Chapter 5 Practice Test
The source of phosphate for a phosphorylation cascade is __________.
ATP
Which of these statements describes some aspect of facilitated diffusion?
Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane.
Which of the following is FALSE in regard to facilitated diffusion?
Facilitated diffusion requires the hydrolysis of ATP.
A G protein is active when __________.
GTP is bound to it
Nitric oxide is unusual among animal signal molecules in that it __________.
is a gas
What event would activate a G protein?
replacement of GDP with GTP
Which statement(s) about the sidedness of the plasma membrane is/are correct?
*All of the listed responses are correct. Every integral membrane protein has a specific orientation in the plasma membrane. The two lipid layers may differ in specific lipid composition. The asymmetrical distribution of membrane proteins, lipids, and carbohydrates across the plasma membrane is determined as the membrane is being constructed. Parts of proteins that are exposed on the cytoplasmic side of the endoplasmic reticulum are also exposed on the cytoplasmic side of the plasma membrane.
Steroid hormones can enter a cell by simple diffusion. Therefore steroids __________.
*None of the listed responses is correct. move up a concentration and are polar move through a channel, down a gradient, and are nonpolar move down a concentration gradient and are polar move up a concentration gradient and are nonpolar
The internal solute concentration of a plant cell is about 0.8 M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what solution?
1.0 M
Green olives may be preserved in brine, which is a 30% salt solution. How does this method of preservation prevent microorganisms from growing in the olives?
A 30% salt solution is hypertonic to the bacteria, so they lose too much water and plasmolyze.
Which of the following is a correct difference between active transport and facilitated diffusion?
Active transport requires energy from ATP, and facilitated diffusion does not.
Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B; cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell __________ because __________.
B ... the diffusion gradient in cell B is steeper
Which of the following statements about cotransport of solutes across a membrane is correct?
Cotransport proteins can couple the "downhill" diffusion of the solute to the "uphill" transport of a second substance against its own concentration gradient.
Which of the following correctly describes a general property of all electrogenic pumps?
It creates a voltage difference across the membrane.
Which of the following statements about diffusion is true?
It is a passive process of a substance across a membrane with no energy investment
Which of the following statements concerning carbohydrates associated with the plasma membrane is correct?
Membrane carbohydrates function primarily in cell-cell recognition.
Testosterone and estrogen are lipid-soluble signal molecules that cross the plasma membrane by simple diffusion. If these molecules can enter all cells, why do only specific cells respond to their presence?
Nontarget cells lack the intracellular receptors that, when activated by the signal molecule, can interact with genes in the cell's nucleus.
Which of the following statements about passive transport is correct?
Passive transport permits the solute to move in either direction, but the net movement of the population of solute occurs down the concentration gradient of the molecule.
Which of the following statements about the role of phospholipids in the structure and function of biological membranes is correct?
Phospholipids form a selectively permeable structure.
The plasma membrane is referred to as a fluid mosaic structure. Which of the following statements about that model is true?
The fluid aspect of the membrane is due to the lateral and rotational movement of phospholipids, and embedded proteins account for the mosaic aspect.
What did Sutherland discover about glycogen metabolism in liver cells?
The hormone that breaks down glycogen into glucose enters the liver cell.
Consider the transport of protons and sucrose into a plant cell by the sucrose-proton cotransport protein. Plant cells continuously produce a proton gradient by using the energy of ATP hydrolysis to pump protons out of the cell. Why, in the absence of sucrose, don't protons move back into the cell through the sucrose-proton cotransport protein?
The movement of protons through the cotransport protein cannot occur unless sucrose also moves at the same time.
Active transport requires an input of energy and can also generate voltages across membranes. Based on this information, which of the following statements is true?
The sodium/potassium pump hydrolyzes ATP and results in a net charge of +1 outside the cell membrane.
A single plant cell is placed in an isotonic solution. Salt is then added to the solution. Which of the following would occur as a result of the salt addition?
Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease.
ATPgammaS is a form of ATP that cannot be hydrolyzed by enzymes. If this compound was introduced to cells so that it replaced the normal ATP present in the cell, which of the following would you predict?
a decrease in phosphorylated proteins in the cell
The concentration of solutes in a red blood cell is about 2%, but red blood cells contain almost no sucrose or urea. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions?
a hypertonic sucrose solution
Which of the following would be LEAST likely to diffuse through a plasma membrane without the help of a transport protein?
a large polar molecule
Ras, a small G protein located at the plasma membrane, is often mutated in different types of cancer. Ras normally signals to a cell that it should divide. Cancer cells divide uncontrollably. Which of the following changes to Ras would you expect to see in a cancer cell that has mutated Ras present?
a mutation that means Ras cannot hydrolyze GTP to GDP
What does the addition of a phosphate group do to a protein?
can either activate or inactivate a protein
Which of the following molecules is most likely to passively diffuse across the plasma membrane?
carbon dioxide
In eukaryotic cells, which of the following is a second messenger that is produced as a response to an external signal such as a hormone?
cyclic AMP
Steroid hormones can enter a cell by simple diffusion. Therefore steroids __________.
do not initiate cell signaling by interacting with a receptor in the plasma membrane
A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via which process?
endocytosis
Which of the following functional processes is not a consequence of the association of proteins with biological membranes?
energy, carbon, and nitrogen storage
Which of the following processes and organelle(s) accounts for the replacement of lipids and proteins lost from the plasma membrane?
exocytosis and smooth and rough ER
A cell has a membrane potential of -100 mV (more negative inside than outside) and has 1,000 times more calcium ions outside the cell than inside. Which of the following best describes a mechanism by which Ca2+ enters the cell?
facilitated diffusion of Ca2+ into the cell down its electrochemical gradient
When a platelet contacts a damaged blood vessel, it is stimulated to release thromboxane A2. Thromboxane A2 in turn stimulates vascular spasm and attracts additional platelets to the injured site. In this example thromboxane A2 is acting as a __________.
local regulator
A mutation in the active site of adenylyl cyclase that inactivates it would most likely lead to __________.
lower activity of protein kinase A
Receptors for signal molecules __________.
may be found embedded in the plasma membrane, or found within the cytoplasm or nucleus
Testosterone does NOT affect all cells of the body because __________.
not all cells have cytoplasmic receptors for testosterone
Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the membrane would carbohydrates most likely be found?
on the outside (external) surface of the membrane
Which of the following pairs correctly matches a membrane transport process to its primary function?
pinocytosis ... the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane
The general name for an enzyme that transfers phosphate groups from ATP to a protein is __________.
protein kinase
cAMP usually directly activates __________.
protein kinase A
Which of the following structural arrangements of the components in biological membranes is most consistent with membrane's property of selective permeability?
proteins embedded in two layers of phospholipid
Second messengers tend to be water-soluble and small. This accounts for their ability to __________.
rapidly move throughout the cell by diffusion
Which of the following enables a cell to pick up and concentrate a specific kind of molecule?
receptor-mediated endocytosis
Which of the following cell structures exhibits selective permeability between a cell and its external environment?
the plasma membrane
Early work on signal transduction and glycogen metabolism by Sutherland indicated that __________.
the signal molecule did not interact directly with the cytosolic enzyme, but required an intact plasma membrane before the enzyme could be activated
The cellular response of a signal pathway that terminates at a transcription factor would be __________.
the synthesis of mRNA
Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the plasma membrane would cholesterol most likely be found?
wedged between phospholipid molecules in the interior of the membrane
