Carbohydrate Flashcards
What are the different types of lactose intolerance?
Primary lactase deficiency (absence of lactase persistence allele, adults)
Secondary lactase deficiency (Caused by injury to small intestine, infants & adults, reversible)
Congenital lactase deficiency (rare, autosomal recessive defect in lactase gene)
How are monosaccharides absorbed
SGLT1: Active transport, from the lumen into the epithelial cells of small intestine
GLUT1-5: Facilitated diffusion
GLUT2: Into blood, found in kidney, liver, pancreatic beta cells, small intestine
GLUT4: Found in adipose issue
4 stages of carbohydrate metabolism
Catabolism of carbohydrate
Glycolysis
Kerbs Cycle
Oxidative phosphorylation
What cells/organs have an absolute requirement of glucose
-RBC
-Neutrophils (mitochondria used to produce free radicals)
-Kidney medulla cells (receive little O2 as cortex uses it)
-Lens of the eye (no capillaries, no O2)
What are the functions of glycolysis
Oxidation of glucose
NADH production
Synthesis of ATP from ADP (net2)
Provides biosynthetic precursors for FA, amino acids and nucleotides
Features of glycolysis
Central pathway of CHO catabolism
Occurs in a ll tissues
Exergonic, oxidative
Irreversible pathway
No loss of CO2
Enzymes involved in glycolysis
Hexokinase (Glucose ➡️ Glucose-6-P) / glucokinase in liver
Phosphofructokinase-1(Fructose-6-P ➡️ Fructose 1,6-bis-P)
Pyruvate kinase (Phosphoenolpyruvate ➡️ Pyruvate)
Why are there so many steps/enzymes involved in glycolysis?
Chemistry easier in small stages
Efficient energy conservation
Gives versatility
Can be controlled
What is the difference between hexokinase and glucokinase ?
Glucokinase is in the liver and has a lower affinity than hexokinase. Therefore, it is not inhibited by its product. This makes glucose more negatively charged preventing it passing it back through the cell membranes.
Important intermediates to glycolysis
Glycerol phosphate
2,3-Bisphosphoglycerate
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