Exam 3 Review:  Chapter 23:  Intestinal Enzymes

intestinal juice - The fluid which is secreted in small quantity in the small intestine, is highly variable in composition, containing mucus and various brush border enzymes (dextrinase, glucoamylase, maltase, lactase, sucrase, carboxypeptidase, dipeptidase, nucleosidases, phosphatases, and enterokinase) and, which, after mixing with bile and pancreatic juice, participates in the final chemical digestion of food.

brush border enzymes - The set of digestive enzymes secreted by the simple columnar cells which line the small intestine, including erepsin, dextrinase, glucoamylase, maltase, lactase, sucrase, dipeptidase, nucleosidases, phosphatases, and enterokinase.

dextrinase - A brush border enzyme secreted by the simple columnar cells which line the small intestine which catalyzes the hydrolysis of dextrins, which are starch fragments containing branching points for glucoses linked in the 1,4 position, into smaller oligosaccharides. [See figure below.]

maltase - A brush border enzyme secreted by the simple columnar cells which line the small intestine which catalyzes the hydrolysis of the disaccharide maltose to two glucoses.

lactase - A brush border enzyme secreted by the simple columnar cells which line the small intestine which catalyzes the hydrolysis of the disaccharide lactose, "milk sugar," to one glucose and one galactose.

peptidases - A group of brush border enzymes secreted by the simple columnar cells which line the small intestine which catalyze the hydrolysis of small peptides into tripeptides, dipeptides and individual amino acids.

nucleosidases - A group of brush border enzymes secreted by the simple columnar cells which line the small intestine which catalyze the hydrolysis of nucleotides (a ribose sugar linked to a nitrogenous base) into the constituent ribose sugar and nitrogenous base.

phosphatases - Any of numerous enzymes that catalyze the hydrolysis of esters of phosphoric acid and are important in the absorption and metabolism of carbohydrates, nucleotides, and phospholipids and in the calcification of bone; in the gastrointestinal tract, the group of brush border enzymes secreted by the simple columnar cells which line the small intestine which catalyze the hydrolysis of  phosphate ions from phosphorylated nutrient molecules.

15.  the functions of the brush border enzymes.