Carbohydrate Metabolism Flashcards

Flashcards for carbohydrate metabolism

Digestion

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, where salivary alpha-amylase catalyzes the hydrolysis of alpha-glycosidic linkages of starch and glycogen to produce smaller polysaccharides and maltose.

Pancreatic alpha-amylase

Breaks down polysaccharide chains into the disaccharide maltose in the small intestine.

Maltase

Converts maltose to glucose on the outer membranes of intestinal mucosal cells.

Sucrase

Converts sucrose to glucose and fructose on the outer membranes of intestinal mucosal cells.

Lactase

Converts lactose to glucose and galactose on the outer membranes of intestinal mucosal cells.

Glycolysis

A metabolic pathway that consists of a six-carbon stage (steps 1-3) and a three-carbon stage (steps 4-10), ultimately breaking down glucose into pyruvate.

Hexokinase

The enzyme that catalyzes the phosphorylation of glucose to glucose-6-phosphate in the first step of glycolysis.

Phosphoglucoisomerase

The enzyme that catalyzes the isomerization of glucose-6-phosphate to fructose-6-phosphate in the second step of glycolysis.

Phosphofructokinase

The enzyme that catalyzes the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate in the third step of glycolysis.

Aldolase

The enzyme that catalyzes the splitting of fructose 1,6-bisphosphate into dihydroxyacetone phosphate and glyceraldehyde 3-phosphate.

Triosephosphate isomerase

The enzyme that catalyzes the isomerization of dihydroxyacetone phosphate to glyceraldehyde 3-phosphate.

Phosphoglycerokinase

The enzyme that catalyzes the transfer of a phosphate group from 1,3-bisphosphoglycerate to ADP, forming ATP.

Phosphoglyceromutase

The enzyme that catalyzes the isomerization of 3-phosphoglycerate to 2-phosphoglycerate.

Enolase

The enzyme that catalyzes the dehydration of 2-phosphoglycerate to phosphoenolpyruvate.

Pyruvate kinase

The enzyme that catalyzes the transfer of a phosphate group from phosphoenolpyruvate to ADP, forming ATP and pyruvate.

Pyruvate Dehydrogenase Complex

Under aerobic conditions, pyruvate is oxidized to acetyl CoA by this complex, which then enters the mitochondrial matrix for further processing.

Lactate Fermentation

The enzymatic anaerobic reduction of pyruvate to lactate, which occurs mainly in muscles. Converts NADH to NAD+ for increased rate of glycolysis.

Ethanol Fermentation

The enzymatic anaerobic conversion of pyruvate to ethanol and carbon dioxide, used by simple organisms like yeast and bacteria to regenerate NAD+.

Glycogenesis

The metabolic pathway by which glycogen is synthesized from glucose.

Glycogenolysis

The breakdown of glycogen to glucose-6-phosphate.

Glycogen phosphorylase

Catalyzes the removal of an end glucose residue from a glycogen molecule as glucose 1-phosphate.

Gluconeogenesis

The metabolic pathway by which glucose is synthesized from non-carbohydrate sources.

Cori Cycle

Gluconeogenesis using lactate as a source of pyruvate. Lactate diffuses from muscle cells to the liver and is converted to pyruvate, then glucose.

Pentose Phosphate Pathway

A metabolic pathway in which glucose is used to produce NADPH, ribose 5-phosphate (a pentose phosphate) and numerous other sugar phosphates.

Insulin

A hormone produced by beta cells of the pancreas that promotes utilization of glucose by cells and involved in lipid metabolism Its function is to lower blood glucose levels.

Glucagon

A hormone produced in the pancreas by alpha cells, released when blood glucose levels are low, whose principal function is to increase blood-glucose concentration by speeding up the conversion of glycogen to glucose (glycogenolysis) in the liver. It elicits the opposite effects of insulin.

Epinephrine

A hormone released by the adrenal glands in response to anger, fear, or excitement, whose function is similar to glucagon and stimulates glycogenolysis and promotes energy generation for quick action.