Acid Hydrolysis

4/6 year 2012/2013 GLYCOGEN

1(By SR Erlander)

GLYCOGEN

INTRODUCTION

Glycogen represents the principal storage form of carbohydrate in the mammalian body,mainly in liver and muscles. It is a branched homoglycan composed of α-D-glucopyranose units which are linked via two types of bonds: α-1,4 and α-1,6. Its corresponding form in plants is a starch but glycogen is more extensively branched (branches occur every twelve to fourteen glucose residues) and more compact than starch. Glycogen is stored mainly in liver (up to 6-8%) and muscles (1%). However, due to the greater mass, muscles contain about three to four times more glycogen than the liver. Glycogen accumulated in liver serves as a reservoir that releases glucose into the blood when the blood glucose level falls below the normal one. Physiological glucose concentration in blood changes within a narrow interval ranged from 4.4 to 6.7mmol/l (80-120 mg/dl). Glycogen accumulated in liver is sufficient to maintain glucose concentration on the appropriate level for 12-18 hours. Glycogen’s role in maintaining blood-glucose level is especially important because glucose is the major metabolic fuel for mammals (except ruminants) and a universal fuel for the fetus. Glucose supply is necessary especially for the nervous system and erythrocytes. Glucose is virtually the only fuel used by the brain, except during prolonged starvation. Moreover, the glucose from glycogen is readily mobilized and is therefore a good source of energy for sudden, strenuous activity. Unlike fatty acids, the released glucose can provide energy in the absence of oxygen and can thus supply energy for anaerobic activity. A decrease in the glucose level below 70mg/dl (hypoglycemia) causes brain dysfunction which can lead to coma and death.

Acid hydrolysis of glycogen.

Quantification of glycogen content in liver (%) based on the released glucose amount

Principle of the method

Glycosidic bonds are fairly stable, they can be broken chemically by strong...