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Photosynthesis Overview
Photosynthesis Cell Respiration Oxygen and
Glucose
CO2 and
Water
Location: Chloroplast
Only in plants Location: Mitochondria
Plants and animals
Plant Anatomy
• Roots
– Anchor plant to the ground
– Absorb water and minerals from soil (by osmosis)
– Store food for plant (glucose made in photosynthesis is stored as starch)
• Stems – Transport water and minerals from the roots up
to the leaves (xylem)
– Transport food (glucose) made in the leaves down to roots for storage (phloem)
• Leaves – Photosynthesis, accomplished by the
cooperation of many different cell types.
Upper epidermis
Chloroplast
Spongy
mesophyll cell
Guard
cell Stoma
Phloem cells (glucose down)
(opening)
Photosynthesis = Process of converting sun energy into glucose energy
Chlorophyll 6 CO2 + 6 H2O + E ---------------> C6H12O6 + 6 O2 (light)
Reactants Products
Gas
diffuses
into leaf
through
stomata
Travels
from
roots to
leaves
via xylem
E captured
by chlorophyll
(inside
chloroplast)
Life’s
primary
food
molecule
Gas
diffuses
out into
air (by-
product)
Factors Affecting Photosynthesis
• Temperature (68° to 95° F)
• Amount of sunlight
• Amount of water
• Amount of CO2
• Room to grow, time, nutrients
Chloroplast
• Plastid that contains chlorophyll and undergoes photosynthesis
Chloroplast
Grana
Thylakoid
Palisade Cells
Leaf Organ
Chloroplast
Stroma
Thylakoid
membrane
contains
chlorophyll
Phospholipid
bilayer
One Chloroplast
Information about Light: The Visible Spectrum
Red Orange Yellow Green Blue Indigo Violet
Low
Energ
y H
igh E
nerg
y
Why are leaves green?
Why is the sky blue?
• Green is green because it reflects green light and absorbs the energy of all other colors
• Absorbed light – stored energy in carbohydrates produced by photosynthesis
• Reflected light – color you see
(doesn’t give plant energy)
Chloroplast
Light
Reflected
light
Absorbed
light
Transmitted
light
Granum
Pigment Molecule that absorbs light energy from the sun; give leaves their color
Chlorophyll a
Chlorophyll b
Carotenoids
Wavelength of light (nm)
Absorption spectra
Ab
so
rpti
on
of
lig
ht
by
ch
loro
pla
st
pig
men
ts
400 500 600 700
• In plants, chlorophyll a and b are the main pigments.
• Found in chloroplasts
• Pigments absorbs energy from visible light spectrum, mostly violet/blue & orange/ red light (reflects green)
LE 10-8a
White
light
Refracting
prism
Chlorophyll
solution
Photoelectric
tube
Galvanometer
The high transmittance
(low absorption)
reading indicates that
chlorophyll absorbs
very little green light.
Green
light
Slit moves to
pass light
of selected
wavelength
0 100
LE 10-8b
White
light
Refracting
prism
Chlorophyll
solution
Photoelectric
tube
The low transmittance
(high absorption)
reading indicates that
chlorophyll absorbs
most blue light.
Blue
light
Slit moves to
pass light
of selected
wavelength
0 100
CH3
CHO
in chlorophyll a
in chlorophyll b
Porphyrin ring:
light-absorbing
“head” of
molecule; note
magnesium atom
at center
Hydrocarbon tail:
interacts with
hydrophobic
regions of proteins inside
thylakoid membranes of
chloroplasts; H atoms not
shown
Accessory Pigments
• Absorb light that chlorophyll can’t
• Allow plants to use more energy from light than could be trapped by chlorophyll alone
Examples: Carotenoids (appears orange, yellow, red
because it reflects these colors)
Xanthophyll I and II (appears yellow because it reflects this colors)
**Remember** More light absorbed = more energy for photosynthesis
Chlorophyll a
Chlorophyll b
Carotenoids
Wavelength of light (nm)
Absorption spectra
Ab
so
rpti
on
of
lig
ht
by
ch
loro
pla
st
pig
men
ts
400 500 600 700
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