BIOL 1081 Lecture Notes - Lecture 18: Lincoln Near-Earth Asteroid Research, Photosystem I, Cytochrome B6F Complex
Wednesday, Oct 7
Photosynthesis & Light reactions Reading: Sections 10.1-10.2 in textbook
1. Distinguish between autotrophs and heterotrophs.
Autotrophs
Heterotrophs
“self-feeders”
Completely dependent, either directly or indirectly,
on photoautotrophs for food- and also for oxygen
Sustain themselves without eating anything
derived from other living beings
Unable to make their own food, they live on
compounds produced by other organisms
Produce their organic molecules from CO2 and
other inorganic raw materials obtained from the
environment
Some heterotrophs consume the remains of dead
organisms by decomposing and feeding on organic
litter such as carcasses, feces, and fallen leaves
decomposers
producers of the biosphere/ the ultimate sources of
organic compounds for all non-autotrophic
organisms
consumers of the biosphere/ “other-feeding”
occurs when when an animal eats plants or other
animals
2. List the inputs and outputs of photosynthesis, describing their sources and how they were
determined.
INPUTS:
• 6 CO2- from roots
• 12 H2O- from roots
• light energy- from the sun
OUTPUTS:
• C6H12O6 (glucose/sugar)- 6 C from the 6 CO2, 12 H from the 12 H2O, 6 O from the 6 CO2
• 6 O2- derived from H2O
• 6 H2O- 6 H2 from the 12 H2O, 6 O from the 6 CO2
3. Describe the basic structure of chlorophyll, explaining why it is a pigment and listing other
pigments found in photosynthetic organisms. Compare and contrast absorption and action spectra,
explaining the cause of the difference.
• Chlorophyll is the green pigment that gives leaves their color and resides in the thylakoid
membranes of the chloroplast. It is the light energy absorbed by chlorophyll that drives the
synthesis of organic molecules in the chloroplast.
• Pigments are substances that absorb visible light. Different pigments absorb light of different
wavelengths, and the wavelengths that are absorbed disappear. The color we see is the color
most reflected or transmitted by the pigment we see green when we look at a leaf because
chlorophyll absorbs violet-blue and red light while transmitting and reflecting green.
o Three types of pigments in chloroplasts:
1. Chlorophyll a- the key light-capturing pigment that participates directly in the
light reactions
2. Chlorophyll b- the accessory pigment
3. Carotenoids- a separate group of accessory pigments
• The action spectrum for photosynthesis is much broader than the absorption spectrum of
chlorophyll a. The absorption spectrum of chlorophyll a alone underestimates the
effectiveness of certain wavelengths in driving photosynthesis. This is partly because
accessory pigments with different absorption spectra also present in chloroplasts- including
chlorophyll b and carotenoids- broaden the spectrum of colors that can be used for
photosynthesis.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Photosynthesis & light reactions reading: sections 10. 1-10. 2 in textbook: distinguish between autotrophs and heterotrophs. Completely dependent, either directly or indirectly, on photoautotrophs for food- and also for oxygen. Unable to make their own food, they live on compounds produced by other organisms. Some heterotrophs consume the remains of dead organisms by decomposing and feeding on organic litter such as carcasses, feces, and fallen leaves decomposers consumers of the biosphere/ other-feeding occurs when when an animal eats plants or other animals. Sustain themselves without eating anything derived from other living beings. Inputs: 6 co2- from roots, 12 h2o- from roots. Compare and contrast absorption and action spectra, explaining the cause of the difference: chlorophyll is the green pigment that gives leaves their color and resides in the thylakoid membranes of the chloroplast. It is the light energy absorbed by chlorophyll that drives the synthesis of organic molecules in the chloroplast: pigments are substances that absorb visible light.
