BIO SCI 93: Lecture 6 (7.2-7.5) Nomenclature

selective permeability, passive & active transport

Tonicity

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

Hypotonic

having a lower solute concentration than that of a cell

Isotonic

having the same solute concentration as a cell

Hypertonic

having higher solute concentration than that of a cell

Osmosis

diffusion of free water across a selectively permeable membrane

Endocytosis

intake of molecules and particulate matter (e.g. food) by forming new vesicles from the plasma membrane

Exocytosis

secretion of molecules via vesicles that fuse with the plasma membrane

Phagocytosis

endocytosis; cellular “eating”

Pinocytosis

endocytosis; cellular “drinking”; nonselective of solutes

Receptor-mediated endocytosis

endocytosis; specified cellular “drinking” regulated by receptor proteins exposed to ECF, to which the desired solutes bind

Hypercholesterolemia

an inherited disease characterized by a high level of cholesterol in the blood; caused by defective LDL receptor proteins (LDL unable to be taken into the cell, remains in bloodstream)

Passive Transport

movement of solutes down their concentration gradient; does not require ATP

Active Transport

movement of solutes across the membrane against their concentration gradient; requires ATP

Electrochemical gradient

the combined force of membrane potential (± charge on either side of membrane) and an ion’s concentration gradient on the flow of ions across the plasma membrane

selective permeability

a property of the plasma membrane that allows some substances to cross more easily than others, or exclude substances altogether; dependent on properties of lipid bilayer and transport proteins built into it

Transport proteins

a transmembrane protein that helps particular substances to cross the membrane (e.g. channel proteins, carrier proteins); specific to the substance it moves

Diffusion

the movement of particles of a substance so they spread out into the available space; result of thermal energy (constant motion) of all molecules

Free water

water molecules that are not forming hydration shells around hydrophilic solute molecules

Facilitated diffusion

the passive diffusion of polar molecules and ions via transport proteins (e.g. aquaporins and water)

gated channels

a channel protein that opens or closes in response to a particular stimulus (e.g. electrical, chemical)

Cotransport

the coupling of the passive diffusion of one molecule (down its concentration gradient) with the active transport of another (against its gradient)