Plasma Membrane Practice Test

Two cell membranes contain identical transport proteins but differ in phospholipid tail composition. Membrane Q has a higher proportion of saturated fatty acids; Membrane R has a higher proportion of unsaturated fatty acids. At the same temperature, lateral movement of membrane proteins is slower in Membrane Q than in Membrane R. Which membrane feature best explains the reduced protein mobility in Membrane Q?

Which feature best explains the slower lateral movement of proteins in Membrane Q?

A phospholipid bilayer contains embedded transport proteins. The hydrophobic tails create a barrier to charged particles, while some proteins form selective pores lined with polar amino acids. A student compares movement of K+ across membranes with and without a functional K+ channel protein. The concentration of K+ is higher outside than inside. Which feature best explains why K+ moves into the cell only when the channel is functional?