Cell membranes

three primary body cavities

cranial cavity

thoracic cavity

abdominopelvic cavity

Physical isolation

physical barrier separating ICF and ECF

Regulation of exchange with the enviornment

controls entry, elimination and release of things into/out of the cell

Communication

contains proteins that allow for responding or interacting with the external environment

structural support

proteins in the membrane are used to make cell to cell connections and to anchor the cytoskeleton

What is the rule for how much protein a cell membrane contains

the more metabolically active the membrane is the more protein in contains

What are the three types of lipids in the cell membrane

phospholipid

sphingolipids

cholestrol

Phospholipids

form bilayers, micelles or liposomes

tails are hydrophobic and heads are hydrophillic

amiphipathic

having one region that is hydrophobic and one region that is hydrophillic

Cholestrol

increases viscosity (holds it together, strength)

decreases permeability (doesn’t allow as much in)

what is the current model of membranes

the fluid mosaic model

intergral protiens

transmembrane protiens

lipid anchored protiens

protiens cannot be removed without disrupting the membrane

integral protiens role

membrane receptors

cell adhesion molecules

transmembrane movement

Peripheral protiens

usually attached to integral protiens

loosely attached to phospholipid heads

Peripheral Protien roles

participate in intracellular signaling

form submembraneous cytoskeleton

lipid rafts

groups of protiens and sphingolipids that stay together with a high cholestrol content

glycoprotiens

protein with a carbohydrate attached, always extracellular

forms a protective coat and helps with cell-cell recogntion/interaction

glycolipid

lipid with a carbohydrate attached, always extracellular

forms protective coat and helps with cell to cell interactions

cell to cell recognitions

identifying whether or not cells are foreign

what % of the human body is made up of water

60%

adipose tissue

90% lipids, majority triglycerides

small fraction water

skeletal muscle

75% water

18% protein

what can change total water content

age, sex and body fat composition can alter total water content in the body

osmotic equalibrium

fluid concentration are equal, the amount of solute per volume of solution

osmosis

the movement of water across a membrane in response to a solute concentration gradient

moves from a low concentration to a high concentration

aquaporin channels

proteins in membranes that have a small pore to allow water to move in and out of the cell freely

What ions are high in extracellular fluid

Na+

Cl-

Ca2+

HCO3 -

what ions are high in intracellular fluid

K+

Anions

Protiens

Osmotic pressure

means of quantifying the driving force of water to move to a higher concentration

Osmolarity

describes the number of particles in solution

isoosmotic

solutions have identical osmolarities

hyperosmotic

solution with the higher molarity

hyposmotic

the solution with the lower osmolarity

tonicity

describes a solution and how that solution would effect cell volume if a cell were placed in a solution

hypotonic solution

solution has a low concentration, causing the cell to swell

isotonic solution

solution has an identical concentration as the cell, causing the cell to stay the same

hypertonic solution

solution has a higher concentration, causing the cell to shrink

what is the difference between osmolarity and tonicity

osmolarity depends on the nature of the solutes, the overall solute concentration of a compartment

tonicity depends on the concentration of non penetrating solutes, solution concentration relative to a cell

Osmoality

osmoles per kg of solvent

selectively permeable

what crosses depends on the properties of the cell membrane and the substance

diffusion

the movement of molecules from an area of higher concentration to an area of lower concentration g

general properties of diffusion

uses kinetic energy of molecular movement

continues until concentrations come to equilibrium

can take place in an open or closed system

what makes diffusion faster

along higher concentration gradients

over shorter distances

at higher temperatures

for smaller molecules

what makes the rate of diffusion across a membrane faster

the membranes surface area is larger

the membrane is thinner

the concentration gradient is larger

the membrane is more permeable to the molecule

what does membrane permeability depend on

the molecules lipid solubility

the molecules size

the lipid composition of the membrane

what is simple diffusion used for

small uncharged lipophilic molecules such as O2 CO2 NH3 Lipids and steroids

ficks law

rate of diffusion is directly proportional to the surface area x concentration gradient x membrane permeability

Protien mediated transport

for molecules that cannot cross the membrane via simple diffusion

Channel protiens

mad of membrane spanning protien subunits that create a cluster of cylinders with a pore through the center

gated channel types

chemically gated

voltage gated

mechanically gated

what is selectivity determined by

the size of the pore and the charge of the amino acids lining the pore

Carrier proteins

large complex proteins that change formation to move molecules. they can move small organic molecules that cannot pass through channels

uniport carriers

carrier protiens that only transport one kind of substrate

symport carriers

carrier protiens that move two or more substrates in the same direction

antiport carriers

move substrates in opposite directions

Facilitated diffusion

diffusion that is facilitated by the use of a protein

Active transport

move molecules against their concentration gradients from an area of low concentration to high concentration

• always by carrier proteins

primary active transport

energy to move molecule comes directly from hydrolyzing ATP (ATPase)

secondary active transport

uses the potential energy stored in the concentration gradient of one molecule to push another molecule against their concentration gradient

High affinity binding

means that the binding sites are very sticky and will grab on to an ion no matter how hard it is

Low affinity binding

binding sites that dont care as much to grab onto ions and will only do so if the ions bump into them

specificity

the ability of a transporter to move one molecule or a closely related group of molecules

Competition

a carrier may move several members of a related group of substances but these substances compete with eachother

saturation

rate of transport depends on concentration and number of transporters. when the transporters are completely full

transport maximum

where saturation occurs. all of the carriers are in use and they cannot move any more

Phagocytosis

creates vesicles by rearranging the cytoskeleton

steps for phagocytosis

1. encounters a bacterium

2. phagocyte uses cytoskeleton to push its cell membrane around the bacterium

3. the phagosome separates from the membrane and moves into the cytoplasm

4. the phagosome fuses with lysosomes containing digestive enzymes

5. bacterium is killed by the enzymes

pinocytosis

allows ECF to enter freely, non selective type of endocytosis

receptor mediated transport

wants a specific substance in the cell, selective type of endocytosis

steps for endocytosis

1. ligand binds to membrane receptor

2. migrates to clathrin-coated pit

3. pit begins to close and move into the cytosol

4. vesicle loses clathrin coat

5. receptors and ligands seperate

6. ligands go to lysosomes or golgi for processing

7. transport vesicle with receptors moves to the cell membrane

Exocytosis

transport vesicle and cell membrane fuse, then the pit opens and releases substances

can occur continuously or intermittantly

epithelial transport

substances entering and exiting the body or moving between compartments often must cross a layer of epithelial cells

absorption

things moving from the lumen of the organ to the extracellular fluid

secretion

things moving from extracellular fluid to lumen of the organ

transcellular epithelial transport

across the epithelial wall, either freely diffusing or protien mediated

paracellular epithelial transport

between tight junctions, depends on how tight the junctions are. does not require ATP

transcytosis epithelial transport

for larger substances that need to pass the epithelial wall. uses endocytosis, vesicular transport and exocytosis

apical surface

outer membrane of the epithelial layer, facing the lumen

basolateral membrane

mix between the basal and lateral membranes

major ions

intracellular: K+ and phosphate ions and protiens

extracellular: Na+ and Cl-

the law of conservation of electrical charge

net amount of charge produced in any process is zero, for every positive charge on an ion there is an electron on another ion

conductor

the material through which positive and negative charges can move towards one another

insulator

the material separating the charges

membrane potential

the electrical disequilibrium that exists between the ECF and ICF

electrochemical gradient

the combination of electrical and concentration gradients

equilibrium potential

the membrane potential that directly opposes the concentration gradient

nernest equation

measures the equilibrium potential for a single ion. assumes that ions can cross the membrane freely

resting membrane potential

the membrane potential of a cell when it is not active

voltmeter

measures the difference between two electrodes in teh CIF and the ECF

resting membrane potential range in excitable cells

ranges from -40 to -90 mV

Sodium Potassium pump

sets up concentration gradients that determine membrane potential

3 Na+ out/ 2 K+ in

maintains the concentration gradients

pump is considered electrogenic as it generates a negative intracellular charge

disturbance of membrane potential

1. the concentration gradients of different ions across of the membrane

   1. the permeability of the membrane to those ions

depolarization

if the membrane potential becomes less negative than the resting potential

repolarization

returning from a depolarized state

hyperpolarization

if the membrane potential becomes more negative

Hyperkalemia

increased blood K+ concentration that brings the membrane closer to the threshold

hypokalemia

decreased blood K+ concentration, hyperpolarizes the membrane

Label the things on this neuron

A - dendrite

B - soma

C- axon

D- myelin

E - gap between myelin sheaths

F - axon terminal