BS 161 Exam #2: Questions And Solutions (Rated A+)
The interior region of a phospholipid bilayer is Right Ans - hydrophobic
What bond/force/interactions are most influential in the formation of the
lipid bilayer Right Ans - 1) hydrogen bond interactions among water
molecules and polar phospholipid heads
2) hydrophobic exclusion of non-polar fatty acid tails
What amino acid would likely be found the hydrophobic region that is
embedded in the membrane Right Ans - alanine
What type of molecule is sometimes found spanning a cell's plasma membrane
with part of the molecule on one side of the membrane, part embedding the
membrane, and part on the other side? Right Ans - protein
An amphipathic molecule is one that: Right Ans - contains both polar and
non-polar regions
Predict how phospholipids would arrange if they were placed in a nonpolar
solution rather than a polar solution like water Right Ans - phospholipid
with long-chain, saturated fatty acids
A researcher has devised a technique that allows her to label all the integral
membrane proteins with a fluorescent tag. She uses a laser to bleach the
fluorescence in a specific area of the cell membrane. After 24 hours, she
notices that fluorescence has returned to the bleached area. What can she
deduce from this experiment? Right Ans - integral membrane proteins are
able to move laterally within the cell membrane.
Imagine a cell that has a membrane composed mostly of lipids with saturated
fatty acid tails, and that this membrane also has low cholesterol content. What
are the characteristics of this cell membrane? Right Ans - Due to its low
cholesterol content, the cell membrane would lose its fluidity at cold
temperatures.
Considering the amino acids that are found in various domains of
transmembrane proteins, which statement would be true? Right Ans -
, Nonpolar amino acids would be prevalent in the transmembrane domain, in
contact with the environment of the inner membrane.
Which part of a cholesterol molecule is polar? Right Ans - OH group
Paramecium is a unicellular organism that lives in fresh water. Suppose you
are studying two populations of this organism. One population lives in a pond
in a cold environment, and the other lives in a pond in a warm environment. If
you examined the fatty acids in plasma membranes of both of these
populations, what difference would you expect to find? Right Ans - The
fatty acid tails from the cold environment would generally be shorter and less
saturated compared to fatty acids from the warm environment.
Which substance could LEAST easily cross a synthetic membrane composed of
phospholipids but not proteins? Right Ans - sodium ions (Na+)
Which choice describes the hydrophilic component of cholesterol? Right
Ans - the hydroxyl head group
The plasma membrane is composed of a phospholipid bilayer and associated
proteins. What else is commonly found in the plasma membranes of animal
cells? Right Ans - he mouse and human proteins would slowly mix over
time in the hybrid cell.
Which choice is considered an integral membrane protein? Right Ans - a
protein with its amino-terminus in the cytoplasm and its carboxy-terminus in
the extracellular space
While many proteins move freely in the plane of the membrane, there are
some proteins that are confined to specific places or regions of the membrane.
If a membrane protein that is confined to a specific membrane region were
labeled in a FRAP experiment, what result would you predict?The bleached
spot will not recover fluorescence over time. Right Ans - The bleached spot
will not recover fluorescence over time.
One unifying feature of prokaryotic and eukaryotic cells is the presence of:
Right Ans - DNA
The interior region of a phospholipid bilayer is Right Ans - hydrophobic
What bond/force/interactions are most influential in the formation of the
lipid bilayer Right Ans - 1) hydrogen bond interactions among water
molecules and polar phospholipid heads
2) hydrophobic exclusion of non-polar fatty acid tails
What amino acid would likely be found the hydrophobic region that is
embedded in the membrane Right Ans - alanine
What type of molecule is sometimes found spanning a cell's plasma membrane
with part of the molecule on one side of the membrane, part embedding the
membrane, and part on the other side? Right Ans - protein
An amphipathic molecule is one that: Right Ans - contains both polar and
non-polar regions
Predict how phospholipids would arrange if they were placed in a nonpolar
solution rather than a polar solution like water Right Ans - phospholipid
with long-chain, saturated fatty acids
A researcher has devised a technique that allows her to label all the integral
membrane proteins with a fluorescent tag. She uses a laser to bleach the
fluorescence in a specific area of the cell membrane. After 24 hours, she
notices that fluorescence has returned to the bleached area. What can she
deduce from this experiment? Right Ans - integral membrane proteins are
able to move laterally within the cell membrane.
Imagine a cell that has a membrane composed mostly of lipids with saturated
fatty acid tails, and that this membrane also has low cholesterol content. What
are the characteristics of this cell membrane? Right Ans - Due to its low
cholesterol content, the cell membrane would lose its fluidity at cold
temperatures.
Considering the amino acids that are found in various domains of
transmembrane proteins, which statement would be true? Right Ans -
, Nonpolar amino acids would be prevalent in the transmembrane domain, in
contact with the environment of the inner membrane.
Which part of a cholesterol molecule is polar? Right Ans - OH group
Paramecium is a unicellular organism that lives in fresh water. Suppose you
are studying two populations of this organism. One population lives in a pond
in a cold environment, and the other lives in a pond in a warm environment. If
you examined the fatty acids in plasma membranes of both of these
populations, what difference would you expect to find? Right Ans - The
fatty acid tails from the cold environment would generally be shorter and less
saturated compared to fatty acids from the warm environment.
Which substance could LEAST easily cross a synthetic membrane composed of
phospholipids but not proteins? Right Ans - sodium ions (Na+)
Which choice describes the hydrophilic component of cholesterol? Right
Ans - the hydroxyl head group
The plasma membrane is composed of a phospholipid bilayer and associated
proteins. What else is commonly found in the plasma membranes of animal
cells? Right Ans - he mouse and human proteins would slowly mix over
time in the hybrid cell.
Which choice is considered an integral membrane protein? Right Ans - a
protein with its amino-terminus in the cytoplasm and its carboxy-terminus in
the extracellular space
While many proteins move freely in the plane of the membrane, there are
some proteins that are confined to specific places or regions of the membrane.
If a membrane protein that is confined to a specific membrane region were
labeled in a FRAP experiment, what result would you predict?The bleached
spot will not recover fluorescence over time. Right Ans - The bleached spot
will not recover fluorescence over time.
One unifying feature of prokaryotic and eukaryotic cells is the presence of:
Right Ans - DNA
