16 - Friday Lecture 16 Announcements 1 Quiz 4 results A 20.7 sd 5.7 B 22.8 sd 4.8 C 23.4 sd 5.2 2 Today at 2:55PM in Comstock B108 The medical

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Friday, September 30, 2011, Lecture 16 Announcements: 1. Quiz 4 results: A 20.7 sd 5.7 B 22.8 sd 4.8 C 23.4 sd 5.2 2. Today at 2:55PM in Comstock B108: “The medical school interview—what are they looking for?” Wednesday’s lecture: An elementary rate constant corresponds to one energy barrier to reach a transition state How to measure Km and Vm by use of the Lineweaver-Burk (double-reciprocal) plot The ES dissociation constant K S = k -1 /k 1 Some enzymes turnover (into products) their substrates in microseconds or even faster (e.g. carbonic anhydrase); others require much longer (e.g. chymotrypsin) Today’s lecture: p. 118 The un catalyzed reaction of CO 2 reacting with water to form the products HCO 3 - + H + , has a forward rate constant k 1 of about 10 -1 sec -1 . So this is a rather fast reaction, even uncatalyzed! On the other hand, the forward rate constant k 1 for un catalyzed peptide hydrolysis is about 10 -8 sec -1 . This uncatalyzed reaction is about 10 7 slower than the uncatalyzed reaction catalyzed by carbonic anhydrase. Yet peptide hydrolysis is only 6 x 10 3 times slower when the enzyme-catalyzed reactions are compared. So, relative to its uncatalyzed reaction, chymotrypsin has speeded up its reaction far more than has carbonic anhydrase. We can calculate that carbonic anhydrase speeds up its rxn by lowering the G oTS by about 40 kJ/mol, whereas chymotrypsin lowers G oTS by about 60 kJ/mol. Therefore we conclude that chymotrypsin is a more "efficient catalyst" compared with carbonic anhydrase, since it lowers the TS free energy of the uncatalyzed rxn by such a large amount. Page 119 Enzyme inhibition is very important for learning exactly how enzymes work. Any reduction in the rxn velocity is a kind of inhibition. But most kinds of inhibition are NOT useful for learning about reaction mechanisms. For example: heat; 8M urea; detergent will all inhibit enzyme-catalyzed rxns, but no useful info comes out.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/01/2012 for the course BIOMG 3310 taught by Professor Feigenson during the Fall '11 term at Cornell University (Engineering School).

Page1 / 5

16 - Friday Lecture 16 Announcements 1 Quiz 4 results A 20.7 sd 5.7 B 22.8 sd 4.8 C 23.4 sd 5.2 2 Today at 2:55PM in Comstock B108 The medical

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online