HBG 8 ( Carbohydrate III)

• Carbohydrate metabolism is the process by which carbohydrates are broken down and the products are used for energy.
• Glycolysis is the metabolic pathway that breaks down glucose into pyruvate.
• The metabolic fate of pyruvate involves its conversion into acetyl-CoA, which is then used in the citric acid cycle.
• Gluconeogenesis is the process by which glucose is synthesized from non-carbohydrate sources.
• The pentose phosphate pathway is a metabolic pathway that converts glucose into ribose.
• Glycogen metabolism involves the storage and breakdown of glycogen.
• Monosaccharides are metabolized through a process called glycolysis.
• Blood glucose is regulated through a process called glycolysis.
• The citric acid cycle is a metabolic pathway that converts acetyl-CoA into CO2.
• Glycogen metabolism involves the synthesis and degradation of glycogen.
• The structure of glycogen involves the presence of glucose, glucose 1 phosphate, UTP, and uridine phosphate.
• Glycogen synthesis involves the activation of glucose, primer, Glycogen with glucose 10 residues, Glycogenin, elongation, a - 1,4 bond formation, Glycogen synthase (rate limiting enzyme), branching, a - 1,6 bond formation, branching enzyme.
• Glycogen degradation involves trimming, phosphorolysis of a 1,4 glycosidic bonds, Glycogen phosphorylase (rate limiting enzyme), debranching, transfer of trisaccharides from branch point (Glucan transferase), and hydrolysis of single glucose from branch point (Debranching enzyme).
• Glycogen metabolism involves the regulation of blood glucose.
• Glucose is the precursor of milk sugar, lactose (breastfeeding).
• Below critical level (hypoglycemia), there is brain dysfunction resulting in coma & death.
• GLUTs (Facilitative bidirectional transporters) include GLUT 1&3 for basal glucose uptake in organs such as brain, kidney, colon, red blood cells, and placenta; GLUT 2 for rapid uptake in liver and pancreas; GLUT4 for insulin dependent skeletal muscle and adipose tissue uptake; and GLUT5 for glucose absorption in small intestine.
• Normal blood glucose level is 80 - 100 mg/dl or 4.5 - 5.5 mmol/L post absorptive (4 - 6 hours after last meal), 120 - 130 mg/dl or 6.5 - 7.2 mmol/L after carbohydrate meal, and 60 - 70 mg/dl or 3.3 - 3.9 mmol/L during fasting.
• The kidney is a Glucostat organ that regulates hypoglycemia.
• Sources of blood glucose include diet, glucogenic compounds, glucogenic amino acids, glycerol, lactate, propionic acid (in ruminants), and liver glycogen.
• All cells require a basal, minimum requirement for glucose.
• The liver is a Glucostat organ that regulates hyperglycemia.
• The brain is a Glucostat organ that regulates satiety.
• GLUTs are freely permeable to glucose (GLUT 2, Insulin independent) and include Glucokinase; High Km (low affinity) & High Vmax (efficient).
• Insulin plays an important role in regulating blood glucose level and is the only hypoglycemic hormone.
• Brain and nervous tissues depend solely on blood glucose as a source of energy.
• Stimulate release of glucocorticoids (11 - oxy steroids)
• Galactose metabolism in liver
• Promote gluconeogenesis
• After birth lactalbumin synthesis is stimulated by Prolactin.
• Induce Glucokinase enzyme in liver
• Galactose Galactose 1 phosphate Glucose 1 phosphate Glucose 6 phosphate Glycolysis Gluconeogenesis Galactokinase Uridyl transferase Epimerase UDP - Glucose UDP - Galactose Glycogen.
• Inhibit gluconeogenesis & glycogenolysis.
• T3 & T4
• Chronic elevation à hyperglycemia à b cell exhaustion à diabetes mellitus
• Cause glycogenolysis & gluconeogenesis in liver
• Anterior pituitary hormones
• Causes glycogenolysis in liver & muscle
• Inhibit glucose uptake
• Growth hormone