CHAPTER 3 Cells: The Living Units
1) Which of the following is true regarding the generation of a membrane potential?
A) Both potassium and sodium ions can ʺleakʺ through the cell membrane due to diffusion.
B) In the polarized state, sodium and potassium ion concentrations are in static equilibrium.
C) The maintenance of the potential is based exclusively on diffusion processes.
D) When the sodium-potassium pump is activated, potassium is pumped into the cell twice
as fast as the sodium is pumped out, thus causing the membrane potential.
2) Transcytosis is ________.
A) combining an endosome with a lysosome and degrading or releasing the contents
B) transporting an endosome from one side of a cell to the other and releasing the contents
C) recycling the contents of the endosome back to the surface of the cell
D) storing the contents of the endosome
3) in certain kinds of muscle cells, calcium ions are stored ________.
A) in the smooth ER
B) in the rough ER
C) in both smooth and rough ER
D) in the cytoplasm
4) The RNA responsible for bringing the amino acids to the ʺfactoryʺ site for protein formation is
5) A red blood cell placed in pure water would ________.
B) swell initially, then shrink as equilibrium is reached
C) neither shrink nor swell
D) swell and burst
6) The plasma membrane is ________.
A) a single-layered membrane that surrounds the nucleus of the cell
B) a double layer of protein enclosing the plasma
C) the phospholipid bilayer surrounding the cell
D) a membrane composed of tiny shelves or cristae
7) Which of these is not a function of the plasma membrane?
A) It is selectively permeable.
B) It prevents potassium ions from leaking out and sodium ions from crossing into the cell.
C) It acts as a site of cell-to-cell interaction and recognition.
D) It encloses the cell contents.
8) Which structures are fingerlike projections that greatly increase the absorbing surface of cells?
9) Which of the following statements is correct regarding diffusion?
A) The rate of diffusion is independent of temperature.
B) The greater the concentration of gradient, the faster the rate of diffusion.
C) Molecular weight of a substance does not affect the rate of diffusion.
D) The lower the temperature, the faster the diffusion rate.
10) Cell junctions that promote the coordinated activity of cells by physically binding them
together into a cell community include all of the following except ________.
A) gap junctions
D) tight junctions
11) If cells are placed in a hypertonic solution containing a solute to which the membrane is
impermeable, what could happen?
A) The cells will swell and ultimately burst.
B) The cells will lose water and shrink.
C) The cells will shrink at first, but will later reach equilibrium with the surrounding
solution and return to their original condition.
D) The cells will show no change due to diffusion of both solute and solvent.
12) Which of the following is not a subcellular structure?
A) intercellular material
13) Once solid material is phagocytized and taken into a vacuole, which of the following
statements best describes what happens?
A) A ribosome enters the vacuole and uses the amino acids in the ʺinvaderʺ to form new
B) A lysosome combines with the vacuole and digests the enclosed solid material.
C) The vacuole remains separated from the cytoplasm and the solid material persists
D) Nitrogen enters the vacuole and ʺburnsʺ the enclosed solid material.
14) Riboswitches are folded RNAs that act as switches to turn protein synthesis on or off in
response to _________.
A) changes in the environment
B) specific tRNAs
C) specific codes from the DNA
D) presence or absence of ubiquitins
15) Which of the following is a function of a plasma membrane protein?
A) circulating antibody
B) molecular transport through the membrane
C) forms a lipid bilayer
D) oxygen transport
16) Which of the following statements is correct regarding RNA?
A) Messenger RNA, transfer RNA, and ribosomal RNA play a role in protein synthesis.
B) If the base sequence of DNA is ATTGCA, the messenger RNA template will be
C) There is exactly one specific type of mRNA for each amino acid.
D) rRNA is always attached to the rough ER.
17) Which of the following would not be a constituent of a plasma membrane?
B) messenger RNA
18) Mitosis ________.
A) is the formation of sex cells
B) produces nucleus replication
C) creates diversity in genetic potential
D) always results in division of a cell
19) The electron microscope has revealed that one of the components within the cell consists of
microtubules arranged to form a hollow tube. This structure is ________.
20) Which of these is an inclusion, not an organelle?
21) Hyperplasia means __________.
A) programmed cell death
B) abnormalities in cell structure
C) a condition where the cell overproduces ʺcell glueʺ
D) accelerated growth
22) If the nucleotide or base sequence of the DNA strand used as a template for messenger RNA
synthesis is ACGTT, then the sequence of bases in the corresponding mRNA would be
23) Which of the following is true regarding cells in humans?
A) Organelles are independent life forms.
B) Maximum cell diameter is limited to 2 micrometers.
C) Cells can be as long as 1 meter.
D) All cells of an adult have a very short life span.
24) Phospholipids ________.
A) are exclusively hydrophilic molecules
B) contain polar tails and nonpolar head groups
C) are both hydrophilic and hydrophobic in nature
D) form the lipid bilayer, with tails directed to the outside
25) Passive membrane transport processes include ________.
A) movement of a substance down its concentration gradient
B) movement of water from an area of low concentration to an area of high concentration
C) consumption of ATP
D) the use of transport proteins when moving substances from areas of low to high
26) Enzymes called _________ destroy the cellʹs DNA and cytoskeleton, producing a quick death
to the cell.
D) DNA polymerase III
27) Mitochondria ________.
A) are always the same shape
B) are single-membrane structures involved in the breakdown of ATP
C) contain some of the DNA and RNA code necessary for their own function
D) synthesize proteins for use outside the cell
28) Ribosomes, endoplasmic reticulum, and the Golgi apparatus functionally act in sequence to
synthesize and modify proteins for secretory use (export) only, never for use by the cell. This
statement is ________.
A) false; proteins thus manufactured are for use inside the cell only
B) false; integral cell membrane proteins are also synthesized this way
C) false; lipids, not proteins, are synthesized this way
29) Peroxisomes ________.
A) also called microbodies, contain acid hydrolases
B) are able to detoxify substances by enzymatic action
C) function to digest particles ingested by endocytosis
D) sometimes function as secretory vesicles
30) DNA replication ________.
A) can also be called mitosis
B) is spontaneous, not requiring enzyme action
C) takes place during interphase of the cell cycle
D) occurs only in translationally active areas
31) Which statement is the most correct regarding transcription/translation?
A) The nucleotide sequence in a mRNA codon is an exact copy of the DNA triplet that
coded for it.
B) The nucleotide sequence in a mRNA codon is an exact copy of the DNA triplet that
coded for it except that uracil is substituted for thymine.
C) The nucleotide sequence in a tRNA anticodon is an exact copy of the DNA triplet that
coded for it.
D) The nucleotide sequence in a tRNA anticodon is an exact copy of the DNA triplet that
coded for it except that uracil is substituted for thymine.
32) In the maintenance of the cell resting membrane potential ________.
A) extracellular sodium levels are high
B) cells are more permeable to Na+ than K+
C) the steady state involves only passive processes in all cells
D) the inside of the cell is positive relative to its outside
33) Which of the following is a concept of the cell theory?
A) Simple cells can arise spontaneously from rotting vegetation.
B) A cell is the basic structural and functional unit of living organisms.
C) The subcellular organelle is the basic unit of life.
D) Only higher organisms are composed of cells.
34) Cells are composed mainly of ________.
A) carbon, potassium, sodium, nitrogen
B) carbon, sodium, nitrogen, calcium
C) calcium, oxygen, sodium, potassium
D) carbon, hydrogen, nitrogen, oxygen
35) Which of the following is a principle of the fluid mosaic model of cell membrane structure?
A) Phospholipids form a bilayer that is largely impermeable to water-soluble molecules.
B) Phospholipids consist of a polar head and a nonpolar tail made of three fatty acid chains.
C) The lipid bilayer is a solid at body temperature, thus protecting the cell.
D) All proteins associated with the cell membrane are contained in a fluid layer on the
outside of the cell.
36) Which of the following statements is most correct regarding the intracellular chemical signals
known as ʺsecond messengersʺ?
A) Second messengers act through receptors called K-proteins.
B) Second messengers usually inactivate protein kinase enzymes.
C) Cyclic AMP and calcium may be second messengers.
D) Second messengers usually act to remove nitric oxide (NO) from the cell.
37) The main component of the cytosol is ________.
38) Lysosomes ________.
A) are always used for the cell to ʺcommit suicideʺ
B) contain acid hydrolases that are potentially dangerous to the cell
C) maintain a highly alkaline internal environment
D) are the major site of protein synthesis
39) The endomembrane system is ________.
A) a system by which cells are riveted together by desmosomes
B) an interactive system of organelles whose membranes are physically or functionally
C) the process by which bacteria took up residence in ancient cells
D) a system of hydrophilic lipid monolayers that surround many cell organelles
40) The functions of centrioles include ________.
A) organizing the mitotic spindle in cell division
B) providing a whiplike beating motion to move substances along cell surfaces
C) serving as the site for ribosomal RNA synthesis
D) producing ATP
41) A gene can best be defined as ________.
A) a three-base triplet that specifies a particular amino acid
B) noncoding segments of DNA up to 100,000 nucleotides long
C) a segment of DNA that carries the instructions for one polypeptide chain
D) an RNA messenger that codes for a particular polypeptide
42) Extracellular matrix is ________.
A) composed of strands of actin protein
B) the most abundant extracellular material
C) a type of impermeable cell junction found in epithelia
D) not present in connective tissue
43) Crenation is likely to occur in ________.
A) blood cells in an isotonic solution
B) blood cells in a hypotonic solution
C) blood cells in a hypertonic solution
D) blood cells in blood plasma
44) Some hormones enter cells via ________.
D) receptor-mediated endocytosis
45) If a tRNA had an AGC anticodon, it could attach to a(n) ________ mRNA codon.
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