Final Exam (Exams 1-3)

Question 1

The three main branches in the phylogenetic “tree” of life are _______________________.

A. Bacteria, Archaea, and Eukaryotes
B. Protozoa, Eukaryotes, and Bacteria
C. Prokaryotes, Eukaryotes, and Archaea
D. Bacteria, Plants, and Animals
E. Plants, Animals, and Fungi

Answer 1

Bacteria, Archaea, and Eukaryotes

Question 2

Tyndall repeated his experiments, but he obtained different results. This was because __________.

A. He did not boil the flasks for as long a time as Pasteur did
B. He used different flasks than Pasteur
C. He did not do his experiment correct
D. The media he was trying to sterilize contained endospores
E. He was working in England, but Pasteur was working in France

Answer 2

The media he was trying to sterilize contained endospores

Question 3

Viroids are __________________.

A. Another name for protozoan viruses
B. Infectious proteins that serve as folding templates for other proteins
C. Empty protein coats without any nucleic acid
D. Small pieces of RNA without a protein coat
E. Small virus-like particles

Answer 3

Small pieces of RNA without a protein coat

Question 4

Why is it important that most intermolecular interactions in cells are weak bonds?

A. They are more easily reversible.
B. Fewer of them are needed to hold molecules together.
C. Very few strong bonds can occur in an aqueous solution.
D. It takes more energy to form them.
E. More energy is released when they are broken.

Answer 4

They are more easily reversible.

Question 5

The pH inside a bacterial cell is 7. The pH outside the cell is 6. What is the size of the H+ gradient?

A. There is one more proton inside than outside the cell.
B. There are twice as many protons outside than inside the cell
C. There are 10 times as many protons inside than outside the cell.
D. There are 10 times as many protons outside than inside the cell.
E. You need more information to answer this question.

Answer 5

There are 10 times as many protons outside than inside the cell.

Question 6

These viruses infect the bacterium Escherichia coli. Which of the following statements MUST also be true?

A. Their diameter (white line) is less than 1 nanometer.
B. The viruses are prokaryotes.
C. They cannot infect humans.
D. They contain no protein.
E. They have a lipid envelope.

Answer 6

They cannot infect humans.

Question 7

What makes a biological strong bond strong?

A. Electron sharing between atoms in the bond.
B. Hydration by water.
C. There are a large number of charge interactions.
D. A large electronegativity difference between atoms in the bond.
E. It forms spontaneously without the involvement of enzymes.

Answer 7

Electron sharing between atoms in the bond.

Question 8

Nucleic acids are put together from their monomers, nucleotides, with ______________ bonds.

A. ionic
B. parallel
C. peptide
D. phosphate
E. phosphodiester

Answer 8

phosphodiester

Question 9

Two molecules are composed of the same atoms, but the molecules have different molecular weights. This can be explained by the existence of _______________.

A. A dipole moment
B. sp3 orbital hybridization
C. ions
D. isotopes
E. isomers

Answer 9

isotopes

Question 10

Which of the following is true about a condensation reaction to produce a macromolecule from its monomers?

A. It is usually regarded as a catabolic reaction.
B. It generally requires energy input.
C. It is one mechanism where cells can “break down” long polymers.
D. It involves the loss of water from the cell in a hypertonic environment.
E. An example is the following reaction:

Answer 10

It generally requires energy input.

Question 11

Which of the following lipids would be the most fluid at room temperature.

A. Lipids with 3 trans-unsaturated fatty acids
B. Lipids with 3 cis-unsaturated fatty acids
C. Lipid with a mixed cis- and trans-unsaturated fatty acids
D. Lipids with 3 saturated fatty acids
E. Phospholipids

Answer 11

Lipids with 3 cis-unsaturated fatty acids

Question 12

What type of microscope measures electric current passing through a probe rather than using part of the electromagnetic spectrum?

A. Bright field
B. Phase contrast
C. Atomic force
D. Differential interference contrast (Nomarski)
E. Dark field

Answer 12

Atomic force

Question 13

How does an amino acid get through the outer membrane of Gram-negative bacteria?

A. Through active transport
B. Through special facilitated diffusion protein channels
C. Through the use of energy from the proton motive force (PMF)
D. Lipid A in the outer membrane is more permeable than phospholipids
E. Through simple diffusion

Answer 13

Through special facilitated diffusion protein channels

Question 14

What type of microscope uses special prisms to make a thin specimen appear pseudo-3-dimensional?

A. Bright field
B. Phase contrast
C. Atomic force
D. Differential interference contrast (Nomarski)
E. Dark field

Answer 14

Differential interference contrast (Nomarski)

Question 15

Is a blood infection with a Gram-negative or Gram-positive cells more dangerous? Why?

A. Gram-negative; because we cannot make antibodies against any Gram-negative structures
B. Gram-negative; because of the O-antigen layer of the outer membrane
C. Gram-negative; because of the toxic shock induced by the LPS “endotoxin”
D. Gram-positive; because the cells cannot be killed with readily available antibiotics
E. Gram-positive; because of the lipoproteins in the membrane

Answer 15

Gram-negative; because of the toxic shock induced by the LPS “endotoxin”

Question 16

A typical bacterial cell is growing in a typical culture. It is using the ATP synthase to make ATP. A scientist adds a chemical to its membrane that permits protons (H+) to flow freely across the phospholipid bilayer. Will the bacteria still be able to use its ATP synthase?

A. Yes, but only as a Type III secretion system, which uses ATP rather than PMF.
B. No. The reaction to make ATP requires that two H+ be donated to ADP.
C. Yes, because electrons can still be donated to ADP to make ATP.
D. No. Without a proton gradient, there is no PMF. Without PMF, ATP synthase does not work.
E. Yes, because it can still have a PMF, even without a proton gradient.

Answer 16

No. Without a proton gradient, there is no PMF. Without PMF, ATP synthase does not work.

Question 17

Amphipathic phospholipids form a membrane bilayer if place in water. What would happen if the membrane were placed in a nonpolar (hydrophobic) solvent instead of water?

A. Nothing. It is amphipathic. It would be the same as in water.
B. The phospholipids would no longer be amphipathic.
C. The bilayer would turn inside out.
D. It would form a micelle.
E. The bilayer would fall apart and form a thin monolayer on top of the solvent.

Answer 17

The bilayer would turn inside out.

Question 18

What would happen to Mycoplasma cells placed in a solution that was hypotonic (hypoosmotic) with respect to the cytoplasm of the cells?

A. They would not experience any changes.
B. They would experience an increase in turgor pressure but would not lyse.
C. They would lyse.
D. They would synthesize osmoprotectants.
E. They would plasmolyze.

Answer 18

They would lyse.

Question 19

What type of transport is carried out by the PTS (phosphotransferase system)?

A. Import of sugars
B. Export of fully folded proteins
C. Import of negatively charged amino acids
D. Export of proteins into the cell membrane
E. Import of positively charged ions such as NH4+

Answer 19

Import of sugars

Question 20

Why does passive transport require energy?

A. To open facilitated diffusion channels in the cytoplasmic membrane.
B. To force a molecule through the hydrophobic interior of the cytoplasmic membrane.
C. To pump a molecule against the PMF.
D. To concentrate a molecule against its concentration gradient.
E. Passive transport does not require any energy.

Answer 20

Passive transport does not require any energy.

Question 21

There is currently much interest in studying efflux pumps that bacterial cells use to eliminate toxins and antibiotics. What is one characteristic of these efflux pumps?

A. They are made of lipids rather than proteins.
B. The toxin is secreted through both bacterial membranes and a host cytoplasmic membrane in one step.
C. The toxin is secreted through both bacterial membranes in one step.
D. Efflux pumps include a long extracellular “needle complex”.
E. Efflux pumps allow secretion of fully folded protein toxins.

Answer 21

The toxin is secreted through both bacterial membranes in one step.

Question 22

Which of the following is NOT a part of the process of endospore formation?

A. Mother cell lyses to release the endospore.
B. The endospore replicates its DNA one last time in case conditions improve for growth.
C. A special layer of peptidoglycan is deposited around the endospore.
D. The mother cell engulfs the developing endospore.
E. The cell divides asymmetrically.

Answer 22

The endospore replicates its DNA one last time in case conditions improve for growth.

Question 23

Which of the following is characteristic of a bacterial type II secretion (export) system?

A. Secretion occurs from a bacterium directly into a eukaryotic host cell.
B. Secretion occurs though both the cytoplasmic and outer membrane simultaneously.
C. Fully folded proteins and nucleic acids can be secreted.
D. Secretion uses a leader peptide (signal sequence) to determine which proteins to secrete.
E. A type II secretion system releases carbohydrates out of a cell.

Answer 23

Secretion uses a leader peptide (signal sequence) to determine which proteins to secrete.

Question 24

Phosphate that will be used to make cellular structures is stored in _____________.

A. ATP
B. Phosphobilisomes
C. PHB granules
D. Volutin granules
E. DNA

Answer 24

Volutin granules

Question 25

What happens to a swimming bacterial cell when its flagella reverse their direction of rotation?

A. Flagella are unidirectional. It is impossible for them to reverse rotation.
B. Nothing. The bacterial cells continue swimming until its flagella become methylated.
C. H+ are pumped out of the cell rather than flowing in.
D. The bacterial cell reorients (repositions) to face a new direction.
E. The bacterial cell reverses its direction of travel.

Answer 25

The bacterial cell reorients (repositions) to face a new direction.

Question 26

Superoxide dismutase is _______________________.

A. An enzyme that allows aerobes to survive in oxygen
B. One of the components of the electron transport system
C. An enzyme that allows thermophiles to survive high temperatures
D. An enzyme that allows autotrophs to reduce CO2
E. A storage granule for lithotrophic electron sources

Answer 26

An enzyme that allows aerobes to survive in oxygen

Question 27

Acidophilic bacteria grow best in low pH environments. One consequence of this type of growth is __________________________________________.

A. A cytoplasmic pH of approximately 4
B. The need to use ATP to pump H+ out of the cell
C. Making proteins with a large number of surface charges that can interact with ions
D. The use of ATP synthase that is powered by Na+ ions instead of H+
E. Rapid growth due to the abundance of “natural” PMF energy

Answer 27

The need to use ATP to pump H+ out of the cell

Question 28

What function do bacterial microcompartments carry out?

A. They concentrate enzymes and their substrates to improve reaction rates.
B. They store phosphate reserves that a bacterial cell will use during times of phosphate starvation.
C. They store carbon reserves that a bacterial cell will use during times of carbon starvation.
D. They concentrate photosynthetic pigments.
E. They orient bacteria in an oxygen gradient.

Answer 28

They concentrate enzymes and their substrates to improve reaction rates.

Question 29

. Which of the following equations would be used to solve this problem? (You do not need a calculator for this.)

How many bacteria would you need to start with to have as many cells as the Earth’s population
(7.9 billion) within 12 hours? The bacterium divides in 30 minutes.

A. (7.9 x 109) = X e(1.39)(12)
B. (7.9 x 109) = X e(0.5)(12)
C. (7.9 x 109) = X e12 x
D. X = (7.9 x 109) e(2)(12)
E. X = (7.9 x 109) e(1.39)(12)

Answer 29

(7.9 x 109) = X e(0.5)(12)

Question 30

One major difference between batch culture and continuous cultures is that ____________.

A. Batch culture never reaches stationary phase.
B. Batch culture is best used to produce primary metabolites, such as ethanol.
C. Continuous culture involves fewer nutrients.
D. Continuous culture is set up in a series of flasks, not just one.
E. Continuous culture allows the researcher to change the bacterial growth rate.

Answer 30

Continuous culture allows the researcher to change the bacterial growth rate.

Question 31

A bacterium that is an obligate intracellular parasite of human cells is most likely a/an _______.

A. acidophile
B. halophile
C. psychrophile
D. obligate anaerobe
E. mesophile

Answer 31

mesophile

Question 32

The Most Probable Number (MPN) method ________________.

A. Is considered to be a direct cell count even though it is statistically based
B. Requires multiple culture tubes but no agar plates
C. Is used for very large samples
D. Is usually performed by pouring a sample of the culture through a filter
E. Is a rough estimate of the actual titer based on optical density

Answer 32

Requires multiple culture tubes but no agar plates

Question 33

A competitive inhibitor of an enzyme ___________________.

A. Can only inhibit enzymes in anabolic pathways
B. Inhibits an enzyme even at a much lower concentration than the substrate
C. Works by denaturing or modifying the shape of the active site
D. Binds to an allosteric site on an enzyme
E. Must structurally resemble the substrate of the enzyme it inhibits

Answer 33

Must structurally resemble the substrate of the enzyme it inhibits

Question 34

Glucose is “broken down” in glycolysis. What does “broken down” mean in this situation?

A. Glucose undergoes hydrolysis first and then is oxidized.
B. Glucose undergoes oxidation first and then is hydrolyzed.
C. Glucose is condensed first and then is oxidized.
D. Glucose undergoes reduction first and then is hydrolyzed.
E. Glucose undergoes reduction alone.

Answer 34

Glucose undergoes hydrolysis first and then is oxidized.

Question 35

Much of the bacterial cytoplasmic membrane is made of lipids. How are lipids produced during bacterial metabolism?

A. Bacteria must ingest lipids from their environment as lipids cannot be synthesized.
B. Lipids are produced from oxidative phosphorylation.
C. Lipids are synthesized from the fermentation of pyruvate.
D. Lipids are produced using glycerol and acetyl CoA.
E. Lipids are synthesized from catabolic reactions involving glucose.

Answer 35

Lipids are produced using glycerol and acetyl CoA.

Question 36

At the molecular level, how is a proton gradient generated by the quinone loop?

A. Light causes the quinone to “flip” a proton to the outside of the membrane.
B. The quinone donates both H+ and electrons, but FeS proteins only accept electrons.
C. The quinone donates 2 protons to O2 to make water, which leaves the cell.
D. The quinone, which is located in the periplasm, accepts H+ from the cytoplasm.
E. Electrons in the quinone are excited by light, and end up in NADH, which creates the PMF

Answer 36

The quinone donates both H+ and electrons, but FeS proteins only accept electrons.

Question 37

Which of the following uses mainly fats and oils as carbon sources, producing acids and CO2 by fermentation?

A. Rhizobium
B. Pseudomonas
C. Propionibacterium
D. Clostridium
E. Caulobacter

Answer 37

Propionibacterium

Question 38

Place the following organisms in order from HARDEST to kill to EASIEST.

(1) Giardia cysts
(2) Bacillus endospores
(3) Pseudomonas cells
(4) naked viruses

A. HARDEST (2) > (4) > (1) > (3) EASIEST
B. HARDEST (4) > (3) > (1) > (2) EASIEST
C. HARDEST (3) > (1) > (2) > (4) EASIEST
D. HARDEST (2) > (1) > (4) > (3) EASIEST
E. HARDEST (1) > (3) > (2) > (4) EASIEST

Answer 38

HARDEST (2) > (4) > (1) > (3) EASIEST

Question 39

Which of the following is true of a three-gene operon under negative control?

A. It will be turned off in response to an environmental signal.
B. It will be regulated by a protein that blocks transcription.
C. It will be off (not transcribed) more frequently than it is on.
D. It will have three promoters.
E. It will have three repressor binding sites.

Answer 39

It will be regulated by a protein that blocks transcription.

Question 40

If a bloom of the alga Pfiesteria were reported in a lake near where you lived, what would you expect to see reported in the local television news soon?

A. Warnings that wild animals may have become infected.
B. Reports of lung infections from inhaling algal spores.
C. A report that the water had turned red.
D. Lots of cases of human intestinal poisonings.
E. Reports of many dead fish.

Answer 40

Reports of many dead fish.

Question 41

Purple sulfur bacteria (PSB) must use reverse electron transport, but green sulfur bacteria (GSB) do not. Why is there a difference?

A. Making the sulfur granules in PSB requires electrons from reverse electron transport.
B. GSB use two photosystems, thereby boosting electrons to higher energy levels.
C. GSB use a bacteriochlorophyll with enough energy to donate its electrons directly to ferredoxin.
D. PSB do not make PMF with their electron transport system.
E. GSB use noncyclic photosynthesis, whereas PSB use cyclic photosynthesis.

Answer 41

GSB use a bacteriochlorophyll with enough energy to donate its electrons directly to ferredoxin.

Question 42

Compared to a dry surface, an oily surface __________________________.

A. should have about the same properties as far as disinfection is concerned
B. will be more susceptible to dry heat than to steam
C. is easier to pasteurize but harder to sterilize
D. will probably require cleaning with antiseptics rather than disinfectants
E. is likely to require a longer decimal reduction time for disinfection

Answer 42

is likely to require a longer decimal reduction time for disinfection

Question 43

In protein synthesis, the transpeptidation reaction __________________

A. makes a peptide bond AND transfers the protein to the tRNA in the A-site.
B. brings a new tRNA to the A-site of the ribosome.
C. moves the ribosome toward the 5’ end of the mRNA.
D. releases an uncharged tRNA from the E-site.
E. makes a peptide bond AND releases the protein from the ribosome.

Answer 43

makes a peptide bond AND transfers the protein to the tRNA in the A-site.

Question 44

How do quaternary ammonium salts (QUATs) kill bacteria?

A. They are detergents that dissolved lipid membranes.
B. They denature proteins by interfering with hydrogen bond formation.
C. They oxidize proteins and lipids.
D. They damage the DNA backbone causing mutations.
E. They alter protein disulfide bonding.

Answer 44

They are detergents that dissolved lipid membranes.

Question 45

Which of the following reactions is carried out by methanogenic Archaea?

A. Glucose is hydrolyzed to CO2 using energy from CH4.
B. CH4 is oxidized to CO2 using electrons from light.
C. CH4 is oxidized to CO2 using an organic electron acceptor.
D. CO2 is reduced to CH4 using electrons from light.
E. CO2 is reduced to CH4 using electrons from H2.

Answer 45

CO2 is reduced to CH4 using electrons from H2.

Question 46

Why are naked viruses more resistant to disinfection than enveloped viruses are?

A. They are not. It is enveloped viruses that are more resistant to disinfectants.
B. Enveloped viruses have transport channels that allow disinfectants into the virus.
C. Naked viruses have a more robust metabolism and are harder to kill.
D. Enveloped viruses require at least some water for the envelope to remain intact.
E. Naked viruses have a tough outer layer that resists chemical treatment.

Answer 46

Enveloped viruses require at least some water for the envelope to remain intact.

Question 47

What is one way plant viruses differ from animal viruses?

A. They are all RNA viruses.
B. Neither membrane fusion nor endocytosis can get them into a plant cell.
C. They have a special outer layer called the plasmodesmata.
D. They cannot cause tumors; animal viruses can.
E. They do not carry any nucleic acid, just protein.

Answer 47

Neither membrane fusion nor endocytosis can get them into a plant cell.

Question 48

Why would you “screen” a DNA library?

A. To find the colony that contains the gene you want to study.
B. To enter the DNA sequence into a computer database.
C. This is how you insert a piece of DNA into a plasmid.
D. To separate the cloning vectors according to the size of the DNA insert.
E. To find a gene whose sequence you do not know.

Answer 48

To find the colony that contains the gene you want to study.

Question 49

The free-living nitrogen fixing bacterium Azotobacter has a much higher rate of cellular respiration than other bacteria. Why?

A. It gives much of its energy to a parasitic symbiont.
B. To protect the enzyme nitrogenase from oxygen.
C. Its respiratory chain is less efficient than usual, since it does not donate electrons to O2.
D. It has a much larger need for ATP than other bacteria.
E. It needs oxygen in large amounts for the metabolically active cysts.

Answer 49

To protect the enzyme nitrogenase from oxygen.

Question 50

Why does a bacterial cell have multiple sigma factors?

A. Some sigma factors activate gene expression while others repress transcription.
B. One sigma factor binds to the leading strand, and one binds to the lagging strand.
C. A different sigma factor is required at each gene.
D. The allows the cell to coordinately transcribe genes with related functions.
E. Some are for transcription, while others are for translation.

Answer 50

The allows the cell to coordinately transcribe genes with related functions.

Question 51

What is the mode of action of the sulfa drugs such as sulfanilamide?

A. inhibit bacterial folic acid biosynthesis
B. interfere with the action of DNA gyrase
C. collapse the bacterial PMF
D. inhibit cell wall cross-linking
E. inhibit protein synthesis

Answer 51

inhibit bacterial folic acid biosynthesis

Question 52

How does a phagocyte “know” not to phagocytose your own cells?

A. Your cells do not have PAMPs for the phagocyte to recognize.
B. The pathogen sends phagocytosis signals to the phagocyte before it is engulfed.
C. The phagocytes antibodies cannot bind to your own cells.
D. The phagocyte must be activated by a TC cell before it can engulf other cells.
E. The phagocytes that recognize self antigens are clonally deleted.

Answer 52

Your cells do not have PAMPs for the phagocyte to recognize.

Question 53

Some bacteria contain a large piece of circular DNA called the Ti plasmid. What is the purpose of this plasmid?

A. to protect nitrogenase from the toxic effects of oxygen
B. to form cysts that allow the bacteria to survive harsh environmental conditions
C. to make an infected plant produce nutrients for the bacterium
D. to increase the number of replication origins so that DNA replication is faster
E. to form symbiotic root nodules for nitrogen fixation

Answer 53

to make an infected plant produce nutrients for the bacterium

Question 54

It is now easy to make mutations in any bacterial gene we choose. What technique can we use to make designer mutations?

A. Microarrays with labeled cDNA from two different species
B. Colony hybridization with radioactive probes
C. Restriction digestion with two different enzymes
D. Probes with sequence mismatches used as replication primers
E. Southern blotting of cloning vectors

Answer 54

Probes with sequence mismatches used as replication primers

Question 55

What type of virus would have the enzyme reverse transcriptase?

A. dsRNA virus
B. ssRNA virus
C. retrovirus
D. ssDNA virus
E. dsDNA virus

Answer 55

retrovirus

Question 56

The most common helminthic infestation in the United State is pinworm. Why is this so?

A. Many cases of pinworm produce mild or no symptoms.
B. The larvae of the worm is common in damp soil.
C. Adult worms mate in the blood vessels surrounding the bladder and the intestine.
D. The eggs are stable outside of the human body for up to three weeks.
E. The worm uses an intermediate host of a snail.

Answer 56

The eggs are stable outside of the human body for up to three weeks.

Question 57

Which of the following best describes the function of a quormone?

A. A congregation of surface-attached bacteria that have become functionally specialized.
B. A protein that binds upstream of a promoter to allow expression of a gene.
C. A response regulator in a two-component regulatory system.
D. A regulator of proton pumping in the electron transport chain.
E. An indirect environmental inducer of certain genes.

Answer 57

An indirect environmental inducer of certain genes.

Question 58

Which of the following DNA replication enzymes is NOT correctly matched with its function?

A. Gyrase – relieves coiling tension ahead of the replication fork.
B. Helicase – rewinds the DNA helix that the gyrase opens up.
C. Polymerase – dimeric enzyme that copies both the leading and lagging strands.
D. Primase – begins replication of each Okazaki fragment.
E. All of the enzymes listed are correctly matched with their functions.

Answer 58

Helicase – rewinds the DNA helix that the gyrase opens up.

Question 59

Which of the following is a desirable property for a new antibiotic to have?

A. It should be acid-sensitive.
B. It should be strong enough to “clean out” (kill) the native flora as well as the infection.
C. It should be bacteriolytic for Gram-negative bacteria.
D. It should be able to be recognized by antibodies.
E. It should have a high therapeutic index.

Answer 59

It should have a high therapeutic index.

Question 60

What will occur if there is an insertion of one nucleotide into the coding region of a gene?

A. It will result in the insertion of three amino acids into the protein.
B. It will result in the insertion of one amino acid into the protein.
C. It will change the protein slightly depending on where the nucleotide is inserted.
D. It will change the entire protein downstream of the insertion.
E. The protein will be constructed as usual since the ribosome knows to skip over extra nucleotides.

Answer 60

It will change the entire protein downstream of the insertion.

Question 61

What advantage does it give prokaryotes to have genes organized into operons?

A. A ribosome only needs to bind once to make all the genes into one large protein.
B. Evolutionary gene transfer mechanisms can operate more efficiently.
C. RNA polymerase can bind many places within a single gene.
D. Related genes can all be regulated by the same environmental signal.
E. The gene can all be replicated on one piece of DNA.

Answer 61

Related genes can all be regulated by the same environmental signal.

Question 62

A 2008 Nobel Prize was awarded to the discoverers of the GFP reporter gene. What is a reporter gene?

A. A gene used as a probe to report the position of another gene.
B. A gene with a visible product used to report the activity of another gene’s promoter.
C. A mutagenic gene used in cloning to make random mutations in other genes.
D. A constitutive gene that is used to activate another gene that would otherwise be repressed.
E. A gene used to isolate pieces of another organism’s chromosome to begin the process of gene cloning.

Answer 62

A gene with a visible product used to report the activity of another gene’s promoter.

Question 63

Which of the following is true regarding the lac operon?

A. It is induced by lactose and induced by cAMP.
B. It is under positive control by lactose and negative control by glucose.
C. It is under positive control by cAMP and negative control by glucose.
D. It is induced by lactose and repressed by cAMP.
E. It is induced by glucose and repressed by lactose.

Answer 63

It is induced by lactose and induced by cAMP.

Question 64

Which of the following is carried out by the spliceosome?

A. removal of introns from prokaryotic DNA
B. removal of exons from prokaryotic RNA
C. removal of introns from eukaryotic RNA
D. removal of exons from eukaryotic RNA
E. removal of introns from eukaryotic DNA

Answer 64

removal of introns from eukaryotic RNA

Question 65

Genetic reassortment is a way for __________________.

A. prions to associate with the proteins they will eventually misfold
B. viral polyproteins to be separated into individual proteins
C. naked viruses to assemble their nucleic acid before budding from their host cell
D. segmented viruses to increase their variability
E. RNA viruses to replicate

Answer 65

segmented viruses to increase their variability

Question 66

What is the mode of action of the antiviral medication acyclovir?

A. It inhibits uncoating of the virus.
B. It acts as a non-nucleoside reverse transcriptase inhibitor.
C. It acts as a nucleoside analog to inhibit DNA/RNA synthesis.
D. It prevents viral assembly and maturation.
E. It inhibits protein synthesis in infected cells.

Answer 66

It acts as a nucleoside analog to inhibit DNA/RNA synthesis.

Question 67

Wobble pairing allows _________________.

A. a ribosome to recognize more than one tRNA at a particular position
B. the 5’ base of the anticodon to recognize more than one 3’ base of the codon
C. more than one reading frame to be used for translation
D. more than one amino acid to attach to a particular tRNA
E. an amino acid to interact with more than one codon

Answer 67

the 5’ base of the anticodon to recognize more than one 3’ base of the codon

Question 68

Which of the following is an example of a mechanical vector?

A. a worm attaches to the intestinal lining and releases cysts
B. a mite causes inflammation when it burrows into skin
C. a flea must take a blood meal to transmit an infection
D. a louse carries bacteria which enter the skin when scratched
E. a fly carries bacterial spores on its legs

Answer 68

a fly carries bacterial spores on its legs

Question 69

Which of the following is NOT a component of the innate immune system?

A. natural killer (NK) cells
B. macrophages
C. ciliated epithelial cells.
D. lysozyme
E. skin

Answer 69

macrophages

Question 70

Varicella-Zoster virus (VZV) can be seen as a plasmid in infected cells from a person who does not show symptoms of virus infection. These infected cells do not contain any viral proteins. Which of the following is true?

A. VZV could reactivate, and the person could show symptoms later.
B. VZV is an example of a chronic virus.
C. VZV could interrupt tumor suppressor genes and cause cancer.
D. The person suffered VZV symptoms earlier but will show no further symptoms.
E. The plasmid may soon become a provirus.

Answer 70

VZV could reactivate, and the person could show symptoms later.

Question 71

Which one of the antimicrobial drugs listed below is an antifungal drug that is the least toxic in humans? It interferes with ergosterol biosynthesis and is frequently taken orally.

A. Amantidine
B. Fluconazole
C. Metronidazole
D. Griseofulvin
E. Amphotericin B

Answer 71

Fluconazole

Question 72

Cytokines do all of the following EXCEPT ________________________.

A. cause fever and inflammation
B. prevent the spread of viruses within a host
C. kill cancer cells
D. recruit polymorphonuclear neutrophils (PMNs) to the site of a bacterial infection
E. allow bacteria to bind specifically to phagocytes

Answer 72

allow bacteria to bind specifically to phagocytes

Question 73

. The process that ensures no circulating B cells recognize “self” antigens is called:

A. Class switching
B. Clonal selection
C. Somatic recombination
D. Clonal deletion
E. Conjugation

Answer 73

Clonal deletion

Question 74

How is interferon produced during an infection?

A. TH cells produce it when they bind to MHC II that is displaying viral antigens.
B. It is produced when MHC I phosphorylates a response regulator in infected cells.
C. A second-messenger pathway induces it when viral RNA binds to an RLR receptor.
D. Bacteria produce it in response to the phagocytic oxidative burst.
E. It is produced by induction of viral genes in the phagolysosome.

Answer 74

A second-messenger pathway induces it when viral RNA binds to an RLR receptor.

Question 75

What is the function of the A part of an AB toxin?

A. It enters the cytoplasm and kills the host cell, often by altering cell metabolism.
B. It activates large numbers of TH cells.
C. It facilitates bacterial spread through tissue into the bloodstream.
D. It hydrolyzes the head group of phospholipids.
E. It binds to surface receptors on the host cell.

Answer 75

It enters the cytoplasm and kills the host cell, often by altering cell metabolism.

Question 76

What is a major difference between an infection and an intoxication?

A. The consequences of an intoxication are not as serious as those of an infection.
B. An infection is more acute than an intoxication.
C. An intoxication usually results in disorientation and neural paralysis.
D. An intoxication is best treated by passive immunization.
E. An infection is best treated by inducing active immunity in an ill patient.

Answer 76

An intoxication is best treated by passive immunization.

Question 77

Which of the following is LEAST likely to be a portal of exit for a disease-causing organism?

A. sweat
B. sebum
C. feces
D. urine
E. semen

Answer 77

sweat

Question 78

The common cold is most frequently caused by _______________.

A. Human rhinovirus
B. Corynebacterium
C. Group A Streptococcus
D. Varicella-Zoster virus
E. Adenovirus

Answer 78

Human rhinovirus

Question 79

According to the “hygiene hypothesis”, ____________________________________.

A. washing hands appropriately is the single best way to reduce disease transmission
B. childhood illness leads to a more robust immune response as an adult
C. lack of exposure to gut flora leads to fewer Treg cells and more autoimmune diseases
D. being “too clean” leads to death of your native flora
E. you need some good bacteria to fight off the bad ones

Answer 79

lack of exposure to gut flora leads to fewer Treg cells and more autoimmune diseases

Question 80

. What is the main function of TC (cytotoxic) cells in the immune system?

A. to release perforin and granzymes
B. to initiate the complement system
C. to activate B cells
D. to activate TH cells
E. to activate PMNs

Answer 80

to release perforin and granzymes

Question 81

A patient is suspected of having been infected with Norovirus, which is an acute viral illness. The patient’s blood serum is tested by direct ELISA, and tests positive at a titer of 1:16. This compares with a pre-immune serum testing positive at a dilution of 1:8. Interpret the result.

A. The test is not valid. An indirect ELISA should have been used for this.
B. The patient currently has no circulating antigens from Norovirus in his blood.
C. The patient has not been infected with Norovirus.
D. The patient is currently infected with Norovirus.
E. The patient has been infected with Norovirus.

Answer 81

The test is not valid. An indirect ELISA should have been used for this.

Question 82

Which of the following is associated with antigen presentation by phagocytes, but not by epithelial cells?

A. MHC-II picks up an antigen from the phagolysosome.
B. MHC-II picks up an external antigen circulating in the blood serum.
C. MHC-I picks up an antigen from the phagolysosome.
D. MHC-II picks up an antigen from the phagocyte’s cytoplasm.
E. MHC-I picks up an external antigen circulating in the blood serum.

Answer 82

MHC-II picks up an antigen from the phagolysosome.

Question 83

What would be the most apparent way to distinguish rubeola from rubella?

A. Patients with rubella have a much higher fever.
B. Jaundice is present in cases of rubeola.
C. Rubella has a much more prominent rash.
D. White spots are present in the lining of the mouth in cases of rubeola.
E. Rubella is a respiratory disease.

Answer 83

White spots are present in the lining of the mouth in cases of rubeola.

Question 84

Antigen drift in influenza virus is ___________________________________.

A. a minor change in the virus spike proteins caused by mutation of the RNA
B. possible because flu virus has a segmented genome
C. the mechanism whereby influenza spreads from person to person around the world
D. a reassortment of H and N proteins between two viruses that infect the same host
E. a major reason for worldwide pandemics

Answer 84

a minor change in the virus spike proteins caused by mutation of the RNA

Question 85

What is a leukocidin?

A. A cytokine that induces apoptosis in infected cells.
B. A toxin produced by macrophages to kill bacteria.
C. A toxin produced by bacteria to kill macrophages.
D. A type of stem cell found in blood.
E. A type of leukocyte.

Answer 85

A toxin produced by bacteria to kill macrophages.

Question 86

What are “pathogenicity islands”?

A. Endemic disease foci with high prevalence of a particular disease.
B. Plasmids on which multiple antibiotic resistance genes are located.
C. Patches of membrane receptors to which pathogenic bacteria bind.
D. Groups of pathogenic bacteria bound to M cells.
E. Clusters of virulence factor genes that can be transmitted by horizontal gene transfer

Answer 86

Clusters of virulence factor genes that can be transmitted by horizontal gene transfer

Question 87

In the disease systemic lupus erythematosus, autoantibodies are directed against (will bind to) _________.

A. almost anything you touch or eat
B. the neurotransmitter acetylcholine
C. epithelial cell receptors
D. B cells
E. DNA and nuclear proteins

Answer 87

DNA and nuclear proteins

Question 88

. What do tetanus and gangrene have in common?

A. There is an effective vaccine for both diseases.
B. Both are generally treated by amputation of the affected body part.
C. They have very similar symptoms, including tissue necrosis.
D. They both require anaerobic conditions for the bacteria to grow.
E. They are both caused by A-B neurotoxins.

Answer 88

They both require anaerobic conditions for the bacteria to grow.

Question 89

The upper part of the healthy respiratory tract has a native flora, but the lower part is axenic. What is mainly responsible for this?

A. rapid exhalation that expels organisms from the lungs
B. IgA produced in the upper respiratory tract
C. the membranous folds of the vocal cords
D. ciliated epithelial cells that line the upper respiratory tract
E. the acidic pH at the back of the throat

Answer 89

ciliated epithelial cells that line the upper respiratory tract

Question 90

The vaccine currently used to provide protection against whooping cough (pertussis) is ________.

A. A whole-cell inactivated vaccine.
B. A live, attenuated vaccine.
C. An acellular subunit vaccine.
D. A polysaccharide conjugate vaccine.
E. A passive vaccine.

Answer 90

An acellular subunit vaccine.

Question 91

How does a phospholipase toxin kill cells?

A. By digesting fatty acids, causing the lipids to not pack together as well
B. By preventing uptake via membrane fusion
C. By adding ADP + ribose to stop protein synthesis
D. By removing the head groups, thus destroying the amphipathic nature of the phospholipid
E. By preventing phospholipid synthesis

Answer 91

By removing the head groups, thus destroying the amphipathic nature of the phospholipid

Question 92

Which of the following is NOT true of the chickenpox (Varicella-Zoster) virus?

A. The spots in the rash all look the same a week after the onset of disease.
B. There is an effective vaccine against it.
C. Once infected, the host retains the virus for their whole life.
D. It can be spread even before the rash develops.
E. It is very serious if acquired by a fetus.

Answer 92

The spots in the rash all look the same a week after the onset of disease.

Question 93

What cellular process allows billions of different antibody Fab fragments to be produced from only a few hundred genes?

A. Somatic Recombination
B. Clonal Selection
C. Clonal Expansion
D. Class Switching
E. Promoter Multiplicity

Answer 93

Somatic Recombination

Question 94

Immune tolerance in T cells involves positive selection. What does that mean?

A. T cells are not allowed to proliferate if their T-cell receptor recognizes MHC-II of thymus cells.
B. T cells are not allowed to proliferate if their antibodies recognize antigen in the thymus.
C. T cells are only allowed to proliferate if their MHC-II recognizes macrophages in the thymus.
D. T cells are only allowed to proliferate if their T-cell receptor recognizes MHC-I of thymus cells.
E. T cells are only allowed to proliferate if their MHC-I recognizes antibodies in the thymus.

Answer 94

T cells are only allowed to proliferate if their T-cell receptor recognizes MHC-I of thymus cells.

Question 95

How does your body response to the presence of a superantigen toxin?

A. Destroying connective tissue resulting in necrosis
B. Engulfing the toxin and disseminating it via blood to the tissues
C. Recruiting the complement cascade to kill host cells as well as bacteria
D. Producing many more antibodies than normal which causes hypersensitivity reactions
E. Secreting lots of cytokines which causes a massive inflammatory response

Answer 95

Secreting lots of cytokines which causes a massive inflammatory response

Question 96

An acute inflammatory respiratory disease associated with inhalation of aerosols from rodent urine, and especially prevalent in the southwest United States is _________________________.

A. Adenovirus
B. Hantavirus
C. Cryptosporidiosis
D. Histoplasmosis
E. Coccidioidomycosis

Answer 96

Hantavirus

Question 97

How are TH (helper T) cells involved in the humoral immune response?

A. Cytokines from TH cells cause B cells to turn into antibody-producing plasma cells.
B. TH cells kill infected cells by releasing perforin and inducing apoptosis.
C. Antibodies are modified by TH cells so that they are active.
D. Macrophages produce antibodies in response to TH cells.
E. TH cells produce antibodies.

Answer 97

Cytokines from TH cells cause B cells to turn into antibody-producing plasma cells.

Question 98

What do precipitin and agglutination tests have in common?

A. Both involve electrophoretic separation of the antigens.
B. Both involve labeled secondary antibodies.
C. Both require diffusion of antigen and antibody through a gel.
D. A positive test is indicated by a white line between the antigen and antibody spots.
E. Both require that the antibodies have at least two antigen binding sites.

Answer 98

Both require that the antibodies have at least two antigen binding sites.

Question 99

What is the function the Staphylococcal protein A?

A. It activates complement C5a.
B. It prevents phagosome and lysosome fusion.
C. It is an adhesin.
D. It is an FC receptor.
E. It is an IgA protease.

Answer 99

It is an FC receptor.

Question 100

What is the role of the B7 protein in the immune response?

A. It is secreted by TH cells to stimulate B cell clonal expansion and differentiation.
B. It is a protein on TC cells that allows them to bind to TH cells.
C. It is a type of antibody produced by effector B cells.
D. It is produced by infected macrophages to help stimulate T cells.
E. It is a receptor on macrophages that recognizes pathogens.

Answer 100

It is produced by infected macrophages to help stimulate T cells.

Question 101

Bob has had tuberculosis. If a TB skin test is performed on Bob, what will happen?

A. Nothing, unless his TB is active at the time of the test.
B. He will form immune complexes to the injected antigen.
C. After a few days, he will show a red rash at the site where the TB antigen was injected.
D. He will show a red rash over his whole body within a few hours.
E. He will show a red rash within a few minutes at the site where the test was performed.

Answer 101

After a few days, he will show a red rash at the site where the TB antigen was injected.

Question 102

A college student who was a cigarette smoker presented to a campus clinic with a high fever and a hacking cough that had developed over the course of a few days. Extreme shortness of breath was apparent. A pink/rust-colored sputum sample was collected and found to have PMNs and Gram-positive cocci. What would be the most likely diagnosis?

A. Tuberculosis
B. Histoplasmosis
C. Pertussis
D. Streptoccal pneumonia
E. Mycoplasmal pneumonia

Answer 102

Streptoccal pneumonia

Question 103

The most effective way to reduce the incidence of nosocomial spread infections is to _______________________.

A. Have health care workers wash their hands between each patient they touch.
B. Separate patients into wards, grouped by the disease they have.
C. Fit HEPA filters in all patient rooms.
D. Use more antibiotics in hospitals.
E. Disinfect operating rooms better between surgeries.

Answer 103

Have health care workers wash their hands between each patient they touch.

Question 104

One reason why a vaccine against malaria has proven difficult to design is that the malaria parasite _______________________________.

A. can swim through a tissue, avoiding humoral immunity
B. lives in red blood cells, where it can avoid both cellular and humoral immunity
C. covers itself with host antigens
D. has a virus-like protective coating that prevents antibody binding
E. has no surface proteins

Answer 104

lives in red blood cells, where it can avoid both cellular and humoral immunity

Question 105

What type of cells do NK cells kill?

A. Any cells without MHC I (or its equivalent) on their surface.
B. T cells that have phagocytized bacteria.
C. TC cells without B7 on their surface.
D. B cells with B cell receptors whose FAB parts the NK cell recognize.
E. Any bacteria with PAMPs (or other recognition signals) exposed.

Answer 105

Any cells without MHC I (or its equivalent) on their surface.

Question 106

Elderly patients on long-term oral penicillin therapy often acquire the infectious disease pseudomembranous colitis, caused by Clostridium difficile. How does penicillin use affect the course of this disease?

A. Penicillin has no effect on the course of this disease.
B. Penicillin reduces the severity of the C. difficile infection.
C. Penicillin triggers a hypersensitivity response in the patient.
D. Penicillin creates a “super” strain of C. difficile that is more infectious.
E. Penicillin kills native flora, allowing C. difficile to colonize.

Answer 106

Penicillin kills native flora, allowing C. difficile to colonize.

Question 107

Infections with which of these organisms are most associated with biofilm formation?

A. Streptococcus pyogenes and Sporothrix schenckii
B. Pseudomonas aeruginosa and Streptococcus pneumoniae
C. Staphylococcus epidermidis and Pseudomonas aeruginosa
D. Streptococcus pneumoniae and Clostridium perfringens
E. Staphylococcus aureus and Streptococcus pneumoniae

Answer 107

Staphylococcus epidermidis and Pseudomonas aeruginosa

Question 108

Which of the following is true for a direct ELISA, but not for an indirect ELISA?

A. The test can be made more sensitive by conjugating latex beads to the known antigen.
B. The test can be used to detect a latent infection.
C. Anti-FC secondary antibodies are used to detect the primary antibodies.
D. The test uses an enzyme reaction to visualize antibodies.
E. To begin the test, known antibodies are bound to the bottom of a microtiter well.

Answer 108

To begin the test, known antibodies are bound to the bottom of a microtiter well.

Question 109

A college student presented to a campus clinic with a low-grade fever and a cough that had developed over the course of a few weeks. She said she felt tired. No lymph node swelling was apparent. A chest X-ray is shown at right. A sputum sample was stained, but no organisms were visible. The diagnosis would most likely be ___________________.

A. Tuberculosis
B. Histoplasmosis
C. Pertussis
D. Streptoccal pneumonia
E. Mycoplasmal pneumonia

Answer 109

Mycoplasmal pneumonia

Question 110

What does it mean for a disease to be a “notifiable” disease?

A. It spreads so quickly that new cases must be placed in quarantine.
B. It is unusual enough that new cases are often reported in medical journals.
C. The disease is serious enough that each case must be reported to the authorities.
D. The symptoms are so painful that you know right away when you get sick.
E. The signs and symptoms are so obvious that the disease can be diagnosed quickly.

Answer 110

The disease is serious enough that each case must be reported to the authorities.