bio quiz 5 on lecture 7
In the term "fluid mosaic model"
"fluid" means the membrane is fluid and "mosaic" means the membrane has different proteins embedded in it or attached to it
Why would a doctor inject a dilute salt solution rather than pure water into the bloodstream of a patient who has suffered severe blood loss?
Because pure water might cause the patient's red blood cells to burst.
Cell membranes are asymmetrical. Which of the following is most likely to explain part of the reason for this asymmetry?
Cell membrane proteins are inserted into the rough ER membrane with a certain orientation as they are being synthesized.
In what way do the membranes of eukaryotic cells vary?
Certain proteins are unique to each membrane.
Which of the following would require an energy expenditure?
Correct Answer all of these answers are correct
Which of the following statements about membranes is FALSE?
Exocytosis results in net transfer of materials into the cell
Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from glucose-rich foods into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?
Facilitated diffusion
Of the following functions, which is most important for the glycoproteins and glycolipids in animal cell membranes?
Helping cells distinguish one type of neighboring cell from another.
Which of the following is a characteristic feature of a carrier protein in a plasma membrane?
It exhibits specificity for a particular type of molecule.
Which of the following statements about diffusion is TRUE?
It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration
Which of the following statements is FALSE?
Lipids comprise >90% of membrane material
Which of the following membrane activities requires a direct input of energy from ATP hydrolysis?
Nat+ ions moving out of the cell
Which of the following shows the correct pathway for synthesis of plasma membrane proteins?
Rough ER to vesicle to Golgi to vesicle to plasma membrane
Which pathway is generally followed by a lipid molecule for incorporation in the endomembrane system?
Smooth ER and/or rough ER, vesicle, Golgi, vesicle
Carbohydrates attached to some proteins and lipids of the plasma membrane are added as the membrane is made and refined in the ER and Golgi apparatus: the new membrane then forms transport vesicles that travel to the cell surface. Which of the following statements is TRUE?
The carbohydrates that are part of the glycolipid and glycoprotein molecules will be on the inside of the vesicle and then on the outside (extracellular side) of the plasma membrane.
Why do grocery stores spray vegetables with water?
The cells of the vegetables will absorb water and expand against their cell walls, making the vegetables crisper.
Use the diagram below to help answer this question. The diagram shows a U-tube, with the two arms of the tube separated at the bottom by a semi-permeable barrier. This semi-permeable barrier is permeable to water and glucose, but not to sucrose. If you add 1 liter of an aqueous solution containing 2 moles of sucrose and 1 mole of glucose to side "A" of the tube, and 1 liter of an aqueous solution containing 1 mole of sucrose and 2 moles of glucose to side "B" of the tube, after the system reaches equilibrium, what changes are observed?
The concentration of glucose on side A is 1.5 M and the concentration of sucrose on side A is less than 2 M.
Which of the following is a reasonable explanation for why unsaturated lipids help keep membranes more fluid at lower temperatures?
The double bonds form kinks in the hydrocarbon chains, forcing adjacent lipid molecules to be further apart.
Use the diagram below to help answer this question. The diagram shows a U-tube, with the two arms of the tube separated at the bottom by a selectively permeable barrier. This selectively permeable barrier is permeable to water and glucose, but not to sucrose. If you add 1 liter of water, 2 moles of sucrose and 1 mole of glucose to side "A" of the tube, and 1 liter of water, 1 mole of sucrose and 2 moles of glucose to side "B" of the tube, after the system reaches equilibrium, what changes are observed?
The water level is higher on side A than on side B.
Why are lipids and some proteins free to move laterally in membranes?
There are only weak hydrophobic interactions in the interior of the membrane.
Which of the following statements regarding integral membrane proteins is TRUE?
They are usually transmembrane proteins.
According to the fluid mosaic model of cell membranes, which of the following statements about membrane phospholipids is TRUE?
They can move laterally along the plane of the membrane.
According to the fluid mosaic model of cell membranes, which of the following statements about membrane phospholipids is TRUE? According to the fluid mosaic model of cell membranes, which of the following statements about membrane phospholipids is TRUE?
They can move laterally along the plane of the membrane.
Which of the following is a form of ACTIVE transport?
Transport by a cotransporter
Which of the following illustrates the concept of "selective permeability"?
a bouncer at a club who only admits appropriately dressed people an usher who only admits people with tickets a screen that keeps out flies but not midges Correct!: all of these answers are correct
Which of the following factors would tend to increase membrane fluidity?
a greater proportion of unsaturated phospholipids
Which of the following will decrease the temperature at which the membranes of your cells will solidify?
adding more unsaturated fatty acids to the phospholipids composing your membranes Correct Answer: all of these answers are correct adding cholesterol to the membranes adding more fatty acids with double bonds to the phospholipids composing your membranes
In order for a protein to be a transmembrane protein it would have to be which of the following?
amphipathic
Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold?
by increasing the percentage of unsaturated phospholipids in the membrane
An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function?
cell-cell recognition
Sucrose-H+ cotransporters transport sucrose and H+ from outside to inside of a cell. Which of the following would increase the rate of sucrose transport into the cell?
decreasing the pH of the solution outside of the cell
Ions always diffuse across membranes down their
electrochemical gradients
According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly
embedded in the lipid bilayer
The presence of cholesterol in the plasma membranes of some animals
enables the membrane to stay fluid more easily when cell temperature drops.
A white blood cell might "eat" a bacteria through the process of
endocytosis
Which of the following would be the most likely mechanism used by a protein exiting a cell?
exocytosis
Channel proteins
form "corridors" that allow specific ions or molecules to cross membranes
Lipid molecules that have carbohydrates attached to them are known as
glycolipids
The two layers of a lipid bilayer
have almost identical lipid compositions as lipid molecules can move freely between the two layers are similar in terms of the types and numbers of their integral membrane proteins as proteins can move freely between the two layers have both similar lipid and integral membrane protein compositions Correct Answer: none of these answers are correct
Amphipathic molecules
have both hydrophilic and hydrophobic regions
Use the diagram below to help answer this question. The diagram shows a U-tube, with the two arms of the tube separated at the bottom by a selectively permeable barrier. This selectively permeable barrier is permeable to water, but not to glucose or sucrose. If you add 3 liters of an aqueous solution containing 2 moles of sucrose and 1 mole of glucose to side "A" of the tube, and 1 liter of an aqueous solution containing 1 mole of sucrose and 2 moles of glucose to side "B" of the tube, the solution in side A with respect to that in side B is
hypotonic
What are the membrane structures that function in active transport?
integral proteins
Water passes quickly through cell membranes because
it moves through aquaporins in the membrane.
A lipid molecule that starts on the inside face of the ER membrane (i.e. the side of the ER membrane that is NOT in contact with the cytosol) and is then transported to the plasma membrane will
most likely end up on the outside (extracellular) face of the plasma membrane
Which of the following membrane activities do NOT require energy from ATP hydrolysis?
movement of solutes by channel proteins Correct Answer all of these answers are correct passive diffusion movement of solutes by carrier proteins
When a hydrogen ion (= a proton) enters a cell, it is
moving down its electrochemical gradient as the hydrogen ion concentration is greater outside of cells and the outsides of cells are positively charged relative to the insides
The sucrose-H+ cotransporter is able to transport sucrose molecules up their concentration gradient, into cells, because
of the energy gained by simultaneously transporting an H+ down its electrochemical gradient
Which of the following processes includes all the others?
passive transport
Which of these are not embedded in the lipid bilayer at all?
peripheral proteins
An organism with a cell wall would have the most difficulty doing which process?
phagocytosis
Which of the following types of molecules are the major structural components of the cell membrane?
phospholipids and proteins
Which of the following membrane activities require energy from ATP hydrolysis?
proton pumps
You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule enters the cell?
similarity of the drug molecule to other molecules transported by the target cells.
What kinds of molecules can pass through a cell membrane most easily?
small and hydrophobic
When a plant cell is submerged in a very hypotonic solution, what is likely to occur?
the cell will become turgid (solid, due to being inflated)
Osmosis refers to
the diffusion of water across a selectively permeable barrier
As material diffuses across a membrane from the side of higher concentration to the side of lower concentration,
the free energy of the system decreases.
Use the diagram below to help answer this question. The diagram shows a U-tube, with the two arms of the tube separated at the bottom by a selectively permeable barrier. This selectively permeable barrier is permeable to water but not to any ions. If you add 1 liter of an aqueous solution containing 1 mole of MgCl2 to side "A" and you add 1 liter of an aqueous solution containing 1 mole of NaCl to side "B", immediately after adding the solutions to the U-tube,
the solution in side "A" will be hypertonic compared with the solution in side "B"
Use the diagram below to help answer this question. The diagram shows a U-tube, with the two arms of the tube separated at the bottom by a selectively permeable barrier. This selectively permeable barrier is permeable to water, but not to glucose. If you add 1 liter of an aqueous solution containing 1 mole of glucose to side "A" and you add 1 liter of an aqueous solution containing 1 mole of glucose to side "B",
there will be no net flow of water between the two sides of the tube
Use the diagram below to help answer this question. The diagram shows a U-tube, with the two arms of the tube separated at the bottom by a selectively permeable barrier. This selectively permeable barrier is permeable to water but not to any ions. If you add 1 liter of an aqueous solution containing 1 mole of MgCl2 to side "A" and you add 1 liter of an aqueous solution containing 1 mole of NaCl to side "B", at equilibrium
there will have been a net flow of water from side "B" to side "A"
Use the diagram below to help answer this question. The diagram shows a U-tube, with the two arms of the tube separated at the bottom by a selectively permeable barrier. This selectively permeable barrier is permeable to water but not to glucose. If you add 1 liter of an aqueous solution containing 2 moles of glucose to side "A" and you add 1 liter of an aqueous solution containing 1 mole of glucose to side "B", what will have happened in order for the system to reach equilibrium?
there will have been a net flow of water from side "B" to side "A"
Which of the following span the phospholipid bilayer, usually a number of times?
transmembrane proteins
Cotransporters
transport two different types of molecules, with one moving down its concentration or electrochemical gradient and the other moving up
