The main source of energy for
MOST ecosystems on Earth is:
What is the process that AUTOTROPHS
use to capture sunlight energy?
The Nature of Sunlight
Sunlight strikes the Earth as a form of
electromagnetic energy.
Electromagnetic energy takes the form of
a wave, with each type having a distinct
wavelength.
Wavelength: the distance between two
adjacent crests in a wave series.
One Wave Length
The Electromagnetic Spectrum
The electromagnetic spectrum represents
the entire range of wavelengths of energy.
10
-5
nanometers (gamma rays)
(very short wavelength, high energy)
3
10 meters (radio waves)
(very long wavelength, low energy)
The Segment of Light Important to
Life on Earth
Visible light has a wavelength range of 380
to 750 nanometers.
Other wavelengths have an impact, but are
not vital for photosynthesis.
Ex: Ultraviolet (UV) rays, Gamma rays,
Infrared rays.
The Three Fates of Light
Visible light that strikes an object can be:
1)Reflected from the surface or internal
structures of the object.
2) Transmitted through the object.
3) Absorbed by the object.
The colors that we can see are either
reflected light or transmitted light.
The Three Fates of Light
Absorbance of Light
Substances that absorb visible light are
called pigments.
We see green plants because chlorophyll in
the plants absorb red and blue wavelengths,
while reflecting green wavelengths.
Plant Pigments
There are several pigments in plants, but
only a few are involved in photosynthesis.
The two pigments most involved with the
capture of sunlight energy are
chlorophyll a and chlorophyll b.
Another important type of pigments are the
carotenoid pigments.
Pigments involved in photosynthesis are
located on the thylakoid membranes of the
chloroplasts.
Structure of Chlorophyll
Chlorophyll has a large
ring assembly with a
magnesium atom
at its center.
A long hydrophobic tail
anchors the pigment to
the chloroplast.
Chlorophyll Absorption Spectrum
Both Cha and Chb absorb wavelengths in
the red and blue parts of the spectrum.
Carotenoids also absorb in the blue part of
the spectrum, and may help absorb excess
energy from light in those wavelengths.
The ABSORBTION SPECTRUM of PLANTS
Photosynthesis: How AUTOTROPHS
gather energy.
Photosynthesis is an ENDOTHERMIC
reaction, meaning it TAKES IN energy.
Where does it get the energy from?
In addition to needing sunlight, plants also
need two chemicals for photosynthesis to
work: Water, or H O
2
Carbon Dioxide, or CO2
H2O and CO2 are called the REACTANTS
in Photosynthesis.
CO2 +
H2O
C6H12O6 +
O2
C6H12O6 (Glucose) and O2 (Oxygen) are
the PRODUCTS of Photosynthesis
What does the plant use the Glucose for?
What does the plant use the Oxygen for?
Thomas Engelmann’s Experiment (1883)
Illuminated long strands of filamentous algae
with different wavelengths, and used aerobic
bacteria to show which segments were
producing oxygen.