Photon
Photon
Water-splitting
photosystem
NADPH-producing
photosystem
ATP
mill
Two types of photosystems
cooperate in the light reactions

9. Cytochrome
complex
Primary
acceptor
Primary
acceptor
H2O
O2
2 H+
+
1
/2
P680
Light
Pigment
molecules
Photosystem II
(PS II)
Photosystem I
(PS I)
Pq
Pc
ATP
1
2
3
5
6
7
8
Electron transport chain
Electron
transport
chain
P700
Light
+ H+
NADP+
NADPH
NADP+
reductase
Fd
e−
e−
e−
e−
4
e−
e−
• Water is split, generating molecular oxygen, stripping electrons
for electron transport chain and leaving H+ to remain
• The flow of electrons through photosystems during light
reaction lead to the production of NADPH and ATP

10. Photosynthesis:
Light Reactions and Chemiosmosis
STROMA
(low H+
concentration)
STROMA
(low H+
concentration)
THYLAKOID SPACE
(high H+
concentration)
Light
Photosystem II
Cytochrome
complex Photosystem I
Light
NADP+
reductase
NADP+
+ H+
To
Calvin
Cycle
ATP
synthase
Thylakoid
membrane
2
1
3
NADPH
Fd
Pc
Pq
4 H+
4 H+
+2 H+
H+
ADP
+
P i
ATP
1
/2
H2O
O2
H+
H+
H+
H+

11. 2 H+
+ 1
/2
Water-splitting
photosystem
Reaction-
center
chlorophyll
Light
Primary
electron
acceptor
Energy
to make
Electron transport chain
Primary
electron
acceptor
Primary
electron
acceptor
NADPH-producing
photosystem
Light
NADP+
1
2
3
Summary: How the Light Reactions Generate ATP and NADPH

12. BIG PICTURE:
•Aka Dark Reactions or Light-
independent reactions
•Anabolic process: making
carbohydrates from smaller
molecules
•Carbon in the form of CO2 goes
into the cycle, and comes out in the
form of sugar.
•ATP and NADPH from the light
reactions serve as an energy
sources that drives the conversion
of CO2 to glucose
•3-carbon sugar is produced with
each turn of the cycle
Calvin Cycle
Question: Will the Calvin Cycle occur in
the dark? WHY or WHY NOT?

13. Review: Photosynthesis uses light energy to make
food molecules
Light
Chloroplast
Photosystem II
Electron
transport
chains
Photosystem I
CALVIN
CYCLE Stroma
Electrons
LIGHT REACTIONS CALVIN CYCLE
Cellular
respiration
Cellulose
Starch
Other
organic
compounds
Connections: What is the
relationship between the light
reactions and the Calvin
Cycle?

14. Create your own mindmap of
photosynthesis