34 - Monday, November 15, 2010 Lecture 34 Announcements: 1....

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Monday, November 15, 2010 Lecture 34 Announcements: 1. Assignments for this week: Reading and problems as in LG. No more PyMOL assignments until the last week of class. 2. Office hours and review times, dates, rooms for the last week of classes are the same as during the rest of the semester. No office hours or reviews for next week (the week of the Thanksgiving Break). 3. The Racker Lectures happen this week: Nobel Prize winner Mario Capecchi will give two talks: Thursday night at 8 PM in Call Auditorium in Kennedy Hall (a talk to a general audience), “The making of a Scientist: An unlikely journey” Friday at 4 PM in G-10 Biotech (a science-focused talk), “Gene targeting into the 21 st Century: Mouse models of human disease from cancer to neuropsychiatric disorders” 4. Alternative meets Western medicine: sponsored by the Ithaca Free Clinic, on Wed 11/17 at 5:30PM live demonstrations by a shiatsu massage therapist and an acupuncturist; tips for stress reduction for college students. p. 238 The mitochondrial matrix is often referred to as the "N" side , and the intermembrane space , which is contiguous with the cytosol because of the permeability of the mitochondrial outer membrane, is often referred to as the "P" side . This is because, relative to each other, the matrix is Negative and the intermembrane space (and the cytosol) is Positive . This separation of charge is a result of: 1. proton pumping from the inside to the outside; 2. consumption of H + from the matrix at Complex III during the Q cycle to form UQH 2 , and consumption of H + from the matrix at Complex IV to form O 2 . This is the proton and electric potential gradient we have been discussing. The free energy available (starting from NADH) is as follows: NADH + H + + 1/2 O 2 NAD + + H 2 O NAD + / NADH E = -0.28 V ( in real mito. matrix, not 1M! ) 1/2 O 2 / H 2 O E = +0.78 V ( in real mito. matrix ) E = +1.06 V G = -nF E = -205 kJ/mol
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The free energy of transport to form the gradient can be written using the pH, since protons are what are being transported: G T = RT ln ([H + ] cyt /[H + ] matrix ) + zF ∆ψ = -2.3 RT (pH cyt - pH matrix ) + F ∆ψ Typical values: T = 310 K (pH cyt - pH matrix ) = (7 - 7.5) = -0.5 (note: the matrix always has higher pH) ∆ψ = +0.15 V (always negative in the matrix) G T = 3.0 kJ/mol + 14.5 kJ/mol = +17.5 kJ/mol (per mole H + transported) Notice that the difference in electrical potential is much more important that the difference in H + concentrations in typical animal mitochondria! This is because so much other metabolism occurs in the mito matrix that its pH must not be allowed to rise very high. The mito matrix is buffered by the presence of the many proteins therein, with their many ionizable groups. Remember that the above 17.5 kJ/mol (per mole H
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34 - Monday, November 15, 2010 Lecture 34 Announcements: 1....

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