In animals, a chamber or tube where digestion takes place.

Toward the top. In plants, at the tip of a branch. In animals, on the side of an epithelial layer that faces the environment and not other body tissues.

Toward the bottom and sides. In animals, the side of an epithelial layer that faces other body tissues and not the environment.

A peptide hormone secreted by cells in the lining of the small intestine. Stimulates the secretion of digestive enzymes from the pancreas and the release of bile by the gallbladder.

A transmembrane protein that facilitates diffusion of an ion down its previously established electrochemical gradient and uses the energy of that process to transport some other substance, in the same or opposite direction, against its concentration gradient.

Spontaneous movement of a substance from one region to another, often with a net movement from a region of high concentration to one of low concentration (i.e., down a concentration gradient).

The mechanical and chemical breakdown of food into molecules that can be absorbed into the body of an animal.

first part of the small intestine, produces hormones and receives secretions from the liver and pancreas

An animal tissue consisting of sheetlike layers of tightly packed cells that line an organ, a gland, a duct, or a body surface.

Passive movement of a substance across a membrane with the assistance of transmembrane carrier proteins or channel proteins.

A hormone produced by cells in the stomach lining in response to the arrival of food or to a neural signal from the brain. Stimulates other stomach cells to release hydrochloric acid.

the major site for food digestion and nutrient absorption; after food enters the mouth, it enters a cell membrane wraps around food particles and then takes them to the interior cavity

Helicobacter pylori

A chemical reaction in which a molecule is split into smaller molecules by reacting with water. In biology, most of these reactions involve the splitting of polymers into monomers.

Referring to a solution that has a higher solute concentration, and therefore a lower water concentration, than another solution.

solution with a lesser concentration of solute, If a cell from a fresh water fish is placed into a beaker of salt water, the cell is said to be --------- to the water.

The third portion of the small intestine, between the jejunum and the cecum.

The act of bringing food into the digestive tract

Any membrane protein that spans the entire lipid bilayer.

Referring to a solution that has the same solute concentration and water concentration as another solution.

1. the part of the small intestine between the duodenum and ileum.

Any organic substance that does not dissolve in water, but dissolves well in nonpolar organic solvents. Include fats and oils.

Tiny protrusions from the surface of an epithelial cell that increase the surface area for absorption of substances.

Diffusion of water across a selectively permeable membrane from a region of lower solute concentration (higher water concentration) to a region of higher solute concentration (lower water concentration).

A protein-digesting enzyme secreted in inactive form by chief cells in the stomach lining.

Rhythmic waves of muscular contraction. In the digestive tract, pushes food along. In animals with hydrostatic skeletons, enables crawling.

Uptake by a cell of small particles or cells by invagination and pinching off of the plasma membrane to form small, membrane-bound vesicles.

made up of a carbon chain with no double bonds, come from animals, solid at room temperature

A peptide hormone secreted by cells in the small intestine in response to the arrival of food from the stomach. Stimulates secretion of bicarbonate ions (HCO₃⁻) by the pancreas.

The property of a membrane that allows some substances to diffuse across it much more readily than other substances.

A type of cell–cell attachment structure that links the plasma membranes of adjacent animal cells, forming a barrier that restricts the movement of substances in the space between the cells. Most abundant in epithelia (e.g., the intestinal lining).

Referring to lipids in which at least one carbon-carbon bond is a double bond. Double bonds produce links in hydrocarbon chains and decrease the compound’s melting point.

Small, fingerlike projections (1) of the lining of the small intestine or (2) of the fetal portion of the placenta adjacent to maternal arteries. Function to increase the surface area available for absorption of nutrients and gas exchange.

A transmembrane protein that forms a pore in a cell membrane, which may open or close in response to a signal. The structure of most channels allows them to admit just one or a few types of ions or molecules.

A transmembrane protein that facilitates diffusion of a small molecule (e.g., glucose) across a membrane by a process involving a reversible change in the shape of the protein.

structural component of cell membranes and serves as a building block for synthesizing various steroid hormones, vitamin D, and bile acids.

A chemical reaction in which two molecules are joined covalently with the removal of an –OH from one and an –H from another to form water.

The covalent bond is formed by a condensation reaction between a carboxyl group and a hydroxyl group.

The concentration of dissolved solutes in a solution, measured in osmoles per liter.

A class of lipid having a hydrophilic head (including a phosphate group) and a hydrophobic tail (consisting of two hydrocarbon chains). Major components of the plasma membrane and organelle membranes.

A member of the domain Bacteria or Archaea; a unicellular organism lacking a nucleus and containing relatively few organelles or cytoskeletal components.

A member of the domain Eukarya; an organism whose cells contain a nucleus, numerous membrane-bound organelles, and an extensive cytoskeleton. May be unicellular or multicellular.

A small, usually circular, supercoiled DNA molecule that exists independently of the cell’s main chromosome(s) in prokaryotes and some eukaryotes.

General term for any pinching off of the plasma membrane that results in the uptake of material from outside the cell.

The covalent bond formed by a condensation reaction between two amino acids.

The sequence of amino acid residues in a protein polymer; also the sequence of nucleotides in a single nucleic acid strand.

• - In proteins, localized folding of a polypeptide chain into regular structures is stabilized by hydrogen bonding between atoms of the peptide backbone.

• - In nucleic acids, elements of structure are stabilized by hydrogen bonding between complementary bases and hydrophobic interactions with the aqueous environment.

• The overall three-dimensional shape of a single polypeptide chain, resulting from multiple interactions among the amino acid side chains and the peptide backbone.

A molecule consisting of a five-carbon sugar (ribose or deoxyribose), one or more phosphate groups, and one of several nitrogen-containing bases.

Chemical linkage between adjacent nucleotide residues in DNA and RNA. Forms when the phosphate group of one nucleotide condenses with the hydroxyl group on the sugar of another nucleotide.

A long fiber, about 7 nm in diameter, composed of two intertwined strands of polymerized actin protein; one of the three types of cytoskeletal fibers. Involved in cell structure and movement.

A long tubular fiber, about 25 nm in diameter, formed by polymerization of tubulin protein dimers; one of the three types of cytoskeletal fibers. Involved in cell structure, movement, and transport of materials within the cell.

A long fiber, about 10 nm in diameter, composed of one of various proteins (e.g., keratins, lamins); one of the three types of cytoskeletal fibers. Used to form networks that help maintain cell shape and hold the nucleus in place.

A small, acidified organelle in animal cells and some plant cells (modified vacuoles) containing enzymes that catalyze hydrolysis reactions and can digest large molecules.

A eukaryotic organelle, consisting of stacks of flattened membranous sacs (cisternae), that functions in processing and sorting proteins and lipids destined to be secreted or directed to other organelles.

A network of interconnected membranous sacs and tubules found inside eukaryotic cells that functions in synthesizing lipids and proteins that reside in the endomembrane system and the plasma membrane or are secreted from the cell.

Secretion of intracellular molecules (e.g., hormones, collagen), contained within membrane-bound vesicles, to the outside of the cell by fusion of vesicles to the plasma membrane.