Question

Please select all that are TRUE regarding glycogen metabolism:

O Glycogen Phosphorylase cleaves alpha(1-->4) glycosidic bonds yielding glucose-6-phosphate molecules
O Debranching enzyme via its glucosidase activity cleaves alpha (1-->6) glycosidic bonds yielding glucose-1-phosphate molecules
O Glycogen Phosphorylase cleaves alpha(1-->4) glycosidic bonds yielding glucose-1-phosphate molecules
O Debranching enzyme via its glucosidase activity cleaves alpha (1-->6) glycosidic bonds yielding glucose molecules OOOO

Answer 1

The debranching enzyme cleaves alpha (1→6) glycosidic bonds in glycogen metabolism, releasing free glucose. During glycogenolysis, glycogen phosphorylase breaks down glycogen until a branching point where glucan transferase and the debranching enzyme act to continue hydrolysis. Glycogenesis involves glycogen synthase and branching enzyme to form and branch the glycogen molecule.

Step-by-step explanation:

One true statement regarding glycogen metabolism is that the debranching enzyme, through its glucosidase activity, cleaves alpha (1→6) glycosidic bonds to release free glucose molecules. During glycogenolysis, glycogen phosphorylase is the primary enzyme and it acts on alpha (1→4) glycosidic linkages, releasing glucose-1-phosphate from the non-reducing ends of glycogen until it approaches a branching point. At this branching point, the enzyme glucan transferase moves a block of three glucose residues to another branch, exposing a single glucose residue linked by an alpha (1→6) bond, which is then cleaved by the debranching enzyme to release free glucose.

Glycogen synthesis, or glycogenesis, involves glycogen synthase, which forms alpha (1→4) glycosidic linkages, and the branching enzyme (glycosyl transferase), which creates alpha (1→6) branching points. This metabolic flexibility allows glycogen to be a highly efficacious storage form of glucose, easily hydrolyzed when energy is needed.