CARB METABOLISM

• Digestion and absorption of carbohydrates are processes that begin in the mouth and continue in the small intestine.
• Glycolysis is a metabolic pathway that produces ATP and NADH-reduced coenzymes.
• The fates of pyruvate include its conversion to acetyl-CoA, which is used in the synthesis of fatty acids and cholesterol.
• ATP production from the complete oxidation of glucose occurs in the mitochondria.
• Glycogen synthesis and degradation are processes that occur in the liver.
• Gluconeogenesis is a metabolic pathway that produces glucose from non-carbohydrate sources.
• The pentose phosphate pathway is a metabolic pathway that produces NADPH, which is used in the synthesis of lipids and proteins.
• Hormonal control of carbohydrate metabolism involves the regulation of insulin and glucagon.
• In gluconeogenesis, there is a net loss in triphosphates (ATP, UTP, etc.).
• In the conversion of a glycogen glucose unit to lactate, there is a net loss in triphosphates (ATP, UTP, etc.).
• In the conversion of a glycogen unit to pyruvate, there is a net gain in triphosphates (ATP, UTP, etc.).
• In glycolysis, there is a net gain in triphosphates (ATP, UTP, etc.).
• In glycogenolysis, there is a net loss in triphosphates (ATP, UTP, etc.).
• In the Cori cycle, there is a net gain in triphosphates (ATP, UTP, etc.).
• In the conversion of a glycogen glucose unit to glucose, there is a net loss in triphosphates (ATP, UTP, etc.).
• B-Vitamin Participation in Chemical Reactions
• B vitamins and carbohydrate metabolism are related as B vitamins are necessary for the conversion of pyruvate to acetyl-CoA, which is used in the synthesis of fatty acids and cholesterol.
• Asynchronous activity is a process that begins in the mouth and continues in the small intestine.
• Enzyme lactate dehydrogenase converts lactate to pyruvate in the liver.
• Glycogenolysis is a process in which glycogen is converted to glucose 6-phosphate.
• Pyruvate is then converted to glucose via gluconeogenesis.
• Gluconeogenesis occurs at the expense of other ATP-producing metabolic processes.
• Overall Reaction: 2 Pyruvate + 4ATP + 2GTP + 2NADH + 2H  glucose + 4ADP + 2GDP + 6P i + 2NAD.
• Lactate is formed during strenuous exercise and diffuses from muscle cells into the bloodstream and is transported to the liver.
• NADPH is the reduced form of NADP+ (nicotinamide adenine dinucleotide phosphate) and is essential for biosynthetic reactions/pathways.
• The glucose enters the bloodstream and is transported to the muscles.
• Gluconeogenesis is an eleven-step process in which pyruvate is converted to glucose.
• Gluconeogenesis requires the expenditures of 4 ATP and 2 GTP.
• Glycolysis is a ten-step process in which glucose is converted to pyruvate.
• Glycogenesis is a three-step process in which glucose 6-phosphate units are added to a growing glycogen molecule.
• Gluconeogenesis uses lactate as a source of pyruvate.
• Digestion begins in the mouth with the breakdown of food molecules by hydrolysis into simpler chemical units that can be used by cells in their metabolic processes.
• Carbohydrate digestion begins in the mouth with the action of salivary -amylase, which catalyzes the hydrolysis of -glycosidic linkages in starch and glycogen to produce smaller polysaccharides and disaccharide maltose.
• A small amount of carbohydrate digestion occurs in the mouth because food is swallowed quickly.
• The primary site for carbohydrate digestion is the small intestine, where pancreatic -amylase breaks down polysaccharide chains into disaccharide maltose.
• The final step in carbohydrate digestion occurs on the outer membranes of intestinal mucosal cells, where disaccharidase enzymes convert disaccharides to monosaccharides.
• Carbohydrate digestion products (glucose, galactose, and fructose) are absorbed into the bloodstream through the intestinal wall.
• Intestinal villi are rich in blood capillaries into which the monosaccharides are actively transported.
• Glycogenolysis involves the phosphorylation of a glucose unit from glycogen and the isomerization of the phosphate group of glucose 1-phosphate.
• About 90% of gluconeogenesis takes place in the liver.