CHAPTER 8:
PHOTOSYNTHESIS
8-1 Energy of Life
Energy= The ability to do work
Living organisms depend on energy.
food
Living things get energy from _______.
The ultimate source of energy is the _____.
sun
A. Autotrophs and Heterotrophs

Autotrophs= Organisms that make their own food
o Example: plants use sunlight to make food

Heterotrophs= Organisms that need to consume
food for energy
herbivores
o Example: ___________eat plants
___________carnivores eat animals that
have stored energy from
plants they eat
detritovores eat decomposing
___________organisms
ATP
B. Chemical Energy
and ATP
Section 8-1of energy: light, heat, electricity, and
•Forms
Chemical energy (stored in bonds)
ATP (Adenosine Triphosphate)=
•_____
The basic energy source (chemical energy) of all cells
Adenine
Ribose
3 Phosphate groups
1.
Storing Energy
2 phosphates
• ADP (Adenosine Diphospate) contains ____
instead of 3.
•
If a cell has extra energy,
Small amounts can be stored by adding a
phosphate group to ADP molecules to produce ATP.
2. Releasing Energy
• To release energy stored in ATP,
The cell can break the high energy bond between
the 2nd and 3rd phosphate group
Figure 8-3 Comparison of ADP and
ATP to a Battery
Section 8-1
ADP
ATP
Energy
Adenosine diphosphate (ADP) + Phosphate
Partially
charged
battery
Energy
Adenosine triphosphate (ATP)
Fully
charged
battery
C. Using Biochemical Energy

How ATP is used in the cell
- Carry out active transport
- aids in moving organelles throughout the cell
- Protein synthesis
- Producing light (ex. fireflys)

Cells contain a small amount of ATP.
Only enough to provide a few seconds of activity.

transferring energy but not good at
ATP is great at ________________
Storing large amounts of energy

90 times more energy than ATP.
Glucose stores ___

The energy stored in Glucose can be used to
regenerate ATP when the cell needs it.
8-2 Photosynthesis: An Overview
Photosynthesis= Process where plants use energy of sunlight
to convert water and carbon dioxide into
high-energy Carbohydrates-sugars-starchesand oxygen, a waste product.
 Plants convert ______________
Sunlight energy into ______________
Chemical energy
through a series of oxidation/reduction reactions.

6 CO2 + 6H2O + SUNLIGHT → C6H12O6 (SUGAR) + 6O2
sunlight
O2
C6H12O6
CO2
H2O
6 CO2 + 6H2O + SUNLIGHT → C6H12O6 (SUGAR) + 6O2
REDOX REACTIONS
Reduction:
Gain electrons
LEO: Lose Electrons Oxidation
goes
GER: Gain Electrons Reduction
Oxidation:
Lose electrons
Photosynthesis: Reactants and Products
Section 8-2
Light Energy
Chloroplast
(Chlorophyll)
CO2 + H2O
Sugars + O2
A. Investigating Photosynthesis
 Investigations into photosynthesis began with the
following question:
“When a tiny seedling grows into
a tall tree with a mass of several tons,
where does the tree’s increase in mass come from?”
Van Helmont’s Experiment (1643)
1. ______________

Put soil in pot and took mass

Took a seedling and took mass

Put seed in soil...watered...waited five years...
the seedling became a tree.

He concluded that the mass came from water

He determined the
“hydrate” in the carbohydrate
portion of photosynthesis
Von Helmont Willow Tree
Experiment
http://www.teachersdomain.org/resource/tdc02.sci.life.stru.photosynth/
5 years
2.3 kg. (5 lb.) plant
90.8 kg (200 lbs). soil
76.8 kg (169 lbs. 3 oz.)
Soil 57 g less
2. ___________
Experiment (1771)
Priestly’s

Put a lit candle in a bell jar- The flame died out.

Placed a mint plant in the jar with the candleFlame lasted longer

Concluded plants release a substance needed
for candle burning.
 He determined plants release oxygen
Alternate Priestly Experiment
•Credit: The National Science Teachers Association
Jan Ingenhousz
3. ________________Experiment
(1779)

Put aquatic plants in light... produced oxygen

Put aquatic plants in dark... No oxygen
 He determined:
Light is needed to produce oxygen
Melvin Calvin
4. _______________
(1948)

He determines carbon’s path to make glucose

Known as the Calvin’s cycle
B. Light and Pigments
water (soil),Carbon
dioxide (air),
 Photosynthesis requires ______
____________
light (sun), and chlorophyll
and ____
________ (a molecule in chloroplasts).
light
 Energy from the sun is in the form of _____.
 Sunlight= perceived as white light= A mixture of different
wavelengths
 The wavelengths you can see are part of the
Visible Spectrum
_______________.
 Plants capture light with light absorbing molecules called
pigments
________.
 The main pigment is chlorophyll (2 kinds)
1. Chlorophyll a
2. Chlorophyll b
 Chlorophyll absorbs
light
inChlorophyll
the __________
Blue-violet
Figure
8-5
Light and
Absorption
red wavelengths
___
Section
8-2
Absorption of Light by
Chlorophyll a and Chlorophyll b RED
ORANGE
YELLOW
Chlorophyll b
GREEN
Chlorophyll a
BLUE
INDIGO
VIOLET
V
Gamma
rays
X-rays
B G YO
UV
Infrared
Visible light
Wavelength (nm)
R
Microwaves
Radio
waves
green wavelengths (that’s why
 Chlorophyll reflects ______
plants appear green)
 The energy absorbed by chlorophyll is transferred to
_________
electrons (in chloroplasts) which makes
photosynthesis work.
QUESTION: So why do plants leaves
change color in the fall?
Colorful leaves signal the changes of
autumn. As nights grow longer and
cooler, the leaves no longer produce
chlorophyll, the pigment that makes
leaves green and enables the
process of photosynthesis. As the
green pigment wanes, other
pigments take over, producing the
brilliant reds, oranges, and yellows of
fall foliage.
• The location and structure of chloroplasts
Chloroplast
LEAF CROSS SECTION
MESOPHYLL CELL
LEAF
Mesophyll
CHLOROPLAST
Intermembrane space
Outer
membrane
Granum
Grana
Figure 7.2
Stroma
Inner
membrane
Stroma
Thylakoid
Thylakoid
compartment
8-3 The Reactions of Photosynthesis
A. Inside a Chloroplast
•Site of Photosynthesis= The chloroplasts
Light
Chloroplast
Absorbed
light
Transmitted
light
Reflected
light

Photosynthesis is a two part process:
1. Light-dependent reactions (located in thylakoid membranes)
-aka: Light Reaction
2. Light-independent reactions (located in stroma)
-aka: Dark reaction
Figure 8-7 Photosynthesis: An Overview
-aka: Calvin Cycle
Section 8-3
-aka:
Carbon fixation
Light
H20
Chloroplast
CO2
NADP+
ADP + P
LightDependent
Reactions
O2
Calvin
Cycle
ATP
NADPH
Sugars
Chloroplast
• An overview of photosynthesis
H2O
CO2
Chloroplast
Light
NADP+
ADP
+ P
LIGHT
REACTIONS
(in grana)
CALVIN
CYCLE
(in stroma)
ATP
NADPH
O2
Figure 7.5
Sugar
B. Electron Carriers
 Sunlight energy is transferred to electrons in chlorophyll.
 The electrons gain a lot of energy.
 High energy electrons require a special carrier
(molecule/compound).
ANALOGY: If you wanted to transfer hot coals from one campfire to another, it requires
a special carrier like a pan or bucket.
 Electron carriers pass electrons from carrier to carrier
to carrier; Forming an electron transport chain.
 A Key electron carrier in photosynthesis is NADP+.
NADP+ +
+ H+ →→ NADPH
2e(electron carrier)
(high energy electrons) (hydrogen ions)
(energy storing compound)
 When energy is needed to do cellular work, the
Covalent bonds of NADPH are broken to release
the high energy electrons.
C.
Light-Dependent Reactions (Requires Light)
thylakoid membrane
· Located in the ___________________________
light energy is used to produce
· In the light reaction, ___________
ATP and _______
NADPH
_____
http://www.fw.vt.edu/dendro/forestbiology/photosynthesis.swf
Overview of the Light Reaction
e~
e~
Electron
Transport Chain
Electron
Transport Chain
e~
e~
e~
2H2O
4e~
PSII
ADP
ATP
e~
NADP+
NADPH
PS
I
O2 + 4H+
http://www2.kumc.edu/netlearning/examples/flash/photosyn2.html
Primary
electron acceptor
Primary
electron acceptor
Photons
Energy for
synthesis of
PHOTOSYSTEM I
PHOTOSYSTEM II
by chemiosmosis
http://www2.kumc.edu/netlearning/examples/flash/photosyn2.html
KEY PLAYERS IN LIGHT REACTION:
 Photosystem I and II: Clusters of chlorophyll pigment
 Electron carriers: ADP and NADP+
 Water: Donates electrons
•
ATP Synthase:
Enzyme (protein) that makes ATP
Primary
electron acceptor
PHOTOSYSTEM
Photon
Reaction center
Pigment
molecules
of antenna
Figure 7.7C
Light Reaction Process:
Hydrogen
Ion Movement
Chloroplast
Photosystem II
ATP synthase
Inner
Thylakoid
Space
Thylakoid
Membrane
Stroma
Electron
Transport Chain
Photosystem I
ATP Formation
• The production of ATP by chemiosmosis in
photosynthesis
Thylakoid
compartment
(high H+)
Light
Light
Thylakoid
membrane
Antenna
molecules
Stroma
(low H+)
Figure 7.9
ELECTRON TRANSPORT
CHAIN
PHOTOSYSTEM II
PHOTOSYSTEM I
ATP SYNTHASE
A. Photosystem II (PSII)
* Absorbs light to split (break up) water molecules
2H2O → 4H+ + 4e- + O2
o e- = Donated to chlorophyll
o O2 = Released into air providing oxygen for us
o H+= Released inside the thylakoid membrane
B. Electron Transport Chain
* The light energy excites electrons increasing
their energy level.
* The electrons get passed
down an electron transport chain to
photosystem I (PSI)
C. Photosystem I
·
Light energy energizes electrons.
·
NADP+ accepts the electrons and an H+ and are
NADPH
used to make _________.
D. Hydrogen Ion Movement
·
When water splits,
H+ ions fill up the inner thylakoid membrane
(making it positively charged). As a result, the
stroma is negatively charged.
·
The difference in charges
Provides the energy to make ATP.
http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120068/bio05.swf::Proton%20Pump
E. ATP Formation
·
_____
Ions do not cross the membrane directly.
It needs the help of a membrane protein.
·
H+ ions pass through the protein:
ATP synthase is an enzyme that converts ADP to ATP
PRODUCTS OF THE LIGHT REACTION:
O2 : Released in the air
· ____
ATP & NADPH These contain abundant chemical
· ______________:
energy but they are unstable. So, they are used to power
the dark reaction to _________________
help build glucose which
can store the energy for longer periods of time.
8-3
D.
The Calvin Cycle (dark reaction; light independent)
Figure 8-11 Calvin Cycle
* Occurs in the Stroma with or without light.
http://faculty.nl.edu/jste/calvin_cycle.htm
CO2 Enters the Cycle
Energy Input
ChloropIast
5-Carbon
Molecules
Regenerated
6-Carbon Sugar
Produced
Sugars and other compounds
The Calvin Cycle
(CO2)
(Unstable intermediate)
(RuPB)
ADP +
ATP
ATP
ADP +
NADPH
NADP+
(PGAL)
(PGAL)
(PGAL)
(Sugars and other carbohydrates)
DARK REACTION PROCESS:
A. CO2 enters the system
• 6 CO2 combines with 6 5-C compounds
• product= 12 3-C compounds
B. Energy input
ATP & NADPH (from the light reaction) are used to
• The _________________________________
convert the 12 3-C compounds into a higher energy form.
C. 6-Carbon Sugar is produced
• ___
2 of the 12 3-C are used to make glucose and
other compounds.
D. 5-Carbon Molecules Regenerated
10 remaining 3-C are converted into 6 5-C molecules
• ___
PRODUCTS OF THE CALVIN CYCLE (DARK REACTION):
* High Energy Sugars
E. Factors Affecting Photosynthesis
* Shortage of water can stop/slow down photosynthesis
waxy coating to protect against
* Plants often have a ______
*
Very low/high temperatures (damages enzymes) can
stop/slow down photosynthesis (optimal temp.= 0°– 35° C
Light intensity the better
* The greater the _____________,
photosynthesis functions (up to a point).
Concept Map
Section 8-3
Photosynthesis
includes
Lightdependent
reactions
Calvin cycle
use
take place in
Energy from
sunlight
Thylakoid
membranes
to produce
ATP
NADPH
O2
takes place in
Stroma
uses
ATP
NADPH
of
to produce
Chloroplasts
High-energy
sugars
California State Standards

Cell Biology
1a: usable energy is captured from
sunlight by chloroplasts and is stored
through the synthesis of sugar from
carbon dioxide
Warm up 8-1

Draw an ATP molecule and describe why it is
considered an energy molecule.

Why do animals have to eat to gain energy and
plants do not?

Why do organisms need energy?
Warm-up 8-2

Describe what the data represents in figure 8-5
pg 207.

Why are plants green?

What do plants need to grow? Where are they
obtaining these substances?
Warm-up 8-3

Diagram the process of photosynthesis in
detail.
United Streaming video:
Photosynthesis (13 min)
http://www.unitedstreaming.com/search/assetDetail.cfm?guidAssetID=083C802D-4438-4FEA-A20C-79909E7CB830