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50 Cards in this Set

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What do phospholipids form in membrane
bilayer, outside heads are highly polar, form hydrophilic interface with water
inside tails are hydrophobic aliphatic chains
What are glycolipids
phospholipids with carbohydrate chains
Describe integral proteins
Lie within lipid bilayer
Functions - transport, receptors, enzymes, signaling
Hydrophobic regions attach proteins to membranes
Describe peripheral proteins
Adjacent to membrane
Provide anchoring sites for cytoskeleton
attach by charge interaction (H bonding)
Name 3 types of transport mechanisms
VESICULAR - membrane mediated - endocytosis and exocytosis
MOLECULAR - protein mediated - channels and carriers
SIMPLE DIFFUSION - lipid soluble solutes and water
Name 3 types of endocytosis
RECEPTOR MEDIATED - activated by receptors - LDL receptors, clathrin coated, occurs at coated pits
PINOCYTOSIS- responsive to changes in pH
PHAGOCYTOSIS-immune response, destroys foreign bodies, debris
What is an exocytosis
Movement out of the cell
example - secretory enzyme release, NT release
Describe voltage gated channels
2 types - VOLTAGE GATED and LIGAND GATED
-change configuration only to open and close
Movement through channels determined by ELECTRICAL and CHEMICAL gradients
Functions - extracellular signaling (AP), intracellular signallng (controling intracellular Ca)
Describe carriers
3 types - COTRANSPORT, ANTIPORT, FACILITATIVE DIFFUSION
Active - uses ATP directly
Passive - doesnt use ATP
Secondary active - indirect need for ATP
-FIXED stoichiometry
-change conformation with every transport cycle
Describe ligand gated channels
Opened by ligands - any chemical that binds to channel (hormone, NT)
Functions - neural decision making (EPSP, IPSP), intracellular signaling (control of intracellular pH, Ca)
Describe cotransport
-Moves more then one solute
-All solutes move in SAME direction
Describe Antiport
-Moves more then one solute
-At least one solute moves in OPPOSITE direction
Facilitated Diffusion
Only ONE solute, makes membrane more permeable
Describe saturation of carriers
Can only transport so many molecules. Maximum is called Tm or Transport maximum, simple diffusion doesnt have transport maximum
Glucose appears in urine of diabetics because proximal tubule transport maximum is exceeded
Simple diffusion
Cell membrane is permeable for lipid soluble substances (hydrophobic)
Cell membrane also has aquaporins - water channels
What is the name for movement between cells
Paracellular route
What is the name for movement thorugh cells
Transcellular route
Give an example of epithelial transport
Oral rehydration therapy
Transcellular movement of Na makes lumen more negative (negative transepithelial potential) which causes paracellular movement of Cl.
Transepithelial movement of solutes NaCl and glucose causes H2O to follow by osmosis
Describe electrical equivalent voltage
Ion movements determine cell membrane potential Vm
Electrical (Vm) and chemical (concentration gradient) forces cause ion movements
Electrical equivalent voltage - Ei is chemical force acting on ion stated in electrical terms
How do you determine net force acting on ion
By combining Vm and Ei
What is the direction of net movement of ions
From higher to lower concentration
What is the prefered direction for Na
From outside to inside
Outside - 140 Mm, inside 8Mm
What is the preferred direction for K
From inside to outsidde
Outside - 4mM, inside - 155 mM
What is the direction for Cl
From outside to inside
Outside - 100 mM, inside - 4 mM
Is Ca higher inside or outside
Outside, very very low inside (0.0001 mM)
Nernst eqution for K
Ek= RT/zF ln [Kin]/[Kout]
Ek= 60 mV log [Kin]/[Kout]

If switch in and out, sign will change
What is the Vm for most neurons
from -70 to -85
What is Vm for muscle
-95 mV
What is the Vm for epithelial cells
Apical and basolateral membranes of epithelial cells have different Vm due to transepithelial potential
WHat is Ek
-90 to -95 mV, always more NEGATIVE then Vm
WHat is E Na
+70-+80, always more POSITIVE then Vm
Is Ecl more positive or negative then Vm
More positive in neurons so it want to enter the neuron, but in small epithelial cells wants to exit
How do you determine net electrochemical driving force
Sum of chemical and electrical driving forces
Force = Ei - Vm
Ei - chemical driving force
Vm- resting membrane potential
In case of Na - Ei and Vm act together
In case of K and Cl, they oppose each other, so driving force determines movement
When does equilibrium exist in cell
When Ei=Vm
Why is Vm of neurons normally around -90?
Many K channels are open and few Na channels are open.
Conductance equals to
1/resistance
What are local potentials
Changes in neurons Vm in response to NT's released from other neurons
How do NT s generate local potentials
by opening ligan gated Na, K and Cl channels
Why does Vm returns to resting potential after AP
1. Na channels closed
2.K channels slowly open
What is the name for transition of open Na voltage gated channels to closed state?
Repolarization phase
Slow transition of voltage gated K channels from resting to open state causes
After hyperpolarization
Overshoot
There are many more open Na than K channels, membrane potential becomes positive since E Na is positive
What is responsible for repolarization phase
close Na channels, open K channels
Absolute refractory period
Na channels in open state automatically start to move to closed state, many of channels must return to RESTING STATE before new AP can be generated. 5 msec
Relative refractory period
Until there are as many Na channels in resting state as there were before AP, greater depolarization is needed to generate second AP. 20 msec
Help prevent repetitive firing, retrograde transmission and cardiac arrhythmias.
What are two gates voltage gated channels have
m gate - activation gate
h gate - inactivation gate
How AP's originate
-in the HILLOCK
-in skeletal and smooth muscle originate at MOTOR END PLATE
-cardiac muscle originate at PACEMAKER CELLS
Which cells conduct faster - at depolarization or hyperpolarization
At depolarization fewer channels are in resting state, so fewer available for AP
Depolarizing factors
HIGH K - drugs, kidney failure, severe trauma, burns
INHIBITION OF Na, K ATPase - digitalis and similar drugs
CELL DAMAGE or HYPOXIA - ischemia, MI
How does myelin increase speed
1. Myelin axon interaction concentrates Na channels at nodes, increasing current and power
2. Myelin reduces impedance by decreasing membrane capacitance, allowing voltage to change more quickly
3. Myelin reduces membrane ion leaks by increasing resistance, increases current flow