Important Root Words
Root Word
Meaning
Photo
Light
Chloro
Green
-phyll
Leaf
Stome
Mouth
Xantho
Yellow
Comprehension Check
How many characteristics of living
things can you remember?
Which characteristic is related to this
chapter?
All Organisms Need Energy
 All organisms require energy to live. There are two
main ways to obtain this necessary energy:
HETEROTROPHS
AUTOTROPHS
 Cells use energy trapped in chemical bonds. When these
bonds are broken, energy is released for cellular activities.
 When cells use several linked chemical pathways to
create the energy needed, this is called a biochemical
pathway.
Cells use Energy
 Cells find energy by breaking bonds in a very
special molecule called . . .
ADENOSINE TRIPHOSPHATE (ATP)
 ADP (adenosine diphosphate) is another
important molecule involved with cellular energy
Storage and Release of Chemical Energy
 Energy is stored (in a “high energy” bond) when a
phosphate group is added to ADP
 Energy is released from ATP when a phosphate group is
removed (the “high energy” bond is broken)…
 Note: This same system works between NADPH and
NADP+
ATP: The Energy
Currency
Visible Light
 Light travels as waves of energy
 Reflection, Transmission, Absorption
Pigments in plants
Pigments: proteins that trap light
energy from the sun, photosynthesis
depends on this absorption of light
to begin
Why do pigments appear as different
colors?
EXAMPLES:
 Chlorophyll : Appears green
 A: Traps Red Light
 B: Traps Blue Light
 Accessory Pigments: Trap
green/yellow
 Carotene: Appears orange
 Xanthophyll: Appears yellow
The least important color
for photosynthesis?
GREEN!!
Chromatography
 Can be used to separate plant
pigments based on their molecular
size
 Watch a video!
 Rf Values: Distance Pigment Moved (mm)
Distance Solvent Moved (mm)
NOTES:
 Rf value will always be less than 1
 The higher the Rf value, the smaller the
pigment
Location of Photosynthesis
Chloroplasts



Thylakoid Membranes
= photosynthetic sacs
(site of light
absorption)
Granum = stack of
thylakoids
Stroma = liquid
outside/surrounds
the thylakoids
http://micro.magnet.fsu.edu
/cells/plants/images/chlorop
last.jpg
Comprehension Check
This weekend your teacher went to the
store and bought a new, hi-tech, green
colored plant growth light. She placed a
plant underneath this light inside of the
fume hood and closed it tightly.
Will the plant be able to undergo
photosynthesis?
Overview of Photosynthesis
Definition: Process in which plants convert energy from the sun into stored chemical
energy (glucose).
2 main reactions in photosynthesis:
1) Light Dependent Reaction
2) Light Independent (Dark) Reaction
The General Reaction for Photosynthesis:
CO2 + H20  C6H12O6 + 02
(can you balance this equation?)
C6
CO2
H12
H20
O6
CO2
Temperature and Light Intensity can both affect the rate of
photosynthesis, but it will either decrease or level off at
some point.
5 things needed for photosynthesis
 Water
 Sunlight
 Carbon Dioxide
 Chlorophyll (a light
capturing pigment)
 Enzymes
The Light-Dependent Reactions
Light-Dependent Reactions:
Location: occurs in the thylakoid membranes
Function of First Stage:

Harvested light energy is converted from
sunlight to electrical energy (ETC)

Uses energy from the sun to produce ATP and
NADPH needed for next reaction
Important events you should know:

Chlorophyll is energized

Water is split

ATP and NADPH are formed

Hydrogen is trapped
The Light-Dependent Reactions
☼ (photons/light energy)
↓
Pigments in photosystem II and then photosystem I absorb energy
↓
Electron Transport Chain
↓
↓
Energy splits H20
↓
O2
ADP +
↓
2H trapped by NADP+
(forms NADPH *)
Both products here
are used in the
dark reaction
Energy used to form
ATP from ADP
 ATP*
Electron Transport Chain
Process starts in a photosystem located
on a thylakoid.

Absorption: Photosystem II absorbs
energy from photons

Passage: electrons are passed to
Photosystem I.

Transfer: electrons are transferred
along the chain generating
“electricity”.

Splitting: Electricity drives the
splitting of water to form H+ and
free oxygen.

Formation: Electrons provide energy
for NADP+ to gain a H+ and form
NADPH, also ATP is formed

ATP and NADPH are then used in the
Dark Reaction/Calvin Cycle
Light Reaction Video
Calvin Cycle
Calvin Cycle (Dark/Light-Independent Reactions):
Location: takes place in the stroma
Function: Uses energy from ATP and NADPH to produce
high energy carbohydrates (sugars)
Does not require light to occur (can actually occur in
light or dark)


Reactions form organic compounds using energy
stored from Light-dependent reactions in bonds of
NADPH and ATP
Named after American scientist, Melvin Calvin, who
discovered this in the early 1950’s
The Calvin Cycle/Dark Reaction
 These reactions can occur with or without Light!!
 This begins and ends with RuBP = a 5-carbon sugar
found in chloroplasts
CO2 + RuBP + ATP*
(from Light Reaction)
↓
2(PGA) + 2H*

2(PGAL)


RuBP (80%) Glucose
CO2 given off
(from Light Reaction)

H20 (released as a waste product)
(20%)
Calvin Cycle Animation
Calvin Cycle
1.
2.
3.
4.

Diffusion: Carbon dioxide diffuses into the stroma
Combination: CO2 binds with 5-carbon molecule called
RuBP. This forms an unstable 6-carbon molecule.
Splitting: This six carbon unstable molecule splits
immediately into two molecules called PGA.
Conversion: PGA is changed into PGAL when:
A. PGA receives phosphate group from an ATP molecule from the
light reaction
B. PGA accepts Hydrogen Ions from NADPH also from the light
reaction
In summary, the Calvin Cycle fixes carbon dioxide and
regenerates RuBP, produces PGA, then PGAL which
may be converted to glucose.
Photosynthesis
Comprehension Check
• Which parts of the process of
photosynthesis can occur in the light?
• Which parts of the process can occur in
the dark?
• How is the structure of the chloroplast
related to its function?
• http://www.pbs.org/wgbh/nova/methusela
h/photosynthesis.html
Regulation of Photosynthesis
•Stomata/Stoma: opening on underside of most
leaves, entry site of carbon dioxide, release of
oxygen from photosynthesis occurs here, water
vapor is released here (transpiration)
•Guard Cells: specialized cells that regulate
opening and closing of stomata, open and close using
a H+ pump and by manipulating the turgor pressure
of the cells