
What is the difference between an autotroph
and a heterotroph?

Why do plants need sunlight?

What gases are exchanged between plants
and animals?



To be able to list the inputs and outputs of
photosynthesis.
To be able to identify the structures in a
chloroplast.
To be able to summarize light-dependent
reactions.

Light energy ------> chemical energy

Used by autotrophs to produce food

All of our energy starts as light energy!
 Plants use sunlight to make food animals eat
plants other animals those animals




Go through Photosynthesis to produce
GLUCOSE…
Autotrophs
“Producers” in the food web
Consist of plants, protists, cyanobacteria

1) Light dependent
 Light energy is absorbed and converted into
chemical energy in the form of ATP and NADPH.
(also produces Oxygen!)

2) Light Independent (Calvin Cycle)
 CO2 ATP and NADPH are used to make glucose.
*Glucose is the basic building block for more complex sugars such as starch.*
Glucose

Thylakoids:
 flattened sac-like membranes arranged in stacks
(stacks are called grana).
 Light-dependent reactions take place here.
 Electron transport occurs in the thylakoid
membrane

Stroma:
 Fluid filled space outside the grana.
 Light-independent reactions take place here.

Step 1: Light energy reaches photosytem
II causing the water molecule to split
H
H
O
H 2O
H+
+
O2
*H+ is released to the electron
transport system.
* O2 is given off as a byproduct.

Step 2: Light energy reaches photosystem I
and electrons flow from photosystem II to
photosystem I. (to replace the electrons
lost)

Step 3: Hydrogen ions (protons) are
pumped across the membrane as the
electrons fall. (think of a hyper child losing
energy)

Step 4: Electrons from photosystem I move
to a protein called ferrodoxin.
**Ferrodoxin = “helper”
protein**

Step 5: Ferrodoxin transfers electrons to
NADP+ forming NADPH. (We need this for
the next part of photosynthesis!)

Step 6: Hydrogen ions move through the
ATP Synthase because of the
concentration gradient, creating ATP.
(Chemiosmosis)
To Calvin Cycle
Lets see it altogether now!
http://www.science.smith.edu/departments/Bi
ology/Bio231/ltrxn.html

What goes into a light dependent reaction?

What is the goal of a light dependent
reaction?

What is given off as a byproduct?

What is the name of the protein needed in a
light dependent reaction?



In what part of the chloroplast do light
reactions occur?
What are the outputs of light-dependent
reactions?
What is the name of the cycle in lightindependent reactions?




List the inputs and outputs of the Calvin Cycle
Define chemiosmosis and it’s role in
photosynthesis.
Summarize light – independent reactions
Perform chromatography to identify the
pigments of green leaves.




Takes place in the stroma
Uses NADPH and ATP from Phase I (light
dependent reactions)
Needs CO2!!!
Produces GLUCOSE 


Functions like a sugar factory within a
chloroplast
**Regenerates the starting material with
each turn
Inputs
-
ATP
NADPH
CO2
Outputs
- Glucose


Mechanism in which ATP is produced as a
result from the flow of electrons down a
concentration gradient.
Ex: Light reactions (H+ ions and ATP
synthase)



Light and Water can limit the amount of
photosynthesis a plant can perform.
Some plants develop alternate pathways to
maximize energy conservation.
Ex: CAM and C4 plants.

http://www.science.smith.edu/departments/
Biology/Bio231/calvin.html