Unit 2 Cells

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Unit 2 Cells

Multiple Choice
Identify the choice that best completes the statement or answers the question.

A primary objective of cell fractionation is to

a.	view the structure of cell membranes.
b.	identify the enzymes outside the organelles.
c.	determine the size of various organelles.
d.	separate the major organelles so their particular functions can be determined.
e.	crack the cell wall so the cytoplasmic contents can be released.

Quantum dots are small (15-30 nm diameter), bright particles visible using light microscopy. If the dots can be specifically bound to individual proteins on a plasma membrane of a cell, which of the following correctly describes the advantage of using quantum dots in examining proteins?

a.	The dots permit the position of the proteins to be determined more precisely.
b.	The dots permit the average distance between the proteins to be determined more precisely.
c.	The dots permit the size of the proteins to be determined more precisely.
d.	The dots permit the motion of the proteins to be determined more precisely.
e.	All of the above are correct.

All of the following are part of a prokaryotic cell except

a.	DNA.
b.	a cell wall.
c.	a plasma membrane.
d.	ribosomes.
e.	an endoplasmic reticulum.

For the following questions, use the lettered answers to match the structure to its proper cell type. Choose the most inclusive category. Each answer may be used once, more than once, or not at all.

A.	a feature of all cells
B.	found in prokaryotic cells only
C.	found in eukaryotic cells only
D.	found in plant cells only
E.	found in animal cells only

plasma membrane

a.	A
b.	B
c.	C
d.	D
e.	E

tonoplast

a.	A
b.	B
c.	C
d.	D
e.	E

Which of the following incorrectly matches the type of cell, type of protein, and site of the protein's synthesis?

a.	prokaryote, cytoplasmic protein, free cytoplasmic ribosome
b.	eukaryote, plasma membrane protein, rough ER
c.	prokaryote, plasma membrane protein, ribosome bound to plasma membrane
d.	eukaryote, cytoplasmic protein, free cytoplasmic ribosome
e.	prokaryote, secreted protein, free cytoplasmic ribosome

Under which of the following conditions would you expect to find a cell with a predominance of free ribosomes?

a.	a cell that is secreting proteins
b.	a cell that is producing cytoplasmic enzymes
c.	a cell that is constructing its cell wall or extracellular matrix
d.	a cell that is digesting food particles
e.	a cell that is enlarging its vacuole

Which type of organelle is primarily involved in the synthesis of oils, phospholipids, and steroids?

a.	ribosome
b.	lysosome
c.	smooth endoplasmic reticulum
d.	mitochondrion
e.	contractile vacuole

Which structure is the site of the synthesis of proteins that may be exported from the cell?

a.	rough ER
b.	lysosomes
c.	plasmodesmata
d.	Golgi vesicles
e.	tight junctions

10.

The Golgi apparatus has a polarity or sidedness to its structure and function. Which of the following statements correctly describes this polarity?

a.	Transport vesicles fuse with one side of the Golgi and leave from the opposite side.
b.	Proteins in the membrane of the Golgi may be sorted and modified as they move from one side of the Golgi to the other.
c.	Lipids in the membrane of the Golgi may be sorted and modified as they move from one side of the Golgi to the other.
d.	Soluble proteins in the cisternae (interior) of the Golgi may be sorted and modified as they move from one side of the Golgi to the other.
e.	All of the above correctly describe polar characteristics of the Golgi function.

11.

Which of the following cell components is not directly involved in synthesis or secretion?

a.	ribosome
b.	rough endoplasmic reticulum
c.	Golgi body
d.	smooth endoplasmic reticulum
e.	lysosome

12.

The difference in lipid and protein composition between the membranes of the endomembrane system is largely determined by

a.	the physical separation of most membranes from each other.
b.	the transportation of membrane among the endomembrane system by small membrane vesicles.
c.	the function of the Golgi apparatus in sorting membrane components.
d.	the modification of the membrane components once they reach their final destination.
e.	the synthesis of lipids and proteins in each of the organelles of the endomembrane system.

13.

In animal cells, hydrolytic enzymes are packaged to prevent general destruction of cellular components. Which of the following organelles functions in this compartmentalization?

a.	chloroplast
b.	lysosome
c.	central vacuole
d.	peroxisome
e.	glyoxysome

Refer to the following five terms to answer the following questions. Choose the most appropriate term for each phrase. Each term may be used once, more than once, or not at all.

A.	lysosome
B.	vacuole
C.	mitochondrion
D.	Golgi apparatus
E.	peroxisome

14.

helps to recycle the cell's organic material

a.	A
b.	B
c.	C
d.	D
e.	E

15.

contains its own DNA and ribosomes

a.	A
b.	B
c.	C
d.	D
e.	E

16.

Grana, thylakoids, and stroma are all components found in

a.	vacuoles.
b.	chloroplasts.
c.	mitochondria.
d.	lysosomes.
e.	nuclei.

17.

A biologist ground up some plant leaf cells and then centrifuged the mixture to fractionate the organelles. Organelles in one of the heavier fractions could produce ATP in the light, while organelles in the lighter fraction could produce ATP in the dark. The heavier and lighter fractions are most likely to contain, respectively,

a.	mitochondria and chloroplasts.
b.	chloroplasts and peroxisomes.
c.	peroxisomes and chloroplasts.
d.	chloroplasts and mitochondria.
e.	mitochondria and peroxisomes.

18.

All of the following are correct matches of the location of a protein and the location of its synthesis except

a.	plasma membrane protein-rough ER.
b.	mitochondrial membrane protein-free cytoplasmic ribosomes.
c.	cytoplasmic proteins-free cytoplasmic ribosomes.
d.	chloroplast stromal protein-chloroplast ribosomes.
e.	mitochondrial matrix protein-rough ER.

19.

Which of the following are capable of converting light energy to chemical energy?

a.	chloroplasts
b.	mitochondria
c.	leucoplasts
d.	peroxisomes
e.	Golgi bodies

20.

A cell has the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and mitochondria. It could be a cell from

a.	a bacterium.
b.	an animal, but not a plant.
c.	a plant, but not an animal.
d.	a plant or an animal.
e.	any kind of organism.

21.

Which of the following is not a known function of the cytoskeleton?

a.	to maintain a critical limit on cell size
b.	to provide mechanical support to the cell
c.	to maintain the characteristic shape of the cell
d.	to hold mitochondria and other organelles in place within the cytosol
e.	to assist in cell motility by interacting with specialized motor proteins

22.

Motor proteins provide for molecular motion in cells by interacting with what types of cellular structures?

a.	sites of energy production in cellular respiration
b.	membrane proteins
c.	ribosomes
d.	cytoskeletons
e.	cellulose fibers in the cell wall

23.

Cells can be described as having a cytoskeleton of internal structures that contribute to the shape, organization, and movement of the cell. All of the following are part of the cytoskeleton except

a.	the nuclear envelope.
b.	microtubules.
c.	microfilaments.
d.	intermediate filaments.
e.	actin.

24.

Of the following, which cell structure would most likely be visible with a light microscope that has been manufactured to the maximum resolving power possible?

a.	mitochondrion
b.	microtubule
c.	ribosome
d.	largest microfilament
e.	nuclear pore

25.

Which of the following contain the 9 + 2 arrangement of microtubules?

a.	cilia
b.	centrioles
c.	flagella
d.	A and C only
e.	A, B, and C

26.

Cells would be unable to form cilia or flagella if they did not have

a.	centrosomes.
b.	ribosomes.
c.	actin.
d.	A and B only
e.	A, B, and C

27.

Which of the following possesses a microtubular structure similar to a basal body?

a.	centriole
b.	lysosome
c.	nucleolus
d.	peroxisome
e.	ribosome

28.

Which of the following statements about the cytoskeleton is incorrect?

a.	The dynamic aspect of cytoskeletal function is made possible by the assembly and disassembly of a few simple types of proteins into large aggregates.
b.	Microfilaments are structurally rigid and resist compression, while microtubules resist tension (stretching).
c.	Movement of cilia and flagella is the result of motor proteins causing microtubules to move relative to each other.
d.	Chemicals that block the assembly of the cytoskeleton would prevent many different processes in cells.
e.	Transport vesicles among the membranes of the endomembrane system depend on the function of the cytoskeleton.

29.

All of the following structures and proteins are directly associated with movement in cells or by cells except

a.	cilia.
b.	dynein.
c.	actin.
d.	flagella.
e.	centrosomes.

30.

The cell walls of bacteria, fungi, and plant cells and the extracellular matrix of animal cells are all external to the plasma membrane. Which of the following is not a characteristic of all of these extracellular structures?

a.	They must be highly permeable to water and small molecules in order to allow cells to exchange matter and energy with their environment.
b.	They must permit information transfer between the cell's external environment and the cytoplasm.
c.	They must provide a rigid structure that maintains an appropriate ratio of cell surface area to volume.
d.	They are constructed of materials that are largely synthesized in the cytoplasm and then transported out of the cell.
e.	They are composed of a mixture of proteins and carbohydrates.

31.

A cell lacking the ability to make and secrete glycoproteins would most likely be deficient in its

a.	nuclear DNA.
b.	extracellular matrix.
c.	Golgi apparatus.
d.	B and C only
e.	A, B, and C

32.

Plasmodesmata in plant cells are most similar in function to which of the following structures in animal cells?

a.	peroxisomes
b.	desmosomes
c.	gap junctions
d.	extracellular matrix
e.	tight junctions

33.

Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through

a.	plasmodesmata.
b.	intermediate filaments.
c.	tight junctions.
d.	desmosomes.
e.	gap junctions.

For the following questions, match the membrane model or description with the scientist(s) who proposed the model. Each choice may be used once, more than once, or not at all.

A.	H. Davson and J. Danielli
B.	I. Langmuir
C.	C. Overton
D.	S. Singer and G. Nicolson
E.	E. Gorter and F. Grendel

34.

Membranes are a phospholipid bilayer between two layers of hydrophilic proteins.

a.	A
b.	B
c.	C
d.	D
e.	E

35.

The membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids.

a.	A
b.	B
c.	C
d.	D
e.	E

For the following questions, match the labeled component of the cell membrane in the figure below with its description.

36.

peripheral protein

a.	A
b.	B
c.	C
d.	D
e.	E

37.

glycolipid

a.	A
b.	B
c.	C
d.	D
e.	E

38.

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

a.	the integral membrane proteins are not strong enough to hold the bilayer together.
b.	water that is present in the middle of the bilayer freezes and is easily fractured.
c.	hydrophilic interactions between the opposite membrane surfaces are destroyed on freezing.
d.	the carbon-carbon bonds of the phospholipid tails are easily broken.
e.	the hydrophobic interactions that hold the membrane together are weakest at this point.

39.

All of the following molecules are part of the cell membrane except

a.	lipids.
b.	nucleic acids.
c.	proteins.
d.	phosphate groups.
e.	steroids.

40.

The original model for the bilayer structure of cell membranes, which was prepared in the 1920s, was based on which of the following?

a.	detailed electron micrographs of freeze-fractured membranes
b.	the presence of proteins as a functional component of biological membranes
c.	the observation that all membranes contain phospholipids and proteins
d.	the understanding that phospholipids are amphipathic molecules
e.	A and B only

41.

The presence of cholesterol in the plasma membranes of some animals

a.	enables the membrane to stay fluid more easily when cell temperature drops.
b.	enables the animal to remove hydrogen atoms from saturated phospholipids.
c.	enables the animal to add hydrogen atoms to unsaturated phospholipids.
d.	makes the membrane less flexible, allowing it to sustain greater pressure from within the cell.
e.	makes the animal more susceptible to circulatory disorders.

42.

The lateral mobility (fluidity) of lipids and proteins in membranes is a consequence of

a.	lack of covalent bonds between the lipid and protein components of the membrane.
b.	weak hydrophobic interactions among the components in the interior of the membrane.
c.	the presence of liquid water in the interior of the membrane.
d.	A and B only
e.	A, B, and C

43.

What is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold?

a.	by increasing the percentage of unsaturated phospholipids in the membrane
b.	by increasing the percentage of cholesterol molecules in the membrane
c.	by decreasing the number of hydrophobic proteins in the membrane
d.	A and B only
e.	A, B, and C

44.

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

a.	peripheral proteins.
b.	phospholipids.
c.	carbohydrates.
d.	integral proteins.
e.	cholesterol molecules.

45.

Which of the following is correct about integral membrane proteins?

a.	They lack tertiary structure.
b.	They are loosely bound to the surface of the bilayer.
c.	They are usually transmembrane proteins.
d.	They are not mobile within the bilayer.
e.	They serve only a structural role in membranes.

46.

Of the following functions, which is most important for the glycoproteins and glycolipids of animal cell membranes?

a.	facilitated diffusion of molecules down their concentration gradients
b.	active transport of molecules against their concentration gradients
c.	maintaining the integrity of a fluid mosaic membrane
d.	maintaining membrane fluidity at low temperatures
e.	a cell's ability to distinguish one type of neighboring cell from another

47.

What membrane-surface molecules are thought to be most important as cells recognize each other?

a.	phospholipids
b.	integral proteins
c.	peripheral proteins
d.	cholesterol
e.	glycoproteins

48.

An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function?

a.	transporting ions against an electrochemical gradient
b.	cell-cell recognition
c.	maintaining fluidity of the phospholipid bilayer
d.	attaching to the cytoskeleton
e.	establishing the diffusion barrier to charged molecules

49.

Which of the following is a characteristic feature of a carrier protein in a plasma membrane?

a.	It is a peripheral membrane protein.
b.	It exhibits a specificity for a particular type of molecule.
c.	It requires the expenditure of cellular energy to function.
d.	It works against diffusion.
e.	It has few, if any, hydrophobic amino acids.

50.

The selective permeability of biological membranes is dependent on which of the following?

a.	the type of transport proteins that are present in the membrane
b.	the lipid bilayer being permeable to primarily small, nonpolar molecules
c.	the types of carbohydrates on the surface of the membrane
d.	A and B only
e.	A, B, and C

51.

Which of the following statements is correct about diffusion?

a.	It is very rapid over long distances.
b.	It requires an expenditure of energy by the cell.
c.	It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
d.	It is an active process in which molecules move from a region of lower concentration to one of higher concentration.
e.	It requires integral proteins in the cell membrane.

52.

Water passes quickly through cell membranes because

a.	the bilayer is hydrophilic.
b.	it moves through hydrophobic channels.
c.	water movement is tied to ATP hydrolysis.
d.	it is a small, polar, charged molecule.
e.	it moves through aquaporins in the membrane.

Use the diagram of the U-tube in the figure below to answer the following questions.

The solutions in the two arms of this U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half filled with a solution of 2 M sucrose and 1 M glucose. Side B is half filled with 1 M sucrose and 2 M glucose. Initially, the liquid levels on both sides are equal.

53.

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?

a.	It will have no unfavorable effect as long as the water is free of viruses and bacteria.
b.	The patient's red blood cells will shrivel up because the blood fluid is hypotonic compared to the cells.
c.	The patient's red blood cells will swell because the blood fluid is hypotonic compared to the cells.
d.	The patient's red blood cells will shrivel up because the blood fluid is hypertonic compared to the cells.
e.	The patient's red blood cells will burst because the blood fluid is hypertonic compared to the cells.

54.

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

a.	hypotonic to both fresh water and the salt solution.
b.	hypertonic to both fresh water and the salt solution.
c.	hypertonic to fresh water but hypotonic to the salt solution.
d.	hypotonic to fresh water but hypertonic to the salt solution.
e.	isotonic with fresh water but hypotonic to the salt solution.

55.

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?

a.	isotonic
b.	hypertonic
c.	hypotonic
d.	flaccid
e.	turgid

Use the figure below to answer the following questions.

The solutions in the arms of a U-tube are separated at the bottom of the tube by a selectively permeable membrane. The membrane is permeable to sodium chloride but not to glucose. Side A is filled with a solution of 0.4 M glucose and 0.5 M sodium chloride (NaCl), and side B is filled with a solution containing 0.8 M glucose and 0.4 M sodium chloride. Initially, the volume in both arms is the same.

56.

Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells?

a.	The animal cell is in a hypotonic solution, and the plant cell is in an isotonic solution.
b.	The animal cell is in an isotonic solution, and the plant cell is in a hypertonic solution.
c.	The animal cell is in a hypertonic solution, and the plant cell is in an isotonic solution.
d.	The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution.
e.	The animal cell is in a hypertonic solution, and the plant cell is in a hypotonic solution.

Read the following information and refer to the figure below to answer the following questions.

Five dialysis bags, constructed from a semi-permeable membrane that is impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed) and the percent change in mass of each bag was graphed.

57.

Which line or lines represent(s) bags that contain a solution that is hypertonic at the end of 60 minutes?

a.	A and B
b.	B
c.	C
d.	D
e.	D and E

58.

You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would not be a factor that determines whether the molecule enters the cell?

a.	size of the drug molecule
b.	polarity of the drug molecule
c.	charge on the drug molecule
d.	similarity of the drug molecule to other molecules transported by the target cells
e.	lipid composition of the target cells' plasma membrane

59.

The movement of a substance across a biological membrane against its concentration gradient with the help of energy input is

a.	diffusion.
b.	active transport.
c.	osmosis.
d.	facilitated diffusion.
e.	exocytosis.

60.

What is the voltage across a membrane called?

a.	water potential
b.	chemical gradient
c.	membrane potential
d.	osmotic potential
e.	electrochemical gradient

61.

If a membrane protein in an animal cell is involved in the cotransport of glucose and sodium ions into the cell, which of the following is most likely not true?

a.	The sodium ions are moving down their electrochemical gradient.
b.	Glucose is entering the cell against its concentration gradient.
c.	Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell.
d.	The higher sodium ion concentration outside the cell is the result of an electrogenic pump.
e.	A substance that blocked sodium ions from binding to the cotransport protein would also block the transport of glucose.

62.

Ions diffuse across membranes down their

a.	chemical gradients.
b.	concentration gradients.
c.	electrical gradients.
d.	electrochemical gradients.
e.	A and B are correct.

63.

An organism with a cell wall would have the most difficulty doing which process?

a.	diffusion
b.	osmosis
c.	active transport
d.	phagocytosis
e.	exocytosis

64.

The membrane activity most nearly opposite to exocytosis is

a.	plasmolysis.
b.	osmosis.
c.	facilitated diffusion.
d.	phagocytosis.
e.	active transport.

65.

White blood cells engulf bacteria through what process?

a.	exocytosis
b.	phagocytosis
c.	pinocytosis
d.	osmosis
e.	receptor-mediated exocytosis

66.

What is the cause of familial hypercholesterolemia?

a.	defective LDL receptors on the cell membranes
b.	poor attachment of the cholesterol to the extracellular matrix of cells
c.	a poorly formed lipid bilayer that cannot incorporate cholesterol into cell membranes
d.	inhibition of the cholesterol active transport system in red blood cells
e.	a general lack of glycolipids in the blood cell membranes

67.

In yeast (Saccharomyces cerevisiae), the two sexes are called

a.	S plus and S minus.
b.	a and .
c.	a and b.
d.	b and .
e.	male and female.

68.

Which of the following is true of the mating signal transduction pathway in yeast?

a.	The pathway carries an electrical signal between mating cell types.
b.	Mating type a secretes a signal called a factor.
c.	The molecular details of the pathway in yeast and in animals are very different.
d.	Scientists think the pathway evolved long after multicellular creatures appeared on Earth.
e.	The signal reception, transduction, and response occur in the nucleus.

69.

Paracrine signaling

a.	involves secreting cells acting on nearby target cells by discharging a local regulator into the extracellular fluid.
b.	requires nerve cells to release a neurotransmitter into the synapse.
c.	occurs only in paracrine yeast cells.
d.	has been found in plants but not animals.
e.	involves mating factors attaching to target cells and causing production of new paracrine cells.

70.

Which of the following is true of synaptic signaling and hormonal signaling?

a.	Hormonal signaling occurs in animals only.
b.	Hormonal signaling is important between cells that are at greater distances apart than in synaptic signaling.
c.	Both act on target cells by a G-protein-signaling pathway.
d.	Only A and B are true.
e.	A, B, and C are true.

71.

The old saying "one rotten apple spoils the whole barrel" is due to chemical signaling in plants via

a.	an increased uptake of carbon dioxide during respiration in target cells.
b.	a local regulator for apple development.
c.	release of ethylene gas, a plant hormone for ripening.
d.	an a/ cell signal system in the rotten apple.
e.	a signal transduction pathway involving glycogen phosphorylase.

72.

When a cell releases a signal molecule into the environment and a number of cells in the immediate vicinity respond, this type of signaling is

a.	typical of hormones.
b.	autocrine signaling.
c.	paracrine signaling.
d.	endocrine signaling.
e.	synaptic signaling.

73.

Of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to

a.	the active site of an enzyme in the cytoplasm that binds to a specific substrate.
b.	RNA specifying the amino acids in a polypeptide.
c.	a particular metabolic pathway operating within a specific organelle.
d.	an enzyme with an optimum pH and temperature for activity.
e.	genes making up a chromosome.

74.

Most signal molecules

a.	bind to specific sites on receptor proteins in a membrane.
b.	are water-soluble.
c.	are able to pass through the plasma membrane by active transport.
d.	A and B only
e.	A, B, and C

75.

G proteins and G-protein-linked receptors

a.	are found only in animal cells.
b.	are found only in bacterial cells.
c.	are thought to have evolved very early, because of their similar structure and function in a wide variety of modern organisms whose common ancestors diverged billions of years ago.
d.	probably evolved from an adaptation of the citric acid cycle.
e.	are not widespread in nature and were unimportant in the evolution of eukaryotes.

76.

Up to 60% of all medicines used today exert their effects by influencing what structures in the cell membrane?

a.	tyrosine-kinases receptors
b.	ligand-gated ion channel receptors
c.	growth factors
d.	G proteins
e.	cholesterol

77.

Which of the following are chemical messengers that pass through the plasma membrane of cells and have receptor molecules in the cytoplasm?

a.	insulin
b.	nitric oxide
c.	testosterone
d.	B and C only
e.	A, B, and C

78.

Testosterone functions inside a cell by

a.	acting as a signal receptor that activates ion-channel proteins.
b.	binding with a receptor protein that enters the nucleus and activates specific genes.
c.	acting as a steroid signal receptor that activates ion-channel proteins.
d.	becoming a second messenger that inhibits adenylyl cyclase.
e.	coordinating a phosphorylation cascade that increases glycogen metabolism.

79.

Chemical signal pathways

a.	operate in animals, but not in plants.
b.	are absent in bacteria, but are plentiful in yeast.
c.	involve the release of hormones into the blood.
d.	often involve the binding of signal molecules to a protein on the surface of a target cell.
e.	use hydrophilic molecules to activate enzymes.

80.

In general, a signal transmitted via phosphorylation of a series of proteins

a.	brings a conformational change to each protein.
b.	requires binding of a hormone to a cytosol receptor.
c.	cannot occur in yeasts because they lack protein phosphatases.
d.	requires phosphorylase activity.
e.	allows target cells to change their shape and therefore their activity.

81.

Which of the following is widely used second messenger in signal transduction pathways?

a.	calcium ions
b.	cyclic AMP
c.	inositol trisphosphate
d.	A and B only
e.	A, B, and C

82.

Sutherland discovered that epinephrine

a.	signals bypass the plasma membrane of cells.
b.	lowers blood glucose by binding to liver cells.
c.	interacts with insulin inside muscle cells.
d.	interacts directly with glycogen phosphorylase.
e.	elevates the cytosolic concentration of cyclic AMP.

83.

Which of the following would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins?

a.	G-protein-linked receptor signaling
b.	ligand-gated ion channel signaling
c.	adenylyl cyclase activity
d.	phosphatase activity
e.	receptor tyrosine kinase activity

84.

Which of the following most likely would be an immediate result of growth factor binding to its receptor?

a.	protein kinase activity
b.	adenylyl cyclase activity
c.	GTPase activity
d.	protein phosphatase activity
e.	phosphorylase activity

85.

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to

a.	design a compound that mimics epinephrine and can bind to the epinephrine receptor.
b.	design a compound that stimulates cAMP production in liver cells.
c.	design a compound to stimulate G protein activity in liver cells.
d.	design a compound that increases phosphodiesterase activity.
e.	All of the above are possible approaches.

86.

An inhibitor of which of the following could be used to block the release of calcium from the endoplasmic reticulum?

a.	tyrosine kinases
b.	serine/threonine kinases
c.	phosphodiesterase
d.	phospholipase C
e.	adenylyl cyclase

87.

Which of the following is an incorrect association?

a.	kinase activity and the addition of a phosphate group
b.	phosphodiesterase activity and the removal of phosphate groups
c.	GTPase activity and hydrolysis of GTP to GDP
d.	phosphorylase activity and the catabolism of glycogen
e.	adenylyl cyclase activity and the conversion of AMP to cAMP

88.

The response of a particular cell to a signal depends on

a.	its particular collection of signal receptor proteins.
b.	its relay proteins.
c.	the proteins needed to carry out the response.
d.	A and B only
e.	A, B, and C

89.

Which example below is a protein that can hold several other relay proteins as it binds to an activated membrane receptor?

a.	active transcription factor
b.	third messenger
c.	ligand
d.	scaffolding protein
e.	protein kinase

90.

What is a chromatid?

a.	a chromosome in G₁ of the cell cycle
b.	a replicated chromosome
c.	a chromosome found outside the nucleus
d.	a special region that holds two centromeres together
e.	another name for the chromosomes found in genetics

91.

Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?

a.	4
b.	8
c.	16
d.	32
e.	64

92.

Which of the following statements is not true?

a.	Mitosis produces new nuclei with exactly the same chromosomal endowment as the parent nucleus.
b.	Mitosis may occur without cytokinesis.
c.	Mitosis and cytokinesis are required for asexual reproduction.
d.	All cells come from a preexisting cell.
e.	The mitotic spindles in prokaryotic cells are composed of microtubules.

The questions below refer to the following terms. Each term may be used once, more than once, or not at all.

A.	telophase
B.	anaphase
C.	prometaphase
D.	metaphase
E.	prophase

93.

Centrioles begin to move apart in animal cells.

a.	A
b.	B
c.	C
d.	D
e.	E

94.

A cell containing 92 chromatids at metaphase of mitosis would, at its completion, produce two nuclei containing how many chromosomes?

a.	12
b.	16
c.	23
d.	46
e.	92

95.

If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis?

a.	10
b.	20
c.	30
d.	40
e.	80

Use the data in the table below to answer the following questions.

The data were obtained from a study of the length of time spent in each phase of the cell cycle by cells of three eukaryotic organisms designated beta, delta, and gamma.

Minutes Spent in Cell Cycle Phases

Cell Type		S		M
Beta	18	24	12	16
Delta	100	0	0	0
Gamma	18	48	14	20

96.

Of the following, the best conclusion concerning the difference between the S phases for beta and gamma is that

a.	gamma contains more DNA than beta.
b.	beta and gamma contain the same amount of DNA.
c.	beta contains more RNA than gamma.
d.	gamma contains 48 times more DNA and RNA than beta.
e.	beta is a plant cell and gamma is an animal cell.

97.

The best conclusion concerning delta is that the cells

a.	contain no DNA.
b.	contain no RNA.
c.	contain only one chromosome that is very short.
d.	are actually in the G₀ phase.
e.	divide in the G₁ phase.

98.

If a cell has 8 chromosomes at metaphase of mitosis, how many chromosomes will it have during anaphase?

a.	1
b.	2
c.	4
d.	8
e.	16

99.

Regarding mitosis and cytokinesis, one difference between higher plants and animals is that in plants

a.	the spindles contain microfibrils in addition to microtubules, whereas animal spindles do not contain microfibrils.
b.	sister chromatids are identical, but they differ from one another in animals.
c.	a cell plate begins to form at telophase, whereas animals a cleavage furrow is initiated at that stage.
d.	chromosomes become attached to the spindle at prophase, whereas in animals chromosomes do not become attached until anaphase.
e.	spindle poles contain centrioles, whereas spindle poles in animals do not.

100.

How do the daughter cells at the end of mitosis and cytokinesis compare with their parent cell when it was in G₁ of the cell cycle?

a.	The daughter cells have half the amount of cytoplasm and half the amount of DNA.
b.	The daughter cells have half the number of chromosomes and half the amount of DNA.
c.	The daughter cells have the same number of chromosomes and half the amount of DNA.
d.	The daughter cells have the same number of chromosomes and the same amount of DNA.
e.	The daughter cells have the same number of chromosomes and twice the amount of DNA.

101.

The formation of a cell plate is beginning across the middle of a cell and nuclei are re-forming at opposite ends of the cell. What kind of cell is this?

a.	an animal cell in metaphase
b.	an animal cell in telophase
c.	an animal cell undergoing cytokinesis
d.	a plant cell in metaphase
e.	a plant cell undergoing cytokinesis

102.

Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, taxol disrupts microtubule formation by binding to microtubules and accelerating their assembly from the protein precursor, tubulin. Surprisingly, this stops mitosis. Specifically, taxol must affect

a.	the fibers of the mitotic spindle.
b.	anaphase.
c.	formation of the centrioles.
d.	chromatid assembly.
e.	the S phase of the cell cycle.

103.

Which of the following organisms does not reproduce cells by mitosis and cytokinesis?

a.	cow
b.	bacterium
c.	mushroom
d.	cockroach
e.	banana tree

104.

Movement of the chromosomes during anaphase would be most affected by a drug that

a.	reduces cyclin concentrations.
b.	increases cyclin concentrations.
c.	prevents elongation of microtubules.
d.	prevents shortening of microtubules.
e.	prevents attachment of the microtubules to the kinetochore.

105.

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. Those cells would have ____ picograms at the end of the S phase and ____ picograms at the end of G₂.

a.	8; 8
b.	8; 16
c.	16; 8
d.	16; 16
e.	12; 16

106.

Imagine looking through a microscope at a squashed onion root tip. The chromosomes of many of the cells are plainly visible. In some cells, replicated chromosomes are aligned along the center (equator) of the cell. These particular cells are in which stage of mitosis?

a.	telophase
b.	prophase
c.	anaphase
d.	metaphase
e.	prometaphase

107.

If mammalian cells receive a go-ahead signal at the G₁ checkpoint, they will

a.	move directly into telophase.
b.	complete the cycle and divide.
c.	exit the cycle and switch to a nondividing state.
d.	show a drop in MPF concentration.
e.	complete cytokinesis and form new cell walls.

108.

Cells that are in a nondividing state are in which phase?

a.	G₀
b.	G₂
c.	G₁
d.	S
e.	M

109.

What causes the decrease in the amount of cyclin at a specific point in the cell cycle?

a.	an increase in production once the restriction point is passed
b.	the cascade of increased production once its protein is phosphorylated by Cdk
c.	the changing ratio of cytoplasm to genome
d.	its destruction by a process initiated by the activity of MPF complexes
e.	the binding of PDGF to receptors on the cell surface

The following questions consist of five phrases or sentences related to the control of cell division. For each one, select the term below that is most closely related to it. Each term may be used once, more than once, or not at all.

A.	PDGF
B.	MPF
C.	protein kinase
D.	cyclin
E.	Cdk

110.

released by platelets in the vicinity of an injury

a.	A
b.	B
c.	C
d.	D
e.	E

111.

a protein synthesized at specific times during the cell cycle that associates with a kinase to form a catalytically active complex

a.	A
b.	B
c.	C
d.	D
e.	E

The questions below consist of five phrases or sentences concerned with the cell cycle. For each one, select the answer below that is most closely related to it. Each answer may be used once, more than once, or not at all.

A.	G₀
B.	G₁
C.	S
D.	G₂
E.	M

112.

Nerve and muscle cells are in this phase.

a.	A
b.	B
c.	C
d.	D
e.	E

113.

the shortest part of the cell cycle

a.	A
b.	B
c.	C
d.	D
e.	E

114.

The cyclin component of MPF is destroyed toward the end of this phase.

a.	A
b.	B
c.	C
d.	D
e.	E

Use the figure below to answer the following question.

115.

Mitosis is represented by which number?

a.	I
b.	II
c.	III
d.	IV
e.	V

116.

Which number represents DNA synthesis?

a.	I
b.	II
c.	III
d.	IV
e.	V

117.

The MPF protein complex turns itself off by

a.	activating a process that destroys cyclin.
b.	activating an enzyme that stimulates cyclin.
c.	binding to chromatin.
d.	exiting the cell.
e.	activating the anaphase-promoting complex.

118.

A mutation results in a cell that no longer produces a normal protein kinase for the M phase checkpoint. Which of the following would likely be the immediate result of this mutation?

a.	The cell would prematurely enter anaphase.
b.	The cell would never leave metaphase.
c.	The cell would never enter metaphase.
d.	The cell would never enter prophase.
e.	The cell would undergo normal mitosis, but fail to enter the next G₁ phase.

119.

Density-dependent inhibition is explained by which of the following?

a.	As cells become more numerous, they begin to squeeze against each other, restricting their size and ability to produce control factors.
b.	As cells become more numerous, the amount of required growth factors and nutrients per cell becomes insufficient to allow for cell growth.
c.	As cells become more numerous, the protein kinases they produce begin to compete with each other, such that the proteins produced by one cell essentially cancel those produced by its neighbor.
d.	As cells become more numerous, more and more of them enter the S phase of the cell cycle.
e.	As cells become more numerous, the level of waste products increases, eventually slowing down metabolism.

120.

Which of the following is (are) true concerning cyclin-dependent kinase (Cdk)?

a.	Cdk is inactive, or "turned off," in the presence of cyclin.
b.	Cdk is present throughout the cell cycle.
c.	Cdk is an enzyme that attaches phosphate groups to other proteins.
d.	Both A and B are true.
e.	Both B and C are true.

121.

A particular cyclin called cyclin E forms a complex with a cyclin-dependent kinase called Cdk 2. This complex is important for the progression of the cell from G₁ into the S phase of the cell cycle. Which of the following statements is correct?

a.	The amount of cyclin E is greatest during the S phase.
b.	The amount of Cdk 2 is greater during G₁ compared to the S phase.
c.	The amount of cyclin E is highest during G₁.
d.	The amount of Cdk 2 is greatest during G₁.
e.	The activity of the cyclin E/Cdk 2 complex is highest during G₂.

122.

What is a genome?

a.	the complete complement of an organism's genes
b.	a specific sequence of polypeptides within each cell
c.	a specialized polymer of four different kinds of monomers
d.	a specific segment of DNA that is found within a prokaryotic chromosome
e.	an ordered display of chromosomes arranged from largest to smallest

123.

How do the two members of a pair of homologous chromosomes differ from each other?

a.	their length
b.	the identity and relative position of the genes present on each of the chromosomes
c.	their staining patterns
d.	the position of the centromere within each of the chromosomes
e.	the precise sequence of the DNA within each of the chromosomes

124.

The human X and Y chromosomes are

a.	both present in every somatic cell of males and females alike.
b.	of approximately equal size.
c.	almost entirely homologous, despite their different names.
d.	called "sex chromosomes" because they determine an individual's sex.
e.	all of the above

125.

Which of the following is true of a species that has a chromosome number of 2n = 16?

a.	The species is diploid with 32 chromosomes.
b.	The species has 16 sets of chromosomes.
c.	There are 8 homologous pairs.
d.	During the S phase of the cell cycle there will be 32 separate chromosomes.
e.	A gamete from this species has 4 chromosomes.

126.

In animals, meiosis results in gametes, and fertilization results in

a.	spores.
b.	gametophytes.
c.	zygotes.
d.	sporophytes.
e.	clones.

127.

Which of the following is an example of alternation of generations?

a.	A grandparent and grandchild each have dark hair, but the parent has blond hair.
b.	A diploid plant (sporophyte) produces, by meiosis, a spore that gives rise to a multicellular, haploid pollen grain (gametophyte).
c.	A diploid animal produces gametes by meiosis, and the gametes undergo fertilization to produce a diploid zygote.
d.	A haploid mushroom produces gametes by mitosis, and the gametes undergo fertilization, which is immediately followed by meiosis.
e.	A diploid cell divides by mitosis to produce two diploid daughter cells, which then fuse to produce a tetraploid cell.

Refer to the life cycles illustrated in the figure below to answer the following questions.

128.

Which of the life cycles is typical for plants and some algae?

a.	I only
b.	II only
c.	III only
d.	I and II
e.	I and III

129.

Which of the following is missing from the life cycle progression shown below?
sporophyte-meiosis-spore-____-gametophyte-mitosis-gametes- fertilization-zygote

a.	meiosis
b.	mitosis
c.	synapsis
d.	karyotype
e.	fertilization

130.

After telophase I of meiosis, the chromosomal makeup of each daughter cell is

a.	diploid, and the chromosomes are composed of a single chromatid.
b.	diploid, and the chromosomes are composed of two chromatids.
c.	haploid, and the chromosomes are composed of a single chromatid.
d.	haploid, and the chromosomes are composed of two chromatids.
e.	tetraploid, and the chromosomes are composed of two chromatids.

131.

When does the synaptonemal complex disappear?

a.	late prophase of meiosis I
b.	during fertilization or fusion of gametes
c.	early anaphase of meiosis I
d.	mid-prophase of meiosis II
e.	late metaphase of meiosis II

132.

Which of the following terms belongs with the words synapsis, tetrads, and chiasmata?

a.	haploid
b.	crossing over
c.	autosomes
d.	prophase II
e.	fertilization

For the following questions, match the key event of meiosis with the stages listed below.

I.	prophase I	V.	prophase II
II.	metaphase I	VI.	metaphase II
III.	anaphase I	VII.	anaphase II
IV.	telophase I	VIII.	telophase II

133.

Tetrads of chromosomes are aligned at the center of the cell; independent assortment soon follows.

a.	I
b.	II
c.	IV
d.	VII
e.	VIII

134.

Synapsis of homologous pairs occurs; crossing over may occur.

a.	I
b.	II
c.	IV
d.	VI
e.	VII

135.

Which of the following happens at the conclusion of meiosis I?

a.	Homologous chromosomes are separated.
b.	The chromosome number is conserved.
c.	Sister chromatids are separated.
d.	Four daughter cells are formed.
e.	The sperm cells elongate to form a head and a tail end.

136.

Which of the following is true of the process of meiosis?

a.	Two diploid cells result.
b.	Four diploid cells result.
c.	Four haploid cells result.
d.	Four autosomes result.
e.	Four chiasmata result.

137.

Crossing over occurs during which phase of meiosis?

a.	prophase I
b.	anaphase I
c.	telophase I
d.	prophase II
e.	metaphase II

Refer to the drawings in the figure below of a single pair of homologous chromosomes as they might appear during various stages of either mitosis or meiosis, and answer the following questions.

138.

Which drawing represents metaphase II of meiosis?

a.	I
b.	II
c.	IV
d.	V
e.	VI

139.

Which drawing represents a stage of meiosis in which independent assortment might occur if there were more than one pair of chromosomes represented?

a.	I
b.	II
c.	IV
d.	V
e.	VI

140.

Centromeres uncouple and chromatids are separated from each other.

a.	A
b.	B
c.	C
d.	D
e.	E

141.

Independent assortment of chromosomes occurs.

a.	A
b.	B
c.	C
d.	D
e.	E

142.

The process is preceded by replication of the DNA.

a.	A
b.	B
c.	C
d.	D
e.	E

143.

You have in your possession a microscope slide with meiotic cells on it and a light microscope. What would you look for if you wanted to identify metaphase I cells on the slide?

a.	a visible nuclear envelope
b.	separated sister chromatids at each pole of the cell
c.	tetrads lined up at the center of the cell
d.	a synaptonemal complex
e.	a cleavage furrow

144.

Which sample of DNA might be from a nerve cell arrested in G₀ of the cell cycle?

a.	I
b.	II
c.	III
d.	either I or II
e.	either II or III

145.

Which sample might represent a sperm cell?

a.	I
b.	II
c.	III
d.	either I or II
e.	either II or III

146.

During mitosis, diploid cells go from what number to what number?

a.	I to III
b.	I to II
c.	II to III
d.	II to I
e.	always remain at II

The following questions refer to the essential steps in meiosis described below.

1. formation of four new nuclei, each with half the chromosomes present in the parental nucleus

2. alignment of tetrads at the metaphase plate

3. separation of sister chromatids

4. separation of the homologues; no uncoupling of the centromere

5. synapsis; chromosomes moving to the middle of the cell in pairs

147.

Which of the steps take place in both mitosis and meiosis?

a.	2
b.	3
c.	5
d.	2 and 3 only
e.	2, 3, and 5

148.

Which of the following occurs in meiosis but not in mitosis?

a.	chromosome replication
b.	synapsis
c.	production of daughter cells
d.	alignment of tetrads at metaphase plate
e.	both B and D

149.

For a species with a haploid number of 23 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes?

a.	23
b.	46
c.	460
d.	920
e.	about 8 million

150.

Which of the following statements about crossing over is incorrect?

a.	Crossing over combines sections of the maternal and paternal chromosomes.
b.	Crossing over plays a role in both sexual and asexual reproduction.
c.	There are on average one to three crossover events per chromosome.
d.	Crossing over increases the extent of genetic variation beyond what is possible through independent assortment alone.
e.	Crossing over results in recombinant chromosomes.