BIOL325 - Membrane Transport Vocab

Solutions

homogeneous mixture containing a relatively large amount of solvent and smaller amounts of one or more dissolved solutes

Concentration

amount of solute dissolved in a specific amount of solution

Solute

Smaller amounts of one or more dissolved substances

Solvent

a relatively large amount of one substance (the dissolving medium, which in the body is water)

Diffusion

Random collisions and intermingling of molecules as a result of their continuous thermally induced random motion

Concertation gradient

A difference in concentration of a particular substance between two adjacent areas

Net diffusion

difference between the opposing movements of two types of molecules in a solution

Dynamic equilibrium

when two opposing passive movements exactly counterbalance each other so that no net movement takes place, with no energy needed to maintain this constancy

Fick’s law of diffusion

rate of net diffusion of a substance across a membrane is directly proportional to the substance’s concentration gradient, the lipid solubility of the substance, and the surface area of the membrane and inversely proportional to the substance’s molecular weight and the diffusion distance

Permeable

Permitting passage of a particular substance

Selectively permeable

membrane that permits some particles to pass through while excluding others

Impermeable

prohibiting passage of a particular substance through the plasma

Passive transport

biological process where molecules move across a cell membrane without requiring energy

Facilitated diffusion

passive carrier-mediated transport involving transport of a substance down its concentration gradient across the membrane

Channel-mediated diffusion

type of facilitated diffusion in which specific membrane channel proteins allow ions or small polar molecules to cross the cell membrane passively (no ATP required)

Aquaporins

composed of membrane proteins that are channels specific for passage of water

Osmosis

movement of water across a membrane down its own concentration gradient toward the area of higher solute concentration

Osmolarity

measure of the concentration of a solution given in terms of milliosmoles/liter (mOsm/L), the number of millimoles of solute particles in a liter of solution

Penetrating solutes

solute particles that can cross a cell membrane, moving freely between the ICF and ECF until concentrations become equal on both sides of the membrane

Nonpenetrating solutes

solutes that cannot cross a cell membrane, meaning they stay on one side and do not equilibrate between the inside and outside of the cell

Tonicity

a measure of the effect a solution has on cell volume when the solution surrounds the cell

Isotonic Solution

a solution with osmolarity equal to that of normal body fluids

Hypertonic solution

a solution with osmolarity greater than that of normal body fluids; more concentrated than normal

Hypotonic solution

a solution with osmolarity less than that of normal body fluids; more dilute than normal

Isometric

cell volume stays the same because there is no net movement of water across the plasma membrane

Hyperosmotic

a solution that has a higher total solute concentration (osmolarity) than another solution

Hypoosmotic

a solution that has a lower solute concentration (osmolarity) than another solution

Total body fluid

the entire amount of water inside the body, including all the fluid in every compartment

Intracellular fluid

the fluid collectively contained within all the body cells

Extracellular fluid

all the fluid outside the cells of the body; consists of interstital fluid and plasma

Carrier-mediated transport

transport of substance across the plasma membrane facilitated by a carrier molecule

Transport maximum

The maximum rate of substance’s carrier-mediated transport across the membrane when the carrier is saturated

Active Transport

active carrier-mediated transport involving transport of a substance against its concentration gradient across the plasma membrane

Primary active transport

a carrier-mediated transport system in which energy is directly required to operate the carrier and move the transported substance against its concentration gradient

Phosphorylation

process of adding a phosphate group to a molecule, usually a protein or an organic compound like ADP

Secondary active transport

a transport mechanism in which a carrier molecule for glucose or an amino acid is driven by a Na+ concentration gradient established by the energy-dependent Na+-K+ pump to transfer the glucose or amino acid uphill without directly expending energy to operate the carrier

NA+K+ ATPase pump

Sodium potassium pump; Primary active transport carrier that control the amount of sodium (Na) and potassium (K) into and out of the cell allowing cells to create action potentials

Symport

the form of secondary active transport in which the driving ion and transported solute move in the same direction across the plasma membrane

Antiport

the form of secondary active transport in which the driving ion and transported solute move in opposite directions across the plasma membrane

Sodium and glucose cotransporter (SGLT)

symport carrier that cotransports Na+ and glucose in epithelial cells

Glucose transporter (GLUT)

glucose carrier molecules that facilitate membrane transport of glucose

Vesicular transport

movement of large molecules or multimolecular materials into or out of the cell within a vesicle, as in endocytosis or exocytosis

Endocytosis

Internalization of extracellular material within a cell as a result of the plasma membrane forming a pouch that contains the extracellular material, then sealing at the surface of the pouch to form an endocytic vesicle

Pinocytosis

Nonselective uptake of a sample of ECF

Receptor-Mediated endocytosis

Import of particular large molecule from the ECF into a cell by formation and pinching off of an endocytic pouch in response to binding of the molecule to a surface membrane receptor specific for it

Exocytosis

A membrane-enclosed vesicle formed within the cell fuses with the plasma membrane, then opens up and releases its contents to the exterior

Phagocytosis

large, multimolecular, solid particles are engulfed by a cell