Glycogen Metabolism

Question 0

____ is the major storage carbohydrate in animals,corresponding to starch in plants; it is a branched poly-mer of α-D-glucose. It occurs mainly in liver 100g (up to 6%)and 400g muscle, where it rarely exceeds 1%. However, be-cause of its greater mass, muscle contains about three tofour times as much glycogen as does liver

Answer 0

Glycogen

Question 1

glucose1-phosphate reacts with uridine triphosphate (UTP) toform the active nucleotide uridine diphosphate glu-cose (UDPGlc)* and pyrophosphate, catalyzed by _____

Answer 1

UDPGlc pyrophosphorylase

Question 2

Rate limiting enzyme of glycogenesis?

Answer 2

Glycogen synthase

Question 3

Rate limiting enzyme of glycogenolysis?

Answer 3

Glycogen phosphorylase

Question 4

______ catalyzes the formation of a gly-coside bond between C1 of the activated glucose ofUDPGlc and C4 of a terminal glucose residue of glyco-gen, liberating uridine diphosphate (UDP).

Answer 4

Glycogen synthase

Question 5

The glycogen primermay in turn be formed on a primer known as ______, which is a 37-kDa protein that is glycosylatedon a specific tyrosine residue by UDPGlc.

Answer 5

glycogenin

Question 6

addition of a glucose residue to a preexisting glyco-gen chain, or “primer,” occurs at the nonreducing,outer end of the molecule so that the “branches” of theglycogen “tree” become elongated as successive 1→4linkages are formed (Figure 18–3). When the chain hasbeen lengthened to at least ____ glucose residues, branch-ing enzyme transfers a part of the 1→4 chain (at leastsix glucose residues) to a neighboring chain to form a→1→6 linkage, establishing a branch point

Answer 6

11

Question 7

In liver (andkidney), but not in muscle, there is a specific enzyme,\_\_\_\_\_\_\_\_\_, that hydrolyzes 
glucose 6-phosphate, yielding glucose that is exported, leadingto an increase in the blood glucose concentration.

Answer 7

glucose-6-phosphatase

Question 8

Secondary messenger that integrates the regulation of glycogen metabolism

Answer 8

cAMP

Question 9

Deficiency of glucose-6-phosphatase
Liver cells and renal tubule cells loaded with glycogen. Hypoglycemia, lactic-
acidemia, ketosis, hyperlipemia.

Answer 9

Von Gierke’s disease

Question 10

Deficiency of lysosomal α-1→4- and
1→6-glucosidase (acid maltase)
Fatal, accumulation of glycogen in lyso-somes, heart failure.

Answer 10

Pompe’s disease

Question 11

Absence of debranching enzyme

Accumulation of a characteristic branched polysaccharide.

Answer 11

Limit dextrinosis, Forbes’ or Cori’s disease

Question 12

Myophosphorylase deficiency, Absence of muscle phosphorylase
Diminished exercise tolerance; muscles have abnormally high glycogen con-
tent (2.5–4.1%). Little or no lactate in
blood after exercise.

Answer 12

McArdle’s syndrome