Question 1

What are the principle features of the fluid mosaic model of membranes?

Accepted Answer

The principle features of the fluid mosa...

Question 2

A protein is found to extend all the way through the membrane of a cell.Describe this protein in terms of the location of particular types of amino acid side chains in its structure and its ability to move within the membrane.

Accepted Answer

This integral membrane protein associate...

Question 3

What is an amphipathic compound? Explain how such compounds contribute to the structure of biological membranes.

Accepted Answer

An amphipathic compound has one region o...

Question 4

Which of these statements about the composition of biological membranes is false?

Accepted Answer

A)  In a given eukaryotic cell type (e.g. ,a hepatocyte) ,all intracellular membranes have essentially the same complement of lipids and proteins.
B)  The carbohydrate found in membranes is virtually all part of either glycolipids or glycoproteins.
C)  The plasma membranes of the cells of vertebrate animals contain more cholesterol than the mitochondrial membranes.
D)  The ratio of lipid to protein varies widely among cell types in a single organism.
E)  Triacylglycerols are not commonly found in membranes.

Question 5

What are three differences between ion channels and ion transporters?

Accepted Answer

(1)The rate of ion movement through chan...

Question 6

A ligand-gated ion channel (such as the nicotinic acetylcholine receptor) is:

Accepted Answer

A)  a charged lipid in the membrane bilayer that allows ions to pass through.
B)  a membrane protein that permits a ligand to pass through the membrane only when opened by the appropriate ion.
C)  a membrane protein that permits an ion to pass through the membrane only when opened by the appropriate ligand.
D)  a molecule that binds to the membrane thereby allowing ions to pass through.
E)  always requires a second ligand to close the channel once it is opened. C

Question 7

A hydropathy plot is used to:

Accepted Answer

A)  determine the water-solubility of a protein.
B)  deduce the quaternary structure of a membrane protein.
C)  determine the water content of a native protein.
D)  extrapolate for the true molecular weight of a membrane protein.
E)  predict whether a given protein sequence contains membrane-spanning segments.

Question 8

Which of the following are not enzymes involved in moving phospholipids from one leaflet to another?

Accepted Answer

A)  Flippases that move phosphatidylethanolamine and phosphatidylserine
B)  Floppases that move phospholipids from the cytosolic leaflet to the extracellular leaflet
C)  Flip-floppases that allow phospholipids to move back and forth between the inner and outer leaflets
D)  Scramblases that allow phospholipids to move down their concentration gradient
E)  Phosphatidylinositol transfer proteins that play a role in lipid signaling

Question 9

Consider the transport of K+ from the blood (where its concentration is about 4 mM) into an erythrocyte that contains 150 mM K+.The transmembrane potential is about 60 mV,inside negative relative to outside.The free-energy change for this transport process is: (These values may be of use to you: R = 8.315 J/mol.K;T = 298 K;9 (Faraday constant) = 96,480 J/V;N = 6.022 *1023/mol. )

Accepted Answer

A)  about 5 J/mol.
B)  about 15 J/mol.
C)  about 5 kJ/mol.
D)  about 15 kJ/mol.
E)  impossible to calculate with the information given.

Question 10

The bacterium E.coli can grow at 20 °C or at 40 °C.At which growth temperature would you expect the membrane phospholipids to have a higher ratio of saturated to unsaturated fatty acids,and why?

Accepted Answer

At 40 °C,the membranes of E.coli will co...

Question 11

The specificity of aquaporins for water is not ensured by which of the following?

Accepted Answer

A)  The channel contains a negatively charged Asp residue to scavenge protons and H3O+.
B)  The diameter of the channel narrows to 2.8 Å.
C)  There are carbonyl backbone residues in the channel that hydrogen bond with water.
D)  Arg and His residues in the channel repel protons and H3O+.
E)  Electric dipoles of short  α\alphaα -helices repel protons and H3O+.  A

Question 12

Distinguish between simple diffusion (SD),facilitated diffusion (FD),and active transport (AT)across a membrane for the following questions.(More than one may be true. )
(a)Which processes are energy dependent?
(b)Which processes need some kind of carrier protein(s)?
(c)Which processes can be saturated by substrate?
(d)Which processes can establish a concentration gradient?
(e)How much energy does it take to transport an uncharged substrate in,if its starting inside concentration is 10-fold greater than outside?

Accepted Answer

(a)AT only
(b)FD and...

Question 13

The fluidity of the lipid side chains in the interior of a bilayer is generally increased by:

Accepted Answer

A)  a decrease in temperature.
B)  an increase in fatty acyl chain length.
C)  an increase in the number of double bonds in fatty acids.
D)  an increase in the percentage of phosphatidyl ethanolamine
E)  the binding of water to the fatty acyl side chains.

Question 14

Transport of histidine into a bacterial cell was measured at several different histidine concentrations.Does histidine uptake operate by passive or facilitated transport,and why?

Accepted Answer

At first glance,the mechanism appears to...

Question 15

If the hydrophobic interior of a membrane were about 3 nm thick,what would be the minimum number of amino acids in a stretch of transmembrane $\alpha$ helix?

Accepted Answer

The dimensions of an $\alpha$helix are about 5.4 Å/turn,and there are 3.6 residues/turn,so each residue extends the helix by about 1.5 Å or 0.15 nm.To span 3 nm of lipid bilayer will therefore require a minimum of 20 residues.

Question 16

Which of these is a general feature of the lipid bilayer in all biological membranes?

Accepted Answer

A)  Individual lipid molecules are free to diffuse laterally in the surface of the bilayer.
B)  Individual lipid molecules in one face (monolayer) of the bilayer readily diffuse (flip-flop) to the other monolayer.
C)  Polar,but uncharged,compounds readily diffuse across the bilayer.
D)  The bilayer is stabilized by covalent bonds between neighboring phospholipid molecules.
E)  The polar head groups face inward toward the inside of the bilayer.

Question 17

An integral membrane protein can be extracted with:

Accepted Answer

A)  a buffer of alkaline or acid pH.
B)  a chelating agent that removes divalent cations.
C)  a solution containing detergent.
D)  a solution of high ionic strength.
E)  hot water.

Question 18

A plant breeder has developed a new frost-resistant variety of tomato that contains higher levels of unsaturated fatty acids in membrane lipids than those found in standard tomato varieties.However,when temperatures climb above 95 °F,this frost-resistant variety dies,whereas the standard variety continues to grow.Provide a likely explanation of the biochemical basis of increased tolerance to cold and increased susceptibility to heat of this new tomato variety.

Accepted Answer

More unsaturated fatty acids will cause ...

Question 19

Glycosphingolipids and cholesterol cluster together in membrane regions known as "__________." These microdomains are more __________ than the surrounding phospholipid-rich membrane due to a high content of __________ fatty acids.These regions are rich in proteins that are anchored to the membrane by covalently attached __________ and __________ groups and also those anchored by GPI linkage.Proteins aggregated in this fashion are often functionally related.Examples are (1)__________ proteins and (2)__________ proteins.

Accepted Answer

"rafts";ordered;satu...

Question 20

ABC transporters are not known to facilitate the following process:

Accepted Answer

A)  moving cancer drugs out of cancer cells.
B)  moving antibiotics out of bacteria.
C)  moving membrane lipids from the inner leaflet to the outer leaflet.
D)  moving chloride ions in the lung.
E)  moving vitamin E into lipocytes.

Exam 11: Biological Membranes and Transport

What are the principle features of the fluid mosaic model of membranes?

Correct Answer
verified
The principle features of the fluid mosa...
View Answer

A protein is found to extend all the way through the membrane of a cell.Describe this protein in terms of the location of particular types of amino acid side chains in its structure and its ability to move within the membrane.

Correct Answer
verified
This integral membrane protein associate...
View Answer

What is an amphipathic compound? Explain how such compounds contribute to the structure of biological membranes.

Correct Answer
verified
An amphipathic compound has one region o...
View Answer

Which of these statements about the composition of biological membranes is false?

Correct Answer
verified

What are three differences between ion channels and ion transporters?

Correct Answer
verified
(1)The rate of ion movement through chan...
View Answer

A ligand-gated ion channel (such as the nicotinic acetylcholine receptor) is:

Correct Answer
verified
C

A hydropathy plot is used to:

Correct Answer
verified

Which of the following are not enzymes involved in moving phospholipids from one leaflet to another?

Correct Answer
verified

Correct Answer
verified

The bacterium E.coli can grow at 20 °C or at 40 °C.At which growth temperature would you expect the membrane phospholipids to have a higher ratio of saturated to unsaturated fatty acids,and why?

Correct Answer
verified
At 40 °C,the membranes of E.coli will co...
View Answer

The specificity of aquaporins for water is not ensured by which of the following?

Correct Answer
verified
A

Correct Answer
verified
(a)AT only
(b)FD and...
View Answer

The fluidity of the lipid side chains in the interior of a bilayer is generally increased by:

Correct Answer
verified

Transport of histidine into a bacterial cell was measured at several different histidine concentrations.Does histidine uptake operate by passive or facilitated transport,and why?

Correct Answer
verified
At first glance,the mechanism appears to...
View Answer

If the hydrophobic interior of a membrane were about 3 nm thick,what would be the minimum number of amino acids in a stretch of transmembrane $\alpha$ helix?

Correct Answer
verified
The dimensions of an \(\alpha\)helix are about 5.4 Å/turn,and there are 3.6 residues/turn,so each residue extends the helix by about 1.5 Å or 0.15 nm.To span 3 nm of lipid bilayer will therefore require a minimum of 20 residues.

Which of these is a general feature of the lipid bilayer in all biological membranes?

Correct Answer
verified

An integral membrane protein can be extracted with:

Correct Answer
verified

Correct Answer
verified
More unsaturated fatty acids will cause ...
View Answer

Correct Answer
verified
"rafts";ordered;satu...
View Answer

ABC transporters are not known to facilitate the following process:

Correct Answer
verified

Exam 11: Biological Membranes and Transport

What are the principle features of the fluid mosaic model of membranes?

Correct AnswerverifiedThe principle features of the fluid mosa...View AnswerShow Answer

A protein is found to extend all the way through the membrane of a cell.Describe this protein in terms of the location of particular types of amino acid side chains in its structure and its ability to move within the membrane.

Correct AnswerverifiedThis integral membrane protein associate...View AnswerShow Answer

What is an amphipathic compound? Explain how such compounds contribute to the structure of biological membranes.

Correct AnswerverifiedAn amphipathic compound has one region o...View AnswerShow Answer

Which of these statements about the composition of biological membranes is false?

Correct AnswerverifiedShow Answer

What are three differences between ion channels and ion transporters?

Correct Answerverified(1)The rate of ion movement through chan...View AnswerShow Answer

A ligand-gated ion channel (such as the nicotinic acetylcholine receptor) is:

Correct AnswerverifiedC

A hydropathy plot is used to:

Correct AnswerverifiedShow Answer

Which of the following are not enzymes involved in moving phospholipids from one leaflet to another?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

The bacterium E.coli can grow at 20 °C or at 40 °C.At which growth temperature would you expect the membrane phospholipids to have a higher ratio of saturated to unsaturated fatty acids,and why?

Correct AnswerverifiedAt 40 °C,the membranes of E.coli will co...View AnswerShow Answer

The specificity of aquaporins for water is not ensured by which of the following?

Correct AnswerverifiedA

Correct Answerverified(a)AT only(b)FD and...View AnswerShow Answer

The fluidity of the lipid side chains in the interior of a bilayer is generally increased by:

Correct AnswerverifiedShow Answer

Transport of histidine into a bacterial cell was measured at several different histidine concentrations.Does histidine uptake operate by passive or facilitated transport,and why?

Correct AnswerverifiedAt first glance,the mechanism appears to...View AnswerShow Answer

If the hydrophobic interior of a membrane were about 3 nm thick,what would be the minimum number of amino acids in a stretch of transmembrane α\alphaα helix?

Correct AnswerverifiedThe dimensions of an \(\alpha\)helix are about 5.4 Å/turn,and there are 3.6 residues/turn,so each residue extends the helix by about 1.5 Å or 0.15 nm.To span 3 nm of lipid bilayer will therefore require a minimum of 20 residues.

Which of these is a general feature of the lipid bilayer in all biological membranes?

Correct AnswerverifiedShow Answer

An integral membrane protein can be extracted with:

Correct AnswerverifiedShow Answer

Correct AnswerverifiedMore unsaturated fatty acids will cause ...View AnswerShow Answer

Correct Answerverified"rafts";ordered;satu...View AnswerShow Answer

ABC transporters are not known to facilitate the following process:

Correct AnswerverifiedShow Answer

Correct Answer
verified
The principle features of the fluid mosa...
View Answer

Correct Answer
verified
This integral membrane protein associate...
View Answer

Correct Answer
verified
An amphipathic compound has one region o...
View Answer

Correct Answer
verified

Correct Answer
verified
(1)The rate of ion movement through chan...
View Answer

Correct Answer
verified
C

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
At 40 °C,the membranes of E.coli will co...
View Answer

Correct Answer
verified
A

Correct Answer
verified
(a)AT only
(b)FD and...
View Answer

Correct Answer
verified

Correct Answer
verified
At first glance,the mechanism appears to...
View Answer

If the hydrophobic interior of a membrane were about 3 nm thick,what would be the minimum number of amino acids in a stretch of transmembrane $\alpha$ helix?

Correct Answer
verified
The dimensions of an \(\alpha\)helix are about 5.4 Å/turn,and there are 3.6 residues/turn,so each residue extends the helix by about 1.5 Å or 0.15 nm.To span 3 nm of lipid bilayer will therefore require a minimum of 20 residues.

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
More unsaturated fatty acids will cause ...
View Answer

Correct Answer
verified
"rafts";ordered;satu...
View Answer

Correct Answer
verified