MMSC490 Practice Exam 1

cytoplasmic organelles are:

a. absent in prokaryotic cells and present in eukaryotic cells.

b. present in both prokaryotic and eukaryotic cells.

c. present in prokaryotic cells and absent in eukaryotic cells.

d. absent in both prokaryotic and eukaryotic cells.

a. absent in prokaryotic cells and present in eukaryotic cells

E. coli is a useful model system for molecular biology studies because:

a. it has a small genome.

b. it reproduces rapidly.

c. mutants can easily be isolated from culture dishes.

d. All of the above

d. all of the above

Arabidopsis thaliana is a model organism for studying the molecular biology of:

a. plants.

b. fungi.

c. fruit flies.

d. vertebrates.

a. plants

The diffraction limited resolving power of a standard light microscope is

approximately:

a. 0.2 mm.

b. 0.2 µm.

c. 0.2 nm.

d. 2 Å.

b. 0.2 um

A common use of green fluorescent protein (GFP) is to:

a. label antibodies.

b. visualize proteins in living cells.

c. photobleach other fluorescent proteins.

d. label DNA sequences.

b. visualize proteins in living cells

Electron microscopes have a resolution advantage over light microscopes

because:

a. electron microscopes allow the viewer to examine living cells.

b. electron microscope lens have a larger numerical aperture.

c. electron microscopes are easier to use.

d. the wavelength of electrons is shorter than that of light

d. the wavelength of electrons is shorter than that of light

In a classic experiment that demonstrated the semiconservative nature of DNA

replication, cells were grown first in 14N-containing media and later in 15N-containing

media, and DNA was separated by:

a. electrophoresis.

b. differential centrifugation.

c. velocity density-gradient centrifugation.

d. equilibrium centrifugation.

d. equilibrium centrifugation

The most abundant molecules in cells are:

a. proteins.

b. carbohydrates.

c. lipids.

d. water.

d. water.

A few sugars joined together are called a(n):

a. glycoside.

b. oligosaccharide.

c. polysaccharide.

d. starch.

b. oligosaccharide

Steroid hormones are derivatives of:

a. cholesterol.

b. phospholipids.

c. amino acids.

d. sugars.

a. cholesterol

Complementary base pairs form _______ bonds to direct replication of DNA.

a. hydrogen

b. phosphodiester

c. glycosidic

d. covalent

a. hydrogen

Polymerization of nucleotides to form nucleic acids involves the formation of

_______ bonds.

a. peptide

b. phosphodiester

c. glycosidic

d. hydrogen

b. phosphodiester

Serine, threonine, asparagine, and glutamine are all _______ amino acids.

a. basic

b. acidic

c. polar

d. nonpolar

c. polar

In the primary structure of a protein, amino acids are joined together by _______

bonds.

a. peptide

b. phosphodiester

c. glycosidic

d. hydrophobic

a. peptide

The interaction of the α and β subunits to form the hemoglobin molecule is an

example of _______ structure.

a. primary

b. secondary

c. tertiary

d. quaternary

d. quaternary

The unique properties of different membranes are primarily a function of their:

a. proteins.

b. phospholipids.

c. cholesterol molecules.

d. glycolipids.

a. proteins

The role of double bonds in the fatty acid tails of membrane phospholipids is to:

a. help stabilize the membrane.

b. react with adjacent double bonds.

c. increase membrane fluidity.

d. interact with membrane proteins

c. increase membrane fluidity

The currently accepted model of membrane structure is called the _______

model.

a. lipid bilayer

b. unit membrane

c. lipid raft

d. fluid mosaic

d. fluid mosaic

Integral membrane proteins are those that:

a. are directly associated with membrane lipids.

b. are associated with the membrane indirectly.

c. never span the membrane bilayer.

d. None of the above

a. are directly associated with membrane lipids

Membrane proteins can be anchored to the cytosolic face of the plasma

membrane by:

a. sugar groups of glycolipids.

b. prenyl groups.

c. sugar groups of glycoproteins.

d. None of the above

b. prenyl groups

Lipid bilayers are permeable only to molecules that are _______ and _______.

a. large; uncharged

b. large; charged

c. small; uncharged

d. small; charged

c. small; uncharged

During formation of eggs and sperm, one member of each chromosome pair is

transmitted to each progeny cell in a type of cell division called:

a. mitosis.

b. gametogenesis.

c. cytokinesis.

d. meiosis.

d. meiosis

Eggs and sperm are:

a. haploid.

b. diploid.

c. euploid.

d. tetraploid.

a. haploid

RNA molecules that serve as templates for protein synthesis are called _______

RNAs.

a. messenger

b. transfer

c. ribosomal

d. small nuclear

a. messenger

Because the genetic code usually has more than one codon for each amino acid,

the code is said to be:

a. redundant.

b. wobbly.

c. a template.

d. degenerate.

d. degenerate

Reverse transcriptase is an enzyme that catalyzes _______ synthesis.

a. DNA-directed RNA

b. RNA-directed DNA

c. DNA-directed DNA

d. RNA-directed RNA

b. RNA-directed DNA

To clone genes, a plasmid vector should contain a(n):

a. origin of replication.

b. restriction nuclease cut site.

c. antibiotic resistance gene.

d. All of the above

d. all of the above

Nucleic acid hybridization is the:

a. mating of two genetically different organisms.

b. formation of hybrid nuclei when two cells are fused.

c. formation of a double-stranded molecule from the interaction of two complementary-sequence single-stranded molecules.

d. recombining of DNA molecules from two different organisms.

c. formation of a double-stranded molecule from the interaction of two complementary-sequence single-stranded molecules

The technique by which fragments of DNA are separated by gel electrophoresis,

denatured, blotted on nitrocellulose paper, labeled with a complementary radioactive

probe, and detected by autoradiography is called _______ blotting.

a. Southern

b. Northern

c. Western

d. Eastern

a. Southern

In 1995, the first complete genome of _______ was sequenced.

a. Escherichia coli

b. Saccharomyces cerevisae

c. Haemophilus influenzae

d. Caenorhabditis elegans

c. Haemophilus influenzae

Analysis of the H. influenza and E. coli genomes revealed that _______% of the

genomes encodes for protein.

a. 25

b. 50

c. 75

d. 90

d. 90

The feature that most clearly distinguishes eukaryotes from prokaryotes is the presence of _____ in eukaryotic cells.

a. Ribosomes

b. Oxidative phosphorylation

c. RNA molecules

d. Nucleus

d. nucleus

Drosophila melanogaster was an organism of choice for the study of:

a. The process of fertilization

b. The process of cell aggregation to form a multicellular organism

c. The process of development

d. Mammalian genetics

c. the process of development

Living cells are commonly visualized by means of _____ microscopy.

a. Phase-contrast

b. Bright-field

c. Fluorescence

d. Electron

a. phase-contrast

Super resolution light microscopes extend the resolution limits of light microscopy to:

a. 0.2 to 0.5 mm

b. 0.2 to 0.5 um

c. 20 to 100 nm

d. 20 to 100 Å

c. 20 to 100 nm

Which fish is proving to be a useful model organism in the study of vertebrate development?

a. Zebrafish

b. Goldfish

c. Salmon

d. Guppy

a. zebrafish

The method by which cell components are separated by centrifugation at progressively higher speeds is called _____ centrifugation.

a. Differential

b. Velocity

c. Density-gradient

d. Equilibrium

a. differential

Cultures grown from cells of a dissociated tissue are called:

a. Transformed cell lines

b. Normal cell lines

c. Primary cell cultures

d. Secondary cell cultures

c. primary cell cultures

In polysaccharides, sugars are linked together by means of _____ bonds.

a. Phosphodiester

b. Peptide

c. Glycosidic

d. Hydrophobic

c. glycosidic

The most common molecules in cellular membranes are the:

a. Glycolipids

b. Phospholipids

c. Cholesterol molecules

d. Protein

b. phospholipids

Phospholipids in a membrane commonly

a. Move laterally in the plane of the bilayer

b. Rotate within the bilayer

c. Move from one bilayer to the other

d. Both a and b

d. both a and b

Transmembrane proteins can span the lipid bilayer as

a. Alpha helices

b. Beta helices

c. Random chains

d. Both a and c

a. alpha helices

Channels form pores through which molecules of appropriate size and charge can cross a membrane. By contrast, carrier molecules that traverse a membrane against their concentration gradient do so by _____ transport.

a. Active

b. Passive

c. Carrier-mediated

d. Channel-mediated

a. active

Animal cells and most cells of higher plants are:

a. Haploid

b. Diploid

c. Euploid

d. Tetraploid

b. diploid

DNA replicates:

a. Conservatively

b. Semi-conservatively

c. Liberally

d. By hybridization

b. semi-conservatively

Which of the following deletions will not change the reading frame of a gene?

a. One nucleotide

b. Two nucleotides

c. Three nucleotides

d. Four nucleotides

c. three nucleotides

Restriction endonucleases are enzymes that:

a. Cleave DNA only at specific sequences

b. Act only on the ends of DNA strands

c. Act only in a single species of bacteria

d. Cleave only nuclear DNA

a. cleave DNA only at specific sequences

The most common method of DNA sequencing is based on premature termination of DNA synthesis by inclusion of:

a. Dideoxynucleotides

b. Endonuclease

c. Ampicillin

d. Puromycin

a. dideoxynucleotides

The original cell was thought to have arisen from the enclosure of self-replicating _____ by a phospholipid membrane.

a. DNA

b. Carbohydrate

c. Protein

d. RNA

d. RNA

The source of the atmospheric oxygen necessary for the development of oxidative metabolism is thought to have been:

a. Glycolysis

b. The formation of Earth

c. Photosynthesis

d. The breakdown of ATP

c. photosynthesis

Chloroplasts are thought to have originated from endosymbiosis of _____ by a large host cell.

a. Anaerobic bacteria

b. Photosynthetic eubacteria such as cyanobacteria

c. Fungi such as yeast

d. Non-photosynthetic aerobic bacteria

b. photosythetic eubacteria such as cyanobacteria

The genome of eukaryotes consists of genes derived from:

a. Archaebacteria alone

b. Bacteria alone

c. Both archaebacteria and bacteria

d. Neither archaebacteria nor bacteria

c. both archaebacteria and bacteria

Which of the following is not a unicellular eukaryote?

a. Saccharomyces cerevisiae

b. Paramecium

c. Archaebacteria

d. Chlamydomonas

c. archaebacteria

Solid tissues in animals include epithelial tissue, _______ tissue, nervous tissue, and

muscle.

a. Blood

b. Connective

c. Ground

d. Epidermal

b. connective

How many genes does an E. coli have?

a. 4,300

b. 6,000

c. 14,000

d. 20,000-25,000

a. 4,300

An E. coli cell under well-defined laboratory conditions divides about every:

a. 20 minutes

b. 2 hours

c. 12 hours

d. 24 hours

a. 20 minutes

Which of the following are the most commonly used mammals for genetic studies?

a. Humans

b. Xenopus laevis

c. Mice

d. Cats

c. mice

What is the theoretical diffraction limit of resolution of a light microscope used to look at a sample through oil?

a. 0.22 micrometer

b. 0.2 nm

c. 1 mm

d. 0.305 micrometer

a. 0.22 um

In fluorescence microscopy, the immediate source of the light detected is light that has been _____ the sample.

a. Absorbed by

b. Emitted by

c. Exciting

d. Scattered from

b. emitted by

Which of the following is a high-resolution light microscope technique for detecting interactions between proteins?

a. FRAP (fluorescence recovery after photobleaching)

b. FRET (fluorescence resonance energy transfer)

c. MPEM (multi-photon excitation microscopy)

d. Confocal microscopy

b. FRET (fluorescence resonance energy transfer)

Transmission electron microscopy is used to:

a. Study in single, thin sections the shapes of whole cells

b. View living cells in three dimensions

c. View fluorescently labeled proteins in cells

d. Observe subcellular organelles and macromolecules

d. observe subcellular organelles and macromolecules

What is the smallest number of ultracentrifugation steps needed to separate nuclei from ribosomes in a cellular lysate?

a. 1

b. 2

c. 4

d. 7

a. 1

Embryonic stem cells are different from primary cell cultures or permanent cell lines

derived from a tissue in that they are capable of:

a. Generating many cell types

b. Growing and dividing

c. Synthesizing their own DNA

d. Transporting nutrients across their plasma membrane

a. generating many cell types

In contrast to animal cells, yeast or bacterial cell cultures can be grown on fairly simple media without the need to add amino acids or various vitamins and hormones. This is primarily because animal cells:

a. Typically live in association with other cells

b. Are less capable of transporting small molecules across their membranes

c. Come from organisms that have specialized cell types

d. Have too many genes to be able to keep track of the biosynthesis of needed metabolites

c. come from organisms that have specialized cell types

Approximately how many doublings can normal human fibroblasts undergo in culture?

a. 5

b. 50 to 100

c. They will go on proliferating indefinitely

d. They will not double at all but dispersing them in culture allows them to be studied in isolating from other cell types

b. 50 to 100

Bacteriophages are:

a. A stain of gram-negative bacteria

b. Bacteria that phagocytose other competing bacteria

c. Bacterial lysosomes

d. Viruses that infect bacteria

d. viruses that infect bacteria

Which of the following is not one of the four major classes or organic molecules in the cell?

a. Carbohydrates

b. Lipids

c. Water

d. Proteins

c. water

What is the major carbohydrate-storage molecule in plants?

a. Starch

b. Cellulose

c. Glycogen

d. Deoxyribonucleic acid

a. starch

Introducing a double bond into a fatty acid has the effect of putting a(n) _____ into the conformation of the molecule.

a. Amino acid bulge

b. Kink

c. Reverse spiral

d. Reinforcing rod

b. kink

Phospholipids consist of a 3-carbon core to which fatty acids and a phosphate group are linked. The most common 3-carbon core is:

a. Dihydroxyacetone

b. Glyceraldehyde

c. Glycerol

d. Serine

c. glycerol

Molecules that are partly water-soluble and partly water-insoluble are:

a. Hydrophilic

b. Amphipathic

c. Hydrophobic

d. Allosteric

b. amphipathic

Cholesterol, a membrane lipid in animals, has a chemical structure similar to:

a. Estradiol

b. Phosphatidylinositol

c. Thymine

d. Triacylglycerol

a. estradiol

Which of the following bases is not found in DNA?

a. Adenine

b. Cytosine

c. Thymine

d. Uracil

d. uracil

How many common amino acids are there?

a. 5

b. 10

c. 20

d. 25

c. 20

A disulfide bond is formed between ____ residues.

a. Cysteine

b. Glycine

c. Methionine

d. Tyrosine

a. cysteine

Which of the following classes of amino acids is buried within the folded structure of the protein?

a. Acidic

b. Basic

c. Nonpolar

d. Polar

c. nonpolar

The three-dimensional structure of a protein is analyzed most definitively by:

a. Electron microscopy

b. Light microscopy

c. Subcellular fractionation

d. X-ray crystallography

d. x-ray crystallography

The alpha helix is an example of which level of protein structure?

a. Primary

b. Quaternary

c. Secondary

d. Tertiary

c. secondary

Proteins must have more than one _____ to have a quaternary structure.

a. Alpha helix

b. Beta sheet

c. Polypeptide chain

d. Transmembrane segment

c. polypeptide chain

Enzymes act by:

a. Lowering the overall change in the free energy of a reaction

b. Decreasing the distance that reactants must diffuse to find one another

c. Increasing the activation energy

d. Decreasing the activation energy

d. decreasing the activation energy

Enzymes affect the transition state of a chemical reaction by:

a. Binding to the substrate(s)

b. Providing a surface on which the reactions converting substrate to product can occur more rapidly

c. Altering the conformation of the substrate(s) to approach that of the transition state

d. All three answer choices

d. all three answer choices

The lock-and-key and induced-fit models are two alternative models that can explain how enzymes and substrates interact. These two models can be distinguished from each other according to changes in the:

a. Viscosity of the reaction solution as the substrate and enzyme bind

b. Shape as the substrate and enzyme bind

c. Reaction solution temperature as a result of the endothermic cooling that occurs during substrate binding

d. Reaction solution color as the substrate and enzyme bind

b. shape as the substrate and enzyme bind

Chymotrypsin, trypsin, elastase, and thrombin are all grouped together as members of the serine protease family because each:

a. Has similar charge and shape properties in its substrate insertion pockets

b. Can form a heptahedral complex with its substrate

c. Uses the same catalytic mechanisms involving the same key amino acids

d. Can be modified by the cell wall biosynthetic degradative enzyme chitinase

c. uses the same catalytic mechanisms involving the same key amino acids

Which of the following is not true of coenzymes?

a. Chemically, they are branched amino acids

b. They serve as carriers of several types of chemical groups

c. They transfer specific chemical groups among a wide range of substrates

d. They work together with enzymes to enhance chemical reactions without being irreversibly altered

a. chemically, they are branched amino acids

Coenzymes are chemically related to:

a. Amino acids

b. Inorganic phosphate

c. Glucose

d. Vitamins

d. vitamins

All of the following are ways in which enzyme activity can be regulated except:

a. By binding to an allosteric site

b. Through feedback inhibition

c. By modulation of intracellular sucrose concentrations

d. Through phosphorylation

c. by modulation of intracellular sucrose concentrations

About 50% of the mass of most biological membranes consists of lipids and about 50% consists of proteins. Therefore:

a. The membranes contain fewer molecules of lipid than of protein

b. The membranes contain equal number of lipid and protein molecules

c. The membranes contain more molecules of lipid than of protein

d. Only a few membrane proteins are exposed at the cell surface

c. the membranes contain more molecules of lipid than of protein

Lipids with unsaturated fatty acids:

a. Decrease the fluidity of membranes

b. Increase the charge associated with the inner face of a membrane

c. Increase the fluidity of membranes

d. Are present only on the inner side of the plasma membrane

c. increase the fluidity of membranes

In the fluid mosaic model of biological membrane structure, transmembrane proteins are:

a. Embedded nearly randomly in the lipid bilayer

b. Almost completely surrounded by membrane lipid

c. Segregated into large protein clusters or rafts

d. Weakly held in place on the surface of the lipid bilayer

a. embedded nearly randomly in the lipid bilayer

What is the effect of a beta barrel on the permeability of a membrane?

a. It decreases permeability

b. It increases permeability

c. It has no effect

d. Beta barrels are never found in membranes

b. it increases permeability

Transport across biological membranes is speeded by what class of biological molecules?

a. Carbohydrates

b. Lipids

c. Nucleic acids

d. Proteins

d. proteins

Whereas small uncharged molecules can diffuse through the hydrophobic core of a phospholipid bilayer, a larger polar substance such as glucose must enter cells by binding to:

a. A non-phospholipid such as cholesterol

b. The carbohydrate portion of glycolipids

c. Peripheral membrane proteins located on the inner side of the membrane

d. Carrier proteins that facilitate the passage of specific molecules across membranes

d. carrier proteins that facilitate the passage of specific molecules across membranes

Passive transport across a membrane refers to:

a. Transport into the interior of a cell

b. Transport out of a cell

c. Transport in the energetically favorable direction

d. Simple diffusion across membranes, without the help of proteins such as channels or carriers

c. transport in the energetically favorable direction

Which of the following correctly represents the distinction between the terms, "genotype" and "phenotype"?

a. The genotype is the genetic composition of an organism, whereas the phenotype is its physical appearance.

b. Phenotype is the genetic composition of an organism, while genotype is the physical appearance.

c. There is no difference between a genotype and a phenotype.

d. A phenotype is dominant, and a genotype is recessive

a. the genotype is the genetic composition of an organism, whereas the phenotype is its physical appearance

In Gregor Mendel's experiments on pea genetics, he determined that yellow seed color, Y, was dominant over green seed color, y. In a cross between two plants, one with yellow seeds and the other with green seeds, all the seeds produced from the offspring were yellow. What was the genotype of the parent plant with yellow seeds?

a. Yy

b. yY

c. YY

d. yy

c. YY

The two strands of DNA in the double helix are held together by:

a. Covalent bonds between the bases of each strand

b. Hydrogen bonds between the bases of each strand

c. Interactions between the sugar residues of each chain

d. Interactions between phosphate residues of each strand

b. hydrogen bonds between the bases of each strand

Which of the following serves as an adapter between amino acids and mRNA during translation?

a. tRNA

b. rRNA

c. DNA

d. siRNA

a. tRNA

The enzyme that synthesizes DNA using RNA templates is called:

a. DNA polymerase

b. RNA polymerase

c. Reverse transcriptase

d. Ribozymes

c. reverse transcriptase

The characterization of restriction endonucleases was a key step in the development of recombinant DNA technology. What is the function of these enzymes?

a. Synthesis of complementary strands of DNA from a DNA template

b. Ligation of two digested DNA strands

c. Synthesis of RNA from a DNA template

d. Cleavage of DNA at specific sequences

d. cleavage of DNA at specific sequences

A restriction enzyme with a four-base recognition site would cleave DNA with a statistical frequency of once every:

a. 4 base pairs

b. 4,096 base pairs

c. 256 base pairs

d. 65.5 kilobases

c. 256 base pairs