Tag: osmosis and plasmolysis

• Active transport can be defined as the movement of molecules or ions across a plasma membrane from a region of lower concentration (of molecules or ions) to a region of higher concentration, against the concentration gradient. 
• For this cellular energy is required which is available in the form of ATP molecule and enzymes.
• So, the correct answer is 'All of the above'.

Absorption of water takes place by both active and passive absorption.
Water, as per some theory, is absorbed against the concentration gradient. This type of absorption is termed active absorption where the movement is against the concentration gradient and requires energy in the form of ATP.

The monosaccharides glucose and galactose are transported into the epithelial cells by common protein carriers via secondary active transport I.e  by co-transport with sodium ions. The monosaccharides leave these cells via facilitated diffusion and enter the capillaries through intercellular clefts.

• Active transport is the transport where the direct expenditure of energy takes place and the molecules move against the gradient which is from lower concentration to the higher concentration.
• Passive absorption is the absorption which takes place without expenditure of energy. The water molecules move from higher concentration to the lower concentration which is towards the gradient. 
• In diffusion, the ions or molecules randomly diffuses the semipermeable membrane along the concentration gradient.
• Osmosis is the process of diffusion of molecules from the region of higher concentration to the lower concentration through a semipermeable membrane. 

Carrier proteins are those which facilitate diffusion of molecules across the cell membrane, they allow movement of molecules in and out of the cells against the concentration gradient. Active transport requires carrier proteins also called as pumps. They need ATP energy because the transport is uphill, against the concentration gradient.

The sodium-potassium pump in a cell membrane works via active transport. It uses a carrier protein and utilizes ATP molecules. It transports the sodium ions to the extracellular space, increasing their concentration there and in turn moves potassium ions inside the cell. This pump moves three potassium ions inside the cell for every two sodium ions moved outside.

Active transport is usually associated with accumulating high concentrations of molecules that the cell needs such as ions, glucose, and amino acids. The processes use chemical energy for this, it comes from the hydrolysis of the ATP molecule which maintains the electrochemical gradient. Hence ATP is required for active transport. 

ATP acts as a solute pump, it's an enzyme that pumps out sodium and pumping potassium in the cells, exports three sodium, and two potassium ions. It is an active transport leading to the hydrolysis of ATP molecules to provide the required energy.

An input of energy is required in the process of active transport as it involves the movement of ions or molecules across a cell membrane from low to high concentration. The movement requires energy to maintain the electrochemical gradient.