DO NOW!! 
What is the difference between an
autotroph and a heterotroph?
Why do plants need sunlight?
What gases are exchanged between
plants and animals?
Overview Of Photosynthesis
Objectives
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 lightdependent reactions.
Photosynthesis
Process of converting light energy to 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 eat those animals
Photosynthetic Organisms
 Go through Photosynthesis to produce GLUCOSE…
 Autotrophs
 “Producers” in the food web
 Consist of plants, protists, cyanobacteria
Photosynthesis: The Chemical
Equation
Overview of Phases
 1) Light dependent
Light energy is absorbed and converted into
chemical energy in the form of ATP and NADPH.
(also produces oxygen as byproduct!)
 2) Light independent (Calvin Cycle)
CO2 ATP and NADPH (from light dependent) are
used to make glucose.
*Glucose is the basic building block for more complex sugars such as starch.*
Do Now!! 
 What are the two phases of photosynthesis?
 What are the inputs and outputs of each
phase?
 What is the chemical equation for
photosynthesis?
Objectives
 To go over the steps of light dependent
reactions
 To understand the inputs and outputs of light
dependent reactions
 To label a light reactions diagram
Glucose
The Chloroplast
Structures within a chloroplast
 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.
Do Now!! 
 What is the equation for photosynthesis?
 Where do light dependent reactions take place?
Independent?
 What are the inputs of light dependent reactions?
The outputs?
Objectives
 To go over the steps of light dependent
reactions
 To understand the inputs and outputs of light
dependent reactions
 To label a light reactions diagram
Diagram!
Please grab 6 different colors!!
Lets label our light dependent reactions
diagram.
Light Dependent Reactions
 Step 1: Light energy reaches photosytem II, exciting electrons and
causing water molecule to split.
- H+ is released, stays in thylakoid space.
- O2 is given off as a byproduct.
- Electron released into electron transport system
Light Dependent Reactions
 Step 2: Excited electrons move from photosystem II
through the membrane
 As they move, protons (H+) are pumped into thylakoid space
Light Dependent Reaction
 Step 3: At photosystem I, electrons are re-energized
and transferred to ferrodoxin (helper protein):
 NADPH (energy storage molecule) is formed from NADP+ (we
need this for the Calvin Cycle!)
Light Dependent Reactions
 Step 5: Hydrogen ions move through the ATP Synthase
because of the concentration gradient, creating ATP
from ADP. (Chemiosmosis)
Do Now!! 
 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 that converts
NADP+ to NADPH?
Objectives
 To review light dependent reactions
 To introduce light independent reactions by
completing a Calvin Cycle activity
Think-pair-share
Please work on the worksheet in front of
you!
Try it by yourself, then you may work with
a partner.
Light Dependent Reactions
http://www.science.smith.edu/departments/Biology/Bio231/ltrxn.html
https://www.youtube.com/watch?v=joZ1EsA5_NY
Do Now!! 
Please take out the light dependent worksheet
from yesterday!
Objectives
 To identify the stages of light independent
reactions
 To identify alternative pathways
 To define C4 and CAM plants
The Calvin Cycle
 Takes place in the STROMA
 Uses NADPH and ATP from Phase I (light dependent
reactions)
 Needs CO2!!!
 Produces GLUCOSE!!
Calvin Cycle
 Functions like
a sugar
factory within
a chloroplast
 Regenerates
the starting
material with
each turn
Calvin Cycle
Inputs
Outputs
- ATP
- NADPH
- CO2
- Glucose
Calvin Cycle
Chemiosmosis
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)
Alternative Pathways
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.
C4 Plants
 These plants minimize water lost
 Turn CO2 into a 4 carbon molecule instead of a 3
carbon molecule
 Keeps stomata (plant cell pores) closed during hot
days
 Ex. Corn and Sugar Cane
CAM Plants
 Occurs in water-conserving plants that live in
deserts and other arid environments
 Stomata ALWAYS closed during the day
 CO2 only enters leaves at night, turns into a “storage
molecule” until daytime
 Ex. Orchids, cacti, pineapples