Chapter 7 test - AP bio
After a membrane freezes and then thaws, it often becomes leaky to solutes. The most reasonable explanation for this is that
After a membrane freezes and then thaws, it often becomes leaky to solutes. The most reasonable explanation for this is that
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.
Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?
CO2
Cell membranes are asymmetrical. Which of the following is a most likely explanation?
Cell membrane proteins are determined as the membrane is being packaged in the ER and Golgi.
Who was/were the first to propose that cell membranes are phospholipid bilayers?
Gorter and F. Grendel
Who proposed that membranes are a phospholipid bilayer between two layers of hydrophilic proteins?
H. Davson and J. Danielli
Why are lipids and proteins free to move laterally in membranes?
Hydrophilic portions of the lipids are in the interior of the membrane.
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.
The formulation of a model for a structure or for a process serves which of the following purposes?
It functions as a testable hypothesis.
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.
Who proposed that the membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids?
S. Singer and G. Nicolson
Which of the following statements 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.
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 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.
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 patientʹs red blood cells will swell because the blood fluid is hypotonic compared to the cells.
Which of the following is true of integral membrane proteins?
They are usually transmembrane proteins.
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.
Of the following functions, which is most important for the glycoproteins and glycolipids of animal cell membranes?
a cellʹs ability to distinguish one type of neighboring cell from another
In order for a protein to be an integral membrane protein it would have to be which of the following?
amphipathic
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
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
The presence of cholesterol in the plasma membranes of some animals
enables the membrane to stay fluid more easily when cell temperature drops.
Which of these often serve as receptors or cell recognition molecules on cell surfaces?
glycoproteins
Chloride ion channels are membrane structures that include which of the following?
hydrophilic proteins
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 but hypotonic to the salt solution.
If a young male child has cystic fibrosis, which of the following would affect his fertility?
incorrect concentrations of ions in semen
When a membrane is 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 these are attached to the extracellular matrix?
integrins
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 not actively transported into the cell, which of the following terms describes the tonicity of the external solution relative to the cytoplasm of the cell?
isotonic
Water passes quickly through cell membranes because
it moves through aquaporins in the membrane.
Which of these are not embedded in the lipid bilayer at all?
peripheral proteins
Which of the following types of molecules are the major structural components of the cell membrane?
phospholipids and proteins
What kinds of molecules pass through a cell membrane most easily?
small and hydrophobic
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.
Which of the following span the phospholipids bilayer, usually a number of times?
transmembrane proteins
