Transcript The Formation of Molecules Necessary for Life

Learning Goal 5 – The Origin of Cells
Conditions of the Early Earth –
The Oparin-Haldane Hypothesis –
New Theories for the Origin of Life –
Protocells –
The First Living Cells –
The Endosymbiotic Hypothesis –
Eukaryote, Bacteria, and Archaean Relationships –
Conditions on Primordial Earth
Due to gravitational compression, the internal temperatures of our planet were 1000 -3000
degrees Celsius.
Metals and heavier substances sank into the core, and lighter substances rose to the
surface.
The crust formed when the surface cooled and solidified into rocks.
The gravitational pull was strong enough to hold an atmosphere, which came partly from
the original dust cloud, and from gasses inside of the planets interior.
The conditions on primordial life met the basic conditions for life to begin. It was the right
distance from the sun for water to stay as a liquid.
As earths surface cooled, sources for energy caused chemical bonds to break and form
leading to the formation of organic material.
The
Oparin-Haldane
Hypothesis
•Initiated Scientific Investigations into the Origin of Life.
•They hypothesized that earth's atmosphere in the past was
different from what it is today.
• COMPOSED OF HYDROGEN, METHANE, AMMONIA, AND WATER.
• This gave the primordial atmosphere a reducing character
•If oxygen was present the newly formed molecules would have
been broken down quickly by oxidation.
•As the surface of Earth cooled again, torrential rains of this mixture
formed the first seas, the “primordial soup”
•Oparin demonstrated that there could have been a great variety of
organic compounds before there were living things, as a result of the
fact that carbon was first present.
New Theories for the Origin of Life
One current theory for the origin of life
is that life developed near
hydrothermal vents in the sea floor.
Many such vents exist in today’s
oceans, emitting bursts of mineral-rich
water superheated to up 400 C by
submarine volcanoes. Scientists
exploring hydrothermal vents find
complex ecosystems associated with
them.
Life might have originated there
because near oceanic hydrothermal
vents reduce conditions that existed
there along with an abundance of the
chemicals essential for life.
Protocells
Definition- A primitive cell-like structure that has
some of the properties of life and that might have
been the precursor of cells.
Made up of only two molecular components: RNA
replicase and a fatty acid membrane.
It is a extremely simple version of a cell.
• The first living cells may have originated from protocells, very simple versions of
regular cells.
• They would have needed a better information system to properly form into modern
cells.
• The first living cells to form were prokaryotes.
• They do not contain a nucleus, but had an area where DNA could reside.
• They also contained ribosomes and the enzymes that are needed to transcribe RNA
into amino acid and therefore protein.
• They also had an oxidation system in their cytoplasm.
The Endosymbiotic hypothesis
first postulated by Lynn Margulis in the 1967.
Dr. Margulis was doing
research on the origin of
eukaryotic cells. She proposed
that the similarities between
prokaryotes and organelles,
together with their appearance
in the fossil record, could best
be explained by "endosymbiosis".
[Endo = "within"]
[Endosymbiosis = cells are
engulfed, but not digested...cells
live together is a mutually
benefitting relationship, or
symbiosis]
Her original hypothesis was that
the aerobic (requires oxygen)
bacteria was ingested by the
anaerobic (poisoned by oxygen)
bacteria. Each would have
benefiting functions from their
symbiosis relationship.
The aerobic bacteria would have
handled the toxic oxygen for the
anaerobic bacteria, and the
anaerobic bacteria would ingested
food and protected the aerobic
Eukaryote, Bacteria, and Archaean
Relationships
Bacteria vs. Archaean
Eukaryote vs. Achaean
Genome organized into a single DNA
molecule
Presence of introns in genes
No nuclear envelope
Archeaen Only
No organelles comparable to
mitochondria chloroplast, the ER, or
Golgi complex
Cell walls, plasma membrane, gene
and rRNA sequences different from all
other organisms.