Answer:
The cell membrane is semi-permeable. It allows some molecules to enter easily inside the cell whereas some molecules are blocked from entering the cell.
Small, polar molecules and hydrophobic molecules enter easily through the cell membrane. But large molecules and ions cannot easily move inside the cell membrane.
A hydrophilic substance like the substance L mentioned in the question enters the cell membrane through the help of carrier proteins. The substance attached to the large protein might enter through active or passive diffusion but it can only enter the cell by attaching to carrier proteins.
tripeptides<span> to the </span>culture dish<span> as the </span>cells<span> are </span>added<span>.</span>
