Question

Storage polysaccharides, like starch and glycogen, often contain over a million glucose units. The energetic cost of synthesizing polysaccharides is high (about one high-energy phosphate bond per sugar residue added). Suppose that in a liver cell, the glucosyl residues in large numbers of glycogen molecules were replaced with an equivalent number of molecules of free glucose. What problems would this cause for the liver cell

Answer 1

Answer:

Glucose present as monomers within the cell will exert more osmotic pressure than a single glycogen molecule, resulting in endosmosis and the lysing of cells.

Also, the presence of free glucose molecules will result in increase in weight of the liver due to lack of efficient packing as in glycogen as well as the association ofnthe glucose molecules with water molecules.

Explanation:

Glycogen is a polysaccharide composed of glucose monomer units linked to Each other by α-1,4-glycosidic binds. α-1,6-branches arises at about every 10th glucose residue in the straight chain. Thus animals more glucose molecules to be stored within a much smaller space, thereby incresing the bulkiness of glycogen. Glycogen molecules are insoluble in the aqueous medium of the cell because it doesn't have enough free polar groups to participate in hydrogen bonding with water and are stored as granules and therefore do not affect the water potential or osmotic balance of the cell.

On the other hand, glucose molecules are highly soluble in water because it has many free polar -OH grours that form hydrogen bonds with water. If the glucosyl residues in large numbers of glycogen molecules were replaced with an equivalent number of molecules of free glucose, the free glucose will exert a high osmotic pressure inside the cell, causing the entry of water in the cell by endosmosis resulting in swelling and lysis ofnthe cell. Also, the space occupied by these free glucose units within the cell will be much larger than that of glycogen whichmenables efficient packing ofthe glucose molecules.