Question

Compare and Contrast Simple diffusion and Primary active transport. In 300 words

Answer 1

Simple diffusion is a type of passive transport which doesnot requires atp molecules for transport and movement of molecules is along the concentration gradient from a region of higher concentration to concentration of lower concentration. And no carrier protein is involved in the transport of molecules as in facilitated diffusion which distinguishes it into simple diffusion. Molecules such as oxygen, carbon dioxide and water molecules moves through the membrane through simple diffusion. Once equilibrium of molecules is attained in either sides of the membrane there will be no net movement of molecules. Transport of small non polar molecules occurs through the phospholipid bilayer of the cellmembrane . And the rate of diffusion is directly proportional to the concentration gradient and membrane permeability of solute molecules. In humans exchange of gases across the alveolar membrane is an example of simple diffusion.  

Primary active transport is a type of transport against the concentration gradient, which uses atp molecules as energy for transport from low concentration to a high concentration. Hydrolysis of atp causes release of high energy which is involved in transport of molecules. Only a single molecule is transported in primary active transport whereas 2 molecules are transported in secondary active transport. Ions like sodium , potassium and calcium are transported. It involves transmembrane protein as carriers. Proton pump in stomach is an example of primary active transport in humans .