The unicellular origins of complex physiology

Published on November 30, 2016   19 min

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My name is John Torday, I'm a Professor of Evolutionary Medicine at UCLA. The title of this lecture is "The Unicellular Origins of Complex Physiology".
Sterols and membrane fluidity in prokaryotes and eukaryotes. Sterols play a fundamental role in membrane fluidity in determining interactions between the external and internal environments of the cell. Bacteria express hopanoids, which determine the structure of the cell membrane. Eukaryotes express cholesterol, which plays the same role that hopanoids do in the cell membrane.
Ancient atmospheric oxygen levels, shown in frames A and B of the slide, had to have been high enough to allow the biosynthesis of cholesterol. It requires 11 atoms of oxygen to synthesize 1 molecule of cholesterol. The insertion of cholesterol into the eukaryotic cell membrane fostered the basic characteristics of vertebrate evolution, metabolism, respiration, and locomotion. Subsequently, the cell membrane cholesterol formed lipid rafts that formed the sites for receptors that mediate cell-cell interactions. Ultimately, cholesterol was the substrate for the steroid hormones and vitamin D, which are a large part of the endocrine system that integrates and orchestrates physiologic functions.

The unicellular origins of complex physiology

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