Carbohydrates Flashcards
GLUT-4
glucose transporter in muscle, adipose and heart. GLUT4 is in cytosol and needs insulin, which causes translocation to plasma membrane, and transports glucose into the cell
What happens when glucose is low? when high? PFK 2 regulation in liver
When glucose low, glucagon released–>adenylate cyclase forming cyclic AMP->activates protein kinase R2C2 to R2->PFK2 to PFK2~P becomes inactive->decrease F2,6,BP->inactivates glycolysis.
When glucose high, insulin releases, activates phosphatase, removes P from PFK2~P, PFK2 active, forms F2,6,BP, glycolysis increases
Epinephrine inhibits glycolysis.
PFK2 in muscles
PFK2 isoenzyme becomes activated with phosphorylated in muscle and heart tissue. Epinephrine causes active PFK2~P.
Lactose intolerance
lack of lactase leads to increase in lactose.
Galactokinase deficiency or galactose 1P Uridyltransferase–>galactosemia. Excess galactose is converted to galacitol, causes cataract formation.
Difference in glycogen usage in liver and muscle
in muscle, catabolized by glycolytic pathway to make ATP. In liver, makes free glucose to help maintain blood glucose levels.
Glycogenesis
UPD glucose is important, used as carrier molecule to attach to sugar
UPD glucose adds to growing change of glycogen, aided by glycogen synthetase
After 11 residues are incorporated, moves 7 residues to side chain
Glycogen synthetase enzyme essential for glycogen production (same as branching enzyme)
Glycogenolysis
G6P only in liver, absent in muscle, heart, and adiposeonly storage. Breakdown of glycogen to produce glucose mainly in the liver.
Low glucose level
liver: Glycogen->Glucose-1-P->G-6-P->Glucose
using: Phosphorylase, mutase, G-6-Phosphatase
muscle: Glycogen->G1P->G6P->ATP
lactic acidosis
build up of lactic acid due to strenous exercise, causes lactate and H+ ions to not be able to leave the cell as rapidly.
What happens when pyruvate kinase is deficient in RBCs?
hemolytic anemia. Causes low ATP–>hemolysis
glucogensis
lactate, amino acids, glycerol needed to produce glucose in steps similar to opposite of glycolysis.
Deficiency of glucose 6 phosphatase causes what?
accumulation of glycogen in liver. Hypoglycemia. (G6Phosphatase breaks down G6P to glucose in glycogen breakdown). hypoglycemia overcome by eating carbs.
What happens when glycogen debrancher enzyme is deficient?
Cori’s Disease. Accumulation of glycogen.
What happens when muscle phosphorylase is deficient?
McCardle’s disease. accumulation of glycogen.
Deficiency of glucose 6 phosphate dehydrogenase in RBC?
hemolytic anemia when taking oxidant drugs like chloroquine. Enzyme is part of pentose phophate pathway. NADP+ is converted to NADPH. Reduced NADPH , can’t regenerate GSH from GSSG. form disulfide bridges, cause rigidity and susceptibility to hemolysis.
