1-2. List two factors that increase membrane flexibility.

Increasing temperature, decreasing saturation of acyl groups (increasing the number of double bonds), adding cholesterol

3. There are at least six classes of integral membrane proteins. Name one method for distinguishing one class from another.

Location (inside or outside face) of each terminus, number of transmembrane helices, whether or not the protein is lipid-anchored, number of chains

4-5. Relate diffusion within the membrane to composition of the inner and outer faces of the bilayer.

Diffusion occurs rapidly within each plane (face) of the membrane but very, very slowly (without flippase) from one face to the other. As a result, each face has a distinctive compostion. That is, the inner face is not the same as the outer face.

Because I had trouble wording this question so that it asked what I wanted to get across, I accepted a wide variety of answers. Understanding the above answer was my goal for you.

6-10. [Cl⁻]_out = 78 mM and [Cl⁻]_in = 1.5 mM. [Ca²⁺]_out = 2.1 mM and [Ca²⁺]_in = 0.10 mM.
R = 8.315 J/mole-K, T = 298 K, and F = 96,480 J/V-mole. Use ΔV = − 0.060 V.

6-7. For moving Cl⁻ into the cell, C₁ =        78 mM            and Z =          − 1               .

8-10. What is ΔG_T for moving Ca²⁺ into the cell?

ΔG_T = R T ln (C₂/C₁) + Z F ΔV
= (8.315 J/mol-K) (298 K) (ln 0.10/2.1) + (2+) (96,480 J/V-mol) (− 0.060V)
= (2477.87 J/mol) (ln 0.0476) + (− 11577.6 J/mol)
= (2477.87 J/mol) (− 3.04) −11577.6 J/mol
= − 7532.7 J/mol − 11577.6 J/mol
= − 19110 J/mol = − 19.1 kJ/mol

What you can see, I hope, is that in this example the membrane potential is more significant in determining ΔT_T than the concentration gradient.

top of page