Biology 6.1

Absorption

the movement of a substance, such as a liquid or solute, across a cell membrane by means of diffusion, osmosis, or active transport.

Amylase

an enzyme, found mainly in saliva and pancreatic fluid, that converts starch and glycogen into simple sugars.

Cellulose

a complex carbohydrate that is composed of glucose units, and forms the main constituent of the cell wall in most plants.

Circular muscles

the inner layer of smooth (involuntary) muscle of the muscle coat (muscularis externa) of the small intestine in which the muscle fibres encircle the lumen.

Dialysis

the separation of smaller molecules from larger molecules, or of dissolved substances in a solution by selective diffusion through a semi-permeable membrane.

Endopeptidase

any of a large group of enzymes that catalyse the hydrolysis of peptide bonds in the interior of a polypeptide chain or protein molecule.

Enzymes

proteins or conjugated proteins produced by living organisms and functioning as biochemical catalysts.

Epithelium

the thin tissue forming the outer layer of a body's surface and lining the alimentary canal and other hollow structures.

Glycogen

a polysaccharide that is the main form of carbohydrate storage in animals and occurs primarily in the liver and muscle tissue. It is readily converted to glucose when needed by the body to satisfy its energy needs.

Lipase

a pancreatic enzyme that catalyses the breakdown of lipids through the hydrolysis of the linkages between fatty acids and glycerol in triglycerides and phospholipids.

Liver

a large glandular organ located in the upper right side of the abdominal cavity active in the secretion of bile and various metabolic processes.

Longitudinal muscles

(of the stomach) the outer longitudinal layer of smooth muscles, continuous with that of the esophagus.

Lumen

the inner open space or cavity of the small intestine.

Macromolecule

a very large molecule, such as a polymer or protein, consisting of many smaller structural units linked together.

Mineral ions

individual elements with an electrical charge.

Monomer

a molecule that can combine with others to form a polymer.

Mucosa

a mucus-secreting membrane lining all bodily passages that are open to the air, such as the digestive tract.

Nucleic acids

complex compounds found in all living cells composed of bases, carbohydrates, and phosphoric acid.

Nucleic acids

in the form of DNA and RNA control cellular function and heredity.

Pancreas

a gland in vertebrates, lying behind the stomach, that secretes pancreatic juice into the duodenum and insulin and glucagon into the bloodstream.

Small intestine

the narrow, winding, upper part of the intestine where digestion is completed and nutrients are absorbed by the blood.

Starch

a polysaccharide composed of glucose units that occurs widely in plant tissues in the form of storage.

Villus (plural villi)

one of the minute finger-shaped processes of the mucous membrane of the small intestine that serve in the absorption of nutrients.

Vitamin

any of various fat-soluble or water-soluble organic substances essential in minute amounts for normal growth and activity of the body and obtained naturally from plant and animal foods.