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63 Cards in this Set
- Front
- Back
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Most abundant lipid? properties?
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Phospholipids - amphipathic
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F(x) of cholesterol in membrane
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stiffens membranes and decreases membrane permeability to small, H20 soluble molcules.
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F(x) of glycolipds in membrane
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lipids with sugars attached almost always on extracellular side.
negatively charged glycolipids will increased concentration of cations, esp Ca2+ |
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Asymmetric distribution of lipids in bilayer
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glycolipids - Extracellular
choline-containing phospholipids - Extracellular Phospholipids with terminal amino (phophatidylserine and phosphatidylehtanolamine are on cytoplasmic surface |
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def and fx of intergral (intrinsic proteins)
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firmly attached or embedded in bilayer. Fx - receptors, channels, enzymes, adhesion molecules, intracellular signaling
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def and fx of peripheral proteins
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loosely bound to proteins on either surface, easily released from membrane by high or low ionic strength solutions or high or low pH, participate in formation of submembranous cytoskeleton.
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fx of glycoproteins
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membrane proteins with carbs attached. involved in cell-cell interactions, act as receptors for viruses and antigenic determinants, contribute to cell surface negativity,
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fx of glycocalyx
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carbohydrate rich coating of cells formed by the glycolipids and glycoproteins. Fx: protect cells from mechanical and chemical damage, enables cells to identify and interact with one another.
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Spontaneous flipping in membrane?
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Only cholesterol due to is simple OH polar region.
enzyme flipase can flip lipids from face to face |
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Fx of biological membranes
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permeability barrier to water-soluble substances
-maintains gradient, localization of cell processes Form cell organelles Package and transport materials within cell |
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Phagocytosis - types
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receptor triggered uptake of large particulate matter.
types: Fc - recognize tail portions of antibodies bound to pathogens receptor for complement, recognize oliggosachs on microorganisms, phosphatidyleserine on apoptotic cells |
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what cells can phagocytosis
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macrophages and nuetrolphils
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pinocytosis
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fluid phase endocytosis, non-triggered.
occurs at membrane sites coated with protein clathrin. |
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receptor-mediated endocytosis
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uptake of specific substances, surface receptors in coated pits of clathrin.
clathrin receptors are recycled. |
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Caveloae endocytosis
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Clathrin- independent endocytosis.
small invaginations of cellmembrane called caveloae. transcytosis. |
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What can be found in caveloea
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cholesterol and sphingomyelin (lipid rafts)
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What is diffusion?
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the movement of atoms, molecules, or ions down their concentration gradient.
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Fick's First Law of Diffusion
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J= -DA x Dc/Dx
J = net rate of diffusion A = area of plane dc/dx = conc gradient across the plane D = diffusion coefficient |
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Diffusion coefficient
aka constant of proportionality |
proportional to the speed at which a substance moves through the surrounding medium
D= T/rn T= temp r= radius of molecule n= viscosity of medium |
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How does the size of the molecule and the viscosity of the medium affect the diffusion coefficient? Temp?
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the larger the molecule or more viscous the medium, the lower the diffusion coefficient.
Higher temp = higher D |
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Rate of diffusion across a barrier
(modified Fick) |
J = -DA x C/X
where C is the concentration gradient across the barrier (inside minus out) and X is thickness of the barrier |
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how does lipid solubility affect how quickly a substance can move across a membrane?
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the more soluble the substance, the greater its ability to diffuse
the smaller the substance the faster it will diffuse |
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what does partition coefficient measure?
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Beta. = [i]oil/[i]h20
lipid solubility |
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Fick's 1st law within a membrane
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J= -PA (Ci-Co) where P is the permeability coefficient DB/x where D is the diffusion constant within the membrane and B is the partition coefficient
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How do gasses, h20, and small uncharged water-soluble molecules react with a membrane?
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pass readily BUT
increase in size decreases permeability MW >200 impermeable |
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How do ions react with the membrane?
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have very low lipid solubility because of their charge and are only moved with aid from intrinsic membrane proteins
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properties of h2o?
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distilled water is 55.55 molar
solute molecules displace h2o and decrease its concentration water flows from regions of high h2o concentration to low h2o concentration |
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osmolarity vs osmolality
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osmoles = # of osmotically active particles (NaCl = 2 osmoles)
osmolarity is # of osmoles/liter osmolality is # osmoles/kg H20 |
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what is osmotic pressure
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it is the pressure which just counterbalances the movement of H20 into a solution. created by a difference in the concentration of impermeant substances across a semipermeable membrane.
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what is a colligative property?
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depends on the number of solute particles. i.e. osmotic pressure, freezing point depression, vapor pressure depression, and BP elevation.
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How do you calculate osmotic pressure of an ideal solution?
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Van't Hoff's Law:
Pi = RTnc Pi= osmotic pressure R=ideal gas constant T= absolute temp C= molar concentration of solute |
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what is isosmotic, hyperosmotic, and hypoosmotic?
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a. solutions of equal osmotic pressure as isoosmotic
b. a solute with higher osmotic strength is hyperosmotic c. a solution with lower osmotic strength is hypoosmotic |
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what is tonicity?
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a solutions ability to influence the volume of cells
iso - no change in cell volume hypertonic - cell shrinks (crenate) hypotonic - cell swells (lyse) |
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when are tonicity and osmotic pressure the same?
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in solutions with only impermeant solutes
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name two impermeate solutes
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manitol and sorbitol
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what happens if you place a cell in solution with ONLY permeate solutes?
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cell lysis. permeate solutes equilibriate but cell is filled with osmoles so water rushes in.
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what is the reflection coefficient?
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sigma. the measure of the permeability of a solute.
0= extremely permeable (h20) 1= impermeate solutes |
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what is effective osmotic pressure?
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amount of pressure required to move h2o across a membrane.
Pi =(sigma)RTnc |
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How do cells acutely respond to shrinkage caused by hypertonic ECF?
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RVI - acute response, increased intracellular accumulation of KCl and/or organic electrolytes such as taurine, betaine, myoinositol and amino acids
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What two conditions can cause hypertonic ECF
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hypernatremia and hyperglycemia
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how do cells chronically respond to shrinkage caused by hypertonic ECF?
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generation of impermeant organic solutes (idiogenic osmoles) within the cell e.g. sorbitol and inositol.
1) particularly active in brain cells |
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what are the dangers in rapidlycorrecting long-term hypertonicity in ECF?
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can cause brain edema, several nuerologic problems, and in some cases death because it takes time for cells to reduce idiogenic osmoles.
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How do cells respond to cell swelling caused by hypotonic ECF, typically hyponatremia?
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RVD - swelling initiates rapid activation of K+ and CL- channels resulting in efflux. Also activation of K-CL symporters.
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what is the problem with rapid correction of long term hyponatremia?
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can cause osmotic demyelination also known as central pontine myelinolysis.
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What is bulk flow?
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movement of ions, molecules and particles in the same direction as a result of some force i.e. blood flow moved by hydrostatic pressure.
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what is ultrafiltration?
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seperation, by size, of solutes in solution achieved by forcing the solution through a filter such as in capillary beds where h2o and solutes move through but proteins and cells stay in blood.
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what is saturation?
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the slowing down of the rate of increase of carrier mediated transport due to the fixed number of transporters in the membrane.
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what is specificity and stereospecificity?
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each molecule only binds to a select group of substances. stereospec will only choose a certain structure i.e. Dglucose over Lglucose.
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What are specific blockers of Na-K ATPase?
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Cardiac glyoside digoxin and Ouabain.
bind with high affinity for site of pump that binds to K+ binding of extracellular K inhibits digoxin binding |
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What is the clinical implications of prescribing digoxin to someone with hypokolemia?
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Hypokalemia potentiates digitalis toxicitiy by competing for the same binding site.
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what is primary active transport? examples?
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ATP hydrolysis supplies energy to pump ATPase.
Na-K ATPase CA2+ - ATPase |
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what is secondary active transport ? types?
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Energy provided by utilizing existing gradient.
Cotransport (symporter) Na and AA Na and Glucose Na-K-2Cl Countertransport (antiport) Na-Ca exchanger Na-H exchanger |
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what is SERCA? where is it located and what does it do?
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Sarcoplasmic and Endoplasmic Reticulum Calcium ATPases
-located on membranes of intracellular organelles -actively sequester Ca2+ in intracellular stores |
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What is PMCA and what does it do?
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Plasma Membrane Calcium ATPases
-play a major role in maintaining low intracellular Ca2+ -as calcium conc raises it binds to calmodulin (CaM) and the CaM binds to the pump increasing its affinity for Ca2+/ |
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What type of transport is H-K Atpase? where is it found?
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Primary active transport.
moves H+ into gastric lumen from the parietal cells |
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What is a common example of an anion exchanger and what is its Fx?
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Chloride-bicarbonate exhanger. Handles CO2 levels. Prevents cytosol from becoming basic.
2ndary active transport, antiporter. |
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Fx of Na-K-2CL transporter? Type?
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Symporter. 2ndary.
Nonepithelial cells and basolateral membrane. regulation of cell volume. |
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types of ATP-Binding Cassete Transporters?
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ABC1, MDR, CFTR
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What is the function of ABC1?
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involved in transport of phospholipids and cholesterol out of macrophages
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What is the function of MDR?
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Multidrug resistant transporters.
a) extrude cationic drugs and metabolites b) variety of cells liver, kidney, GI c) pumper anticancer drugs out of cells :( |
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Fx of CFTR?
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Cystic Fibrosis Transmembrane Regulator
a) CL- channel found in apical membrane b) ATP regulates fx by binding to regulatory domainds and nucleotide binding domains |
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What transporters are used in RVI?
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a) activiation of Na-H exchanger
-increases Na uptake and alkalinizes cytoplasm b) this activates CL-HCO3 exchanger c) Na-K ATPase extrudes Na for K, results in net increase of KCL d) activation of Na/K/CL cotransporter e) activation of 2ndary osmolytes and AAs |
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What transporters are used in RVD?
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movement of K and CL out of cell.
-K-selective and Cl-selective channels as well as KCl cotransporter. |
