Week 2 Membrane Transport Lecture Flashcards
What is passive transport? what are three types of passive transport?
movement down a concentration gradient that does not require energy input. Simple diffusion, ion channels, facilitated diffusion
What is active transport? what are two types of active transport?
movement against a concentration gradient. primary active and secondary active transport
What is Fick’s law? what type of membrane transport does it apply to?
Net flux=((Kp)(A)(deltaCs))/(deltaX)
Kp: solute partition coefficient’
A: area
x: thickness
deltaCs: solute concentration gradient
Simple diffusion
As thickness increases, net flux…
decreases
As the partition coefficient, area, and concentration gradient increases, net flux…
increases
Describe simple diffusion
movement across a membrane without the aid of energy or transport proteins
The partition constant of simple diffusion is directly proportional to _____ and inversely proportional to _____
directly to lipid solubility
inversely to size of solute
rank the permeability of the following: CO2, glucose, Na+, water
Highly permeable: CO2
low permeability: water
almost no permeability: glucose
not permeable: Na+
What is pulmonary edema?
accumulation of fluid in the interstitial space
High altitude pulmonary edme: cause
low oxygen content @ high altitude is compensated for by increased blood flow. This increases NFP which causes net filtration at capillaries and the accumulation of interstitial fluid. The increased interstitial fluid decreases oxygen diffusion from alveoli to the lungs
What are the intracellular and extracellular concentrations of: Na, K, Ca
Na+: 140 mM ext, 10 mM intra
K+: 4.5 mM ext, 140 mM intra
Ca2+: 2-3 mM extra, 0.1 uM intra
What type of gated ion channels are there (3)? how do they open?
ligand gated: activated by binding of a chemical signaling agent
voltage gated: activated or inactivated by changes in the membrane potential
mechanically gated: activated by physical deformation of the surrounding plasma membrane
rank the speed of transport of: simple diffusion, ion channels, facilitated diffusion
ion channels>facilitated diffusion>simple diffusion
How does glucose cross the plasma membrane?
Via facilitated diffusion using the GLUT transporter protein.
the GLUT transporter has how many transmembrane domain?
12 transmembrane domains
what is primary active transport?
movement against a concentration gradient with the use of ATP
what % of total cell ATP does the N/K-ATPase use?
30%
What is the most well known example of a primary active transport protein?
Na/K ATPase
What is secondary active transport?
uses the energy released from pushing a molecule (Na) down its concentration gradient to pump another molecule against its concentration gradient
What are three examples of symporters that utilize secondary active transport?
Glucose/Na, AA/Na, and Cl/K/Na symporters (all pump inside of cells)
what are two examples of antiporters that utilize secondary active transport?
H/Na, and Ca/Na antiporters. H and Ca are pumped out of the cells.
Which types of transport experience saturation?
any that involve a protein (except ions because that one is just a pore) so Facilitated, prim active, and second active transport.
what are the “sides” of an epithelial cell?
apical/luminal side: faces the lumen
Basolateral side: faces the blood vessels
secretion refers to movement:
from the blood to the lumen
reabsorption refers to movement:
from the lumen to the blood
Define transcellular
movement through a cell
define paracellular
movement not through a cell
how does water flow through a membrane?
passively
define osmosis:
diffusion of water across a selectively permeable membrane from high concentration of water to low concentration of water
hyper-tonic means
high solute concentration
hypo-tonic mean
low solute concentration
how do you calculate osmolality?
mOsm=n(deltaC)
n: number of particles/moles
deltaC: concentration in mM
what is the normal osmolarity of a cell?
300 mOsm
if a cell is placed in a hypotonic soln what occurs?
cell will swell
what are aquaporins?
a water channel (not present in all cells)
how many aquaporins does a typical RBC contain?
200,000
what are three causes of edema?
higher than normal blood pressure, lower than normal protein content in blood, lymphatic obstruction
Cells in our body are in _____ equilibrium but in _____ AND _____ disequilibrium
osmotic equilibrium (300 mOsm in and out)
chemical and electrical disequilibrium (different concentrations of solutes inside and outside, more negative inside the cell -70 to -90 mV)
define Nernst equilibrium potential
the membrane potential in which a certain ion would not move into or out of the cell
which ion largely maintains the resting membrane potential?
potassium ion. it is a positively charged ion with a Nernst potential of -98mV. This means that at normal resting potential, K+ leaves the cell. A loss of positive cells creates a net negative. Usually about 95% of potassium channels are open.
in normal cellular conditions (-70mV) are any ions at their Nernst equilibrium?
No, this means that Na, K, Ca and Cl move across membrane
