Question

Discuss the structural differences between the polysaccharides starch and glycogen, explaining how the differences in structure contribute to the functional properties of the molecule

Answer 1

Starch in plants has two components, amylose (linear) and amylopectin (less branched), while glycogen in animals is highly branched for rapid glucose release. The branching pattern and glycosidic linkages lead to different functional properties, including stability and energy-release rates that suit the organism's needs.

Step-by-step explanation:

The structural differences between the polysaccharides starch and glycogen are significant in terms of their function as energy storage molecules. Starch, found in plants, is composed of two glucose polymers: amylose and amylopectin. Amylose is a linear polymer, while amylopectin is branched, albeit less so than glycogen. On the other hand, glycogen is the main energy-storage molecule in animals and is highly branched, which enables more rapid release of glucose. The branching in glycogen is greater than that found in amylopectin, with branches occurring every 8 to 10 glucose units in glycogen compared to every 12 to 30 in amylopectin.

This increased branching in glycogen allows for a larger surface area, facilitating more rapid glucose release to meet the energy demands of animals. In contrast, starch, with its less frequent branching, serves as a more stable long-term energy reserve in plants. The orientation of the glycosidic linkages also differs: amylose and amylopectin contain α-1,4 and α-1,6 linkages, but glycogen's branches are more frequent due to the α-1,6 linkages between its chains. These molecular differences contribute to each polysaccharide's unique functional properties.

Answer 2

Starch, cellulose and glycogen are all polymers of glucose. But they differ in function as optical isomerism is involved here.

starch is a mixture of two polysaccharides: amylose and amylopectin. The alpha-1,4 glycosidic bonds and branching is responsible for its physical properties. Starch can be easily hydrolyzed and is powdery than cellulose, which exists as tough microfibrils.

Glycogen, is a branched polymer, like starch . It is similar to amylopectin, being composed of alpha-glucose molecules, but it is larger and there are more alpha-1,6 links. This makes it highly branched, more soluble, and more easily hydrolized than starch.

Cellulose is an long chain, unbranched, glucose polymer held by beta-1,4 glycosidic bonds. The straight, tightly packed chains give cellulose high tensile strength and resistance to hydrolysis.