Question 1

In the 1950s,J.D.Robertson reported that any membrane that he observed in the electron microscope looked the same.This led to his proposal of the Unit Membrane model of membrane structure suggesting that all membranes were exactly alike.Why was this model eventually rejected?

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Question 2

You are studying a transport molecule.It appears to bind temporarily to the molecule to be transported.During normal transport,no energy is expended.The addition of a particular molecule that closely resembles the normally transported molecule inhibits transport.An increase in the concentration of the normally transported molecule in the presence of a constant concentration of the inhibitor increases the rate of transport.What kind of transport is described and what is the inhibiting molecule?

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Question 3

Synaptic malfunction or dysfunction may cause which of the following diseases?

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Synaptic malfunction or dysfunction can cause a variety of neurological and psychological disorders. Myasthenia gravis is a neurological disorder that affects the neuromuscular junction or the synapse between nerve and muscle cells, leading to muscle weakness and fatigue. Parkinson's disease is a degenerative disorder of the central nervous system that affects movement, caused by the loss of neurotransmitters in certain regions of the brain. Schizophrenia is a mental disorder that affects perception, thought processes, and behavior, believed to be caused by an imbalance in neurotransmitters such as dopamine and serotonin. Depression is a mood disorder that may be caused by a lack of neurotransmitters such as serotonin in the brain. Therefore, all of these options are correct.

Question 4

You are investigating the transition temperature of a membrane,the origin of which you do not know.The temperature of transition for this membrane is very sharp,occurring over an extremely narrow range of temperatures.What can you say about the composition of the membrane?

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Question 5

A membrane's transition temperature is determined and found to stretch over a wide range of temperatures.The membrane also exhibits high stability and a reduced permeability similar to that in most mammals.What membrane component is responsible for these traits and how does it do it?

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Question 6

How might a lack of Cl- transport cause the respiratory tract symptoms of cystic fibrosis (CF),specifically the thickened mucus?

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Question 7

How was it proved that the cystic fibrosis transmembrane conductance regulator (CFTR)was actually a chloride transporter?

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Question 8

If you were able to study nerve conduction in vitro and you added ouabain,an inhibitor of the Na+-K+ ATPase,to the system,would you expect to see the conduction of nerve impulses cease immediately?

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Question 9

In the middle of the winter,the membranes from a tissue sample from an organism dwelling in a pond are analyzed for their phospholipid content.In the middle of the summer,another tissue sample is taken from the same type of organism and the membrane lipid content determined.The lipid content has changed.How has it changed and why?

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Question 10

The rate of nerve impulse conduction in two different nerve cell axons differs.The first cell exhibits a rate of conduction substantially higher (about 20 times faster)than the second cell.Both cells have axons of the same diameter.What is a possible explanation for the difference in nerve conduction rate?

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Question 11

A molecule normally enters a cell by simple diffusion through the lipid bilayer.What happens if you artificially reverse the molecule's concentration gradient?

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Question 12

You are exploring a rather inhospitable planet,which has seas that are somewhat hydrophobic in nature.Surprisingly,there are living organisms in the seas whose cytoplasm is hydrophobic to a similar degree.These organisms have membranes made primarily of phospholipids arranged in a bilayer.What is the most probable orientation of these phospholipids?

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Question 13

A new,promising drug in the treatment of cystic fibrosis (CF)and the improvement in the quality of life in CF patients is Bronchitol.What is Bronchitol's overall effect on the patient that allows it to improve their situation? What sugar is a major constituent of Bronchitol? How does Bronchitol cause water to move into the extracellular fluid of the airways after being inhaled? What other kinds of compounds might be used in CF treatment in the future?

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Question 14

How might a liposome be prepared that could potentially be used in the treatment of a tumor whose cells have a protein called tumor cell antigen (TCA)in their membranes? This protein is missing from all normal cells.

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Question 15

You are characterizing an isolated membrane protein.The protein is exposed on both sides of the membrane.Over much of the central part of its surface,there are hydrophobic amino acids,while the ends are hydrophilic.It crosses the membrane a number of times.There is an opening in the center of this protein lined by hydrophilic amino acids.What kind of protein is this and what is its probable function?

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Question 16

A process in liver cells stops when they are exposed to the inhibitor ouabain,which is an inhibitor of the Na+-K+ pump.What do you conclude about the liver cell process?

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Question 17

What are some possible explanations for the tendency of CF patients to develop chronic lung infections?

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Question 18

You are the biologist on an interstellar spacecraft and discover a life form.It appears similar to life forms on Earth.You extract a number of molecules from the organism and characterize them.From the described properties,what kind of molecules are they likely to be and where are they likely to be found?
A.an amphipathic molecule that has two long hydrocarbon chains and a polar oligosaccharide head group.
B.another amphipathic molecule with two hydrocarbon chains and a phosphate-containing head group.
C.a polymer made of amino acids with hydrophobic amino acids on its outer surface in the middle of the molecule and hydrophilic amino acids on its outer surface on each end of the molecule.

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Question 19

You determine the transition temperatures for two membranes.The first has a transition temperature of 28°C,the second a transition temperature of 15°C.What can you conclude about the compositions of the two membranes?

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The answer of You determine the transition temperatures for two...

Question 20

A rat cell and a chimpanzee cell are fused together.Antibodies to chimpanzee membrane antigens are labeled with rhodamine (a red fluorescent molecule)and antibodies against rat antigens are labeled with fluorescein (a green fluorescent molecule).What do the cells look like immediately after fusion? What about 40 minutes later? If the temperature of the cell is increased,what should happen?

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The answer of A rat cell and a chimpanzee cell...

Quiz 4: The Structure and Function of the Plasma Membrane