GENERAL HISTOLOGY

Detailed explanation-1: -Cell membranes serve as barriers and gatekeepers. They are semi-permeable, which means that some molecules can diffuse across the lipid bilayer but others cannot. Small hydrophobic molecules and gases like oxygen and carbon dioxide cross membranes rapidly.

Detailed explanation-2: -Small nonpolar molecules, such as O2 and CO2, are soluble in the lipid bilayer and therefore can readily cross cell membranes. Small uncharged polar molecules, such as H2O, also can diffuse through membranes, but larger uncharged polar molecules, such as glucose, cannot.

Detailed explanation-3: -3 – Simple Diffusion Across the Cell (Plasma) Membrane: The structure of the lipid bilayer allows small, uncharged substances such as oxygen and carbon dioxide, and hydrophobic molecules such as lipids, to pass through the cell membrane, down their concentration gradient, by simple diffusion.

Detailed explanation-4: -The cell membrane is a semi-permeable membrane that allows only selected molecular entities to pass through it. The ease with which a molecule can pass through the cell membrane is known as the permeability of the cell membrane. It also refers to the rate at which the passive diffusion occurs through the cell membrane.

Detailed explanation-5: -When referring to membrane permeability there are two types found in living things: semi-permeable and selectively permeable. Both allow molecules and water to move in and out of the cell, as needed to maintain homeostasis.