3. In the following diagram, determine the type of transport protein in A. Justify your answer with specific reference to the role that Ca²+ and galactose have in this scenario.

The formation of a membrane vesicle is a complex choreographed process, however very little energy is required for this event to occur. What is the only step of vesicle formation that requires the input of energy? Explain why the rest of the processes energetically favorable?

7. Specificity of membrane transporters. A protein that transports amino acids across the cell membrane was found to bind only a few amino acids efficiently. To find the specificity, many different amino acids and substrate analogs were used as competitive inhibitors in transport studies at pH 5.9 with L-histidine (Km = 10 μM). The Ki values calculated from Lineweaver-Burk plots are shown in the table below. Comparing the structures of L-histidine and the competitive inhibitors (for which most of them, you should know their structures!), what can you conclude about the characteristics of molecules that this transport protein binds at its active site? K; (10-€ M) Amino acid or analog L-Lys L-Arg Gly L-Asp D-His Histamine Dehydrourocanate D-Arg 2 3 285 450 340 390 285 355 HN- + HN + Structure -ΝΗ -NH3 histamine ΝΗ -COO™ dehydrourocanate

8. The cartoon at the right depicts a hypothetical cell that has a Lit-K* ATPase (shown as the filled circle with arrows). The cell also contains Lit and K* channels. The membrane is three times more permeable to K* than it is to Li*. The following are the steady state concentrations of Li* and K*: [Li*]out = 100 mM [Li*]in = 5 mM [K*]out = 4 mM Lit ADP + P, ATP [K*lin = 80 mM = 10°C Temp = Assuming that the Vm is produced only by the diffusion of Li* and K*, calculate the Vm.

Label the diagram below as either passive transport (diffusion or facilitated diffusion) or active transport. Provide examples of solutes that are transported in these various ways across the cell membrane

1. Which of these compounds will cross the cell membrane without the aid of a membrane transport protein, and why? H3 NH NH 2. By what transport process will the above compound be transported? What are the factors which drive movement across the membrane in this process? Does this process require input of energy?

A cell with a K+1 concentration of 0.3 eq/L is placed into a solution with a K+1 concentration of 0.2 eq/L.  It is assumed that the K+1 can pass through the cell membrane (the K+1 transport protein is open). Answer the following true or false questions. 1. K+1 will diffuse through the membrane down its concentration gradient due to Kinetic Theory  2. Movement of a solute through the membrane is called dialysis 3. K+1 will move out of the cell