Which of the following would not be expected to diffuse thro

Which of the following would not be expected to diffuse through a lipid bilayer membrane?

a. K+ in the presence of the carrier ionophore valinomycin

b. the amino acid tryptophan

c. K+ in the absence of the acrrier ionophore valinomycin

d. both b and c

e. water

Solution

Answer:

d. both b and c

Explanation:

All cells need to acquire the molecules and ions that they need from their surrounding extracellular fluid. There exists an exchange of molecules and ions in and out of the cell wall, as well as in and out of membrane-bounded intracellular compartments such as the nucleus, ER, and mitrochondria.

Glucose, Na²⁺, and Ca²⁺, ATP, mRNA, etc. are the xamples of substances that exchange through the membrane.The lipid bilayer of cell membranes is impermeable to large and polar molecules but permeable to water molecules and other small uncharged molecules like O₂ and CO₂. The cell membrane contains proteins that are selective for unique, water soluble molecules. A carrier ionophore is valinomycin, a molecule that transports a single potassium cation.