In order for a protein to be an integral membrane protein it would have to be
amphipathic, with at least one hydrophobic region
Cell membranes are asymmetrical. What is the most likely explanation?
the two sides of a cell membrane face different environments and carry out different functions
What statement correctly describes the normal tonicity conditions for typical plant and animal cells?
The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution.
Several epidemic microbial diseases of earlier centuries incurred high death rates because they resulted in severe dehydration due to vomiting and diarrhea. Today they are usually not fatal because we have developed what?
hydrating drinks that include high concentrations of salts and glucose
How would the lack of a functional chloride channel in cystic fibrosis patients affect sodium ion transport and the volume of the airway surface liquid?
Sodium ion transport will decrease; lower osmotic potential will decrease airway surface liquid volume
What factor would tend to increase membrane fluidity?
a greater proportion of unsaturated phopholipids
What 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, preventing adjacent lipids from packing tightly
What is not embedded in the hydrophobic portion of the lipid bilayer at all?
What statement 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
The sodium-potassium pump in animal cells require 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?
on the cytoplasmic side of the ER
Some regions of the plasma membrane, called lipid rafts, have a higher concentration of cholesterol molecules. As a result, these lipid rafts
are more rigid than the surrounding membrane
According to the fluid mosaic model of cell membranes, what is a true statement about membrane phopholipids?
They can move laterally along the plane of the membrane
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
An animal cell lacking oligosaccharides on the external surface of its plasma membrane would like be impaired in which function?
What is true of integral membrane proteins?
They are usually transmembrane proteins
Nitrous oxide gas molecules diffusing across a cell's plasma membrane is an example of
diffusion across the lipid bilayer
What would increase the electrochemical potential across a membrane?
a proton pump
If the sodium ion concentration outside the cell increases, and the CFTR channel is open, in what direction will chloride ions and water move across the cell membrane?
both chloride ions and water will move out of the cell
What types of molecules are the major structural components of the cell membrane?
phopholipids and proteins
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
Mammalian blood contains the equivalent of 0.15M NaCl. Seawater contains the equivalent of 0.45M NaCl. What will happen if red blood cells are transferred to seawater?
Water will leave the cells, causing them to shrivel and collapse
What would be the greatest need for osmoregulation?
Cells of a tidepool animal such as an anemone
The movement of potassium into an animal cell requires
an energy source such as ATP
Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this probably mean?
Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life
The presence of cholesterol in the plasma membranes of some animals
enables the membrane to stay fluid more easily when cell temperature drops
What is one way that the membranes of winter wheat are able to remain fluid when it is extremely cold?
by increasing the percentage of unsaturated phopholipids in the membrane
When a membrane is freeze fractured, the bilayer splits down the middle between the two layers of phopholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are
The primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell membranes is
to mediate cell-to-cell recognition
The formulation of a model for a structure or for a process serves which of the following purposes?
It functions as a testable hypothesis
Ions diffuse across membranes through specific ion channels
down their electrochemical gradients
Using live-cell fluorescence microscopy, researchers observed that a red fluorescent spot moved from the plasma membrane into the interior of target cells when red fluorescent dye-labeled HIV was added to the cells. What is the best conclusion from these observations?
The hypothesis that HIV enters the cell via fusion with the target cell plasma membrane is not supported
The cell membranes of Antarctic ice fish might have what adaptation?
a high percentage of polyunsaturated fatty acids
What would likely move through the lipid bilayer of a plasma membrane most rapidly?
Cystuc fribrosis is a genetic disease in humans in which the CFTR protein, which functions as a chloride ion channel, is missing or nunfunctional in cell membranes. The CFTR protein belongs to what category of membrane proteins?
electrogenic ion pumps
A protein that spans the phospholipid bilayer one or more times is
a transmembrane protein
In a paramecium, cell surface integral membrane proteins are synthesized
by ribosomes bound to the rough endoplasmic reticulum (rough ER)
What is a characteristic feature of a carrier protein in a plasma membrane?
it exhibits a specificity for a particular type of molecule
What is true of the evolution of cell membranes?
All components of membranes evolve in response to natural selection
The difference between pinocytosis and receptor-mediated endocytosis is that
pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity
embedded in a lipid bilayer
decreasing extracellular pH
Why are lipids and proteins free to move laterally in membranes?
there are only weak hydrophobic interactions in the interior of the membrane
The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phophate outside the cell is much lower than the cytoplasmic phophate concentration. Phophate import depends on a pH gradient across the membrane-more acidic outside the cell than inside the cell. Phophate transport is an example of
Glucose diffuses slowly through artificial phopholipid 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 info, which transport mechanism is most probably functioning the intestinal cells?
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
An organism with a cell wall would most likely be unable to take in materials through
What kinds of molecules pass through a cell membrane most easily?
small and hydrophobic
Water passes quickly through cell membranes because
it moves through aquaporins in the membrane
Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a 0.15M salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are
hypertonic to fresh water but not hypotonic to the solution
What membrane activity requires energy from ATP hydrolysis?
Na+ ions moving out of a mammalian cell bathed in physiological saline
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
The sodium-potassium pump is called an electrogenic pump because it
contributes to the membrane potential
What is the voltage across a membrane called?
White blood cells engulf bacteria through what process?
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
A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in
the water level is higher in side A than in side B
side A is hypotonic to side B
a decrease in the concentration of NaCl and a decrease in the water level
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 probable result of this transfusion?
The patient's red blood cells will swell because the blood fluid has become hypotonic compared to the cells
You are working on a new team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. What would be a factor that determines whether the molecule selectively enters the target cells?
similarity of the drug molecule to other molecules transported by the target cells
In what way do the membranes of a eukaryotic cell vary?
certain proteins are unique to each membrane
Want to see the other 68 Flashcards in Chapter 7 Questions?JOIN TODAY FOR FREE!