PHOTOSYNTHESIS
AUTOTROPHS
Auto = self
 Troph = eating
 Organisms that can produce their own food
(energy) from inorganic materials (sunlight)

HETEROTROPH
Hetero = other
 Troph = eating
 Organisms that cannot make its own food.
Requires organic compounds (other organisms)
for its principle source of food.

CHEMICAL ENERGY AND ATP
All cells use chemical energy carried by ATPAdenosine triphosphate.
 Cells use ATP for functions such as building
molecules and moving material through active
transport.

ATP
The energy carried by
ATP is released when a
phosphate group is
removed from the
molecule.
 ATP become ADP
(Adenosine
diphosphate)
 ADP can become ATP
again through a series
of chemical reactions.

ATP
ATP is produced during
the breakdown of
carbon-based
molecules.
 Different foods provide
different amounts of
ATP.
 Carbohydrates
(glucose) can make ~
36 molecules of ATP
 Lipids can make ~ 146
molecules

SPECIAL CREATURES

Some organisms do not need
sunlight and photosynthesis
as a source of energy.


Some organisms live near
cracks in the ocean and never
see sunlight
Chemosynthesis

Process by which some
organisms use chemical
energy instead of light
energy to make energystoring carbon-based
molecules
PHOTOSYNTHETIC ORGANISMS ARE
PRODUCERS.
•
Producers
–
•
Photosynthesis
–
•
Produce the chemical
energy for themselves and
for other organisms.
A process that captures
energy from sunlight to
make sugars that store
chemical energy.
Chlorophyll
–
A molecule in chloroplasts
that absorb some of the
energy in visible light
PHOTOSYNTHESIS IN CHLOROPLASTS
Chloroplasts are in
leaf cells
 Grana are stacks of
coin-shaped
membrane-enclosed
compartments called
thylakoids.

The membranes of
thylakoids contain
chlorophyll and protein
 Stroma is the fluid that
surrounds the grana
inside the chloroplast.

PHOTOSYNTHESIS IN CHLOROPLASTS

Light-dependent reactions
1. chlorophyll absorbs light.
 2. energy is transferred to
molecules that carry energy
(ATP).


Light-independent
reactions
3. CO2 is added to build
larger molecules. Energy
from the light-dependent
reactions is used.
 4. A molecule of simple
sugar is formed. C6H12O6

(glucose)
FIRST STAGE: LIGHT-DEPENDENT
REACTION

Capture and transfer energy.

There are two photosystems involved: photosystem II
and photosystem I
LIGHT-DEPENDENT REACTION
Chlorophyll and other lightabsorbing molecules
capture energy from
sunlight.
 Water molecules are broken
down into hydrogen ions,
electrons, and oxygen gas
(waste)
 Sugars are NOT MADE
during this part of
photosynthesis

Day 1
LIGHT DEPENDENT REACTION: PHOTOSYSTEM
II AND ELECTRON TRANSPORT
•
•
Chlorophyll and other light
absorbing molecules absorb
energy from sunlight and that
energy is transferred into
chloropyll.
The energy is then transferred
to electrons.
–
1. Energy is absorbed in sunlight
•
High energy electrons leave the
chorophyll and enter the electron
transport chain (a series of proteins
in the thylakoid)
2. Water molecules split
– 3. Hydrogen ions transported
–
LIGHT DEPENDENT REACTION: PHOTOSYSTEM
I AND ENERGY-CARRYING MOLECULES

Chlorophyll and other
light-absorbing molecules
absorb sunlight and add it
to the electrons from
photosystem II


4. Energy is absorbed from
sunlight. Electrons are
energized.
5. NADPH produced.
In photosynthesis NADPH
functions like ATP.
 The molecules of NADPH go
to light-independent
reactions.

ATP PRODUCTION

Final part of the light-reaction.

6. Hydrogen ion diffusion


H+ ions flow through the thylakoid.
7. ATP produced

ATP synthase take the ions as they flow and makes ATP by
adding phosphate groups to ADP.
LIGHT DEPENDENT REACTION:
PHOTOSYSTEM II AND PHOTOSYSTEM I
SUMMARY OF LIGHT-DEPENDENT
REACTIONS

PRODUCTS ARE:

NADPH


ATP


Used later to make sugar.
Used later to make sugar.
Oxygen

Given off as a waste.
2ND STAGE: LIGHT INDEPENDENT
REACTION
Uses energy from the
first stage to make
sugar.
 Light-independent
reactions take place ANY
time that energy is
available (it doesn’t need
sunlight).


Light-independent
reactions use the NADPH
and ATP made during the
light-dependent reactions
to make sugar.
THE CALVIN CYCLE

Uses the NADPH and
ATP from the lightdependent reaction,
and CO2 from the
atmosphere to make
simple sugars.
THE CALVIN CYCLE

1. Carbon dioxide added.
CO2 molecules are added
to five-carbon molecules
already in the Calvin
Cycle.
 Six-carbon molecules are
formed.


2. Three-carbon
molecules formed.

ATP and NADPH is used
to split the six-carbon
molecules into two threecarbon molecules.
THE CALVIN CYCLE

3. Three-carbon molecules
exit.
Most of the three-carbon
molecules will stay IN the
Calvin Cycle.
 ONE high energy threecarbon molecule will leave
the cycle.
 When TWO three-carbon
molecules leave the cycle,
they will bond together to
build a six-carbon sugar
molecule.


Glucose (C6H12O6)
THE CALVIN CYCLE

4. Three-carbon
molecules recycled.
Energy from ATP is
used to change the
three-carbon molecules
that stayed in the cycle
to five-carbon
molecules.
 These five-carbon
molecules stay in the
Calvin Cycle.
 They are added to new
CO2 molecules that
enter the cycle.

THE CALVIN CYCLE
SUMMARY OF LIGHT-INDEPENDENT
REACTIONS

PRODUCTS ARE:

Glucose


NADP+


Used to store energy.
Return to the lightdependent reaction.
 Will be changed into
NADPH there.
ADP

Return to the lightdependent reaction.
 Will be changed into
ATP there.
FUNCTIONS OF PHOTOSYNTHESIS
Provides material for plant
growth and development.
 Simple sugars are bonded
together to form complex sugars
like cellulose and starch.

Starches store energy for the
plant.
 Cellulose is a major component of
the cell wall.


Helps regulate the Earth’s
environment.

Removes CO2 from the
atmosphere.
PHOTOSYNTHETIC EQUATION
6CO2 + 6H2O
C6H12O6 + 6O2
 Light Dependent
Reactions


Includes
Photosystem II



Electron Transport
Chain
Photosystem I
Light Independent
Reactions

Includes the Calvin
Cycle
PHOTOSYNTHETIC EQUATION