BIOL 2160 EXAM 2 CROUSILLAC
QUESTIONS AND ANSWERS 100% PASS
2026 EDITION
In the semi-permeable plasma membrane, how do nonpolar molecules get across it? -
ANS Passive transport (they freely diffuse)
In the semi-permeable plasma membrane, how do polar molecules get across it? -
ANS Active transport (they need carrier proteins)
In the semi-permeable plasma membrane, the heads of the phospholipid bilayer are ___, and
the tails are ___. - ANS hydrophilic (polar); hydrophobic (nonpolar)
The membrane potential describes the charge where? - ANS Inside the cell, as compared to
the outside
What is the membrane potential always approaching? - ANS The equilibrium potential (a
number) of the MOST permeable ion
What does "membrane potential is negative" mean? - ANS The intracellular fluid is slightly
more negative, and the extracellular fluid is slightly more positive
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,What is the equilibrium potential? - ANS the membrane potential in which the electrical
driving force is equal and opposite to the chemical driving force, making the electrochemical
driving force zero
The equilibrium potential can also called described as the number it takes to ___ -
ANS change the electrochemical gradient
NA+'s equilibrium potential is - ANS +55 mV
K+'s equilibrium potential is - ANS -94 mV
Passive transport (does or does not?) require energy, moves from an area of ___ concentration
to an area of ____ concentration, and is energetically ___. - ANS Does not; high to low;
downhill
Active transport (does or does not) require energy, moves from an area of ___ concentration to
an area of ___ concentration, and is energetically. - ANS Does; low to high; uphill
Driving force is the difference in ___ - ANS energy across a membrane (does it push from
higher to lower or lower to higher?)
The direction of net flux is passive transport is - ANS DOWN its electrochemical gradient
In passive transport, what is the carriers' preference, and which way is the carrier most likely to
transport molecules in the absence of an electrochemical gradient? - ANS No preference, so
equally likely to transport molecules in either direction in the absence of an electrochemical
gradient.
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, More solute= - ANS more energy
Carrier proteins in passive transport have what kind of affinity for molecules? - ANS Equal
affinities for molecules on either side of the membrane
Transport proteins in active transport have what kind of affinity for molecules? - ANS Have
greater affinity for one molecule when the binding site is open to its side than for the other
molecule when the binding site is closed to its side
Difference in diffusion through ion channels and facilitated diffusion is? - ANS An empty
channel's binding sites are accessible from both sides of the membrane at the same time. A
carrier's site is only accessible from one site at one time.
What are the 3 mechanisms are passive transport? - ANS Simple diffusion, facilitated
diffusion, and diffusion through ion channels.
Simple diffusion's special entry way?
Disclaimer:
Don't judge me for saying "special entryway"...that is Crousillac's exact quoted terminology. -
ANS Does not require a special entryway
Why does simple diffusion occur? - ANS Because of random thermal motion
@COPYRIGHT 2026 ALLRIGHTS RESERVED 3
QUESTIONS AND ANSWERS 100% PASS
2026 EDITION
In the semi-permeable plasma membrane, how do nonpolar molecules get across it? -
ANS Passive transport (they freely diffuse)
In the semi-permeable plasma membrane, how do polar molecules get across it? -
ANS Active transport (they need carrier proteins)
In the semi-permeable plasma membrane, the heads of the phospholipid bilayer are ___, and
the tails are ___. - ANS hydrophilic (polar); hydrophobic (nonpolar)
The membrane potential describes the charge where? - ANS Inside the cell, as compared to
the outside
What is the membrane potential always approaching? - ANS The equilibrium potential (a
number) of the MOST permeable ion
What does "membrane potential is negative" mean? - ANS The intracellular fluid is slightly
more negative, and the extracellular fluid is slightly more positive
@COPYRIGHT 2026 ALLRIGHTS RESERVED 1
,What is the equilibrium potential? - ANS the membrane potential in which the electrical
driving force is equal and opposite to the chemical driving force, making the electrochemical
driving force zero
The equilibrium potential can also called described as the number it takes to ___ -
ANS change the electrochemical gradient
NA+'s equilibrium potential is - ANS +55 mV
K+'s equilibrium potential is - ANS -94 mV
Passive transport (does or does not?) require energy, moves from an area of ___ concentration
to an area of ____ concentration, and is energetically ___. - ANS Does not; high to low;
downhill
Active transport (does or does not) require energy, moves from an area of ___ concentration to
an area of ___ concentration, and is energetically. - ANS Does; low to high; uphill
Driving force is the difference in ___ - ANS energy across a membrane (does it push from
higher to lower or lower to higher?)
The direction of net flux is passive transport is - ANS DOWN its electrochemical gradient
In passive transport, what is the carriers' preference, and which way is the carrier most likely to
transport molecules in the absence of an electrochemical gradient? - ANS No preference, so
equally likely to transport molecules in either direction in the absence of an electrochemical
gradient.
@COPYRIGHT 2026 ALLRIGHTS RESERVED 2
, More solute= - ANS more energy
Carrier proteins in passive transport have what kind of affinity for molecules? - ANS Equal
affinities for molecules on either side of the membrane
Transport proteins in active transport have what kind of affinity for molecules? - ANS Have
greater affinity for one molecule when the binding site is open to its side than for the other
molecule when the binding site is closed to its side
Difference in diffusion through ion channels and facilitated diffusion is? - ANS An empty
channel's binding sites are accessible from both sides of the membrane at the same time. A
carrier's site is only accessible from one site at one time.
What are the 3 mechanisms are passive transport? - ANS Simple diffusion, facilitated
diffusion, and diffusion through ion channels.
Simple diffusion's special entry way?
Disclaimer:
Don't judge me for saying "special entryway"...that is Crousillac's exact quoted terminology. -
ANS Does not require a special entryway
Why does simple diffusion occur? - ANS Because of random thermal motion
@COPYRIGHT 2026 ALLRIGHTS RESERVED 3
