Origin of Life

I. How did the first cell form? A) Spontaneous formation of monomers and macromolecules from chemicals in environment **** Only possible if no free O2 B) monomers join to make macromolecules C) cell membranes form D) nucleic acids pass on Genetic infromation

II. Monomer Synthesis A. humans created organic monomers from non-living chemicals B.Miller and Urey - created “Early Earth Apparatus” C. Archaean atmosphere in the top D. electrodes to produce “lightning” E. primordial pond in the bottom

F. Results: 12 of 20 most common amino acids synthesized + monomers Showed monomers can form from non-living source next step: polymerization

III. Macromolecules chains of molecules proteins carbohydrates lipids nucleic acids

IV. Requirements for macromolecules to form on their own A. energy source: 1. lightning 2. geothermal vents B. concentration: to bring materials together 1. tide pools/evaporation 2. clay

clay a. Forms platelets b. platelets are: very small flat with negative charge on surface

V. Cell membrane formation each phospholipid has a hydrophobic end and a hydrophilic end when surrounded by water, phospholipids form a sphere hydrophobic ends protected on the inside

Protobionts fatty acid spheres that form naturally Macromolecules & enzymes inside reactions occur inside Grow divide selectively absorb & release compounds digest starch store & release energy

Experiments by Sidney W. Fox and Sidney w Experiments by Sidney W. Fox and Sidney w. Fox and Aleksandr Oparin have demonstrated that protobionts form spontaneously. They formed liposomes and microspheres, which have membrane structure similar to the phospholipid bilayer found in cells may be formed spontaneously, in conditions similar to the environment thought to exist on an early Earth. These experiments formed

Are Protobionts Alive? No they can’t replicate themselves (pass on their traits to offspring)

VI. Nucleic acid reproduction RNA can assemble on its own Can replicate (make more copies) Can pass on genetic info when cell divides

VII. Earliest Life Forms 3.5 bya 3.4 byo, South Africa 1) prokaryotic bacteria 2) anaerobic: live without O2 4) heterotrophs 3) fermenters: use organic molecules for energy modern

VIII. The First Energy Crunch organic molecules become scarce competitive advantage goes to – organisms that can make their own food photosynthesis

Photosynthesis light-absorbing pigments (like chlorophyll) already present chlorophyll form spontaneously

First Cyanobacteria 3.5 bya O2 released as a by-product problem: O2 breaks bonds of organic molecules (i.e. - it’s toxic) 6CO2 + 6H2O carbon dioxide water C6H12O6 + 3O2 sugar oxygen energy from sunlight

Living Precambrian Cyanobacteria Ancient vs. Modern

Earliest (Undisputed) Fossils = Stromatolites 2.2 byo Michigan

Stromatolites dome-shaped, layered structures Up to 3.5 byo consist of layers of bacteria upper layers aerobic, photosynthetic lower layers anaerobic produce abundant oxygen how do we know?

They are still alive today in special environments, notably Shark Bay, Australia Tide In Tide Out

Formation of Stromatolites Cyanobacteria form a mat on top of sediment A new layer of sediment is deposited on top 1 cm Bacteria grow up through new layer

Stromatolites provide evidence for the occurrence of cyanobacteria in the fossil record. Modern Ancient

Aerobic Bacteria some bacteria evolved antioxidants allowed those bacteria to survive rising O2 levels by 1.8 bya some bacteria even evolved to use O2… By doing aerobic respiration

Origin of Nucleus & E. R.

Nucleus formation = First Eukaryotes Mid-Proterozoic Eon Fossils 1.5 – 2 bya

Origin of Mitochondria & Chloroplasts Endosymbiotic theory Eukaryotic cells take in bacteria as endosymbionts Bacteria become mitochondria Cyanobacteria become chloroplasts

Evidence for Endosymbiotic T 1) Two layers of membrane Outer membrane like host cell Inner membrane like a bacteria

Evidence for Endosymbiotic T 2) Mito. & chloro. have their own DNA Circular Chromosome like bacteria Different genes than are in the host nucleus

Evidence for Endosymbiotic T 3) Mito. & Chloro have own ribosomes & Make their own proteins different from host Ribosomes like bacteria

Evidence for Endosymbiotic T 4) Mito & Chloro grow and reproduce on own