membrane physio

what makes up the majority of the cell membrane

phospholipids

what keeps the phospholipid bilayer together

hydrophilic-hydrophobic interactions

how is cell membrane fluidity reduced

cholesterol

what is the major function of the cell membrane?

selective barrier

what gives a cell shape?

cytoskeleton and polarity

is the cell membrane uniform?

no, there are micro domains and membrane proteins

integrins are an example of what kind of junction

cell-matrix

function of integrins

transmembrane links between extracellular contacts and the actin microfilaments of the cytoskeleton

what is responsible for giving cells polarity

integrins and cytoskeleton

what is cell polarity

asymmetrical distribution of cellular content and membrane structures

what are tight junctions

large protein complexes

example of a protein in tight junctions

claudins

what is the function of tight junctions

regulates paracellular transport

where are tight junctions found?

blood-brain barrier and GI tract

what creates adhering junctions

e-cadherin

where are adhering junctions found

between barrier cells / highly polarized cell layers

contact inhibition

regulates cell growth and proliferation

desmosomes

specialized and highly ordered membrane domains that mediate cell-cell contact

gap junctions

specialized intercellular connections that directly connect the cytoplasm of two cells, allowing various small molecules and ions to pass freely between cells

what composes a gap junction

2 connexons

diffusion

a net transport of molecules from a region of higher concentration to one of lower concentration

two types of diffusion

simple and facilitated

active transport

energy expended to generate the force to move an impermeant solute against its concentration gradient t

what types of molecules can freely move through the plasma membrane?

small, uncharged and highly lipid soluble molecules

what can’t freely pass through the plasma membrane?

large molecules with low lipid solubility and charged particles

Fick’s law of diffusion only applies to

uncharged, solute molecules w

what directly effects diffusion

permeability

osmosis

net diffusion of water down its concentration gradient

aquaporins

protein channels specific for the passage of water

aquaporin function

increases membrane water permeability

what is the driving force of water movement

osmolarity / the concentration of osmotically active solutes

how does water move in relation to osmolarity

low osmolarity to high osmolarity

isoosmotic

equal osmotic pressure in two solutions

hyper osmotic

greater osmotic pressure in solution A than solution B

hypoosmotic

less osmotic pressure in solution A than B

tonicity

measures the ability of a solution to exert an osmotic pressure upon the plasma membrane of a cell

tonicity is determined by

the concentration of non-penetrating solutes in solution

what would happen to a RBC in a hypotonic solution

swell

what would happen to a RBC in hypertonic solution

shrink

moving ions and non-permeable molecules requires

membrane proteins such as channels and carrier protein s

two methods of moving ions and non-permeable molecules across the cell membrane

facilitated diffusion and active transport

two types of assisted membrane transport

carrier-mediated and vesicular

5 properties of all carrier-mediated transport

faster than simple diffusion, saturation kinetics, chemical specificity, competition, and transport inhibition

active transport

uses ATP move solute against concentration gradient

primary active transport

directly uses ATP to move solute against concentration gradient

secondary active transport

creates a concentration gradient in the form of chemical potential energy to help move another solute

types of secondary active transport

symporter and antiporter

symporter

the transported solute moves in the same direction as the gradient of the driving iona

antiporter

the transported solute moves in the opposite direction of the driving ion gradient

membrane potential

separation of charges across the membrane

electrochemical potential

combination of chemical potential and electrical potential

resting membrane potential

difference in electrical charge along the membrane-fluid interface

resting membrane potential value

-70 mV

is the inside or outside of the cell negative?

inside

what 3 things affect membrane potential?

Na-K pumps, leak channels, and cytoplasmic proteins

what has the greatest effect on membrane potential

K leak channels

depolarization

membrane potential becomes less negative (move toward zero)

hyper polarization

membrane potential becomes more negative (further from zero)

Nernst for Na

+60 mV

nernst for K

-90 mV