Bio Chapter 7 test
Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?
A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.
Which of the following allows water to move much faster across cell membranes?
Aquaporins
Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?
CO2
According to the fluid mosaic model of cell membranes, phospholipids
Can move laterally along the plane of 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 phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane—more acidic outside the cell than inside the cell. Phosphate transport is an example of _____.
Cotransport
In some cells, there are many ion electrochemical gradients across the plasma membrane even though there are usually only one or two proton pumps present in the membrane. The gradients of the other ions are most likely accounted for by _____.
Cotransport proteins
Which of the following is true of osmosis?
In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration.
A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in _____.
Lysosomes
Which of the following most accurately describes selective permeability?
Only certain molecules can cross a cell membrane.
Which of the following processes includes all others?
Passive transport
You have a planar bilayer with equal amounts of saturated and unsaturated phospholipids. After testing the permeability of this membrane to glucose, you increase the proportion of unsaturated phospholipids in the bilayer. What will happen to the membrane's permeability to glucose?
Permeability to glucose will increase.
An organism with a cell wall would most likely be unable to take in materials through _____.
Phagocytosis
White blood cells engulf bacteria using _____.
Phagocytosis
Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this most probably mean?
Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life.
What kinds of molecules pass through a cell membrane most easily?
Small and hydrophobic
Which of the following is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures?
The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.
A patient was involved a serious accident and lost a large quantity of blood. In an attempt to replenish body fluids, distilled water—equal to the volume of blood lost—is added to the blood directly via one of his veins. What will be the most probable result of this transfusion?
The patient's red blood cells will swell and possibly burst because the blood has become hypotonic compared to the cells.
Cell membranes are asymmetrical. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?
The two sides of a cell membrane face different environments and carry out different functions.
Why are lipids and proteins free to move laterally in membranes?
There are only weak hydrophobic interactions in the interior of the membrane.
When a cell is in equilibrium with its environment, which of the following occurs for substances that can diffuse through the cell?
There is random movement of substances into and out of the cell.
Which of the following would increase the electrochemical gradient across a membrane?
a proton pump
For a protein to be an integral membrane protein, it would have to be _____.
amphipathic, with at least one hydrophobic region
Some regions of the plasma membrane, called lipid rafts, have a higher concentration of cholesterol molecules. At higher temperatures, these regions _____.
are less fluid than the surrounding membrane
Singer and Nicolson's fluid mosaic model of the membrane proposed that membranes_____.
consist of protein molecules embedded in a fluid bilayer of phospholipids
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 which of the following?
hydrating drinks with high concentrations of salts and glucose
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
Diffusion _____.
is a passive process in which molecules move from a region of higher concentration to a region of lower concentration
The voltage across a membrane is called the _____.
membrane potential
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
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.
You are working on a team that is designing a new drug. 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 selectively enters the target cells?
similarity of the drug molecule to other molecules transported by the target cells
The force driving simple diffusion is _____, while the energy source for active transport is _____.
the concentration gradient; ATP
Ions diffuse across membranes through specific ion channels down _____.
their electrochemical gradients