3rd_lecture - MCB 102 Professor Fyodor Urnov 06/23/10...

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MCB 102 Professor Fyodor Urnov 06/23/10 Lecture 3 ASUC Lecture Notes Online is the only authorized note-taking service at UC Berkeley. Do not share, copy, or illegally distribute (electronically or otherwise) these notes. Our student-run program depends on your individual subscription for its continued existence. These notes are copyrighted by the University of California and are for your personal use only. D O N O T C O P Y Sharing or copying these notes is illegal and could end note taking for this course. ANNOUNCEMENTS I’d first like to make an announcement before I start about the role of evolution in biology. Most biology text books today embody this quote by Theodosius Dobzhansky in one form or another, “Nothing in biology makes sense except in light of evolution.” This means that living things of all shapes and sizes have evolved. And that fact provides an amazing, powerful tool to understand the biology of the world. It also helps explain the point that I was trying to get at yesterday about our need for niacin in our diets. LECTURE I would like to again talk about our lack of ability to synthesize niacin despite the crucial role it plays in biochemistry. To highlight its importance, I would first like to give an example. In the US South, a large portion of the population was susceptible to the illness pellagra. Pellagra was characterized by skin lesions and gastrointestinal and neurological disturbances. At first, the government thought it was a genetic disease because certain families were more likely to get it than others. In fact, pellagra is a deficiency in niacin (B3). It occurred in specific families because of poverty; these families subsisted on corn, which is niacin poor. Niacin forms NAD + , which is vital to cellular respiration because it is the “flame” that allows for carbon breakdown, and so a lack of niacin results in digestive problems. Vitamins as a whole are absolutely necessary to human metabolism. They are cofactors that make up the core of human biochemistry, and we will learn about at least six of them in this class. This brings us back to the previous question. Why would we rely so heavily on something that we cannot make? Because we can consume it to make up for our inability to synthesize it, since all organisms need it. Niacin But then would it not be simpler to just stop relying on vitamins altogether? Why didn’t we just develop metabolisms that didn’t need these vitamins? The answer to this lies in the fact that our core metabolisms evolved three billion years ago. They are so ingrained into who we are that we would never be able to change it. Any small steps to alter this dependence would most likely harm other processes, and it would not be beneficial. An analogy would be gun-related deaths in the US. The United States leads the world in gun-related deaths partly because the right to bear arms is a fundamental part of our Constitution. Even though the political situation in the modern day is completely different from the 1770s, a core decision back then has greatly affected key features of the modern day.
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3rd_lecture - MCB 102 Professor Fyodor Urnov 06/23/10...

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