Ch 13 Glycogen and Gluconeogenesis Flashcards
Who was Gerty Cori?
First American woman to win the Nobel Prize
She won the Nobel Prize for her work on carbohydrate metabolism.
What significant discoveries did Gerty Cori contribute to?
Glycogen synthesis, glycogen phosphorylase, insulin effects, the Cori cycle
These discoveries were made at Washington University in St. Louis.
What is gluconeogenesis?
Formation of new glucose
It is crucial for tissues requiring a continuous supply of glucose.
Which tissues require a continuous supply of glucose?
- Brain
- RBCs
- Kidney medulla
- Testes
- Embryonic tissues
- Exercising muscle
How much glucose does the human brain require daily?
Over 120 gm (~0.26 pounds or ~1/2 cup)
How long can liver glycogen meet glucose needs without dietary carbohydrate?
10 to 18 hours
What is the main precursor for gluconeogenesis?
Pyruvate
What is the net result of gluconeogenesis?
Reversal of three steps in glycolysis using different reactions and enzymes
What are the control points in glycolysis that gluconeogenesis must reverse?
- Step 1
- Step 3
- Step 10
What enzyme catalyzes the conversion of glucose-1-phosphate to glucose-6-phosphate?
Phosphoglucomutase
What is glycogen?
A polymer of a-D-glucose with a main chain of a(1→4) linkages and branches of a(1→6) linkages
Which enzyme is primarily responsible for glycogen synthesis?
Glycogen synthase
What is the role of UDP-glucose pyrophosphorylase?
Catalyzes the formation of UDP-glucose
What is the action of glycogen phosphorylase?
Breaks down glycogen to glucose-1-phosphate
What is the difference between phosphorolysis and hydrolysis?
Phosphorolysis cleaves bonds using phosphate, while hydrolysis uses water
What are the goals of the Pentose Phosphate Pathway?
- Makes 5-carbon ribose sugar for DNA and RNA
- Produces NADPH for fatty acid generation
What enzyme converts ribose to deoxyribose?
Ribonucleotide reductase
What are glycogen storage diseases?
Enzyme deficiencies affecting red blood cells, liver cells, and muscle cells
What are some symptoms of glycogen storage diseases?
- Hypoglycemia
- Muscle weakness
- Liver damage
What is the enzyme deficiency in GSD1?
Glucose-6-phosphatase
What unique feature do transgenic Mighty Mice exhibit?
100X concentration of the PEPCK-C enzyme in their muscles
What is the significance of PEPCK-C in metabolism?
Allows mice to utilize primarily fatty acids for energy
What happens to glycogen during prolonged fasting?
Hepatic stores of glycogen are depleted
What is the role of the debranching enzyme in glycogen breakdown?
Moves glucose units to another chain and cleaves off final glucose
What are the major enzymes involved in glycogen breakdown?
- Glycogen phosphorylase
- Debranching enzyme
Fill in the blank: The formation of glucose from non-hexose precursors is called _______.
gluconeogenesis
True or False: Humans synthesize vitamins.
False
