APBIO- Chapter 7

Unit 2; chapter 7

Amphipathis

having both a hydrophilic region and hydrophobic region

Fluid mosaic model

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

Integral proteins

a transmembrane protein with hydrophobic regions that extend ito 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)

Transmembrane proteins

A type of integral protein that spans the entire membrane

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

Integrins

in aminal cells, a transmembrane receptor protein with two subunits that interconnects the extracellular matrix and the cytoskeleton

Glycolipids

A lipid with one or more covalently attached carbohydrates

Glycoproteins

A protein with one or more covalently attached carbohydrates

Selective permeability -A property of biological membranes that allows them to regulate the passage of substances across them

Selective permeability

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

Transport proteins

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

Aquaporins

A channel protein in a cellular membrane that specifically facilitates osmosis, the diffusion of free water across the membrane

Diffusion

movement of particles of any substance so that they spread out into available space

Concentration radiant

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

Passive Transport

diffusion of substance across biological membrane, requires no energy

Osmosis

diffusion of free water across a selectively permeable membrane whether artificial or cellular

Tonocity

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

Isotonic

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

Hypertonic

referring to a solution that, when surrounding a cell, will cause a cell to lose water

Hypotonic

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

Osmoregulation

regulation of solute concentrations and water balance by a cell or organism

Turgor pressure

The force directed against a plant cell wall after the influx of water and swelling of the cell due to osmosis

Turgid

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

Flaccid

limp. Lacking turgor, as in a plant cell in surroundings where there is a tendency for water to leave the cell

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

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

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

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

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

Electrochemical gradient

The diffusion gradient of an ion, which is affected by both the concentration difference of an ion across a membrane,and the ion's tendency to move relative to the membrane potential

Electrogenic pump

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

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

Cotransport

the coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient

Endocytosis

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

Exocytosis

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

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)

Pseudopodium

A cellular extension of amoeboid cells used in moving and feeding

Pinocytosis

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

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