Photosynthesis
Overview
6 CO2 + 6 H20  C6H12O6 + 6 O2
Structure of a Leaf
Photosynthesis
• Process by which plants and other
autotrophs store the energy of
sunlight into sugars.
• Occurs in the leaves of plants in
organelles called chloroplasts.
• Requires sunlight, water, and carbon
dioxide.
Structure of a Chloroplast
It’s a TWO part process!
• Process #1: Requires Light (Light Reactions)
• Process #2: Does NOT require light (Dark
Reactions)
Misnomer: Dark reactions don’t require “dark.”
They can take place independent of light.
Overview
Light Reactions
chloroplasts
individual cell
Elodea leaf cells, 100 X
So where are pigments?
Groups of pigments called PHOTOSYSTEMS
are located on the surface of the thylakoid.
Pigments
Chlorophyll b is one of many
different versions of chlorophyll.
Photosynthesis requires chlorophyll and other
pigments to absorb solar energy.
Plants
containing
chlorophyll
appear green.
Why?
Because chlorophyll absorbs
everything but green!
GREEN is
being
reflected
back to your
eye.
Some Light Reflected, Some Light Absorbed
Reflected
Colors are
what you see
Absorbs
Certain Colors
Think
some
more!
Why does a plant
need to use both
primary and
accessory pigments?
Animation
http://www.pbs.org/wgbh/nova/nature/photos
ynthesis.html
Light Reactions in Detail
“Energy cannot be created nor
destroyed, only transformed!”
A photosystem can be considered a
“light-harvesting complex.”
A bunch of them together make a
“light-gathering antenna.”
Photon = packet of light energy!
But there are TWO photosystems!
Figure 7.8A
Light
Photosystem II
Stroma
Electron transport chain
Provides energy for
synthesis of ATP
by chemiosmosis
NADP  H
Light
Photosystem I
1
Primary
acceptor
Thylakoid membrane
Primary
acceptor
2
4
P700
P680
Thylakoid
space
3
H2O
1
2
5
O2  2 H
6
NADPH
Photosystem II and I Animation
• http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/
free/0072437316/120072/bio13.swf::Photosynthetic%20Elect
ron%20Transport%20and%20ATP%20Synthesis
What are the two main products of the
light reactions (both photosystems)?
1.)
2.)
These are both sent to the Calvin Cycle (dark
reactions/light independent reactions).
Photosynthesis Part Two
The Calvin Cycle
Textbook page 116
How are the two parts linked?
By ATP
and
NADPH
Calvin Cycle Animation
• http://highered.mcgrawhill.com/sites/0070960526/student_view0/chapter5/animatio
n_quiz_1.html
Do NOT worry about the specific molecule
names. Pay close attention to how the light
reactions interact with the dark reactions.
What are the start and end points and
“materials” used?
My Movie Clip Notes
• Location? _____________________________
STROMA
CO2
• What enters the Calvin Cycle? ____________
• What is used from the light reactions?
_____________________________________
• What is formed?
________________________
Producing glucose…
To synthesize one glucose molecule,
the Calvin Cycle uses 6 CO2 molecules,
18 ATP, and 12 NADPH.
Mini “Quiz”
Directions: Grab a white board and
marker. Answer each of the following
questions individually. Reveal your
answer when directed by holding up
your board.
Question #1
What is the main
purpose of the light
reactions?
ANSWER : To Produce ATP and NADPH
Question #2
What is the main
purpose of
photosynthesis?
Question #3
What is the main
purpose of cellular
respiration?
Question #4
What is the main
purpose of
fermentation?
Question #5
The Calvin Cycle takes place in the
________ of chloroplasts.
A)matrix
B)stroma
C)thylakoid membrane
D)inner membrane
E)outer membrane
Question #6
The Calvin Cycle uses ________, which
are products of the light reactions of
photosynthesis.
A)CO2 and H2O
B)RuBP and O2
C)ADP and NADH
D)ATP and NADPH
E)3-phosphoglycerate and glucose
Question #7
How do gases enter and exit the
plant cell in photosynthesis?
A) veins
B) roots
C) stomata
D) mesophyll
E) choroplasts
Question #8
Predict (and draw) what the
graph would look like relating
the rate of photosynthesis to the
concentration of carbon dioxide.