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BIOA01H3 Study Guide - Midterm Guide: Ribose, Photosynthetic Efficiency, Absorption Spectroscopy

Biological Sciences
Course Code
Ivana Stehlik
Study Guide

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Biology is the study of life.
*Liquid water is the fundamental prerequisite for the development of life*
Earth is ~ 4.6 Billion years old and lies within the habitable zone around the sun. (this is the position were heat
from the sun allows water to exist in liquid state)
In order to be considered alive it must have the 7 characteristics:
But what is life?
Display order
Harness and utilize energy
Respond to stimuli
Growth and develop
This characteristics are "emergent" (there is a hierarchy of interactions where simpler things do not
have the properties found in higher levels)
Evolve (adapt to change) *Key for diversity*
Diversity and unity through evolution
Theory of evolution through natural selection (single common ancestor)
Charles darwin (natural selection, 1859) created a unifying framework
Live in diff environments
Adapt to changing environments
Differences enables them to:
Reproduction with potential for errors, errors lead to evolution.
Cell theory: cells come from pre-existing cells, all organisms are composed by it. Cells are the basic unit of
How is all life on earth related?
Cells (Lipid bilayer)
Genetic system based on DNA
System of information transfer (DNA, RNA, PROTEIN)
system of protein assembly using ribosomes and mRNA, tRNA,
ATP as source for chemical energy
Metabolic pathway to generate ATP
Proteins: Major structure and catalytic molecule
How is life on earth unifyied?
Classifications are made on the basis of share features (structure/function)
Taxonomy (classification of life) developed by Linnaeus in 1735
1) Genus
2) Species
All organisms have 2 parts for their scientific name (in italics)
Phylogeny (geneological relationship)
Tree of life (still in progress)
CHP3 Biology and The Tree of Life
7:59 PM
BIOA01 Module 1 (revized) página 1

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How important molecules for life came to be?
Is hypothesized that they came to be in 4 main stages
1st stage Abiotic synthesis of monomers (NOT SYNTHESIZED BY LIVING ORGANISMS) :
Primordial atmosphere contained large quantities of H2, CO2, NH3 (ammonia),CH4 (methane)
1) Oparin-Haldane hypothesis: reducing atmosphere where molecules in premordial atmosphere
contained abundance of electrons and H2, reacting with one another producing larger more complex
Because there was no oxygen, there was no ozone layer, therefore, UV light + lighting provided the
energy needed for the formation of the molecules
Note: Today's atmosphere is considered oxidizing due to large amounts of oxygen present (because
of its affinity it accepts the electrons and reduces chances for complex macromolecules to form)
Miller-Urey experiment was the first to demonstrate the abiotic formation of important molecules
can be easily produced in the laboratory
2)Deep sea vents: Release superheated nutrient rich water, as well as reduced molecules
(CH4,NH3,H2S) which created a geochemical gradient that with the extreme pressures of the
environment gave rise to the building macromolecules of life.
"Carbon chondrites"- rich in organic molecules
Clay hypothesis charged layers of clay allows for molecular adhesion forces to bring
monomers together (clay stores potential energy) It also accelerates formation of lipid
2nd stage Polymerization
3) Extraterrestrial Origins (Panspermia): organic molecules tha came from meteorites
one of the key attributes of a modern cell is that it has a membrane-defined
comparment, where it provides a distinction from external environment and the
concentration of key molecules within the membrane creates better chances for the
formation of more complex molecules.
3rd stage Protobionts (similar to lisosomes which are lipid vesicles with lipid bilayer similar to
cell membrane)
Protobionts are capable of simple reproduction and metabolism all within a selectively
permeable membrane.
4th stage Central Dogma
Ribozymes: a group of RNA molecules that could themselves act as a catalyst. They are
single stranded molecules that can fold into very specific shapes on intramolecular
hydrogen bonding or base pairing. (critical for reacting with substrate molecules)
Are the steps from DNA to RNA to ribosomes for the formation of proteins which is aid by
enzymes (which are proteins)… but... there were no proteins! so wth, how did it happen then?
"RNA world" from RNA to RNA, protein to DNA,RNA,PROTEIN
From RNA world to DNA world.
Why DNA? DNA is more stale, better at storaging information and is double stranded which aids in
DNA repair (Base uracil is replaced with thymine).
CHP3 The Origins & Chemical Building Blocks of Life
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DNA repair (Base uracil is replaced with thymine).
more variety (22 diff amino acids, compare to 4 nucleotides)
Aminoacids interact chemically with each other giving rise to many many combinations
grater rate of catalysis (10-100x greater)
From RNA catalyst to Proteins.
Membrane defined compartment
System to store information
way to harness and utilize energy
The model of the origin of life must explain:
Early protobionts used molecules present in the environment for growth and replication
Heterotrophs (other-feeding)- they obtain carbon from organic molecules and produce
Anoxygenic photosynthesis, Evolution of oxygenic pho, produce O2.
Autotrophs (self-feeding) obtain carbon from inorganic molecules (CO2)
*Primordial heterotrophs did not survive the change in environment and those who did
evolved the capacity for aerobic respiration
How did life evolve?
BIOA01 Module 1 (revized) página 3
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