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FHD Block 1 Exam Questions and Answers 100% Solved | Graded A+
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FHD Block 1 Exam Questions and Answers 100% Solved | Graded A+ Some rules for membrane potentials: 1) The resting membrane potential is always near the Nernst Equilibrium potential for the ____________ permeable ion. 2) A ____________ driving force will drive a positive ion out of the cell or ...

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  • December 8, 2024
  • 58
  • 2024/2025
  • Exam (elaborations)
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FHD Block 1 Exam Questions and

Answers 100% Solved | Graded A+


Some rules for membrane potentials:

1) The resting membrane potential is always near the Nernst Equilibrium

potential for the ____________ permeable ion.

2) A ____________ driving force will drive a positive ion out of the cell or a

negative ion into the cell. A ____________ driving force will drive a

negative ion out of the cell or a positive ion into the cell.

3) The greater the driving force, the ____________ the magnitude of ion

current. - ✔✔most; positive; negative; larger

____________ tells whether a cell will initially shrink or swell and counts all

solutes in a solution. ____________ tells what the steady state condition of

the cell will be and counts only impermeable solutes like NaCl. -

✔✔osmolarity; tonicity

A red blood cell remains at a stable volume in a salt solution with an

osmolarity equal to 290 mOs. Inulin, an impermeant solute, is added to the

external solution. Over a time course of seconds, what would happen to the


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©JOSHCLAY 2024/2025. YEAR PUBLISHED 2024.

,potassium equilibrium potential? - ✔✔more negative (Addition of an

impermeable solute would cause water to leave the cell - the cell would

shrink. All intracellular concentrations would immediately increase.

Increased intracellular potassium would make EK more negative (EK = 60

log [K]o/[K]i.))

A surgeon washes out a surgical wound from which a tumor has been

removed with sterile distilled water (no ions) rather than sterile physiologic

saline. What effect will this have on any remaining tumor cells? - ✔✔swell

and burst

A cell membrane is equally permeable to two positive ions X and Y. X has

an equilibrium potential of +70mV and Y has an equilibrium potential of -

90mV. The membrane is then made permeable to a third positive ion Z, but

no flux of Z across the membrane is measured. What is the equilibrium

potential of ion Z? - ✔✔-10 mV (By the Chord Conductance equation:

(0.5/1)(+70) + (0.5/1)(-90) = -10mV, so for the driving force of Z to be zero

it must have an equilibrium potential equal to the membrane potential)

A mammalian muscle cell is put into an isotonic solution whose

composition mimics that of blood plasma. This cell maintains its normal

volume overtime. Adding which of the following to the bathing solution

would cause the cell to swell and eventually burst?
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©JOSHCLAY 2024/2025. YEAR PUBLISHED 2024.

,a. An inhibitor of the voltage gated sodium

b. An inhibitor of voltage gated calcium channels

c. An inhibitor of the sodium/potassium ATPase

d. An inhibitor of sodium glucose cotransport - ✔✔C (the influx of sodium

would increase the cell's osmolarity, causing it to swell and maybe burst)

Assume you have a mammalian cell with normal extracellular and

intracellular ionic composition. Further assume that the cell membrane

potential = -70 mV and that ENa = +50 mV; EK = -90 mV; ECa = +120 mV

and Ecl = -70 mV. Which of the ions is actively transported into the cell? -

✔✔Potassium (Sodium and calcium are cations - for each, comparing

membrane potential and the respective equilibrium potential, the net driving

force is negative. Net passive flux for both of these cations must be into the

cell. Active transport for both must be outward. Potassium is a cation

whose driving force is positive. Passive potassium flux is out of the cell and

active transport is inward. (For this question the easy analysis is to

remember that the Na,K-ATPase actively transports Sodium out of the cell

and potassium into the cell).)

____________ is low capacity, high affinity, while ____________ is high

capacity, low affinity. Both are secondarily active transporters using

sodium. - ✔✔SGLT1; SGLT2
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©JOSHCLAY 2024/2025. YEAR PUBLISHED 2024.

, NCX, PMCA and SERCA work to maintain low ____________ calcium

concentration. Both PMCA and SERCA are ____________ transporters

that directly hydrolyze ATP. The so-called ____________ receptor is a

calcium channel present on the SR membrane. This channel mediates

____________ calcium movement from the lumen of the SR to the

cytoplasm. Free calcium concentration must be higher inside the SR than

in the cytoplasm. - ✔✔intracellular; primary active; ryanodine; passive

The resting membrane potential in neurons is closer to -70mV as opposed

to the -90mV in muscle cells. This has much to do with the ____________

channel which is structurally similar to its voltage-gated counterpart but

does not inactivate or require a voltage to open. - ✔✔Na leak channel

(NALCN)

The ____________ constant determines how far depolarization spreads.

This is ____________ with increasing diameter and with increasing

membrane resistance (e.g. myelin sheaths), and ____________ with

axoplasm resistance. - ✔✔length; increased; decreased

____________ targets VG Na channels, preventing action potentials, while

____________ targets VG K channels, causing a slowed return to resting

potential. Additionally, ____________ targets nicotinic ACh receptors. -

✔✔tetrodotoxin; TEA (tetraethylammonium); curare (or d-tubocurarine)
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©JOSHCLAY 2024/2025. YEAR PUBLISHED 2024.

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