What is the social impact of transportation? At the aggregate level, efficient transportation reduces costs in many economic sectors, while inefficient transportation increases these costs. What is the role of transport in the economy?īecause of its intensive use of infrastructures, the transport sector is an important component of the economy and a common tool used for development. Public transportation reduces air pollution:.What are the advantages of transport system? It is suitable to carry only heavy and bulky goods over long distances where time is not an important factor. Water transport is the cheapest mode of transport. Motor transport saves packing and handling costs. Motor transport is best suited and economical to carry small traffic over short distances. Which is the most suitable mode of transport? It allows hydrophobic molecules and small polar molecules diffuse through the lipid layer, but does not allow ions and large polar molecules cannot diffuse through the membrane. The plasma membrane is called a selectively permeable membrane as it permits the movement of only certain molecules in and out of the cells. Why do you think the plasma membrane is a selectively permeable? If a molecule is tiny enough to fit through a special protein channel in the plasma membrane, it will use a form of active or passive transport to move through.
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What is meant by selectively permeable and why this term is applied to the cell membrane?Ī selectively permeable cell membrane is one that allows certain molecules or ions to pass through it by means of active or passive transport. A semipermeable membrane, also termed a selectively permeable membrane, a partially permeable membrane or a differentially permeable membrane, is a membrane that will allow certain molecules or ions to pass through it by diffusion and occasionally specialized “facilitated diffusion.