Moed Bet Biophysics – Questions and CORRECT answers
Summary of exam:
– 70 questions, multiple choice
– Membrane Transport had long-worded questions and each was worth 2%
– Muscle and Synapse had fewer and shorter questions, worth 1% each
– Muscle was the shortest section
Membrane Transport
1. An animal red blood cell is brought to equilibrium in 250 mOsm of impenetrable
solute and 50mOsm of penetrable solute. The cell is then transferred to a solution
with 275 mOsm impenetrable solute. If the reflection coefficient of the penetrable
solution is 0.5, what will happen
a. The initial volume will be 0
b. NOT final volume will be greater than the initial
c. NOT initially, the volume will shrink and then return to normal
d. NOT it will immediately increase in size
WHY?? What will happen after>
2. In a simple diffusion scenario with 0 concentration initially inside the cell, the time is
measured for the inside concentration to be half of the outside concentration. The
time will be a function of
a. Temperature
b. Radius
c. Solubility of the solute in fat
d. NOT Concentration on the outside
On graph, the higher concentration doesn’t make it go faster?
3. Two solvents A and B with similar beta (division coefficient) and size. The
penetrance of A is checked in RBC and the penetrance of B is checked in liver cells.
Which of the following is correct regarding their penetrance
a. None
b. NOT similar
c. NOT same if the cells are from the same body
d. NOT different
4. A RBC is placed in 300 mOsm of sucrose, and then transferred to another solution
containing 250 mOsm of NaCl and another solute with a reflection coefficient of
0.25. What is the concentration of the penetrating solute such that the initial flux is 0
a. 200 mOsm
b. NOT 400, 100, 25
5. In a case with catalyzed transport where the same carrier system is used, the K(A) is
5mM and the K(B) is 20 mM.
a. A will be an efficient inhibitor of B
b. NOT B will be an efficient inhibitor of A
c. They will inhibit each other similarly
d. There will be no influence of one on the other
6. Ethanol in a human RBC is comprised of different isotopes of O, C and H. If the
molecule increases in size, the reflection constant will
a. Increase
b. NOT decrease
c. NOT won’t change
d. NOT can’t tell
What is the secret here?
7. Two solutions have different osmotic pressures. This could be because
a. The total concentration of particles is different
b. NOT difference in the volume of the container
c. NOT because of the difference in the molecular weight of the particles
d. NOT because of the level of breakdown of the particles
8. Chlorine ions have an equilibrium potential of -60mV and a membrane potential of --70mV. Net flow will be
a. Out of the membrane
b. NOT into the membrane
c. NOT dependent on cation flow
d. NOT no net flow
Where are the Chlorine ions? How to figure out?
9. A student is taking penetrance measurements in human RBCs on different days.
There is a 20% difference in measurement. How do you explain this difference
a. Error in calculation of nonpenetrating concentrations outside the cell
b. NOT difference in 2 degrees celscius
c. NOT difference in density
d. NOT 20% difference in the concentration of A on the outside
10. What happens to K on the inside of a RBC if Na is exchanged with single value
choline on the outside
a. Quantity will decrease
b. NOT there will be no change
c. NOT initially it will decrease and then return to original
Explanation
11. A patient with kidney disease has a loss of protein in his urine. How will this affect
the fluid exchange between the capillaries and tissue?
a. Edema in tissues
b. NOT tissue dehydration
c. NOT not difference
d. NOT no Oxygen supply to the tissue or removal of Carbon Dioxide from the
tissue
Explanation – I thought protein helps with creating pressure to push stuff in, and if not
enough, then less pushed in ???
12. If the penetrance of Na is increased by 10 times that of Chlorine and the penetrance of
K is decreased by 10 times relative to Cl, but the concentrations don’t change, how
will the equilibrium potential change
a. No change
b. NOT Na increases by a factor of 10
c. NOT K decreases by a factor of 10
13. 50 mM of A3B2 has a freezing temperature of -0.35 degrees Celcius when the
cryostatic constant is 1.8C/Osm. From this, we learn that
a. Breakdown is not complete
b. NOT complexes made of A6B4
c. NOT breakdown is complete
d. NOT no breakdown at all
WHAT DO YOU LOOK AT
14. 500mOsm of urea causes hemolysis of the human RBC. This does not happen in
green aliens. What would explain this phenomenon
a. Hard and resistant membrane against hydrostatic pressure difference
b. Membrane is not penetrable to water
c. Membrane is not penetrable to urea
15. Flow of K out of a RBC when Quabain is administered is
a. Linear function of the concentration gradient of k
b. NOT shows saturation
c. NOT function of Na outside
d. NOT will stop immediately due to anaerobic metabolic toxicity
EXPLANATION
16. In a scenario with catalyzed diffusion, solute x has K=5 mM. In a non-competitive
inhibitor with 20mM K and 20mM concentration, what is the concentration of X to
get ½ Jmax
a. 5 mM
b. NOT 20, 10, 25
EXPLANATION – the equation is confusing me…
17. Simple diffusion in animal cells
a. The flux is a function of linear gradient from both sides of the membrane in
all areas
b. NOT competition between solutes with similar chemical structure
c. NOT respiratory toxicity anaerobic and aerobic won’t stop flux immediately
d. NOT ??concentration of flux in is equal to flux out
EXPLANATION – the equation is confusing me…
18. What experiment should be done to determine if amino acids are using the same
carrier system
a. Measure the disassociation constant k of each amino acid separately and each
in the presence of each other
b. NOT measure Jmax of each separately
c. NOT check if they are non competitive or competitive
d. NOT compare the disassociation constant for the chemical structure
19. If [Na]in = 12, [K]in = 140, [Na]out = 145, [K]out = 3.5, Vm = -90 mV and P(K) =
50 P (Na) and Quabain is added, what will happen
a. Quick increase in membrane potential
b. NOT slow change toward 0
c. NOT quick drop
EXPLANATION –..is 152 vs 148.5 and why increase?
20. CANCELLED QUESTION: microelectrodes are placed in a salt solution of X2Y.
The potential is measured at -60mV when we know it is -70mV..this is because
a. Diffusion constant of x < Y??
21. Apolar something is soluble in fate. The reflection constant is measured. The
filtration constant is then increased. How will this impact the reflection constant
a. Increase (sigma ~ Lp/penetrance)
b. NOT decrease
c. NOT no change
d. NOT function of diameter
Excitability
22. In flow through single channels, the direction of flow at a given voltage is based on
a. Sign of the activating force
b. NOT from the penetrance of the channel
c. NOT from the kinetics of the channel
d. NOT from the charge of the ion
23. What is essential such that the protein will have a voltage dependent membrane
a. None of the answers below
b. NOT positive charge and a hole inside the membrane
c. NOT negative charge and a hole inside the membrane
d. NOT protein has to be an ion channel
24. What is RIGHT about the Hodgkin Huxley model regarding velocity constants (m, h,
h)
a. Increase/decrease exponentially as a function of voltage
b. Respond to change in voltage quickly
c. Express the height of energy boundaries to change between states
d. NOT Change as a function of time
25. Penetrance versus conductivity
a. Conductivity is a function of penetrance and concentration
b. NOT penetrance is a function of interaction between ion type, channel and ion
concnentration
c. NOT penetrance is the slope of the I/V curve
26. The connection between an activating force and voltage dependence
a. No connection between activating force and h, m, n to open voltage dependent
channels
b. NOT decrease in activating force causes an increase in velocity for NaK
c. NOT decrease in activating force causes a decrease in velocity
d. NOT K is different from the Na channels and an increase in activating force
causes an increase in velocity
27. Rhythmic cells
a. Have no threshold to make an action potential
b. Firing is periodic
c. Have no external stimuli
d. No rest potential
28. From the average time a channel is closed ,we can calculate
a. None of the following
b. NOT g of channel
c. NOT alpha of channel
d. NOT beta of channel
29. Without the inactivation of the stimulating force, will have
a. 2 stable positions
b. NOT 3 stable points
c. NOT firing without stopping
d. NOT infinite stable points
EXPLANATION –
30. Why on the I/V curve is the left most value higher than the Nernst of K
a. None true
b. NOT inactivation of Na channels
c. NOT left value is actually lower
d. NOT summation of Mg, K, Leak
EXPLANATION –
31. The conductive velocity of non-myelinated nerve is a function of the fiber
a. Radius
b. NOT length
c. NOT length and radius
32. What happens if K accumulates on the outside of a cell
a. The membrane potential at rest will be more depolarized
b. NOT more K on the inside
c. NOT membrane potential will become negative because the gk is
inactivating/dampens force
33. Na inactivates from
a. Blocked by change in the protein structure after the channel opnes
b. NOT Ca ions bond
c. NOT block of Magnesium
34. A nerve with myelin and a membrane covered in myelin
a. Voltage depresses with distance linearly
b. NOT no depression on membrane with distance
c. NOT get action potential but its not record
d. NOT no flow via myelin
35. The rest potential of an excitable cell is from
a. None of the following
b. NOT combination of conductive and activating force of cations only
c. NOT from Na and K only
d. NOT from m, n
36. The following are all wrong
a. Leakage conductance is of Na channels in inactivation
b. Nernst of leakeage changes with action potential
c. Nernst of leakage determined by the interaction of the Nernst of Na and K
37. The refractory period is
a. Time when excitable system returns to state without an action potential
b. NOT when Na recovers from inactivation
c. NOT when Na channels are closed
d. NOT when K channels are closed
38. I/V graph changes with action potential because of
a. Inactivation of Na
b. NOT change in activating force of Na current
c. NOT activation of Na conductivity
d. NOT activation of K conductivity
39. Blocking the Na-K channels will cause
a. Rest potential to go to 0
b. NOT channel blocking
c. NOT increase in channel activity
d. NOT won’t influence excitability
40. “fixing voltage” useful for determining
a. selection and kinetics of membrane conductivity
b. NOT cell size
c. NOT cell thickness
41. The length of time a channel stays open is
a. None of the following
b. NOT deterministic
c. NOT constant
d. NOT random or deterministic
Synapse
42. I/V curve for acetylcholine
a. Linear and crosses axis at the inversion potential
b. NOT nonconstant slope and increases with concentraition
c. NOT cross axis as function of concentration
d. NOT slop show conductivity
e. NOT increases with depolarization
43. Increase in K conductivity in the dendrite will effect the EPSP
a. Max of EPSP will decrease and time/duration will shorten
b. NOT no change
c. NOT will go further on dendrite as result of distance constant
44. We know that a poison is acting on pre-synaptic side because
a. Frequency of MEPP is lower than usual, but the average amplitude is same as
control
b. Depolarization of motor neurons doesn’t cause an increase in Ca
concentration
c. Giving transmitter causes the post synaptic response
45. Record at the axon and dendrite to see if an action potential can go from the axon to
the dendrite. These were the results
a. See the action potential at the axon before the dendrite, and with a higher
amplitude
b. NOT no time difference
c. NOT dendrite first
d. NOT only in axon but will see synaptic voltage in dendrite
46. IPSP can cause depolarization in a paradoxical way when
a. Inversion potential is higher than membrane voltage
b. NOT inversion potential is higher than threshold
c. NOT inversion potential is lower than the threshold
d. NOT membrane voltage is higher than the threshold
47. Mutant synapsin with bad phosphorylation sites will cause
a. Transmitter on repeated activity will not be released to the synaptic space
b. NOT transmitter on 1st activation will not be released to the synaptic space
c. NOT boutons will be damaged
d. NOT no synaptic release
e. NOT filling boutons damaged and quantal size decreases
48. Decrease in Calcium concentration outside will cause
a. Decrease in quantal content (m)
b. NOT decrease in quantal size (n)
c. NOT increase in post synaptic response
d. NOT can’t create action potential in presynaptic cell
49. In the CNS, most synapses take place
a. On the dendritic spines
b. NOT on the cell body
c. NOT on the dendrite close to the cell body
d. NOT on the axons
50. End of Acetylcholine activity happens because of
a. Enzymatic breakdown of acetylcholine
b. Diffusion of acetylcholine to synaptic space
c. Breakdown by glial cells
51. Synaptic delay is from
a. Time for the Ca channels to open
b. NOT fusion of bouttons
c. NOT recycle bouttons
d. NOT diffusion in synaptic space
52. Rest potential of a cell is -60mV, the threshold is -45 mV, and they record a
depolarization of 3mV, what do we learn
a. Not enough info
b. NOT excitatory
c. NOT inhibitory
d. NOT Ach is transmitter
e. NOT inverstion potential at -57 mV
EXPLANATION
53. Inversion potential is 0, rest potential is -60mV, after 1 stimulus, goes up -30mV,
after 2 goes to -15mV, after 5 stimuli, what will happen
a. Local voltage won’t go higher than 0
b. NOT 15, 30 mV
c. NOT definitely have action potential
54. Intercellular calcium is required for synapse because it
a. Leads to fusion of boutons
b. NOT leads to depolarization on pre-synaptic side
c. NOT used for filling bouttons
d. NOT finding transmitter
55. Myosthenia gravis is characterized by
a. None of the following
b. NOT amplitude of mEPP doesn’t change
c. NOT decrease in activity of Ach esterase
d. NOT partial block of Ca in presynaptic terminal
e. NOT quantity of Ach that is released decreases
56. Faster hydrolysis of ATP and decreased ATP in the cytoplasm will cause
a. Increase in myosin binding action
b. Increase in Ca binding troponin
c. Decrease in Ca concentration in SER
d. NOT hyperpolarization of rest potential
57. Bond between myosin head and actin breaks apart by
a. ATP binding myosin head
b. NOT Ca separating from troponin
c. NOT end of depolarization in T tubules
d. NOT change in conformation of tropomyosin from actin
58. If Ca binding troponin is blocked, we get
a. Decrease in myosin binding actin
b. NOT decrease in cytoplasmic concentration of Ca
c. NOT maximum contraction of muscle
d. NOT decrease in ATP in muscle
e. NOT increased tetanus power
59. Ryanodine receptor is
a. NOT Channel with Na conductivity
b. NOT Binding Ca and enters intercellular storage
c. NOT in T tubule
60. Relaxation takes place in
a. Actin
b. Myosin
c. Troponin
d. RyR
e. NOT Tropomyosin
EXPLANATION
61. If a weight is lifted in muscle contracting
a. A is constant
b. NOT I constant
c. NOT decrease in actin
d. NOT decrease in overlap of actin and myosin
e. NOT sarcomere length constant
62. If myosin is 1.5 microns and the actin is 2 microns divided over 2 sarcomeres, and .3
area isn’t counted, where is the maximum contraction
a. None of the following
b. NOT 2.6
c. NOT 2.8
d. NOT 2.9
e. NOT 3.1
EXPLANATION
63. An increase in fast/white fibers and decrease in slow red fibers will cause
a. Decrease in fat consumption as an energy source
b. NOT increase in distance running
c. NOT decrease in general energy supply
d. NOT get less tired after working out for a long time
64. Actin fiber binds how many thick fiber or myosin
a. 2
b. NOT 1, 3, 4, 6
65. Myosin has none of the following
a. Dystrophin
b. Calcineurin
c. Tropmyosin
d. troponin
66. Power of contraction comes from
a. Frequency of action potential
b. Type of muscle
c. Initial muscle length
d. Number of motor units recruited
67. Definition of motor unit
a. All muscles innervated by LMN
b. NOT UMN from motor cortex
c. NOT muscles contributing to activation of joint
d. NOT all muscles acting at once
EXPLANATION
68. If Ca ATPase is accerlerated in the the SER, it will ause
a. Decrease in duration of a single contraction
b. Decrease in duration to get to maximum tetanus
c. Decrease in maximum tetanus power
d. Decrease in maximum isolated contraction
EXPLANATION
69. Regarding slow and fast fibers
a. Fast are rich in glycogen and use glucose as a source
b. NOT motor neuron innervates a mixture
c. NOT slow fatigue fast with tetanus stimulation
d. NOT slow work on anaerobic metabolism
70. membrane T tubules are
a. rich in voltage dependent Ca channels
b. are continuous with muscle cells
c. are close to the terminal cister of SER
d. NOT rich in Ach receptors
Tetanus: A state of continuous muscular contraction, especially when induced artificially
by rapidly repeated stimuli.
The different membrane voltages, etc.