a tiny spherical droplet of assorted organic molecules (specifically, lipid molecules) which is held together by hydrophobic forces from a surrounding liquid

protein-like molecules formed inorganically from amino acids; 

an organism that cannot synthesize its own food from inorganic raw materials and therefore must obtain energy and body-building materials from other organisms; 

a molecule of RNA that has catalytic properties; 

biological process that captures light energy and transforms it into the chemical energy of organic molecules (carbohydrates), manufactured from CO2 and H2O; 

a columnlike rock that consists of many minute layers of prokaryotic cells (cyanobacteria); 

assemblages of organic polymers that spontaneously form under certain conditions (involved in chemical evolution); 

a tiny bubble (vesicle), made out of the same material as a cell membrane; 

the biological conversion of one or more carbon molecules (usually carbon dioxide or methane) and nutrients into organic matter using the oxidation of inorganic molecules (e.g. hydrogen gas, hydrogen sulfide) or methane as a source of energy, rather than sunlight, as in photosynthesis; 

non-fossil evidence:

isotopic fingerprints of organic compounds

(i.e. euks. leave certain traces of sterols)

microfossils:

rich deposits filled with squiggles left by proks.

(stromatolites: rock-like columns with many layers)

Oparin/Haldane: simple organic molecules such as sugars, nucleotide bases, and amino acids could form spontaneously from simpler (inorganic) raw materials

• prebiotic soup hypothesis-organic molecules formed near Earth's surface

Oparin: org. mols. accumulate in shallow seas to form a "sea of organic soup"

• smaller organic molecules (monomers) combining to form larger ones (polymers)
• organic polymers formed on clay surfaces (clay-consists of microscopic particles of weathered rock; binds organic monomers and contains zinc and iron ions-acts as catalyst
• reducing atmosphere of early life were the raw materials for the evolution of life
• (diff. types of coacervates might have formed)

Haldane: primitive CO2, NH3, and water-vapor atmosphere would give rise to organic mols. that accumulate in Earth's ocean

Miller and Urey: exposed atmosphere rich in H2, CH4, H2O, and NH3 to an electric discharge that simulated lighting in a pond-->a.a. and other organic molecules formed

• -formed some of the nitrogenous bases of DNA and RNA, but no nucleotides-->not part of the early organic soup

Provide plausible evidence to support the hypothesis that chemical evolution resulting in life's origin occurred in four stages:

a. Abiotic synthesis of organic monomers.

b. Abiotic systhesis of polymers.

c. Formation of probionts.

d. Origin of genetic information.

a. conditions on early Earth (reducing atmosphere) favored the synthesis of organic compounds from inorganic precursors

• -reducing environment promoted the joining of simple molecules to form more complex ones
• -It is likely that small “pockets” of the early atmosphere near volcanic openings were reducing

• 
  
• -high levels of oxygen in the atmosphere attack chemical bonds
• 
  
• -lightning and the intense UV radiation that penetrated the primitive atmosphere-->energy to make org. mols
• -Young suns emit more UV radiation-->lack of an ozone layer in the early atmosphere would have allowed this radiation to reach Earth
• 
  
• -Miller-Urey-type experiments with such atmospheres have not produced organic molecules

• •  
    • 
      
  • -Alternate sites proposed for the synthesis of organic molecules include submerged volcanoes and deep-sea vents where hot water and minerals gush into the deep ocean
    • -rich in inorganic sulfur and iron compounds-->ATP synthesis
    • 
      
    • -Some of the organic compounds from which the first life on Earth arose may have come from space
    • -meteorites had a.a. and equal amts. of D and L isomers-->Earth favors L-isomers only
    • 
      
  • b. Laboratory simulations of early-Earth conditions have produced organic polymers.
  • -The abiotic origin hypothesis predicts that monomers should link to form polymers without enzymes and other cellular equipment.-mixing a.a. and clay together
  • -Researchers have produced polymers, including polypeptides, after dripping solutions of monomers onto hot sand, clay (weak catalysts), or rock.
  • -Similar conditions likely existed on early Earth at deep-sea vents or when dilute solutions of monomers splashed onto fresh lava.
  • • 
      
    • c. Protobionts (cell-like, but not a cell) can form by self-assembly from abiotically prod. org compounds
    • -protobionts-aggregates of abiotically produced molecules surrounded by a membrane or membrane-like structure
    • -Life defined by two properties: 
    • 1. accurate replication
    • 2. metabolism
    • *(Neither property can exist without the other.)
    • -DNA molecules carry genetic information needed for accurate replication
    • -The replication of DNA requires nucleotide building blocks provided by cell metabolism
    • 
      
    • -Self-replicating molecules and a metabolism-like source of the building blocks must have appeared together
    • 
      
    • -Protobionts exhibit some of the properties associated with life: 
    • 1. reproduction
    • 2. metabolism
    • 3. can maintain an internal chemical environment different from surroundings
    • 
      
    • -droplets of abiotically produced organic compounds called liposomes form when lipids and other organic molecules are added to water
    • -lipids form a molecular bilayer at the droplet surface, much like the lipid bilayer of a membrane
    -liposomes (lipids+ water)-->hydrophobic mols. from bilayer-->form metabolic rxns.
    -droplets can undergo osmotic swelling or shrinking in different salt concentrations
    -Some liposomes store energy in the form of a membrane potential
    -Liposomes behave dynamically, growing by engulfing smaller liposomes or “giving birth” to smaller liposomes
    -If similar droplets forming in ponds on early Earth incorporate random polymers of linked amino acids into their membranes, and if some of these polymers made the membranes permeable to molecules, then those droplets could have selectively taken up organic molecules from their environment
    
    
    • d. RNA may have been the first genetic material
    • 
      
    • -Ribozymes-RNA catalysts:
    • 1. remove their own introns
    • 2. modify tRNA molecules to make them fully functional
    • 3. help catalyze the synthesis of new RNA polymers
    • 4. can assume a variety of 3-D shapes specified by their nucleotide sequences (unlike DNA)
    • 5. RNA molecules have both a genotype (nucleotide sequence) and a phenotype (three-dimensional shape) that interacts with surrounding molecules
    • 6. Under particular conditions, some RNA sequences are more stable and replicate faster and with fewer errors than other sequences
    • 
      
    • -Laboratory experiments have demonstrated that RNA sequences can evolve under abiotic conditions.
    • 
      
    • -Beginning with a diversity of RNA molecules that must compete for monomers to replicate, the sequence best suited to the temperature, salt concentration, and other features of the surrounding environment and having the greatest autocatalytic activity will increase in frequency

Refer to the following terms.

A. coacervate B. liposomes C. mesosomes

D. microspheres E. proteinoids

Formed by dehydration sysnthesis of monomers: E. proteinoids

A droplet that self-assembles from only polypeptides in cold (?) water: D. microspheres

A droplet that self-assembles from organic ingredients that include lipids: B. liposomes

A colliodal droplet that forms when polypeptides, nucleic acids, and polysaccharides are shaken together: A. coacervate