Explain the types of transport mechanisms in the body

Answer 1

The movement of nutrients and other substances across a cell membrane occurs through a variety of processes, which are referred to collectively as transport mechanisms. A transport mechanism that does not require energy (ATP) is called a passive transport mechanism, whereas one that does require energy is called an active transport mechanism. There are three types of passive transport mechanisms: osmosis, simple diffusion, and facilitated diffusion. Osmosis is the diffusion of water molecules across a cell membrane. Fluids in the body contain different types of dissolved substances, referred to as solutes. The concentrations of dissolved substances (solutes) inside and outside the cell determine whether water molecules move into or out of a cell. Specifically, water moves toward a higher concentration of dissolved substances, until the concentration of dissolved substances is equalized on both sides of the cell membrane. Simple diffusion enables a substance to cross a cell membrane from a region of higher concentration to a region of lower concentration without using energy in the process. In simple diffusion, a substance moves without assistance, like a raft floating downstream. In facilitated diffusion, a substance moves passively from a higher to a lower concentration, but only with the assistance of a carrier molecule. Unlike the example of a raft moving downstream with the water current (simple diffusion), you can think of carrier molecules in facilitated diffusion as oars that help guide a boat in a specific direction.Some substances must cross cell membranes against the prevailing concentration gradient, moving from a region of lower concentration to one of a higher concentration. Because energy is needed to pump the molecule across a cell membrane, this type of transport mechanism is considered active. Carrier-mediated active transport is a transport mechanism whereby a substance uses energy to move from a region of lower concentration to a region of higher concentration with the assistance of a carrier protein. The process of carrier-mediated active transport is similar to that of a motorboat because it requires energy to move upstream.