Bio 211 Chapter 7

Cnu

What process involves the secretion of large molecules when a vesicle fuses with the plasma membrane?

Exocytosis

What type of transport requires energy to move solutes against their gradients?

Active transport

Which type of transport does not require energy and may involve transport proteins?

Passive transport

What is the main component of the plasma membrane?

Phospholipid bilayer

What term describes the cellular process of taking in large molecules by pinching inward of the plasma membrane?

Endocytosis

What property of cellular membranes allows them to regulate the exchange of substances with their environment?

Selective permeability

What model describes the structure of cellular membranes as a fluid combination of lipids and proteins?

Fluid mosaic model

Glycoprotein

A molecule that consists of a carbohydrate plus a protein, spanning the plasma membrane.

Transport Proteins

Proteins that help move substances across a cell membrane.

Aquaporins

Channel proteins that facilitate the passage of water molecules through the cell membrane.

Lipid Bilayer

A double layer of lipids that makes up the cell membrane and provides a barrier to the passage of ions and polar molecules.

Channel Proteins

Transport proteins that provide a hydrophilic channel through which certain molecules or ions can pass.

Concentration Gradient

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

Tonicity

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

Plasmolysis

The phenomenon where a plant cell's plasma membrane pulls away from the cell wall due to loss of water in a hypertonic environment.

Contractile Vacuole

An organelle in some protists that pumps excess water out of the cell.

Osmosis

The diffusion of water across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Receptor-mediated endocytosis

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

Exocytosis

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

Gated channels

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

Endocytosis

Cellular uptake of biological molecules and particulate matter via formation of vesicles from the plasma membrane.

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.

Pinocytosis

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

Flaccid

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

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

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).

Integral proteins

A transmembrane protein with hydrophobic regions that extend 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).

Hypotonic

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

Hydrophobic interactions

A type of weak chemical interaction caused when molecules that do not mix with water coalesce to exclude water.

Hypertonic

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

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.)

Fluid mosaic model

The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids.

Passive transport

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

Ion channels

A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.

Diffusion

The random thermal motion of particles of liquids, 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 concentrated to a region where it is less concentrated.

Cotransport

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

Electrogenic pump

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

Transmembrane proteins

A type of integral protein that spans the entire membrane.

Active transport

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

Selective permeability

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

Osmoregulation

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

Concentration gradient

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

Membrane potential

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

Peripheral proteins

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

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).

Amphipathic

Having both a hydrophilic region and a hydrophobic region.

Sodium-potassium pump

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

Glycolipids

A lipid with one or more covalently attached carbohydrates.

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.

Gated channels

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