Rna

ss RNA as template

New ds RNA

Protein ss RNA used as message

Protein

Folded protein

Primitive photosynthesis probably used sulfur compounds as a source of electrons, more advanced photosynthesis resulted in the release of oxygen from water.

shared the enzymatic functions. Later, RNA lost most of its enzymatic roles as the more versatile proteins took these over (Fig. 20.07). It is generally thought that RNA was the first information storage molecule and that DNA was a later invention. Because DNA is more stable than RNA, it would store and transmit information with fewer errors.

This primitive cell vaguely resembles primitive bacteria, and lived off the organic compounds in the primitive soup. Eventually the supply of pre-made organic molecules was consumed. The proto-cell was forced to find a new source of energy and it turned to the sun (Fig. 20.08A). The earliest forms of photosynthesis probably used solar energy coupled to the use of sulfur compounds to provide reducing power. Later, more advanced photosynthesis used water instead of sulfur compounds. The water was split, releasing oxygen into the atmosphere.

Before this, the atmosphere had been void of oxygen.The addition of oxygen completely altered the primitive earth. Once oxygen became available, respiration could

Was this article helpful?

0 0

Post a comment