Pollard: Cell Biology, 2nd Edition

Test Bank

Chapter 1: Introduction to Cells

MULTIPLE CHOICE

	1.	Which statement is NOT true of the prokaryotic cell?
a.	DNA is circular. 	
b.	It is enclosed by plasma membrane.	
c.	It lacks a cytoskeletal support structure.	
d.	Contains many organelles.	

ANS:	D
Presence of organelles is a distinguishing feature of eukaryotic cells.

	2.	Plasma membranes expand by
a.	de novo synthesis. 	
b.	endocytosis of bacterial membranes.	
c.	budding of endoplasmic reticulum	
d.	Do not expand over the lifetime of the cell.	

ANS:	C
Membranes grow only by expansion of preexisting membranes, usually endoplasmic reticulum not directly, pass through Golgi first.

	3.	The sequence of amino acids in a protein determines its
a.	Location in the cell.	
b.	Function.	
c.	Transcription.	
d.	None of the above.	

ANS:	A
Improperly folded proteins lack biological function.

	4.	Genetic information
a.	is encoded only in eukaryotic cells.	
b.	is stored in long polymers of DNA. 	
c.	is stored in messenger RNA molecules.	
d.	None of the above.	

ANS:	B
DNA, a basic carrier of genetic information, is a linear molecule composed of complementary nucleotides. Both prokaryotes and eukaryotes use DNA as hereditary information.

	5.	The pairing between complementary nucleotide bases in DNA is stabilized by
a.	peptide bonds.	
b.	cytosine bonds.	
c.	noncovalent bonds.	
d.	disulfide bonds.	

ANS:	C
Specific noncovalent bonds stabilize the complementary bases and form a double helix.

	6.	Subcellular localization of the protein is determined by
a.	signal sequences within protein sequence.	
b.	signal sequences in the mitochondria.	
c.	phospholipid synthesis.	
d.	electrochemical gradients.	

ANS:	A
Signal recognition sequences that are integral part of the polypeptide sequence direct the protein to the proper destination.

	7.	ATP
a.	is a common energy “currency” used both by prokaryotes and eukaryotes.	
b.	can be used to power molecular motors.	
c.	is a nucleotide used in the assembly of RNA and DNA.	
d.	All of the above.	

ANS:	D
Molecular motor proteins require energy to move their cargo. The energy is delivered from the universal source, ATP both in prokaryotes and eukaryotes.

	8.	The cytoskeleton 
a.	is a common feature of all cells.	
b.	acts as tracks for cellular motors.	
c.	is necessary for protein targeting.	
d.	None of the above.	

ANS:	B

	9.	Activation of cell surface receptors can
a.	change cell metabolism.	
b.	affect gene transcription.	
c.	cause the cell to die.	
d.	All of the above.	

ANS:	D
Activation of cell receptors allows cells to perceive environmental conditions and adapt their behavior to those conditions.

	10.	Signal transduction mechanisms 
a.	are activated by stimulation of the receptor molecules on the cell surface.	
b.	conserved through phylogenesis.	
c.	transmit an environmental signal to intracellular effector molecules.	
d.	All of the above.	

ANS:	D
Many of the signal transduction systems are very ancient, although some of them have arisen later in evolution. Their main role is to relay an extracellular signal to a specific effector molecule to allow the cell to adjust its behavior to environmental signal.

	11.	The nucleus
a.	contains hereditary information submerged in the nucleoplasm.	
b.	is separated from the cytoplasm by a nuclear envelope in eucaryotic cells.	
c.	is metabolically isolated from the cytoplasm by the double membrane.	
d.	Only a and b.	

ANS:	D
The nucleus is an organelle that contains hereditary information in the form of chromosomes. It is separated from the cytoplasm by a double membrane but not isolated from it. Many proteins and nucleic acids cross the nuclear membrane through nuclear pores.

	12.	Nuclear pores allow transport of which of the following molecules?
a.	proteins 	
b.	DNA	
c.	RNA	
d.	All of the above. 	

ANS:	C
Nuclear pores are selective filters for transport between cytoplasm and inside of the nucleus. Transported molecules include mRNA, ribosomal subunits, and proteins such as DNA polymerase.

	13.	The endoplasmic reticulum
a.	is a site of phospholipid synthesis.	
b.	is continuous with the nuclear envelope.	
c.	regulates cytoplasmic Ca2+ concentration.	
d.	All of the above.	

ANS:	D
Endoplasmic reticulum is a membranous structure for protein and phospholipid synthesis. It is network of interconnected closed membrane spaces that are continuous with the outer membrane of nuclear envelope. In addition it contains a variety of pumps and channels that allow to control cytoplasmic Ca2+ concentration.

	14.	The rough endoplasmic reticulum is a primary place of 
a.	phospholipid synthesis.	
b.	protein synthesis.	
c.	fatty acid synthesis.	
d.	a and b.	

ANS:	D
Ribosomes on the surface of the rough ER are the site of synthesis of secretory and membrane proteins.

	15.	Which statement about Golgi apparatus is INCORRECT?
a.	It forms a delivery system of the cell.	
b.	It is a site of posttranslational protein modifications.	
c.	It is a site of protein synthesis.	
d.	It contains different sets of modifying enzymes.	

ANS:	C
The Golgi apparatus is the “delivery system” of the cell. It processes, packages, and distributes molecules synthesized in the ER

	16.	Posttranslational modifications of sugar side chains take place
a.	In the cytoplasm	
b.	In the ER	
c.	In the Golgi apparatus	
d.	All of the above	

ANS:	C
After synthesis in the ER, proteins are sorted to Golgi apparatus where the enzymes for the modification of sugar side chains in glycoproteins are located.

	17.	Lysosomes 
a.	are a site sorting of secretory proteins.		
b.	contain acid hydrolases that carry out the degradation of “worn” cell components. 	
c.	arise by budding from the endoplasmic reticulum. 	
d.	All of the above.	

ANS:	B
Lysosomes contain acid hydrolases that carry out the degradation of “worn” cell components.

	18.	Mitochondria
a.	are the site of oxidative phosphorylation in the cell.	
b.	are enclosed by a double membrane.	
c.	contain ribosomes upon which some of the mitochondrial proteins are synthesized.	
d.	All of the above.	

ANS:	D
Mitochondria are the double membrane organelles that are the place of oxidative metabolism and ATP production.

	19.	Oxidation of fatty acids occurs in
a.	lysosomes.	
b.	peroxisomes.	
c.	Golgi apparatus.	
d.	None of the above.	

ANS:	B
Peroxisomes are the second organelle (in addition to mitochondria) that can oxidize fatty acids.

	20.	Which functions are NOT attributed to intermediate filaments?
a.	They support cell locomotion.	
b.	They support the plasma membrane.	
c.	They reinforce the nuclear envelope.	
d.	They integrate cells into tissues.	

ANS:	A
Intermediate filaments reinforce cell structures and by interactions with cell adhesion molecules integrate cells into tissues but unlike actin and microtubules do not serve as tracks for cellular motors.

	21.	A function of cell membrane proteins is
a.	reception of signals from the extracellular environment.	
b.	functional connection with other cells.	
c.	generate a permeability barrier. 	
d.	a and b only.	

ANS:	D
Cell membrane separates the interior of the cell from the extracellular environment. At the same time the cell membrane is a place of communication and selective transport from the outside.  Membrane lipids are responsible or the permeability barrier function of the p.m.

	22.	Which of the following organelles is enclosed by a double membrane?
a.	Endoplasmic reticulum	
b.	Mitochondrion	
c.	Lysosome	
d.	Peroxisome	

ANS:	B
Mitochondria have double membrane that allows them to create proton gradient and use it in ATP synthesis.

	23.	Which of the following components are not found in prokaryotes?
a.	Nucleic acids	
b.	Phospholipid bilayers	
c.	Ribosomes	
d.	Actin fibers	

ANS:	D
Cytoskeleton is a specific feature of eukaryotic cells not present in prokaryotes.