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Chapter 7 - Flashcards

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Class:BSC 2010 - Bio I - Cellular Processes
Subject:Biological Sciences
University:University of South Florida
Term:Fall 2010
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If, after many hours, the protein distribution still looked like a hybrid cell (2 cells partially joined together), would you be able to conclude that proteins don't move within the membrane? what other explanation could there be? You couldn't rule out movement of proteins within the cell membrane of the same species. You might speculate that the membrane lipids and proteins from one species weren't able to mingle with those from the other species because of some incompatibility.
Some transmembrane proteins can bind to a particular extracellular matrix (ECM) molecule and, when bound, transmit a signal into the cell. Explain how this might occur. A transmembrane protein like the integrin dimer might change its shape upon binding to a particular ECM molecule. The new shape might enable the interior portion of the protein to bind to a second, cytoplasmic protein that would relay the mssage to the inside of the cell
If an orange dye capable of passing through the membrane was added to the left side of a tube of lower concentration of solute (sugar) how would it be distributed at the end of the process? would the solution levels in the tube on the side with the higher concentration of sugar be affected? The orange solute would be evenly distributed throughout the solution on both sides of the membrane. The solution levels would not be affected because the orange solute can diffuse through the membrane and equalize its concentration. Thus, no additional osmosis of water would take place in either direction.
The carbs attached to some proteins and lipids of the plasma membrane are added as the membrane is made and refined in the ER and Golgi app; the new membrane then forms transport vesicles that travel to the cell surface. On which side of the vesicle membrane are the carbs? They are on the inner side of the transport vesicle membrane
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How would you expect the saturation levels of membrane phospholipid fatty acids to differ in plants adapted to cold environments & plants adapted to hot environments? Plants adapted to cold environments would be expected to have more unsaturated fatty acids in their membranes because those remain fluid at lower temperatures. Plants adapted to hot environments would be expected to have more saturated fatty acids, which would allow the fatty acids to "stack" more closely, making the membranes less fluid and therefore helping them to stay intact at higher temperatures.
2 molecules that can cross a lipid bilayer without help from membrane proteins are O2 and CO2. What properties allow this to occur? O2 and CO2 are both small nonpolar molecules that can easily pass through the hydrophobic core of a membrane.
Why would water molecules need a transport protein to move rapidly and in large quantities across a membrane? Water is a polar molecule, so it cannot pass very rapidly through the hydrophobic region in the middle of a phospholipid bilayer.
Aquaporins exclude passage of hydronium ions (H+). but recent research has revealed a role for some aquaporins in fat metabolism, in which they allow passage of glycerol, a 3-carbon alcohol as well as H2O. since H+ is much closer in size to water than is glycerol, what do u suppose is the basis of this selectivity? THe hydronium (H+) is charged, while glycerol is not. Charge is probably more significant than size as a basis for exclusion by the aquaporin channel.
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How do you think a cell performing cellular respiration rids itself of the resulting CO2? CO2 is a small nonpolar molecule that can diffuse through the plasma membrane. as long as it diffuses away so the concentration remains low outsides the cell, it will continue to exit the cell in this way. (this is the opposite case for O2)
In the supermarket, produce is often sprayed with water. Explain why this makes vegetables look crisp. The water is hypotonic to the plant cells, so they take up water and the cells of the vegetable remain turgid, rather than plasmolyzing.
If a paramecium swims from a hypotonic environment to an isotonic one, will its contractile vacuole become more active or less? why? The activity of the paramecium's contractile vacuole will decrease. The vacuole pumps out excess water that flows into the cell; this flow occurs only in a hypotonic environment.
When nerve cells establish a voltage across their membrane with a sodium-potassium pump, does this pump use ATP or does it produce ATP? why? The pump uses ATP. To establish a voltage, ions have to be pumped against their gradients, which requires energy.
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Explain why the sodium-potassium pump would not be considered a cotransporter. Each ion is being transported against its electrochemical gradient. If either ion were flowing down its electrochemical gradient, this WOULD be considered cotransport
What would happen if cells had a channel protein allowing unregulated passage of hydrogen ions? Even if proton pumps were still using ATP and moving protons, no proton gradient would become established. This would have serious consequences for the cells, because processes like the cotranpsort of sucrose (as well as synthesis of ATP) depend on establishment of a proton gradient
As a cell grows, its plasma membrane expands. Does this involve endocytosis or exocytosis? exlain. EXOCYTOSIS. when a transport vesicle fuses with the plasma membrane, the vesicle membrane becomes part of the plasma membrane.
To send a signal, a neuron may carry out exocytosis of signaling molecules that are recognized by a second neuron. Iin some cases, the first neuron ends the signal by taking up the molecules by endocytosis. Would you expect this to occur by pinocytosis or by receptor-mediated endocytosis? explain Receptor-mediated endocytosis. In this case, one specific kind of molecule needs to be taken up at a particular time; pinocytosis takes up substances in a nonspecific manner.
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In what way do the membranes of a euk cell vary? Certain proteins are unique to each membrane
T/F: only certain membranes are constructed from amphiphatic molecules FALSE...they all are
According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly.... embedded in the lipid layer
Name a factor that would tend to increase membrane fluidity a greater proportion of unsaturated phospholipids! the other is higher temperature
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What process includes all the others out of this list? (osmosis, diffusion of a solute across a membrane, facilitated diffusion, passive transport, transport of an ion down its electrochemical gradient) PASSIVE TRANSPORT! (osmosis, diffusion of a solute across a membrane, facilitated diffusion and transport of an ion down its electrochemical gradient are all types of passive transport)
Name an experimental treatment that would increase the rate of sucrose transport into a cell decreasing extracellular pH! (ie making the outside of the cell more acidic)
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 If, after many hours, the protein distribution still looked like a hybrid cell (2 cells partially joined together), would you be able to conclude that proteins don't move within the membrane? what other explanation could there be?You couldn't rule out movement of proteins within the cell membrane of the same species. You might speculate that the membrane lipids and proteins from one species weren't able to mingle with those from the other species because of some incompatibility.
 Some transmembrane proteins can bind to a particular extracellular matrix (ECM) molecule and, when bound, transmit a signal into the cell. Explain how this might occur.A transmembrane protein like the integrin dimer might change its shape upon binding to a particular ECM molecule. The new shape might enable the interior portion of the protein to bind to a second, cytoplasmic protein that would relay the mssage to the inside of the cell
 If an orange dye capable of passing through the membrane was added to the left side of a tube of lower concentration of solute (sugar) how would it be distributed at the end of the process? would the solution levels in the tube on the side with the higher concentration of sugar be affected?The orange solute would be evenly distributed throughout the solution on both sides of the membrane. The solution levels would not be affected because the orange solute can diffuse through the membrane and equalize its concentration. Thus, no additional osmosis of water would take place in either direction.
 The carbs attached to some proteins and lipids of the plasma membrane are added as the membrane is made and refined in the ER and Golgi app; the new membrane then forms transport vesicles that travel to the cell surface. On which side of the vesicle membrane are the carbs?They are on the inner side of the transport vesicle membrane
 How would you expect the saturation levels of membrane phospholipid fatty acids to differ in plants adapted to cold environments & plants adapted to hot environments?Plants adapted to cold environments would be expected to have more unsaturated fatty acids in their membranes because those remain fluid at lower temperatures. Plants adapted to hot environments would be expected to have more saturated fatty acids, which would allow the fatty acids to "stack" more closely, making the membranes less fluid and therefore helping them to stay intact at higher temperatures.
 2 molecules that can cross a lipid bilayer without help from membrane proteins are O2 and CO2. What properties allow this to occur?O2 and CO2 are both small nonpolar molecules that can easily pass through the hydrophobic core of a membrane.
 Why would water molecules need a transport protein to move rapidly and in large quantities across a membrane?Water is a polar molecule, so it cannot pass very rapidly through the hydrophobic region in the middle of a phospholipid bilayer.
 Aquaporins exclude passage of hydronium ions (H+). but recent research has revealed a role for some aquaporins in fat metabolism, in which they allow passage of glycerol, a 3-carbon alcohol as well as H2O. since H+ is much closer in size to water than is glycerol, what do u suppose is the basis of this selectivity?THe hydronium (H+) is charged, while glycerol is not. Charge is probably more significant than size as a basis for exclusion by the aquaporin channel.
 How do you think a cell performing cellular respiration rids itself of the resulting CO2?CO2 is a small nonpolar molecule that can diffuse through the plasma membrane. as long as it diffuses away so the concentration remains low outsides the cell, it will continue to exit the cell in this way. (this is the opposite case for O2)
 In the supermarket, produce is often sprayed with water. Explain why this makes vegetables look crisp.The water is hypotonic to the plant cells, so they take up water and the cells of the vegetable remain turgid, rather than plasmolyzing.
 If a paramecium swims from a hypotonic environment to an isotonic one, will its contractile vacuole become more active or less? why?The activity of the paramecium's contractile vacuole will decrease. The vacuole pumps out excess water that flows into the cell; this flow occurs only in a hypotonic environment.
 When nerve cells establish a voltage across their membrane with a sodium-potassium pump, does this pump use ATP or does it produce ATP? why?The pump uses ATP. To establish a voltage, ions have to be pumped against their gradients, which requires energy.
 Explain why the sodium-potassium pump would not be considered a cotransporter.Each ion is being transported against its electrochemical gradient. If either ion were flowing down its electrochemical gradient, this WOULD be considered cotransport
 What would happen if cells had a channel protein allowing unregulated passage of hydrogen ions?Even if proton pumps were still using ATP and moving protons, no proton gradient would become established. This would have serious consequences for the cells, because processes like the cotranpsort of sucrose (as well as synthesis of ATP) depend on establishment of a proton gradient
 As a cell grows, its plasma membrane expands. Does this involve endocytosis or exocytosis? exlain.EXOCYTOSIS. when a transport vesicle fuses with the plasma membrane, the vesicle membrane becomes part of the plasma membrane.
 To send a signal, a neuron may carry out exocytosis of signaling molecules that are recognized by a second neuron. Iin some cases, the first neuron ends the signal by taking up the molecules by endocytosis. Would you expect this to occur by pinocytosis or by receptor-mediated endocytosis? explainReceptor-mediated endocytosis. In this case, one specific kind of molecule needs to be taken up at a particular time; pinocytosis takes up substances in a nonspecific manner.
 In what way do the membranes of a euk cell vary?Certain proteins are unique to each membrane
 T/F: only certain membranes are constructed from amphiphatic moleculesFALSE...they all are
 According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly....embedded in the lipid layer
 Name a factor that would tend to increase membrane fluiditya greater proportion of unsaturated phospholipids!

the other is higher temperature
 What process includes all the others out of this list? (osmosis, diffusion of a solute across a membrane, facilitated diffusion, passive transport, transport of an ion down its electrochemical gradient)PASSIVE TRANSPORT! (osmosis, diffusion of a solute across a membrane, facilitated diffusion and transport of an ion down its electrochemical gradient are all types of passive transport)
 Name an experimental treatment that would increase the rate of sucrose transport into a celldecreasing extracellular pH! (ie making the outside of the cell more acidic)
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