Discuss the following cartoon with a partner.
Which of the above responses is MOST correct?
Learn the answer in THIS VIDEO.
CELLULAR PROCESSES
Photosynthesis
WHAT IS PHOTOSYNTHESIS?


process whereby light
energy from the sun is
converted to chemical
energy stored in the
bonds of sugar (glucose)
occurs in the chloroplasts
of plants, algae, and some
bacteria
OVERALL EQUATION FOR PHOTOSYNTHESIS
UNDERSTANDING CHEMICAL EQUATIONS


Reactants are on the left side of the
equation
Products on the right side of the
equation
Reactants
Reactants
A
+
B

Products
yield
Products

C
+
D
PHOTOSYNTHESIS
Carried out in two phases:
1. Light-Dependent Reaction
Requires light energy
2. Light-Independent Reaction
Does not require light energy
Also known as Calvin Cycle
OVERVIEW OF PHOTOSYNTHESIS
PHASE 1: LIGHT-DEPENDENT REACTION
Thylakoid
Occurs in the thylakoids within the chloroplast
PHASE 1: LIGHT-DEPENDENT REACTION
1. Light splits the water molecule at the thylakoids
 H2O is broken down into Hydrogen ions, an electron,
and Oxygen atom
 Oxygen is released to the atmosphere
 Hydrogen is kept to make NADPH, an energy
storage molecule
 Electrons are passed into the next step, the electron
transport chain
PHASE 1: LIGHT-DEPENDENT REACTION
2. Electron Transport Chain (ETC)
• made of proteins that accept and transfer the
electrons
• electrons pass from protein to protein along the ETC
PHASE 1: LIGHT-DEPENDENT REACTION
3. Formation of NADPH and ATP
•
Electrons at the end of the “chain” are used to
make NADPH from NADP+
NADP+ + 2e- + H+  NADPH
•
•
NADPH is an energy carrier molecule that
takes energy to the stroma for the Calvin Cycle
Phosphate is added
to ADP to form ATP
and is carried to the
Calvin Cycle
ENERGY CURRENCY = ATP
Chemical Energy and ATP
Energy can be stored in many forms:
• Light
• Heat
• Electricity
• Chemical Bonds!
ENERGY CURRENCY = ATP (VIDEO)
ENERGY CURRENCY = ATP
• Energy in ATP is released when it is converted to
ADP
• The characteristics of ATP make it an exceptionally
useful molecule that is used by all types of cells as
their basic energy source
PHASE 2: LIGHT-INDEPENDENT REACTION
Occurs in the stroma, the colorless fluid that
fills the chloroplast
Stroma
PHASE 2: LIGHT-INDEPENDENT REACTION
•
•
NADPH and ATP lose their stored energy and
hydrogen is fixed to CO2 to build glucose
six molecules of carbon dioxide enter the Calvin
Cycle and eventually produce one molecule of
glucose (C6H12O6)
6 molecules of
Carbon Dioxide
1 molecule
glucose
OVERVIEW OF PHOTOSYNTHESIS
SUMMARIZE: 3-2-1
Tell me
3 steps of the light-dependent reaction
2 phases in photosynthesis
1 main goal of photosynthesis