Ch. 8: Biological Membranes Flashcards
cell (plasma) membrane general function and structure
semipermeable phospholipid bilayer
glycoprotein coat
created by carbohydrates associated with membrane-bound proteins
lipid rafts
collections of similar lips with or without associated proteins that serve as attachment points for other biomolecules
flippases
assist in the energetically unfavorable process of “flipping” a phospholipid from one side to the other
fatty acids
carboxylic acids that contain a hydrocarbon chain and terminal carboxyl group
triacylglycerols/tryglycerides
storage lipids involved in human metabolic processes
three fatty acid chains esterified to a glycerol molecule
unsaturated fatty acids
one or more double bond in hydrocarbon tail, creates kinks, allows for fluidity
liquid at room temp
“healthier”
saturated fatty acids
no double bonding = stack tightly = limited fluidity
main components of animal fats, solid at room temp, processed food, “unhealthy”
glycerophospholipid
phospholipid. two fatty acid chains, glycerol molecule, phosphate head
micelles vs liposomes
micelles (single layer) and liposomes (double layer)
sphingolipids
similar in structure to phospholipids but lack glycerol. Modified to form a variety of biologically necessary molecules (ceramics, sphingomyelins, cerebrosides, gangliosides)
role of cholesterol
- regulates membrane fluidity by stabilizing adjacent phospholipids (increases fluidity at low temps, decreases at high temps)
- precursor to steroids
waxes
long-chain fatty acid, long-chain alcohol = hydrophobic, high melting point
stability and rigidity to non polar region
cell membranes of plants, not animals, for protection/waterproofing
transmembrane proteins
pass through entirety of the bilayer
embedded proteins
associated with either cytoplasmic or extracellular aspect of the cell membrane
integral proteins
transmembrane + embedded proteins
those that interact with interior of the membrane
peripheral proteins
bound through electrostatic interactions with the bilayer
“membrane-associated” proteins
where do carbohydrates interact with the membrane
attach to protein molecules on extracellular surface
can form a coat around the cell (d/t interaction with water) or act as signaling/recognition molecules
membrane receptors
typically transmembrane proteins that activate/deactivate transporters
cell adhesion molecules (CAM)
proteins that forming cell-cell junctions and allow cells to recognize and contribute to each other
gap junctions
also called connexons
pores that allow for direct movement of water/solute between cells
formed by the alignment and interaction of six monomers of connexin
tight junctions
physical link between cells forming a single layer of tissue
prevent solutes from leaking into intercellular space
desmosomes
bind adjacent cells by anchoring to their cytoskeletons
links layers of (usually epithelial) tissue
passive transport
- spontaneous
- negative delta G (do not require energy)
active transport
- non spontaneous
- positive delta G (require energy)
simple diffusion
substrates move down their concentration gradients directly across the membrane
osmosis
diffusion of WATER down it’s con’c gradient
moves from regions of lower solute con’c (dilute) to high solute con’c (concentrated)
osmotic pressure and osmosis
osmotic pressure drives osmosis
allows entropy to increase
equation for osmotic pressure (PI)
PI = iMRT
osmotic pressure = van’t Hoff factor * molarity * ideal gas constant * absolute temperature (in Kelvins)
van’t Hoff factor
number of particles obtained from the molecule when in solution
glucose = 1, NaCl = 2 (b/c Na+ and Cl-)
facilitated diffusion
simple diffusion (down con’c gradient) of molecules impermeable to a membrane
integral membranes act as transporters or channels
carriers
transport impermeable molecules following a conformation change
active transport
net movement of solute against its concentration gradient, requiring energy
primary active transport energy source
ATP or another energy molecule
powers directly
secondary active transport energy source
uses energy molecules to transport by coupling energy released from one molecule going DOWN con’c gradient to drive different particle UP con’c gradient
symport
when coupled molecule move in same direction across membrane in secondary active transport
antiport
when coupled molecules move in opposite direction across membrane
endocytosis
cell membrane invaginate and engulfs material to bring it into the cell within a vesicle
pinocytosis
endocytosis of fluids and dissolved particles
phagocytosis
endocytosis of large solids (like bacteria)
exocytosis
secretory vesicles fuse with membrane and release material from the cell
membrane potential
difference in electric potential across cell membranes
function of the sodium-potassium pump
Na+ / K + ATPase
regulates concentration of intracellular and extracellular sodium and potassium ions
how does Na+ / K+ ATPase maintain appropriate stable resting potential
inside of the cell = low Na + and high K+
pumps three Na out for every two K pumped in
restores concentration gradients for leak channels
outer mitochondrial membrane
large pores = highly permeable to ions and proteins
inner mitochondrial membrane
contains cristae (interfoldings) which increase surface area for integral proteins and mitochondrial matrix
