Which of the following types of molecules are the major structural component of the cell membrane?
phospholipids and proteins
When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that
the hydrophobic interactions that hold the membrane together are weakest at this point
The presence of cholesterol in the plasma membranes of some animals
enables the membrane to stay fluid more easily when cell temperatures drop
According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?
they can move laterally along the plane of the membrane
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
In order for a protein to be an integral membrane protein it would have to be which of the following?
amphipathic
When a membrane you freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are
integral proteins
Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures?
the double bonds form kinks in the fatty acid tails, forcing adjacent lipids to be further apart
Which of the following is true of integral membrane proteins?
they are usually transmembrane proteins
Of the following function, which is most important for the glycoproteins and glycolipids of animal cell membranes?
a cell ability to distinguish one type of neighboring cell from another
An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function?
cell-cell recognition
In the years since the proposal of the fluid mosaic model of the cell membrane, which of the following observations has been added to the model?
the concentration of protein molecules is now known to be much higher
Which of the following span the phospholipids bilayer, usually a number of times?
transmembrane proteins
Which of these are not embedded in the lipid bilayer at all?
peripheral proteins
Which of these are attached to the extracellular matrix?
integrins
Which of these often serve as receptors or cell recognition molecules on cell surfaces?
glycoproteins
The formulation of a model for a structure or for a structure or for a process serves which of the following purposes?
It functions as a testable hypothesis
Cell membranes are asymmetrical. Which of the following is a most likely explanation?
Cell membranes proteins are determined as the membrane is being packaged in the ER and Golgi
Which of the following is true of the evolution of cell membranes?
As populations of organisms evolve, different properties of their cell membranes are selected for or against
Why are lipids and proteins free to move laterally in membranes?
Hydrophilic portions of the lipids are in the interior of the membrane
What kinds of molecules pass through a cell membrane most easily?
small and hydrophobic
Which of the following is a characteristic feature of a carrier protein in a plasma membrane?
It exhibits a specificity for a particular type of molecule
After a membrane freezes then thaws, it often becomes leaky to solutes. The most reasonable explanation for this is that
the integrity of the lipid bilayer is broken when the membrane freezes
Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?
CO2
Which of the following statements is correct about diffusion?
It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration
Water passes quickly through cell membranes because
it moves through aquaporins in the membrane
Cystic fibrosis is a genetic disease in humans in which chloride ion channels in cell membranes are
missing or nonfunctional.
Chloride ion channels are membrane structures that include which of the following?
hydrophilic proteins
Cystic fibrosis is a genetic disease in humans in which chloride ion channels in cell membranes are
missing or nonfunctional.
Which of the following would you expect to be a problem for someone with nonfunctional chloride channeling?
buildup of excessive secretions in organs such as lungs
Cystic fibrosis is a genetic disease in humans in which chloride ion channels in cell membranes are
missing or nonfunctional.
If a young male has cystic fibrosis, which of the following would affect his fertility?
incorrect concentrations of ions in semen
A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water, equal to the volume of blood lost, is transferred directly into one of his veins. What will be the most probably result of this transfus
The patient's red blood cells will swell because the blood fluid is hypotonic compared to the cells
Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are
hypertonic to fresh water by hypotonic to the salt solution
A cell whose cytoplasm has a concentration of 0.02 molar glucose is placed in a test tube of water containing 0.02 molar glucose. Assuming that glucose is nor actively transported into the cell, which of the following terms describes the tonicity of the e
isotonic
Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells?
The animal cells is in an isotonic solution, and that the plant cell is in a hypotonic solution
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
In which of the following would there be the greatest need for osmoregulation?
a terrestrial animal such as a snake
When a plant cell, such as one from a peony stem, is submerged in a very hypotonic solution, what is likely to occur?
the cell will become turgid
Which of the following membrane activities require energy from ATP hydrolysis?
Na? ions moving out of the cell
What are the membrane structures that function in active transport?
integral proteins
Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport
facilitated diffusion
What is the voltage across across a membrane called?
membrane potential
In most cells, there are electrochemical gradients of many ions across the plasma membrane even though there are usually only one or two electrogenic pumps present in the membrane. The gradients of the other ions are most likely accounted for by
cotransport proteins
The sodium-potassium pump is called an electrogenic pump because it
contributes to the membrane potential
If a membrane protein in an animal cell is involved in the cotransport of glucose and sodium ions into the cell, which of the following is most likely true?
a substance that blocked sodium ions from binding to the cotransport protein would also block the transport of glucose
The movement of potassium into an animal cell requires
an energy source such as ATO or a proton gradient
Ions diffuse across membranes down their
electrochemical gradients
What mechanisms do plants use to load sucrose produced by photosynthesis into specialized cells in the veins of leaves
an electrogenic pump, a proton pump, a cotransport protein
The sodium-potassium pump in animal cells requires a cytoplasmic ATP to pump ions across the plasma membrane. When the proteins of the pump are first synthesized in the rough ER, what side of the ER membrane will the ATP binding site be on?
It will be on the cytoplasmic side of the ER
Proton pumps are used in various ways by members of every kingdom of organisms. What does this most probably mean?
cells with proton pumps were maintained in each Kingdom by natural selection
Several seriously epidemic viral diseases of earlier centuries were then incurable because they resulted in severe dehydration due to vomiting and diarrhea. Today they are unusually not fatal because we have developed which of the following?
hydrating drinks that include high concentrations of salts and glucose
An organism with a cell wall would have the most difficulty doing which process?
phagocytosis
White blood cells engulf bacteria through what process?
phagocytosis
Familial hypercholesterolemia is characterized by which of the following?
defective LDL receptors on the cell membranes
The difference between pinocytosis and receptor-mediated endocytosis is that
pinocytosis brings only water into the cell, but receptor-mediated endocytosis brings in other molecules as well
In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis?
on the inside surface of the vesicle