cell interactions & the extracellular environment

Extracellular Environment

Includes everything that lies outside of cells, including the ECM, or extracellular matrix.

Ground Substance

Gel-like hydrated material in the extracellular environment.

Glycoproteins

Glycoproteins found in the extracellular matrix such as integrins.

Collagen

A type of protein fiber found in the extracellular matrix.

Elastin

A type of protein fiber found in the extracellular matrix.

Diffusion

The net diffusion of solute from a region of higher concentration to a region of lower concentration.

Simple diffusion

The non-carrier-mediated, “downhill” movement of some molecules across a cell membrane.

Osmosis

The net diffusion of H2O (solvent) across a membrane, from regions of higher [H2O] to lower [H2O].

Osmotic pressure

The force needed to counteract osmosis.

Concentration

Amount of solute relative to the amount of solution (or solvent).

Molarity (M)

1M soln = (1mol solute)/(1L soln).

Molality (m)

1m soln = (1mol solute)/(1kg solvent).

Osmolality (Osm)

The total molality of the solution = the sum of the molalities of all solutes present.

Tonicity

Refers to the total concentration of solutes.

Isotonic

Same concentration of solutes.

Hypotonic

Lower concentration of solutes.

Hypertonic

Higher concentration of solutes.

Carrier proteins/ Membrane transport proteins

Proteins that help molecules across the membrane.

Pumps

ATPases; a class of membrane transport proteins.

Carriers

Transporters; a class of membrane transport proteins.

Channels

A class of membrane transport proteins that always use passive transport.

Passive transport

Energetically downhill transport; includes all channels & some carriers (uniporters).

Active transport

Energetically uphill transport; includes all pumps & some carriers such as symporters and antiporters.

Facilitated diffusion

Direction of transport is energetically downhill; All channels & some carriers (uniporters).

Primary active transport

A type of active transport that uses pumps.

Secondary active transport

A type of active transport that uses symporters and antiporters.

Sodium pump

The Na+/K+-ATPase; creates & maintains the primary ionic gradients across the plasma membranes of our cells

Sodium pump

Moves 3 Na+ ions out of the cell and 2 K+ ions into the cell for each ATP burned.

Sodium/glucose cotransporter

One such example couples the uphill movement of ions or molecules to the downhill movement of Na+ or K+.

Large molecules

Requires vesicles to enter or exit cells.

Endocytosis

Enter cells via this process.

Exocytosis

Exit cells via this process.

Membrane potential

The unequal charge distribution creating a charge gradient across cell membranes.

Resting membrane potential (Vr)

A typical cell at rest usually is -60 to - 80 mV.

Nernst equilibrium potential for K+ ions

The voltage that the membrane would assume if it were only permeable to K+ ions.

Chemical signals

Chemicals released from one cell into the ECF and then “sensed” by other cells for cell communication.

Receptor proteins

Target cells respond to these chemical signals via these.