Transcript Keratin: A hard durable protein found in Hair and Nails/Claws

Objectives:
1. Be able to Summarize the Miller-Urey
Experiment
2. Relate the structure of Clay beds to the
polymerization of nucleotides
3. Understand the role of meteorite impacts in
polymerization of Proteins
4. Relate the structure of phospho-lipids to the
formation of cell membranes.
Two Characteristics of a Living Thing
Must be able to store information
(RNA or DNA)
Express that information (proteins)
Actin /Mysosin:
Proteins that are
used in muscle
fibers.
Collagen:
Found in
connective
tissue
PSD-95: Protein
that builds
connections
between synapses
Proteases:
Protiens that help
digest proteins
(meat)
Keratin: A hard
durable protein
found in Hair and
Nails/Claws
What came first
The protein that makes up our body, or the
RNA/DNA that codes for the protein?
Conditions of the Early Earth
• Little oxygen in the atmosphere: Atmosphere
is composed of CN, NH4, CH4, H2
• Violent electrical storms
• Heavy Bombardment: A time when the earth
is constantly hit with meteorites.
Miller-Urey Experiment
• Adds early atmospheric gases to a flask
connected to another flask with water
(simulating the early oceans).
• Shot electrodes (simulate lightning) through
the gases.
• Produced amino acids (building blocks of
Proteins) from the gases.
The Murchinson Meteorite
• In 1969 a meorite hit earth in Australia
• The meteorite was covered in thousands of
amino acids, the building block of proteins.
• Panspermian hypothesis: that life actually
originated in space and was brought to this
planet.
Experiments with Amino Acids
under large impact pressures
• Scientist hypothesized that if amino acids
were placed under meteorite impact pressure,
Dr. then
Jennifer they
Blank would vaporize.
• The hypothesis was proved wrong: Amino
acids Polymerized into long chains of protein.
The Formation of Nucleotides
• Each of the 4 Nucleotides found in DNA:
Adenine, Thymine, Cytosine, and Guanine
have been synthesized in the laboratory using
early atmospheric gases and an electrical
discharge.
Polymerization of Nucleotides
into Nucleic Acids
• Polymerization: to attach smaller building
blocks into long chains
Clay beds may have polymerized
Nucleotides into long chains
A
T
C
G
A
C
G
Evidence for Clay Beds
• Many Organic Molecules are Chiral (mirror
images), and come in two different isomers,
either left-handed and right handed.
• Clay beds only polymerize the L-isomer of
nucleotides.
• The L-isomer is the only form that nucleotides
are found in living organisms.
Ribozymes
• Ribozyme: A sequence of RNA (nucleic acid)
that can catalyze chemical reaction.
• It can act as both a heritary molecule (store
information) and performs a function
(expresses that information).
• Biologist have discovered a Ribozyme that can
catalyze its own synthesis.
• Some of these Ribozymes would have been
enclosed and protected in a lipid by-layer,
creating the first living cell.
Natural Selection on the Molecular
Level
• Once the first molecule of RNA began to selfreplicate Natural Selection can go to work.
• Sequences that were more efficient at selfreplicating increased in population.
• Walter Gilbert proposed that
the cell used RNA as both the
genetic material and the
catalytic molecule, rather
than dividing these functions
between DNA and protein as
they are today.
• This hypothesis became
known as the " RNA world
hypothesis” of the origin of
life.
Essay Question on the Exam
You meet a man named bob who notices you
studying your biology Cornell notes. “Oh” say
Bob, “ I’ve always wondered how life came to
be covering our planet.”
Explain to Bob the RNA world hypothesis.