Biology 20 Digestive System

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Accessory Organs

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Refers to the pancreas, liver and gall bladder, because their role is vital in digestion but they directly are not apart of the digestive track.

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Amylase

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enzyme in saliva that breaks down starch into simpler sugars

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Acid

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enzyme that catalyses the hydrolysis of carbohydrates

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catalyst

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a chemical that speeds up a chemical reaction but is not used up in the reaction.

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hydrolysis

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chemical reaction in which the addition of a water molecule cleaves a macromolecule into subunits; one hydrogen atom is bonded to one subunit and a hydroxyl group is bonded to the other subunit, breaking a covalent bond in the macromolecule.

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chyme

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a thick liquid formed by mixing food with gastric juice in the stomach.

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digestive tract

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In animals a long tube that extends from the mouth to the anus, through which food moves and is broken down into simpler compounds, that are used for energy, growth, and cell repair.

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bolus

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a smooth, lump like mass of food rolled by the tongue to aid swallowing.

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macromolecule

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a large, complex assembly of organic molecules; four categories are, Carbohydrates, Lipids, Proteins, and Nucleic acids.

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Liver

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organ found in the abdomen that performs hundreds of functions as an accessory organ of the digestive system, including the secretion of bile to digest fats; other functions include plasma protein production, blood detoxification, and glycogen storage

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disaccharide

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Sugar that can be hydrolysized into two monosaccharide sub units. maltose and sucrose.

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monosaccharide

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simple sugar that cannot be hydrolyzed into simpler sugars; fructose glucose and galactose.

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Upper Esophageal (Cardiac) Sphincter

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a muscular ring between the esophagus and the stomach that controls the movement of food into and out of the stomach

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dehydration synthesis

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chemical reaction that results in the formation of a covalent bond between two subunit molecules by the removal of an -OH (Hydroxyl) group from one subunit and a hydrogen from the other, making a water molecule.

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gall bladder

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the organ that stores bile produced by the liver.

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Gastrin

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stomach hormone that stimulates the secretion of hydrochloric acid and the inactive precursor molecule of pepsin from glands in the stomach

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homeostasis

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the tendency of the body to maintain a relatively constant internal environment.

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Steapsin

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enzyme that catalyzes the hydrolysis of triglycerides into glycerol and fatty acids

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bioavailability

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the amount of a nutrient that a person absorbs from a source, rather than the total amount actually in the source.

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Enzyme

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protein molecule that acts as a catalyst to increase the rate of a reaction

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pancreas

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small gland in the abdomen that secretes digestive enzymes into the small intestine, as well as bicarbonate to neutralize hydrochloric acid from the stomach.

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inhibitor

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molecule that attaches to an enzyme and reduces its availability to bind substrate; competitive and non competitive are its two classes.

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Pepsin

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protein-digesting enzyme secreted in the stomach; remains inactive until hydrochloric acid is present

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peristalsis

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a wave like series of muscular contractions and relaxations of the circular and longitudinal muscles that surround the various parts of the digestive track; aiding the movement of food.

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polysaccharide

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a complex carbohydrate containing many simple sugars linked together; examples include starch, cellulose, and glycogen.

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Peptide Bonds

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enzyme that hydrolyzes the peptide bonds that link amino acids in proteins and peptides

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Substrate

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substance on which an enzyme acts

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triglyceride

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high energy and organic molecule composed of one glycerol molecule and three fatty acids; main component of fats and oils.

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villus (villi)

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finger like projection on the inside of the small intestine, increasing the surface area aiding in the absorption of nutrients.

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essential amino acid

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refers to the 9 out of 20 amino acids that come from the diet because the body can’t synthesize them

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nucleic acid

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macromolecule formed from a long chain of nucleotide subunits, each consisting of a five-carbon simple sugar, a nitrogen containing base, and a phosphate group; DNA and RNA.

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Peptide Bond

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bond between the amino group of one amino acid and the carboxyl group of another in a protein

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protein

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organic macromolecule assembled from subunits of amino acids

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segmentation

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a process by which physical digestion occurs in the small intestine; chyme sloshes back and forth between segments of the small intestine that form when bands of circular muscle briefly contract.

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lower esophageal (pyloric) sphincter

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muscular ring that acts as a valve between the stomach and the first part of the small intestine (duodenum), controlling the passage of food out of the stomach

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Small Intestine

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length of the digestive tract comprised of the duodenum, jejunum, and ileum; main function is to complete the digestion of macromolecules and to absorb their component subunits

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Large Intestine

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portion of the digestive system comprised of the caecum, colon, rectum, and anal canal; main function is to concentrate and eliminate waste materials

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Duodenum

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the first 25cm of the small intestine; important site of chemical digestion of chyme from the stomach.

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Microvilli

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microscopic projection found along exposed ell surfaces that greatly increase the surface area of the cell; found on the villi of the small intestine and on the membranes of certain cells.

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Nuclease

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enzyme that hydrolyses the bonds between nucleotides in nucleic acids

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Secretin

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A hormone released into the bloodstream by the duodenum (esp. in response to acidity) to stimulate secretion by the liver and pancreas.

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CCK (cholecystokinin)

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A polypeptide hormone produced principally by the small intestine in response to the presence of fats, causing contraction of the gallbladder, release of bile, and secretion of pancreatic digestive enzymes. Also called pancreozymin.

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GIP (gastric inhibitory polypeptide)

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a GI hormone found in the mucosa of the small intestine. Release of the hormone, mediated by the presence of glucose or fatty acids in the duodenum, results in the release of insulin by the pancreas and inhibition of gastric mobility acid secretion.