Lec 2- Cell Membrane and Transport Flashcards
Fluid mosaic model
View of the membrane to show its contents as “icebergs”.
Amphipathic
Containing both hydrophobic and hydrophilic parts.
Makes up the phopholipid bilayer.
Diffusion
Simple: uniform spreading out of molecules due to their random intermingling.
Dynamic equilibrium
Movement of molecules is equally matched on both sides.
Channels
Proteins found across the membrane that are water filled.
Carriers/Transporters
Other proteins that span the membrane; they transfer across membrane specific substances that are unable to cross on their own.
Active transporters/pumps
Requires energy to move a substance across the membrane.
Cations
Positively charged ions.
Anions
Negatively charged ions.
Permeability
A substance is able to cross the membrane on its own.
Ligand or Voltage-Gated
These channels open or close in response to changes in membrane potential.
Uniporter
An integral membrane protein that transports a single type of substrate species (charged or uncharged) across a cell membrane.
Antiporter
An antiporter (also called exchanger or counter-transporter) is a cotransporter and integral membrane protein involved in secondary active transport of two or more different molecules or ions across a phospholipid membrane such as the plasma membrane in opposite directions.
Tm - Transport maximum
The amount of a substance carriers can transport across the membrane in a given time is limited.
Na+/K+ ATPase (pump)
Transports Na+ out of the cell and picks up K+ for the cell.
Endocytosis
The plasma membrane surrounds the substance to be ingested and then fuses over the surface, pinching off a membrane-enclosed vesicle so that the engulfed material is trapped within the cell.
Exocytosis
A membrane-enclosed secretory vesicle formed within the cell fuses with the plasma membrane and then open up and releases its contents to the exterior.
Phagocytosis
Selective uptake of a multimolecular particle.
Tight-junction
Adjacent cells bind firmly with each other at points of direct contact to seal off the passageway between cells.
Apical
Faces lumen.
Basolateral
Faces interstitial fluid and blood stream.
Lumen
Inside of a tubular structure.
Osmosis
Diffusion of water from an area of high concentration to an area of low concentration.
Osmolarity
A measure of total solute concentration given in terms of the number of particles (molecules or ions).
mOsmol
The expression of osmolarity in body fluids.
Osmol
The expression of osmolarity.
Solute
Molecule suspended in a solution. In a solvent.
Hydrostatic/osmotic pressure
Is the pressure exterted by a standing, or stationary, fluid on an object.
Osmotic pressure- a measure of the tendency for osmotic flow of water into that solution because of its relative concentration of nonpenetrating solutes and water.
Semi-permeable membrane
Permits some particles to pass through. Some can’t.
Isotonic
Has the same concentration of nonpenetrating solutes as normal body cells do.
Hypotonic
A solution with a below normal concentration of nonpenetrating solutes. Water enters the cell by osmosis. Cell swell and rupture.
Hypertonic
A solution with above normal concentration of nonpenetrating solutes. Water leave the cell by osmosis.
Cell shrink.
Isosmotic
Having the same osmotic pressure.
