Table 4.3. Thermo. of Metabolism pp : Like Problem S1. Phosphorylations involving ATP. 361 Lec 21 Fri., 6oct17

Transcription

1 Table 4.3 Thermo. of Metabolism pp : Like Problem S1. Phosphorylations involving ATP 361 Lec 21 Fri., 6oct17 1

2 Table 4.3 Thermo. of Metabolism pp : Like Problem S1. Oxidations and Reductions involving NADH NAD Lec 21 Fri., 6oct17 Oxidation Reduction Reduction 2

3 Table 4.3 Thermo. of Metabolism pp : Like Problem S1. Isomerizations 361 Lec 21 Fri., 6oct17 Isomerization Dismuation Isomerization Isomerization Dehydration Decarboxylation 3

4 Like Problem S1. Find G 0 for the HYDROLYSIS of D-glucose-6-phosphate NOT in Table Reverse the above and add it to the ATP equation Hexokinase ATP PO 4 3 ADP - H 2 O Glucose 6 phosphatase The first step of burning glucose is add a phosphate to the 6 position This a very uphill reaction, as can be seen for the G 0 when coupled to hydrolysis of ATP. Half of the -31 kj/mol is used to put on the phosphate! 10/08/12 4

5 The first step of burning glucose is add a phosphate to the 6 position This a very uphill reaction, as can be seen for the G 0 when coupled to hydrolysis of ATP. Half of the -31 kj/mol is used to put on the phosphate! Find G 0 for hydrolysis of D-Glucose-6-phosphate: USE HESSE S LAW: First, reverse the above and then add it to the ATP equation You can see that hydrolysis of D-glucose-6-phosphate has large negative G 0 Therefore putting the phosphate on is a large positive G 0 5

6 But, ATP CANNOT drive this reaction WITHOUT an enzyme that COUPLES the two reactions. Remember the statement: Enzymes are the pulleys of biochemistry? No reaction will happen by putting ATP + glucose in water without enzyme for many years! ATP is bound close to glucose in a positon to transfer phosphate Glucose 10/08/12 6

7 I made up these numbers, but it must be something like this. 10/08/12 7

8 Thermodynamics of Metabolism pp Adapted from D.A. Harris, Bioenergetics at a Glance; Blackwell, Oxford 1995 * * * * 8

9 Gluose is partly reduced and partly oxidized A more easily Reduced Species 9

10 transport protons across the inner mitochondrial membrane, in a process called chemiosmosis. This generates potential free energy in the form of a ph gradient and an electrical potential... Electron transfer is coupled to PROTON transfer about 1000 mitrochondria /cell x cells in body = approx mitrochondria in our bodies. They cycle ~100 lbs of ADP---> ATP--->ADP per day.

11 CITRIC ACID CYCLE (where the NADH comes from) 11

12 Electron transfer is coupled to PROTON transfer 12

13 MORE Electron transfer is coupled to PROTON transfer 13

14 Myoglobin 14

15 Even MORE Electron transfer is coupled to PROTON transfer, as electronsfinally arrive at O

16 Reading for Monday: Chapter 7: pp (Electrochemistry) Why Electrochemistry in this course??: Electron transfer Useful work (w other ) from harnessing electron transfer reactions These voltages are merely another way to express Gibbs Free Energy 16

17 Standard Reduction Potentials electrons from H 2 (g) electrons spontaneously go from negative to positive potential 17

18 Reading: Chapter 7: pp Electrochemistry: Harnessing electron transfer reactions Consider Zn(s) + Cu 2+ (aq) Zn 2+ (aq) + Cu(s) G 0 = -214 kj/mol ; What will happen? Zn(s) Cu(s) e - Cu 2+ Zn 2+ on left: electrons flow from Zn(s) to Cu 2+ But, only a little tiny bit. Why? Answer: + charge builds up in Zn and electrons can t get out. 18

19 Consider Zn(s) + Cu 2+ (aq) Zn 2+ (aq) + Cu(s) Make the electrons go the long way around and grab on to them negative charge builds up e - Volt e- meter has HIGH resistance Zn(s) Cu(s) e - Zn 2+ salt bridge Cu 2+ 19

20 361 Lec 22 Mon., 5oct15 Continue with Electrochemistry Chap. 5 pp which will be on Exam 2 20

21 max (reversible) Volts = J/coulomb is a measure of G G = -T S univ + w useful at const T, P for reversible process: -T S univ = 0 (as current---> 0) G = w other, rev = -nfξ = coulombs x volts= MAX useful work where n = moles of electrons and F = coulombs/mol ξ = equilibrium voltage in J/coulomb ξ = G/(-nF) ξ 0 = - G 0 /(nf) = STANDARD REDUCTION POTENTIAL 21