BIO 240 Cell Membrane

Sodium-potassium pump

Actively transports sodium ions out of the cell and potassium ions into the cell. For every 3 Na+ trasported out of the cell, two K+ are let inside, lowering the charge of the cytoplasm by 1+.

Fasclitated Diffusion

diffusion across a membrane with the help of membrane proteins

Synaptic signaling

local cell signaling in nerve cells where an electrical signal triggers the release of molecules that travel across a synapse to a target cell; can also be long distance signaling when the signal "jumps" sections of the axon

Paracrine signaling

local cell signaling through the use of molecules called growth regulators

Active Transport

moving a substance up its concentration gradient, from lower concentration to higher concentration, requiring the use of ATP

Fluid mosaic model

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

Osmosis

The diffusion of water across a selectively permeable membrane. Water moves from hypo to hyper.

Peripheral proteins

Protein appendages loosely bound to the surface of the membrane or integral proteins and not embedded in the lipid bilayer.

G protein-coupled receptor

a cell surface transmembrane receptor that works with a g protein

Phagocytosis

a cell takes in food

Pinocytosis

a cell takes in samples of extracellular fluid to bring a mixture of substances/materials inside the cell

G protein

a protein that binds GTP (energy source similar to ATP) to a protein

signal transduction pathway

a series of changes, usually involving the change in shape of many molecules, that results in a triggering a cellular response

Transduction

a series of steps through a signal transduction pathway that transforms the chemical signal into one that can be interpreted by the cell

Transport proteins

a transmembrane protein that helps a substance or a group of substances exit or enter the cell; channel and carrier proteins are examples

Electrogenic pump

a transport protein that helps create voltage by transporting ions

cyclic AMP

cAMP, a second messenger; a sudden increase or decrease in the concentration of cAMP can act as a transduction signal; usually activates protein kinase A.

Receptor Mediated endocytosis

cells take in a large amount of one substance at a time by using receptors on the extracellular side of the membrane to capture them

local cell signaling

occurs by sending molecules through junctions; ex: paracrine and synaptic signaling

carbohydrates

used in cell-cell recognition by acting as 'tags' or labels; usually short branched chains that bond to other molecules to make glycoproteins or glycolipids

Concentration gradient

the regions where the concentration of a substance increases or decreases

Reception

the target cell detects the signaling molecule (ligand) when it binds to a receptor on the membrane

Response

the translated signal from transduction causes a cellular response, usually regulation of proteins and protein synthesis

Channel proteins

transport proteins that have hollow hydrophilic channels that let certain charged molecules or ions go in and out of a cell; ex: aquaporins

amphipathic

A molecule that has both a hydrophilic region and a hydrophobic region.

Ligand

A molecule that is specific to bind to a receptor site of another molecule.

selective permeability

A property of biological membranes that allows some substances to cross more easily than others.

Ion channels

Channel proteins that functin as gated channels for ions, opening or closing in response to stimuli

Hypertonic

Having a higher concentration of solute than another solution. An animal cell shrivels in this solution. A plant cell is plasmolysed.

Hypotonic

Having a lower concentration of solute than another solution. An animal cell lyses in this solution. A plant cell is turgid and healthy.

Isotonic

Having a stable concentration of solute in two regions separated by a selectively permeable membrane. An animal cells is healthy in this solution. A plant cell is flaccid.

Cholesterol

In animal cell membranes they help resist changes in membrane fluidity

Diffusion

The tendency for molecules to move from an area of higher concentration to an area of lower concentration. Requires NO energy.

phosphorylation

The transfer of a phosphate group, usually from ATP, to a molecule.

function of membrane proteins

Transport, enzymatic activity, cell-cell recognition, intercellular joining, attachment to the cytoskeleton or extracellular matrix, signal transduction

Integral proteins

Typically transmembrane proteins with hydrophobic regions that completely span the hydrophobic interior of the membrane. Usually contain nonpolar amino acids chains that form alpha helices

Endocrine signaling

hormones released by cells travel all over the body through the circulatory system

lignad-gated ion channels

proteins that change into a gated ion channel when a signal molecule binds to it

Carrier proteins

proteins that shuttle charged molecules across a membrane by changing its shape (opening one end causes the other to close)

stages of cell signaling

reception, transduction, response

Long distance cell signaling

signaling that occurs through the use of hormones in the endocrine system

Second messengers

small, nonprotein, water soluble molecules or ions that can spread easily through cell diffusion and continue a signal in a cell

Coupled transport

the coupling of the "downhill" transport of one substance with the active "uphill" transport of another

Electrochemical gradient

the diffusion gradient of an ion due to its concentration gradient AND membrane potential (an ion will diffuse down its concentration gradient and toward charge balance)

Membrane potential

the electrical potential energy, or voltage, across the plasma membrane. The cytoplasm is negatively charged compared to the extracellular side of a cell, due to differences in ion concentrations.

protein kinase

the enzyme that transfers a phosphate from ATP to a molecule, usually activating a molecule

protein phosphatase

the enzyme that transfers a phosphate from a molecule to ADP, usually deactivatin a molecule

Endocytosis

the formation of vesicles from the plasma membrane, encasing molecules to bring them inside a cell

Exocytosis

the fussion of a vesicle with the cell membrane, expelling or secreting the vesicles contents outside the cell

Phospholipids

the hydrophobic interactions of these molecules are what hold a cell membrane together