PS1-08answ - Name Section TA Problem Set 1 Biochemistry...

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

View Full Document Right Arrow Icon
Name: ________________________ TA: __________________________ Section: _______________________ Problem Set 1 Biochemistry 462b Spring 2008 Due Jan 25, 2007 Question 1. (3 points) The parietal cells of the stomach lining contain membrane pumps that transport hydrogen ions from the cytosol of these cells (pH 7.0) into the stomach, contributing to the acidity of gastric juice (pH 1.0). Calculate the free energy required to transport 1 mol of hydrogen ions through these pumps. Assume a temperature of 37 °C and a neutral electrochemical gradient across the membrane. Ans : The reaction is written as C inside C outside Since there is no chemical transformation involved in the transport of H + across a membrane, at equilibrium the Δ G'° is zero (- RT ln(1/1) = 0). The intracellular H + concentration is 10 -7 M and outside of the cell is 10 -1 M. Δ G = Δ G'° + RT ln (10 -1 M/10 -7 M) = 0 kJ/mol + (2.58 kJ/mol) ln (10 -1 M/10 -7 M) = 35 kJ/mol Question 2. (4 points) Cells typically have low [Na + ] (12 mM) inside and much higher [Na + ] outside (145 mM). The Na + K + ATPase maintains the Na + gradient, causing the inside to be negative (-70 mV) relative to the outside of the cell. The free energy driving the entry of Na + into the cell results from both the concentration gradient ( Δ Gc) and membrane potential ( Δ Gm). Calculate the contribution to Δ G from each, and well as the total free energy difference across the membrane resulting from the Na+ ion gradient. Assume the system is at 20°C. Ans
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 homework help was uploaded on 04/02/2008 for the course BIOC 462b taught by Professor Grimes,tsao,borque during the Spring '08 term at Arizona.

Page1 / 3

PS1-08answ - Name Section TA Problem Set 1 Biochemistry...

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