17th lecture

17th lecture - MCB 102 Professor Fyodor Urnov 07/20/10...

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Professor Fyodor Urnov 07/20/10 Lecture 17 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 If you're wondering about re-grades for the midterm, you're free to turn one in. Be aware, though, that a random number of midterms were photocopied. So, yes, you can change your answer if you'd like, but there's a definite possibility that you will be caught. Is it worth it? LECTURE Something very important I want to stress is that enzymes have an optimal coordinated temperature, usually at around 37 degrees Celsius. However, the outside temperature is always much less than this, so our body must strive to maintain a higher condition inside. We can keep this temperature up by burning carbon, and that is my poor transition back into glycolysis. Hexokinases As far as I remember, we were able to get through one reaction yesterday. It uses the enzyme hexokinase, a rare example where the enzyme is named after what it actually does: adding a phosphate group to the glucose. For the process to work, the enzyme does an induced fit fold around its substrate and an ATP. The addition of this phosphate traps the molecule inside the bloodstream. If you had breakfast, that's what your body is doing right about now. I want to take a look at glucokinase , which is the horrible alternative name for hexokinase IV. You must know both names, though, because glucokinase often appears in various articles you may read. Hexokinase IV actually resides in the nucleus of a cell most of the time. By sequestering it off, the cell assures that the hexokinase IV won't start working prematurely. Isolating enzymes in organelles that don't contain their substrate is a general regulation for regulating protein function in eukaryotes . Once you eat something and blood sugars rise above 5 millimolar, the hexokinase IV is then released. A regulator protein, GCKR , is able to tell how high the blood sugar is, and it lets go of the enzyme. A portion of hexokinase IV tells the cell that it functions in the cytoplasm. GCKR usually masks this signal, so when it detaches, the cell realizes the enzyme is misplaced and sends it into the cytoplasm. I don't have time to talk about this much more, so if you're interested, look up the article with the PubMed ID 18726182. Midterm Question : What will be on the final, though, is a comparison between this and the use of steroids to treat asthma. Corticosteroids use the exact same process, so if you remember this one, you'll understand both systems. The only big difference is that corticosteroids work the other way around; cortisol goes from the cytoplasm to the nucleus. Hexokinase with GCKR
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This note was uploaded on 10/31/2010 for the course MCB 70456 taught by Professor Urnov during the Summer '10 term at Berkeley.

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17th lecture - MCB 102 Professor Fyodor Urnov 07/20/10...

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