Question

list and describe all types of passive transport found in cells.

Answer 1

Cellular transport in which there is no energy consumption and the ,olecules move along their concentration gradient is termed as passive transport. Unlike active transport, it does not require an input of cellular energy because it is instead driven by the tendency of the system to grow in entropy. The rate of passive transport depends on the permeability of the cell membrane, which, in turn, depends on the organization and characteristics of the membrane lipids and proteins. The four main kinds of passive transport are simple diffusion, facilitated diffusion, filtration, and osmosis.

• Diffusion: It is the simple movement of molecules along the concentration gradient, i.e., from its higher concentration to lower concentration. This type of transport is also referred to as movement of molecules down the concentration gradient. Simple diffusion is the passive movement of solute from a high concentration to a lower concentration until the concentration of the solute is uniform throughout and reaches equilibrium.
• Facilitated Diffusion: In this type of passive transport, diffusion is mediated by some sort of carrier molecules which are special transport proteins that are embedded within the cellular membrane. Large, insoluble molecules, such as glucose, vesicles and proteins require a carrier molecule to move through the plasma membrane. Therefore, it will bind with its specific carrier proteins, and the complex will then be bonded to a receptor site and moved through the cellular membrane. Facilitated diffusion is a passive process: the solutes move down their concentration gradient and do not require the expenditure of cellular energy for this process. Carrier proteins and channel proteins allow for the diffusion of molecules across the cell membrane. Carrier proteins undergo conformational alterations to allow molecules to pass, while channel proteins form unblocked pores.
• Filteration: It is the movement of water and solute molecules because of the hydrostatic pressure created along the membrane. Depending on the size of the membrane pores, only solutes of a certain size may pass through it.
• Osmosis: It is described as the movement of water across the semi-permeable membrane. The net movement of water molecules through a partially permeable membrane from a solution of high water potential to an area of low water potential.