Day 2 Glucose Metabolism Flashcards
GLUT 1 and GLUT 3
In all mammalian tissues especially the skeletal muscle and adipose tissue. They allow for glucose uptake into the cell
GLUT 2
-Regulate insulin in the pancreas and remove excess glucose from blood in the liver.
GLUT 4
Available in the SK muscle and fat cells plasma membrane and their amount increases with endurance training
GLUT 5
Located in the small intestines and is primarily a fructose transporter.
Fates of Pyruvate
- Can undergo oxidative decarboxylation to form acetyl CoA under aerobic conditions and enter the TCA cycle
- can be reduced to lactate or ethanol under anaerobic conditions
Formation of lactate
- Under anaerobic conditons lactate dehydrogenase converts pyruvate into lactate which releases an NAD+ that can be used to convert GAP into 1-3 bisphophoglycerate
- The heart will convert lactate back into pyruvate
Ethanol fermentation
- Formed under anaerobic conditions in yeast.
- Consist of 2 steps
1. Decarboxylation of pyruvate to acetyladehyde
2. Reduction of acetylaldehyde to ethanol
Classic Galactosemia
-Mutation in the Gal-1-P-uridyl transferase
results to high intracellular levels of Gal-1-P
-High levels of Gal-1-P can inhibit galactokinase and phosphoglucomutase.
Gal-1-P inhibition of phosphoglucokinase
- Inhibition of this enzyme does not allow Gal-1-P to be converted into Glu-6-P which can enter the glycolytic pathway.
- Will result in: hypoglycemia, neurological deficit, enlarged liver, jaundice.
Gal-1-P inhibition of Galactokinase
- Inhibiton of this enzyme does not allow galactose to be converted into Gal-1-P
- Results in high blood serum galactose, cataracts and reducing sugar in urine.
Cataract
results from galactose accumulation because of no galactokinase activity. The enzyme aldose reductase will convert galactose into galactitol which leads to water in the lens clouding it.
Non-Classical Galactosemia
-Mutation in Galactokinase that results in cataracts and reduced sugar in the urine.
Fructose
- Enters the glycolytic pathway as F-6-P in adipose tissue
- Enters the glycolysis through the F-1-P pathways as DHAP and GAP when in the liver which bypasses the main regulatory step in glycolysis.
Glyconeogenesis
Synthesis of glucose from non carbohydrate sources such as Lactate, Alanine and Glycerol. The 3 irreversible steps must be bypassed.
Pyruvate to Phosphoenol pyruvate
two step reaction;
- Carboxylation: hydrolyze ATP to carboxylate pyruvate forming OAA (in mitochondria)
- Decarboxylation and phosphorylation of OAA (in cytoplasm)
