Biol 320 Exam 3
BIOL 320 EXAM 3 NEWEST 2025 ACTUAL EXAM COMPLETE
QUESTIONS AND CORRECT ANSWERS(VERIFIED ANSWERS)
|ALREADY GRADED A+
Many transmembrane proteins contain a single alpha helix. What chemical properties of an
alpha helix are important for its interaction with membrane phospholipids?
All covalent bonds in the alpha helix are nonpolar, which allows the helix to interact with the
hydrophobic fatty acid tails
The backbone of every polypeptide is hydrophobic, which means that an alpha helix can
interact with the hydrophobic fatty acid tails
Amino acids within an alpha helix can have hydrophobic side chains that interact with the
hydrophobic fatty acid tails
An attraction occurs between the positively charged alpha helix and the negatively charged
phospholipids - ANSWER-Amino acids within an alpha helix can have hydrophobic side chains
that interact with the hydrophobic fatty acid tails
Select all of the following options that would give you the MOST fluid membrane:
26 hydrocarbon phospholipid tail
14 hydrocarbon phospholipid tail
saturated tails
unsaturated tails - ANSWER-14 hydrocarbon phospholipid tail
unsaturated tails
Cortisol is a molecule that is capable of crossing through the membrane unassisted.
Select all true statements below regarding this process:
cortisol is a lipid soluble molecule
cortisol can cross the membrane against its gradient
cortisol is capable of simple diffusion
1|Page
, Biol 320 Exam 3
Cortisol enters the cell via facilitated diffusion - ANSWER-cortisol is a lipid soluble molecule
cortisol is capable of simple diffusion
The sodium potassium pump is an example of a protein that has several different domains. One
specialized region of the protein is responsible for breaking the bond between a phosphate
group and adenosine triphosphate, ultimately attaching that phosphate to an amino acid side
chain found within itself.
What would be an appropriate name for this domain of the sodium potassium pump?
sodium binding domain
potassium binding domain
phosphorylation domain
voltage sensing domain - ANSWER-phosphorylation domain
Which of the following explains why Ouabain, a chemical derived from a plant found in some
regions of the world, is capable of killing a massive mammal like a hippo?
the molecule leads to an increase in extracellular sodium
the molecule prevents heart muscle cells from maintaining the sodium gradient
ouabain directly blocks the coupled pump for calcium
ouabain prevents facilitated diffusion of sodium up its gradient - ANSWER-the molecule
prevents heart muscle cells from maintaining the sodium gradient
Ion channels have different gating mechanisms. Which of the following is NOT an example of
how these mechanisms work?
voltage gated ion channels open in response to a change in water distribution across the
membrane
a mechanically gated potassium channel opens in response to physical stimulus
ligand gated ion channels require the binding of a molecule that causes a conformation shift in
the channel protein
2|Page
, Biol 320 Exam 3
voltage gated ion channels can be affected by the concentration gradients of positive or
negatively charged ions - ANSWER-voltage gated ion channels open in response to a change in
water distribution across the membrane
As long as a channel is open, it will allow selective diffusion of a particular solute DOWN its
gradient.
True
False - ANSWER-true
Most proteins that transport hydrophilic molecules across the membrane contain one alpha
helix that crosses the plasma membrane a single time.
True
False - ANSWER-false
Phosphorylation of the Na+-K+ pump is performed by a kinase that diffuses through the cytosol
of a cell.
True
False - ANSWER-false
The direction that glucose is transported across the membrane is determined by:
The concentration gradient
The membrane potential
The molecule's charge
The molecule's size - ANSWER-The concentration gradient
Which of the following are differences between channels and transporters?
Only transporters are selective in which solutes they transport
3|Page
, Biol 320 Exam 3
Transporters are only used for active transport, while channels are only used for facilitated
diffusion.
Only transporters change shape each time a solute is moved
Only transporters are regulated by ligands and voltage changes - ANSWER-Only transporters
change shape each time a solute is moved
Channels use the energy from ATP hydrolysis to move ions UP (against) their electrochemical
gradient.
True
False - ANSWER-false
The energy for secondary active transport is supplied by
ATP phosphorylation of the coupled transporter
An ATP hydrolysis reaction performed by the coupled transporter
An electrochemical gradient of another ion
Moving glucose from high to low concentration - ANSWER-An electrochemical gradient of
another ion
True or False: In secondary active transport, solutes are transported across the membrane in
tandem with another molecule, with both moving from lower concentration to higher
concentration.
True
False - ANSWER-false
Which statement about a cell's resting membrane potential is TRUE?
(reminder: "resting" membrane potential is the overall charge difference between inside and
outside the cell when the cell is at "rest" or in standard conditions)
4|Page
BIOL 320 EXAM 3 NEWEST 2025 ACTUAL EXAM COMPLETE
QUESTIONS AND CORRECT ANSWERS(VERIFIED ANSWERS)
|ALREADY GRADED A+
Many transmembrane proteins contain a single alpha helix. What chemical properties of an
alpha helix are important for its interaction with membrane phospholipids?
All covalent bonds in the alpha helix are nonpolar, which allows the helix to interact with the
hydrophobic fatty acid tails
The backbone of every polypeptide is hydrophobic, which means that an alpha helix can
interact with the hydrophobic fatty acid tails
Amino acids within an alpha helix can have hydrophobic side chains that interact with the
hydrophobic fatty acid tails
An attraction occurs between the positively charged alpha helix and the negatively charged
phospholipids - ANSWER-Amino acids within an alpha helix can have hydrophobic side chains
that interact with the hydrophobic fatty acid tails
Select all of the following options that would give you the MOST fluid membrane:
26 hydrocarbon phospholipid tail
14 hydrocarbon phospholipid tail
saturated tails
unsaturated tails - ANSWER-14 hydrocarbon phospholipid tail
unsaturated tails
Cortisol is a molecule that is capable of crossing through the membrane unassisted.
Select all true statements below regarding this process:
cortisol is a lipid soluble molecule
cortisol can cross the membrane against its gradient
cortisol is capable of simple diffusion
1|Page
, Biol 320 Exam 3
Cortisol enters the cell via facilitated diffusion - ANSWER-cortisol is a lipid soluble molecule
cortisol is capable of simple diffusion
The sodium potassium pump is an example of a protein that has several different domains. One
specialized region of the protein is responsible for breaking the bond between a phosphate
group and adenosine triphosphate, ultimately attaching that phosphate to an amino acid side
chain found within itself.
What would be an appropriate name for this domain of the sodium potassium pump?
sodium binding domain
potassium binding domain
phosphorylation domain
voltage sensing domain - ANSWER-phosphorylation domain
Which of the following explains why Ouabain, a chemical derived from a plant found in some
regions of the world, is capable of killing a massive mammal like a hippo?
the molecule leads to an increase in extracellular sodium
the molecule prevents heart muscle cells from maintaining the sodium gradient
ouabain directly blocks the coupled pump for calcium
ouabain prevents facilitated diffusion of sodium up its gradient - ANSWER-the molecule
prevents heart muscle cells from maintaining the sodium gradient
Ion channels have different gating mechanisms. Which of the following is NOT an example of
how these mechanisms work?
voltage gated ion channels open in response to a change in water distribution across the
membrane
a mechanically gated potassium channel opens in response to physical stimulus
ligand gated ion channels require the binding of a molecule that causes a conformation shift in
the channel protein
2|Page
, Biol 320 Exam 3
voltage gated ion channels can be affected by the concentration gradients of positive or
negatively charged ions - ANSWER-voltage gated ion channels open in response to a change in
water distribution across the membrane
As long as a channel is open, it will allow selective diffusion of a particular solute DOWN its
gradient.
True
False - ANSWER-true
Most proteins that transport hydrophilic molecules across the membrane contain one alpha
helix that crosses the plasma membrane a single time.
True
False - ANSWER-false
Phosphorylation of the Na+-K+ pump is performed by a kinase that diffuses through the cytosol
of a cell.
True
False - ANSWER-false
The direction that glucose is transported across the membrane is determined by:
The concentration gradient
The membrane potential
The molecule's charge
The molecule's size - ANSWER-The concentration gradient
Which of the following are differences between channels and transporters?
Only transporters are selective in which solutes they transport
3|Page
, Biol 320 Exam 3
Transporters are only used for active transport, while channels are only used for facilitated
diffusion.
Only transporters change shape each time a solute is moved
Only transporters are regulated by ligands and voltage changes - ANSWER-Only transporters
change shape each time a solute is moved
Channels use the energy from ATP hydrolysis to move ions UP (against) their electrochemical
gradient.
True
False - ANSWER-false
The energy for secondary active transport is supplied by
ATP phosphorylation of the coupled transporter
An ATP hydrolysis reaction performed by the coupled transporter
An electrochemical gradient of another ion
Moving glucose from high to low concentration - ANSWER-An electrochemical gradient of
another ion
True or False: In secondary active transport, solutes are transported across the membrane in
tandem with another molecule, with both moving from lower concentration to higher
concentration.
True
False - ANSWER-false
Which statement about a cell's resting membrane potential is TRUE?
(reminder: "resting" membrane potential is the overall charge difference between inside and
outside the cell when the cell is at "rest" or in standard conditions)
4|Page
