AP BIOLOGY

Detailed explanation-1: -Plasma membrane controls the flow of substances in and out of cell.

Detailed explanation-2: -Cell membrane It maintains the integrity of a cell and controls passage of materials into and out of the cell. All materials within a cell must have access to the cell membrane (the cell’s boundary) for the needed exchange. The cell membrane is a double layer of phospholipid molecules.

Detailed explanation-3: -The plasma membrane is the border between the interior and exterior of a cell. As such, it controls passage of various molecules-including sugars, amino acids, ions, and water-into and out of the cell.

Detailed explanation-4: -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-5: -Certain proteins in the membrane assist facilitated diffusion by permitting only certain molecules to pass across the membrane. The proteins encourage movement in the direction that diffusion would normally take place, from a region with a higher concentration of molecules to a region of lower concentration.