Download PHOTOSYNTHESIS

Photosynthesis
What is the ultimate
source of all energy
How does the energy get
from the sun into the
foods we eat?
Why do we see colors?
 The
sun sends downs little
packets of light energy called:
PHOTONS
Why do we see colors?
 Photons
group together in waves
 The waves have different lengths
 Each “wavelength” presents
itself as a color
Photons
Wavelengths
Why do we see colors?
Plants reflect this color
of light. That’s why
most plants are GREEN
Plant pigments like chlorophyll absorb these
colors of light so these colors are not seen.
What colors of light would a plant
with purple leaves absorb?
What colors are being absorbed
and what colors are being
reflected?
Photos courtesy of flowerpictures.net and picturesof.net
Why do we see colors?
What do we call the compounds that
absorb and reflect wavelengths of
light?
 Which compound reflects the green
wavelengths thereby making plants
green?
 Where would we find this
compound?

Chloroplast structure
Disks called GRANA contain the pigment
CHLOROPHYLL.
The liquid portion of a chloroplast is the STROMA
Where do
we find
chloroplasts?
Chloroplasts are found
in cells of leaves.
Chloroplast containing chlorophyll
stoma
Review
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5.
What is the ultimate source of
all energy?
In what form does light energy
come to the earth?
What compounds absorbs
wavelengths?
How do we see colors?
Where in a leaf do we find
pigments?
What process captures
the light energy and
uses it to make food?
OVERVIEW OF
PHOTOSYNTHESIS
SUNLIGHT PROVIDES
THE ENERGY
FOR PHOTOSYNTHESIS
PLANTS MAKE GLUCOSE
AND OXYGEN
PLANTS TAKE IN
CO2 AND H2O
Photosynthesis
 What
is photosynthesis?
 Photosynthesis is the process
by which:
light
TAKE IN
AND USING
water
carbon dioxide
PLANTS
(producers)
chlorophyll
MAKE
oxygen
glucose
Photosynthesis
2
steps:
 Light reactions
 Dark reactions (aka Calvin cycle)
Light Reaction
Dark Reaction
Who was Calvin anyway?

A member of the faculty
at UC Berkeley since
1937, Melvin Calvin
received the 1961 Nobel
prize in chemistry for
identifying the path of
carbon in
photosynthesis.

The cycle of reactions in the dark phase
of photosynthesis was named after him
for his work in identifying the processes
taking place.
Photosynthesis
 Light
reaction:
 Occurs in the grana
 Must have light
light
LIGHT
Light REACTION
Reaction
grana
(chlorophyll)
Dark Reaction
Photosynthesis

Dark reactions (aka Calvin cycle):




Occurs in the stroma
Occurs in the light and dark
Light Reaction
DARK
Dark REACTION
Reaction
stroma
(liquid)
Step 1: Light Reactions
O2isiskept
light
water
H
energy
released
is split
for the
by
reacts
the
dark
light
reaction
with
energy
the
chlorophyll
O2
O2
O2
O
H2O
O2
O2
H H H2
How does
the O2 leave
the leaf?
Step 2: Dark Reactions
 AKA:
CALVIN CYCLE
glucose
H
CO
the
from
enters
the
is the
water
theHproduct
and
splitCO
in2
2reactants
the light reaction is
chloroplast
combine
present
COdoes
2
How
CO2
CO
enter
2 the plant?
CO2
H H

CO2
H + CO2
C6H12O6
Other carbohydrates besides glucose
may be made in photosynthesis
Photosynthesis Review
Light reactions: H2O split into H2 + O
 Dark reactions: H + CO2 = C6H12O6

H2O
Light Reaction
chlorophyll
Dark Reaction
C6H12O6
Photosynthesis Formula
How would this be written as a
chemical equation?
 What goes in? (the reactants)


What comes out? (the products)
H2O
H2O
CO2
Light Reaction
chlorophyll
C6H12O6
O2
Dark Reaction C6H12O6
Photosynthesis Formula
What’s wrong with this equation?
 The number of atoms is not equal on
both sides of the equation.

one carbon
atom reactant
6 H2O
6 CO2
6 carbon
atoms product
(1) C6H12O6
6 O2

Balance the equation so that the
number of atoms of each element is
equal on both sides.

Now balance it as if TWO glucose
molecules were being produced.
Photosynthesis Review
 What

goes in? (the reactants)
What comes out? (the products)
light
6CO2 + 6H2O
H2O
chlorophyll
Light Reaction
chlorophyll
6O2 + C6H12O6
Dark Reaction C6H12O6