AP Biology Vocabulary Chapter 5

for my class, use if you like

Integral Protein

A transmembrane protein with hydrophobic regions that expand into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on one or both sides of the membrane (or lining the channel in the case of a channel protein).

Osmosis

The diffusion of free water across a selectively permeable membrane.

Transport Protein

A transmembrane protein that helps a certain substance of class of closely related substances to cross the membrane.

Glycoprotein

A protein with one or more carbohydrates covalently attached to it.

Concentration Gradient

A region along which the density of a chemical substance increases or decreases.

Facilitated Diffusion

The passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure.

Glycolipid

A lipid with one or more covalently attached carbohydrates.

Diffusion

The random thermal motion of particles of lipids, gases, or solids. In the presence of a concentration or electrochemical gradient, diffusion results in the net movement of a substance from a region where it is more concentration to a region where it is less concentrated.

Peripheral Protein

A protein loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer.

Isotonic

Referring to a solution that, when surrounding a cell, causes no net movement of water into or out of the cell.

Turgid

Swollen or distended, as in plant cells. (A walled cell becomes turgid if it has a lower water potential than its surroundings, resulting in entry of water.)

Tonicity

The ability of a solution to cause a cell to gain or lose water.

Passive Transport

The diffusion of a substance across a biological membrane with no expenditure of energy.

Osmoregulation

Regulation of solute concentrations and water balance by a cell or organism.

Hypertonic

Referring to a solution that, when surrounding a cell, will cause the cell to lose water.

Hypotonic

Referring to a solution, that when surrounding a cell, will cause the cell to take up water.

Flaccid

Lacking turgor (stiffness or firmness), as in the plant cell in surroundings where there is a tendency for water to leave the cell. (A wall cell becomes flaccid if it has a higher water potential than its surroundings, resulting in the loss of water.)

Plasmolysis

A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment.

Selective Permeability

A property of biological membranes that allows them to regulate the passage of substances across them.

Proton Pump

An active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient, generating a membrane potential in the process.

Phagocytosis

A type of endocytosis in which large particulate substances or small organisms are taken up by a cell. It is carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophils, and dendritic cells).

Phosphorylation Cascade

A series of chemical reactions during cell signaling meditated by enzymes (kinases), in which each kinase in turn phosphorylates and activates another, ultimately leading to phosphorylation of many proteins.

Protein Kinase

An enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein.

Sodium-Potassium Pump

A transport protein in the plasma membrane of animal cells that actively transports sodium out of the cells and potassium into the cell.

Excoytosis

The cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane.

Pinocytosis

A type of endocytosis in which the cell ingests extracellular fluid and is dissolved in solutes.

Electrogenic Pump

An active transport protein that generates voltage across a membrane while pumping ions.

Protein Phosphate

An enzyme that removes phosphate groups from (dephosphorylates) proteins, often functioning to reverse the effect of a protein kinase.

Second Messenger

A small, nonprotein, water-soluble molecule or ion, such as calcium ion or cyclic AMP, that relays a signal to a cell’s interior in response to a signal received by a signal receptor protein.

Membrane Potential

The difference in electrical charge (voltage) across a cell’s plasma membrane due to the differential distribution affects the activity of excitable cells and the transmembrane movement of all charged substances.

Gated Chemicals

A transmembrane protein channel that opens or closes in response to a particular stimulus.

Receptor-Mediated Endocytosis

The movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances.

Cotransport

The coupling of the “downhill” diffusion of one substance to the “uphill” transport of another against its own concentration gradient.

Electrochemical Gradient

The diffusion gradient of an ion, which is affected by both the concentration difference of an ion across a membrane (a chemical force) and the ion’s tendency to move relative to the membrane potential (an electrical force).

Ligand Gated Ion Channel

A transmembrane protein containing a pore that opens or closes as it changes shape in response to a signaling molecule (ligand), allowing or blocking the flow of specific ions; also called and ionotropic receptor.

Ligand

A molecule that binds specifically to another molecule, usually a larger one.

Signal Transduction Pathway

A series of steps linking a mechanical, chemical, or electrical stimulus to a specific cellular response.

Active Transport

The movement of a substance across a cell membrane against its concentration or electrochemical gradient, medicated by specific transport proteins and requiring an expenditure of energy.