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Lecture 3

BIOL 215 Lecture Notes - Lecture 3: Cyanobacteria, Diatom, Digestion

Course Code
BIOL 215
Neil Price

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-Certain RNA molecules can store information and acts as catalysts as well
-RNA can be made to evolve to perform many functions
-In an experiment, an RNA was isolated from Tetrahymena
-Designed a system where variants of the ribozyme that were active with calcium were
able to replicate whereas the magnesium variants were not (this is artificial selection)
-After a while, the ribozymes were active with calcium instead of magnesium
-Ribozyme produced in lab can synthesize RNA of 14 nucleotides and template does
not have to bind to ribozyme
RNA —> Protein & DNA
-RNA may have begun encoding proteins with catalytic properties
-One of the enzymes may be reverse transcriptase (copies RNA into DNA)
-DNA is better for storing info since it is more chemically stable than RNA
-Final step in evolution must have been the formation of outer membranes that enclose
nucleic acids and proteins
-Micelles (lipid droplets) fuse to form vesicles
Nucleic acids and membranes eventually lead to the formation of a stable entity that
displays cell behaviour
Cellular behaviour is established from
1. Osmotic stress
2. Creation of an electrochemical gradient (energy)
RNA is negatively charged within the protocell and counter ions in the solution makes
the protocell swell
Protocell acts as a regular cell by dividing
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Where Life First Evolved
-One theory is that life first evolved in the deep ocean since UV radiation would have
damaged life forms near the surface.
-There was no ozone layer at the time because oxygen was not produced in the
atmosphere yet.
Requirements on Life
1. Liquid water: All chemical reactions necessary for life occur in water, it is the
universal solvent (H-bonding polar molecule)
2. Energy source: Used to assemble elements into complex molecules for
organisms. 3 main sources of energy—light (photosynthesis), organic molecules,
inorganic molecules (chemosynthesis).
3. Elements for biomolecules
Trophic Classification of Organisms
-Organisms are classified by how they obtain energy
Autotrophs (self-feeder)—inorganic C-CO2 for energy and carbon
-Photosynthetic (light-electromagnetic energy) —> Photoautotroph
-Chemosynthetic (inorganic molecules- chemical bond energy) —> chemoautotroph
Tube worms & Bacteria (symbiotic relationship): Chemoautotrophic bacteria live inside
trophosome of tube and provide energy for the tube worms
Heterotrophs (other-feeders)—organicmolecules for energy and Carbon (chemical bond
energy) i.e.. carbs, fats, proteins
Herbivores, Carnivores, Omnivores, Detrivores, Saprovores
Why energy is important
-Rate at which energy can be taken is limited
-Limitation might be caused by external constraints such as
-Shortage of food
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