Glycogen Metabolism

Energy is stored in mammals in three forms: ___________________

serum glucose, glycogen, and fat

________ is a polymer of glucose.

glycogen

_______________ are referred to as the "end of glycogen molecules" where hydroxyl (OH group) is _____________involved in a glycosidic linkage with another glucose molecule

Non-reducing ends, NOT

Glycogen is branched to increase the number of ___________________ so that much glucose can be added or removed simultaneously.

non-reducing ends

Glycogen is a highly branched homopolymer of glucose present in _________________ of all tissues.

the cytoplasm

The largest stores of glycogen are in ___________________

the liver and skeletal muscle.

The ________________ breaks down glycogen and releases glucose into the blood to provide energy for the brain and red blood cells.

liver

Muscle glycogen stores are mobilized to provide energy for _________________

muscle contraction.

_________________________, the key enzyme in glycogen breakdown, cleaves its substrate by the addition of Pi to yield glucose 1-phosphate, which is termed _________________

Glycogen phosphorylase, phosphorolysis

_________________ adds glucose to extend the glycogen polymer

Glycogen synthase

_________________ are active when energy or blood glucose is needed

kinases

__________________ are active when blood glucose is adequate and no energy is need

phosphatases

Glycogenesis Step 1

Hexokinase reaction

- Glucose to glucose-6-phosphate

Glycogenesis Step 2

Phosphoglucomutase reaction

- Glucose-6-phosphate to glucose-1-phosphate

Glycogenesis Step 3

UDP glucose pyrophosphorylase reaction

- Glucose-1-phosphate to UDP glucose

Glycogenesis Step 4

Glycogen synthase reaction

- UDP glucose + glycogen —>> glycogen +1

Glycogenolysis Step 1

Glycogen phosphorylase reaction

- Glycogen and Pi react to become glucose-1-phosphate

Glycogenolysis Step 2

Phosphoglucomutase reaction

- Glucose-1-phosphate becomes glucose-6-phosphate

Glycogenolysis Step 3

Glucose-6-phosphatase

- Glucose-6-phosphate becomes glucose

pentose-phosphate pathway step 1

Glucose-6-phosphate dehydrogenase reaction

- Glucose-6-phosphate and NADP+ are reactants, with NADPH and 6-phosphogluconolactone as products

- Irreversible transfer of hydride ion

pentose-phosphate pathway step 2

6-phosphogluconolactonase reaction

- 6-phosphogluconolactone becomes 6-phosphogluconate

pentose-phosphate pathway step 3

6-phosphogluconate dehydrogenase reaction

- Oxidative decarboxylation

- 6-phosphogluconate and NADP+ are reactants, with NADPH, CO2, and ribulose-5-phosphate as products

pentose-phosphate pathway step 4

Ribulose-5-phosphate isomerase

- Ribulose-5-phosphate becomes ribose-5-phosphate