Objectives:

1.Be able to Summarize the Miller-Urey Experiment2.Relate the structure of Clay beds to the polymerization of nucleotides3.Understand the role of meteorite impacts in polymerization of Proteins4.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)

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

Proteases: Protiens that help digest proteins (meat)

Actin /Mysosin: Proteins that are used in muscle fibers.

Collagen: Found in connective tissue

PSD-95: Protein that builds connections between synapses

What came firstThe 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, then they would vaporize.

• The hypothesis was proved wrong: Amino acids Polymerized into long chains of protein.

Dr. Jennifer Blank

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 Nucleotidesinto 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 self-replicate Natural Selection can go to work.

• Sequences that were more efficient at self-replicating 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.