"Chemistry is in the News"
By Richard Ellis, LA Times, October 16, 2001.
NOTE: Start at the 17th paragraph, e.g. "At the 1992 Nobel Symposium ..."
The origin of life has been a mystery debated and pondered by scientists for hundreds of years. Recently, new light was shed on this murky quagmire in the form of a new theory, speculated and tested by Gunter Wchtershuser: the "iron sulfur world theory", or the formation of life from elements available near hydrothermic vents deep in the ocean. [Read an article about Waechtersaehuser's research in Science News - includes molecular diagrams!]
Hydrothermal vents occur at places on the sea floor where lithospheric plates interact through collisions, sliding under each other, or pulling apart. This creates trenches and fissures where volcanic activity beneath the crust escapes in the form of hot gases and dissolved minerals, spewing into the ocean in water heated to around 371 degrees celsius. It is here that extreme forms of life have been discovered, living not off oxygen, but on hydrogen sulfide, a substance deadly to most living organisms. And it is here where life is thought to have originated, in a toxic, heated, " prebiotic broth" filled with raw elements and basic inorganic compounds.
The common theory of "Prebiotic Broth" is in question: the primordial atmosphere of the earth (consisting of methane, ammonia, and water is in contradiction with recent suggestions (an atmosphere composed of CO2, N2 and H2O). Waechtersaehuser's idea is based on a series of interactions: metallic ions in sulfides, like iron sulfide, interacted with gases from earth's hydrothermic vents (energy source) to create acetic acid. This catalyzed the addition of carbon molecules to produce pyruvic acid, which reacts with ammonia to form amino acids (the building block of proteins, i.e. LIFE!)
George Cody et al. verified the speculation experimentally in the lab: he recreated "proper" conditions and produced pyruvic acid using iron sulfide. Waechtershaeuser's theory is further backed up by the argument that pyruvate is too unstable to slowly accumulate, as is suggested by the "prebiotic broth" theory.
theory may not be the solution to the puzzle of
origin, but by incorporating organic chemistry it brings us closer to the
truth of the mystery. Perhaps the question of where we all have
originated will soon be concluded!
Pertinent Text References
Chapter 1. Introduction and Review.
Chapter 2.15D Carboxylic Acids
Chapter 4.9 Activation Energy and Temperature Dependence of Rates
Chapter 4.10 Transition States and Catalysts
Evidence for life on Earth before 3,800 million years ago
Amino Acid Repository
Carboxylic Acids (structure)
Question 1: Draw the Lewis dot structure of CO2 and H2O. Analyze bond angles and bonding pairs. Which of these molecule(s) is polar? Why is there a difference in bonding angles between water and carbon dioxide?
Question 2: Draw the Lewis-Kekule structure of NH3 and N2.
Question 3: Draw the structure of acetic acid and name the main structural property of carboxylic acids.
Question 4: The gas from the hydrothermal vents is hot before the seawater cools it. What does this say about the energy of and the molecules released by the vents? Based on this and the article, would you say the first reactions to proceed to life were endothermic or exothermic?
Question 5: What is the iron sulfur theory and what is the purpose of catalysts in reactions?
Question 6: Draw the structure of pyruvic acid. Give the chemical formula and the common name of the molecule added to create alanine from pyruvic acid. (HINT: See Insert Above.)
The origin of life has been accredited to a number of different causes. There are a vast number of theories and speculations, all of which contribute to the skepticism of scientists and inquirers everywhere, even to those theorizing according to religion. Comparing the "Prebiotic Broth" theory and W_chtersh_userfs theory, does either one seem more convincing than the other? Can either be assumed accurate? What speculations or ideas can you come up with to suggest a source for energy under suggested conditions?