AP BIOLOGY

Detailed explanation-1: -Facilitated diffusion is the passive movement of molecules along the concentration gradient. It is a selective process, i.e., the membrane allows only selective molecules and ions to pass through it.

Detailed explanation-2: -The Na+ gradient established by the Na+-K+ pump provides a source of energy that is frequently used to power the active transport of sugars, amino acids, and ions in mammalian cells.

Detailed explanation-3: -An example of passive transport is diffusion, the movement of molecules from an area of high concentration to an area of low concentration. Carrier proteins and channel proteins are involved in facilitated diffusion.

Detailed explanation-4: -In simple diffusion, small noncharged molecules or lipid soluble molecules pass between the phospholipids to enter or leave the cell, moving from areas of high concentration to areas of low concentration (they move down their concentration gradient).

Detailed explanation-5: -In facilitated transport, also called facilitated diffusion, material moves across the plasma membrane with the assistance of transmembrane proteins down a concentration gradient (from high to low concentration) without the expenditure of cellular energy.