Transcript You Light Up My Life - Biology Study Guide Dr. Scearce

Photosynthesis
I
Energy, Light and pigments
The basics
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 Green plants capture energy from the
sun
 They turn CO2 (carbon dioxide) into plant
sugars
 O2 (oxygen) is released in the process
 This process is the basis of nearly all
food webs on the planet (Exception: A few
types of bacteria can oxidize minerals and
make simple sugars)
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Sunlight as an Energy
Source
 Photosynthesis runs on a fraction of the
electromagnetic spectrum, or the full
range of energy radiating from the sun
Electromagnetic
Spectrum
Shortest
wavelength
Longest
wavelength
Gamma rays
X-rays
UV radiation
Visible light
Infrared radiation
Microwaves
Radio waves
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Visible Light
 Wavelengths humans perceive as
different colors
 Violet (380 nm) to red (750 nm)
 Longer wavelengths, lower energy
Photons
 Packets of light energy
 Each type of photon has fixed amount
of energy
 Photons having most energy travel as
shortest wavelength (blue-green light)
Pigments
 Light-absorbing molecules
 Absorb some wavelengths and
transmit others
 Color you see are the
wavelengths not absorbed
Pigment Structure
 Light-catching part of molecule
often has alternating single and
double bonds
 These bonds contain electrons
that are capable of being moved
to higher energy levels by
absorbing light
Variety of Pigments
Chlorophylls a and b
Carotenoids
Xanthophylls
Phycobilins
Anthocyanins
Chlorophylls
Wavelength absorption (%)
Main pigments in most plants
chlorophyll a
chlorophyll b
Wavelength (nanometers)
Carotenoids
 Found in all photoautotrophs
 Absorb blue-violet and blue-green that
chlorophylls miss
 Reflect red, yellow, orange wavelengths
 Two types
 Carotenes - pure
hydrocarbons
 Xanthophylls - contain
oxygen
Xanthophylls
Yellow, brown, purple, or blue
accessory pigments
Phycobilins &
Anthocyanins
Red to purple pigments
 Phycobilins
 Found in red algae and cyanobacteria
 Anthocyanins
 Give many flowers their colors
Carbon and Energy
Sources
 Photoautotrophs (Plants, some bacteria & many
protists)
 Capture sunlight energy and use it to carry out
photosynthesis
 Carbon source is carbon dioxide
 Energy source is sunlight
 Heterotrophs (as in ?)
 Get carbon and energy by eating autotrophs or one another
Photosynthesis Equation
Where does the oxygen gas come from?
Simplify the equation by dividing by 6
CO2 + 2 H2O  CH2O + H2O + O2
CO2 + 2 H2O  CH2O + H2O + O2
What does the chemistry
look like?
 6 CO2 + 12 H2O  C6H12O6 + 6 O2 + 6
H20
 Where does the oxygen gas come from?
•Simplify the equation by dividing by 6
•CO2 + 2 H2O  CH2O + H2O + O2
CO2 + 2 H2O  CH2O + H2O + O2