c340 Key to Exercise on Membrane Function

Key to Exercise on Membrane Function
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Table 1: Movement Across Membranes
type of movement	Is energy required?	Is a protein required?	Is it specific?	Is it saturable?
diffusion through a bilayer	No	No	No	No
diffusion through an ion channel	No	Yes	Yes	No
diffusion using a carrier	No	Yes	Yes	Yes
active transport	Yes	Yes	Yes	Yes

2. a. − 4.0 kJ/mol; b. − 12.9 kJ/mol; c. + 12.9 kJ/mol; d. − 38.0 kJ/mol; e. + 38.0 kJ/mol

Table 2: Solute Concentrations for Question 2
solute	glucose	Na⁺	Ca²⁺
extracellular concentration	5 mM	145 mM	2 mM
intracellular concentration	1 mM	12 mM	1 x 10^-4 mM

3. a. + 25.1 kJ/mol; b. + 12.2 kJ/mol; c. − 0.7 kJ/mol; d. − 13.6 kJ/mol; d. Use 3 Na⁺/Ca²⁺

4. a.
b. The GLUT1 binding site probably doesn't have space for the phosphoryl group. Also,
the phosphoryl group may bind water more firmly, and hydrated glucose-phosphate
definitely doesn't fit the binding site.

5. a. − 12.9 kJ/mol; b. − 7.2 kJ/mol; c. − 1.5 kJ/mol; d. + 4.2 kJ/mol; e. When C₂/C₁ ratio is greater than ∼ 100.

6. a. E → A → F → B → D → C → G
b. The cytosol is at the bottom of the membrane and the extracellular side of the membrane is at the top.

2	5
1	4
6	3

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