Answer:
The correct answer is option d. "Protein movement is limited by the presence of a diffusion barrier".
Explanation:
There are transportation mechanisms that allow to take up nutrients to the apical surface of the epithelial cells. The transportation process is best describes as protein movement limited by the presence of a diffusion barrier. There are structures known as tight junctions, located just below the apical surface . These tight junctions acts as diffusion barriers, separating the extracellular fluids surrounding the apical and basolateral membranes.
DNA is a negatively charged component so the amino acids most probably to combine with the DNA are going to exhibit a positive charge at pH 7. Thus, the likely amino acids would be Arginine, Histidine, and Lysine.
There are three amino acids, which possess basic side chains at neutral pH. These are lysine, arginine, and histidine. Their side chains comprise nitrogen and bear a resemblance to ammonia that is a base. Their pKa values are high enough that they seem to combine with protons, thus, attaining a positive charge in the process.
Marble A moved first, and marble B moved last, thats why marble A moved farther, sorry if im wrong