D.1a: Origin of Life: Organic molecules

10/08/2013 § Leave a comment

Hi. It’s me. Let’s skip the formalities and cut to the chase. Seven units to go, and our first one is Evolution. As review of what we should already know, cells can only be formed from other cells. However, obviously at some point in the history of the Earth, the first living cells must have come from somewhere and there are four necessary processes for that to happen:

  1. simple organic molecules were produced by chemical reactions (e.g. amino acids, ammonia, and water)
  2. the simple organic molecules would need to assemble into polymers, e.g. polypeptides
  3. the polymers could self-replicate (allowing for inheritance)
  4. membranes were developed to package the molecules

There are three major possible locations where organic compounds could have been synthesized to begin the origin of life. The first was in 1953 in an experiment by scientists Stanley Miller and Harold Urey wherein they recreated the conditions of the Earth (back then) to synthesize the chemical reactions of the atmosphere, water, and on the surface of the earth. This involved electrical discharges, boiling and condensing water, and mixing gases like ammonia, methane and hydrogen.

Secondly, hydrothermal deep-sea vents were said to create the chemical reactions through the gushing hot water. The chemicals here held all the necessary energy and raw material needed to create monomer organic chemicals.

Finally, some scientists think aliens were involved.

(NASA thinks they might have come to Earth via meteorite, comets, or interplanetary dust seeing as plenty of meteorites collided into the Earth those 4000 million years ago.)

DATA BASED QUESTIONS

The Murchison meteorite, page 308

1. Compare the amino acids found in the meteorite with those produced in the Miller-Urey experiment. Refer to named examples.

There is the same amount of glycine in both the Murchison meteorite and Miller-Urey experiment. While there are six dots for Proline in the Murchison meteorite, there are only two in the Miller-Urey experiment. Another big difference is in the a-aminoisobutyric acid, wherein the Murchison meteorite has eight dots and the Miller-Urey experiment only has four.

2. Suggest a conclusion based on your comparison.

While most of the amino acids are roughly the same amount in the Murchison meteorite and the Miller-Urey experiment, there are enough differences suggesting that the experiment isn’t completely reliable to compare to the meteorite that delivered the first organic molecules to Earth. (This is assuming that we accept the meteorite theory.)

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