Cell Membrane

cell membrane

thin, flexible barrier around a cell; regulates what enters and leaves the cell, has a fluid mosaic model, has proteins inserted in the lipid bilateral to conduct some molecules across the layer

phospholipid bilayer

A double layer of phospholipids that makes up plasma and organelle membranes.

4 components of cell membrane

phospholipid bilayer, transmembrane proteins, interior protein network, cell surface markers

transmembrane proteins

Integral proteins that span the membrane.

Interior protein network

membranes are structurally supported by intracellular proteins that reinforce the membrane's shapes

cell surface markers

a membrane protein that identifies the cell type: includes glycoproteins and glycolipids

What microscopes are used to study membranes

Transmission electron electron microscopes and scanning electron microscopes

membrane protein functions

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

passive transport

Requires NO energy, Movement of molecules from high to low concentration, Moves with the concentration gradient

facilitated diffusion

Movement of specific molecules across cell membranes through protein channels

ion channels

A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.

carrier proteins (transporters)

integral membrane proteins that move ions or molecules from one side of the plasma membrane to the other

Saturation

the state or process that occurs when no more of something can be absorbed, combined with, or added.

Osmosis

Diffusion of water through a selectively permeable membrane

Hypertonic

Having a higher concentration of solute than another solution.

Hypotonic

Having a lower concentration of solute than another solution

Aquaporins

A transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane

How many water molecules are let in by each aquaporin?

3billion or 3x10^9

osmotic pressure

the external pressure that must be applied to stop osmosis

active transport

Energy-requiring process that moves material across a cell membrane against a concentration difference

Uniporter

A carrier protein that transports a single molecule across the plasma membrane.

symporter

transporter that carries two different ions or small molecules, both in the same direction

antiporter

A carrier protein that transports two molecules acrss the plasma membrane in opposite directions.

Carrier porter in active transport

Uniporters, symporters, antiporters

sodium-potassium pump

a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell

Exocytosis

Process by which a cell releases large amounts of material

Endocytosis

process by which a cell takes material into the cell by infolding of the cell membrane

amphipathic

having both a hydrophilic region and a hydrophobic region

fluid mosaic model

model that describes the arrangement and movement of the molecules that make up a cell membrane

Fluid hydrocarbons tails

Viscous hydrocarbons

Cholesterol hydrocarbon

integral proteins

penetrate the hydrophobic interior of the lipid bilayer

peripheral proteins

The proteins of a membrane that are not embedded in the lipid bilayer; they are appendages loosely bound to the surface of the membrane.

transmembrane proteins

integral proteins that do not extend all the way through the membrane.

structure of transmembrane protein

cell-cell recognition

The function of membrane proteins in which some glycoproteins serve as ID tags that are recognized by membrane proteins of other cells.

What are Glycolipids

Membrane carbohydrates that are covalently bonded to lipids.

Glycoproteins

Membrane carbohydrates that are covalently bonded to proteins.

transport proteins

allow passage of hydrophilic substances across the membrane; also called channel proteins

channel proteins

have a hydrophilic channel that certain molecules or ions can use as a tunnel

carrier proteins

bind to molecules and change shape to shuttle them across the membrane and hold onto their passengers

concentration gradient

difference in the concentration of a substance from one location to another; the region along which the density of a chemical substance increases or decreases

Tonicity

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

Isotonic

when the concentration of two solutions is the same

Hypertonic

when comparing two solutions, the solution with the greater concentration of solutes

Hypotonic

Having a lower concentration of solute than another solution

Osmoregulation

regulation of solute concentrations and water balance by a cell or organism

turgor pressure

The pressure inside of a cell as a cell pushes itself against the cell wall.

turgid

(adj.) swollen, bloated, filled to excess; overdecorated or excessive in language

flaccid

(adj.) limp, not firm; lacking vigor or effectiveness

healthy state for most plant cells

turgid

Plasmolysis

Collapse of a walled cell's cytoplasm due to a lack of water

gate channels

open and close in response to a stimulus

sodium-potassium pump

a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell

membrane potential

The voltage across a cell's plasma membrane. -50 to -200 mV

electrochemical gradient

The diffusion gradient of an ion, which is affected by both the concentration difference of an ion across a membrane (a chemical force) and the ion's tendency to move relative to the membrane potential (an electrical force) and when a molecule goes from positive to negative

electrochemical gradient

The diffusion gradient of an ion, representing a type of potential energy that accounts for both the concentration difference of the ion across a membrane and its tendency to move relative to the membrane potential.

Electrochemical pump

a transport protein that generates voltage across a membrane

proton pump

An active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient, generating a membrane potential in the process.

ligand

A molecule that binds specifically to another molecule, usually a larger one.

Anchoring molecules

Modified lipids with nonpolar regions that insert into the internal portion of the lipid bilayer and chemical bonding domains that link directly to proteins

self-repair

Amoeba Ingestion

- pseudopods capture food (phagocytosis)

Nerve cell chart

Major Histocompatibility Complex (MHC)

A family of genes that encode a large set of cell surface proteins called MHC molecules. Class I and class II MHC molecules function in antigen presentation to T cells. Foreign MHC molecules on transplanted tissue can trigger T cell responses that may lead to rejection of the transplant

sodium-potassium pump in nerve cell

When the neuronal membrane is at rest, the resting potential is negative due to the accumulation of more sodium ions outside than potassium ions inside the cell