Photosynthesis
 Is defined as…
 A process by which light energy is
converted into chemical energy
 Where does this take place?
 In the chloroplasts of plant cells
The Basics:
Reactants and Products
The main source of energy
for all life is….
 The SUN
 Photosynthesis is the process of
converting sunlight into ATP then into
organic molecules that store energy.
ATP
 How is ATP like money?
 It is: Energy currency -- the only form of
energy living things can use (spend).
 How does ATP release energy?
 By breaking the bond between the 2nd
and 3rd phosphate and becoming ADP.
Autotrophs are…
Plants or other organisms that make their
own energy from the sun or inorganic
compounds (they are producers)
 Heterotrophs are consumers that…
 Get energy from food by eating plants and
animals that eat plants
Where are the stroma and thylakoid
space relative to the thylakoid
membrane?
 The chloroplast contains thylakoids in a
fluid-filled space called the stroma.
 The thylakoid space is inside the
thylakoid and the membrane surrounds it.
Where is chlorophyll
located?
 On the thylakoid membrane
 What is chlorophyll?
 A pigment that absorbs and reflects light
What are the three
products of photolysis?
 1 Oxygen to the atmosphere
 2 H+ ions inside the thylakoid
membrane
 3 Electrons to chlorophyll to replace
those lost to the ETC
What frequencies of light are absorbed
and reflected by chlorophyll?
 Red and blue are absorbed
 Green is reflected
What happens to chlorophyll when it
absorbs light energy?
 It loses excited electrons to the electron
transport chain.
 How are these electrons replaced?
 Photolysis= light splitting water with an
enzyme.
Describe the ETC:
electron transport chain.
 A series of protein molecules embedded
on the membrane where each one has a
higher attraction for electrons than the
previous one.
What happens as the
energy is released in each
redox reaction?
 This energy is used to actively transport
H+ ions into the thylakoid space against
the gradient.
 This builds up a higher concentration of
H+ in the thylakoid space.
Are H+ freely permeable to the thylakoid
membrane? (can they cross easily?)
 No-- they are charged!
 How do H+ ions diffuse out of the thylakoid
space into the stroma?
 Through a transport protein called…
 ATP Synthetase
Is the flow of H+ ions through ATP
Synthase “energy requiring” or “energy
releasing”?
 Energy releasing
 This energy is used to form ATP
Is the formation of ATP
energy requiring or energy
releasing?
 Energy requiring
 Energy is needed to create the bond
between the 2nd and 3rd phosphate
making ATP from ADP + P
What serves as the final electron
acceptor at the end of the electron
transport chain?
 NADP+
 What happens to create NADPH?
 NADP+ combines with the final e- and
H+ from the stroma to make NADPH.
 NADPH is used in the next phase.
What three things are needed for the light
reactions? What three things are produced in
the light reactions?
 Needed--Light, water, chlorophyll
 Produced--oxygen (to atmosphere), ATP,
and NADPH (to dark reactions)
The dark reactions, AKA -- the light
independent reactions, are also known
as…
 The Calvin Cycle
 What is carbon fixation and where does the
carbon come from?
 CO2 from the air is added to a 5 Carbon sugar
= this is “carbon fixation”
 Glucose is produced
What is NADPH used for?
 It carries electrons and H+ ions to the
Calvin Cycle.
 These are used to build glucose
molecules.
 What enzyme is key to this process?
 Rubisco
Explain the results of the
Photosynthesis Lab
 What light treatments had the highest
and the lowest rate of reaction?
 What role did DPIP (blue stuff) play in the
photosynthesis reaction?
Now that you know all
about photosynthesis..
 Don’t forget to hug a tree!
 Without photosynthesis, we would not
have air to breath or food to eat.
 THE END ?