chapter 8 notes

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Published on 20 Mar 2011
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Chapter 8
Photosynthesis
Life depends on absorption of light energy
from sun
not very efficient ~ 4% of light actually
used
process responsible for aerobic oxygenic
atmosphere
occurs in photoautotrophic organisms
Site of photo synthesis
In internal membranes in prokaryotes
In chloroplast in Eukaryotes
Photosynthetic Process
involves light (photo”) reactions and
dark (“synthesis”) reactions
traps energy from sunlight into bonds
of energy carriers (ATP and NADPH + H+)
energy then transferred to and stored
in chemical bonds of carbohydrates
Stages within Photosynthesis
Light Reactions with Chemiosmotic ATP
Synthesis ( thylakoid membranes)
Light-Independent Reactions = Calvin
Cycle - (stroma)
Conversion of Light Energy to Chemical
Energy
Light energy comes in packets (photons)
with wavelike characteristics
Photons may be transmitted, reflected or
absorbed (energy transferred to molecule,
photo disappears)producing chemical
energy
Light Energy
Electromagnetic energy is absorbed by all
molecules
Pigments absorb light in visible spectrum
(400 – 700nm)
Photosynthetic Pigments
most common pigment in all
photoautotrophs is chlorophyll
plants, some algae an cyanobacteria
havechlorophyll a
Absorbtion in blue (400-450 nm) and red
(650-700 nm)
Chlorophyll appears green because it
reflects
green wavelengths (500 to 600 nm)
Accessory Pigments
include carotene, phycocyanin,
phycoerythrin, xanthophylls
have characteristic absorption spectra
that reveals their biological effectiveness
at different wavelengths of light
Chlorophyll Molecule Reaction Center
a special pigment molecule where
energy from photons of light is
concentrated
act as antennae to maximize light
absorption
electrons pass down energy gradient
from higher energy (shorter λ) to lower
energy (longer λ)
Electrons pass from one to another
pigment molecule within photsystem
Light Dependent Reactions
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Document Summary

Life depends on absorption of light energy from sun not very efficient ~ 4% of light actually used. Pigments absorb light in visible spectrum (400 700nm: most common pigment in all photoautotrophs is chlorophyll plants, some algae an cyanobacteria havechlorophyll a. Absorbtion in blue (400-450 nm) and red (650-700 nm) Chlorophyll appears green because it reflects green wavelengths (500 to 600 nm) Accessory pigments include carotene, phycocyanin, phycoerythrin, xanthophylls have characteristic absorption spectra that reveals their biological effectiveness at different wavelengths of light. Chlorophyll molecule reaction center a special pigment molecule where energy from photons of light is concentrated act as antennae to maximize light absorption electrons pass down energy gradient from higher energy (shorter l energy (longer l. Electrons pass from one to another pigment molecule within photsystem. Light dependent reactions process responsible for aerobic oxygenic atmosphere occurs in photoautotrophic organisms.

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