Chapter Questions
A doctor injects a patient with what the doctor thinks is an isotonic saline solution. The patient dies, and an autopsy reveals that many red blood cells have been destroyed. Do you think the Solution the doctor injected was really isotonic?
Injecting a potassium solution into a person's blood is lethal. Capital punishment and euthanasia utilize this method in their subjects. Why do you think a potassium solution injection is lethal?
If the pH outside the cell decreases, would you expect the amount of amino acids transported into the cell to increase or decrease? a. its headb. cholesterolc. a saturated fatty acid taild. double bonds in the fatty acid tail
Which plasma membrane component can be either found on its surface or embedded in the membrane structure?a. proteinb. cholesterolc. carbohydrated. phospholipid
Which characteristic of a phospholipid contributes to the fluidity of the membrane?a. its headb. cholesterolc. a saturated fatty acid taild. double bonds in the fatty acid tail
What is the primary function of carbohydrates attached to the exterior of cell membranes?a. identification of the cellb. flexibility of the membranec. strengthening the membraned. channels through membrane
A scientist compares the plasma membrane composition of an animal from the Mediterranean coast with one from the Mojave Desert. Which hypothesis is most likely to be correct?a. The cells from the Mediterranean coast animal will have more fluid plasma membranes.b. The cells from the Mojave Desert animal will have a higher cholesterol concentration in the plasma membranes.c. The cells' plasma membranes will be indistinguishable.d. The cells from the Mediterranean coast animal will have a higher glycoprotein content, while the cells from the Mojave Desert animal will have a higher lipoprotein content.
Water moves via osmosis _____________ .a. throughout the cytoplasmb. from an area with a high concentration of other solutes to a lower onec. from an area with a high concentration of water to one of lower concentrationd. from an area with a low concentration of water to higher concentration
The principal force driving movement in diffusion is the ______________a. temperature b. particle size c. concentration gradient d. membrane surface area
What problem is faced by organisms that live in fresh water?a. Their bodies tend to take in too much water.b. They have no way of controlling their tonicity.c. Only salt water poses problems for animals that live in it.d. Their bodies tend to lose too much water to their environment.
In which situation would passive transport not use a transport protein for entry into a cell?a. water flowing into a hypertonic environmentb. glucose being absorbed from the bloodc. an ion flowing into a nerve cell to create an electrical potentiald. oxygen moving into a cell after oxygen deprivation
Active transport must function continuously becausea. plasma membranes wear outb. not all membranes are amphiphilicc. facilitated transport opposes active transportd. diffusion is constantly moving solutes in opposite directions
How does the sodium-potassium pump make the interior of the cell negatively charged?a. by expelling anionsb. by pulling in anionsc. by expelling more cations than are taken ind. by taking in and expelling an equal number of cations
What is the combination of an electrical gradient and a concentration gradient called?a. potential gradientb. electrical potentialc. concentration potentiald. electrochemical gradient
What happens to the membrane of a vesicle after exocytosis?a. It leaves the cell.b. It is disassembled by the cell.c. It fuses with and becomes part of the plasma membrane.d. It is used again in another exocytosis event.
Which transport mechanism can bring whole cells into a cell?a. pinocytosisb. phagocytosisc. facilitated transportd. primary active transport
In what important way does receptor-mediated endocytosis differ from phagocytosis?a. It transports only small amounts of fluid.b. It does not involve the pinching off of membrane.c. It brings in only a specifically targeted substance.d. It brings substances into the cell, while phagocytosis removes substances.
Many viruses enter host cells through receptormediated endocytosis. What is an advantage of this entry strategy?a. The virus directly enters the cytoplasm of the cell.b. The virus is protected from recognition by white blood cells.c. The virus only enters its target host cell type.d. The virus can directly inject its genome into the cell's nucleus.
Which of the following organelles relies on exocytosis to complete its function?a. Golgi apparatusb. vacuolec. mitochondriad. endoplasmic reticulum
Imagine a cell can perform exocytosis, but only minimal endocytosis. What would happen to the cell?a. The cell would secrete all its intracellular proteins.b. The plasma membrane would increase in size over time.c. The cell would stop expressing integral receptor proteins in its plasma membrane.d. The cell would lyse.
Why is it advantageous for the cell membrane to be fluid in nature?
Why do phospholipids tend to spontaneously orient themselves into something resembling a membrane?
How can a cell use an extracellular peripheral protein as the receptor to transmit a signal into the cell?
Discuss why the following affect the rate of diffusion: molecular size, temperature, solution density, and the distance that must be traveled.
Why does water move through a membrane?
Both of the regular intravenous solutions administered in medicine, normal saline and lactated Ringer's solution, are isotonic. Why is this important?
Describe two ways that decreasing temperature would affect the rate of diffusion of molecules across a cell's plasma membrane.
A cell develops a mutation in its potassium channels that prevents the ions from leaving the cell.If the cell's aquaporins are still active, what will happen to the cell? Be sure to describe the tonicity and osmolarity of the cell.
Where does the cell get energy for active transport processes?
How does the sodium-potassium pump contribute to the net negative charge of the interior of the cell?
Glucose from digested food enters intestinal epithelial cells by active transport. Why would intestinal cells use active transport when most body cells use facilitated diffusion?
The sodium/calcium exchanger (NCX) transports sodium into and calcium out of cardiac muscle cells. Describe why this transporter is classified as secondary active transport.
Why is it important that there are different types of proteins in plasma membranes for the transport of materials into and out of a cell?
Why do ions have a difficult time getting through plasma membranes despite their small size?