Lecture 1 Flashcards
What type of transport does the Na/K pump use? be specific. (3 words)
Primary active transport
General makeup of the PM:
lipid and protein, 50/50
In what tissues are PM’s electrically excitable?
nerve and muscle cells
What types of signals can a PM transduce into specific cellular responses and activities?
electrical, chemical, and mechanical
Molecules that can freely diffuse across PM?
O2, CO2, N2, benzene
Name 3 small uncharged polar molecules that can diffuse across the PM.
H2O, urea, glycerol
Rate of diffusion equation:
(SA X conc. gradient X PM permeability) / PM thickness
PM permeability is proportional to:
lipid solubility / molecular size
about how many AA is the transmembrane alpha-helical polypeptide segment made of?
20
Do peripheral proteins create a pathway for the movement of molecules from one side of the membrane to the other?
No
This is the “revolving door” type of transport protein:
Carrier protein
T or F? Carrier proteins are open simultaneously to both the inside and outside of the cell.
F.
Do carrier proteins use energy directly, indirectly, or both?
both
Can carrier proteins move molecules against their concentration gradient?
Yes
T or F? Channel proteins selectively allows for specific molecules to be transported across the membrane.
F. It has no control over what diffuses or the rate of difusion
From where is energy derived in secondary transport?
the potential energy of the concentration gradient of a molecule (used to move another molecule against gradient)
What molecule is frequently used in secondary transport to create the concentration gradient from which the energy is derived to transport the other molecule in secondary active transport?
Na
Is there typically a higher concentration of Na inside or outside the cell?
Outside
T or F? 2 Na are pumped out for every 3 K that are pumped in.
F. 3 Na out/ 2 K in
Does the Na/K pump make the inside of the cell more or less positive with every pump?
less positive
How many transmembrane segments does the large alhpa subunit the Na-K pump have?
10
Which subunit positions the Na-K pump in the membrane?
extracellular beta subunit
How many times does the gamma subunit of the Na-K pump cross the membrane?
1 time
How many subunits does the Na-K pump have and name them.
3, alpha, beta, gamma
What is required for the transitional changed bw open and closed states of the Na-K pump?
ATPase activity, P binds to the protein carrier
What charge does P have?
-
What should you add to a protein if you want to change its shape?
P
How is the conformation of the Na-K pump changed once the Na has been released to the ECF and K has bound?
P is removed, causing the change in shape
How many ATP are required for each cycle of opening and closing of the Na-K pump?
1 ATP
What percentage of the energy of the body is consumed by the Na-K pump?
about 25%
What percentage of the energy of the brain is consumed by the Na-K pump?
about 70%
T or F? The more Na outside the cell, the lower the stored PE
F. greater PE
Creates a charge gradient:
electrogenic
Does the Na-K contribute a large amount to the resting negative MP of neurons?
No
Does the Na-K contribute a large amount to the resting negative MP of smooth muscles?
Yes
T or F? The Na-K contributes more to the resting negative MP of the neuron than of smooth muscle.
F. contributes more to the smooth muscle
The transport of Na into the cell is often coupled with the transport of this into the cell:
glucose
What is the name of the protein carrier involved in the coupled transport of Na and glucose into the cell?
SGLT protein
The binding of what molecule causes the change in conformation of the SGLT protein?
glucose
Which molecule is both the first to bind on the EC side and release on the IC side of the SGLT protein?
Na+
What other pump/exchanger depends on the Na-K pump?
Na-Ca exchanger
How would the Ca concentration be effected, if at all, if the Na-K pump was non-functional while the Na-Ca exchanger was functional?
Ca++ will build up in the cell
What effect will digitalis have on a cell?
it will raise the Ca++ levels in the cell
What effect will digitalis have on the heart?
enhance muscle contraction, improving muscle function
What type of transport does the Na-Ca use?
Secondary Active Transport
What effect does ouabain have on a cell?
blocks the Na-K pump
What 2 drugs can block the Na-K pump?
ouabain and digitalis
What effect will low doses of digitalis have on the heart muscle?
raise Na inside heart muscle
How will the Ca levels in the heart muscle be effect with low doses of digitalis?
Na levels will be raised and this will slow the removal of Ca via the Na-Ca exchanger
Another name for potential difference:
voltage
T or F? The Na/K pump creates a lare negative charge inside the cell.
F. Only creates a small neg charge in cell
You should always assume he net charge outside the cell is:
zero
When is the resting MP the EP (equilibrium potential)?
electrical gradient exactly opposes the chemical gradient
Around how much K would have to leave the typical cell to reach EP (equilibrium potential)?
very little, less than 1/10th
Functions of electrical signals in neurons:
- combine info from many inputs
- transmit info
- activate mem proteins
- stimulate transmitter release
Mathematic term for membrane potential difference:
Vm
70 mV = 70 ____ th of a volt:
thousandth
in what type of solution is a cell placed when measuring internal voltage with a voltmeter?
saline solution
How can you measure a current?
count the # of ions passing through (ions/sec)
This is the energy to move charge:
voltage
How is conductance calculated?
1/Resistance
This is a measure of the ease of moving a charge across a membrane:
conductance
2 ways to decrease conductance:
make path longer or more narrow
T or F? Excitation is occurring when a cell is made more positive.
T
T or F? Excitation is occurring when a cell is made more negative.
F. inhibition
T or F? Excitation of the cell leads to polarization of the cell.
F. Depolarization
T or F? The flow of Cl- into a cell will lead to depolarization.
F. hyperpolarization
Will the outflow of K+ from a cell depolarize of hyper polarize the cell?
hyperpolarize
2 ways to hyperpolarize a cell:
Increase flow of Cl- in or increase flow of K+ out
Depolarization initiates what 2 events?
AP production and neurotransmitter release at synapse
Would hyperpolarization make the production of an AP more or less difficult?
more
T or F? When the cell depolarizes the membrane potential increases.
F. The membrane potential decreases.
T or F? When the cell hyperpolarizes the membrane potential increases.
T
What do aquaporin channels allow the passage of?
water, glycerol, ammonia, and urea
Can charge molecules pass through aquaporins?
No
How many times does the aquaporin span the membrane?
6-transmembrane structure
Where are aquaporins most prominent?
kidney
T or F? Facilitated diffusion can move molecules across a membrane that would normally not cross the membrane over any amount of time, no matter how long.
F. Any of the molecules would pass through, some just very slowly
is the carboxylic end of the aquaporin positioned on the L or R side?
R
T or F? As the solute concentration of a fixed volume of water increases, the concentration of the water increases.
F. the concentration of the water decreases
Will the concentration of water increase of decrease when salt is added to 1L of water?
decrease
symbol for osmotic pressure:
symbol for pi
define osmotic pressure:
hydrostatic pressure (force) required to counterbalance osmosis
Which solution has a higher water concentration, 0.1 M sucrose solution or 0.01 M sucrose solution?
0.01 M sucrose solution
This is the pressure water exerts on a membrane dividing two compartments filled with solution:
osmotic pressure
Equation for osmolarity:
molarity of solute X # of solute particles that dissociate in solution
What is the osmolarity of 0.15 M NaCl?
0.3 osm
What is the osmolarity of 0.1 M MgCl2?
O.3 osm
What is the osmolarity of body fluids, e.g. CSF?
.35 osm
if the cell’s volume increases when placed in a solution, the solution is (hyper/hypo)tonic?
hypo
if the cell’s volume decreases when placed in a solution, the solution is (hyper/hypo)tonic?
hyper
whether water would go in or out of a cell when placed in solution:
tonicity
Molarity of blood:
0.15 M (check)
What can happen to neurons when they are under stress such as in a stroke?
they can lyse
T or F? All isosmotic solutions are isotonic solutions.
F
What would happen to a RBC placed in a 0.3M glycerol solution?
it will lyse
How can a cell avoid lysing if it is place in a hypotonic solution?
swell channels, allowing solute to leave the cell
What molecule(s) can leave the cell via swell channels?
Cl- (and K+?)
