Micro Exam 2 Answers

Which structural feature enables influenza viruses to enter and exit host cells?

Hemagglutinin and neuraminidase spikes

A virusoid differs from a viroid in that it:

Requires a helper virus for replication

Which of the following is NOT considered a cytopathic effect of viral infection?

Mononucleated cell morphology

Which of the following is NOT considered a cytopathic effect of viral infection?

Tail fibers- bind to specific receptors on the host cell

Which best describes specialized transduction?

Transfer of host genes adjacent to a prophage upon excision

In the context of microbial ID, which method involves conversion of fatty acids to volatile esters analyzed via gas chromatography

FAME

Which step in the viral life cycle is unique to animal viruses and not observed in bacteriophages?

Assembly of new virions

A hemagglutination inhibition assay is used to detect:

The presence of antibodies against a virus

What causes the sharp increase in the one-step viral growth curve?

Simultaneous host cell lysis and virion release

Which of the following is most likely to be found in a +ssRNA virus?

RNA that can serve directly as mRNA

Which of the following would not be considerd a phenotypic biochemical trait for identifying bacteria?

16S rRNA gene sequence

A provirus differs from a prophage in that:

A provirus cannot be excised and re-enter the lytic cycle

Enantiomers differ from each other in:

The spatial arrangement of atoms around a chiral center

Which of the following is an organism that obtains its energy from the transfer of electrons originating from chemical compounds and its carbon from an inorganic source?

Chemoautotroph

The molecular structures of glucose, galactose, and fructose are examples of:

Structural isomers

Which is the location of electron transport systems in prokaryotes?

The cytoplasmic membrane

Which of the following is not a name for the cycle resulting in the conversion of a two-carbon acetyl to one ATP, two CO2, one FADH, and three NADH molecules?

Calvin cycle

What distinguishes glycogen from cellulose?

Glycogen has branched a-1,4 and a-1,6 linkages; celluloe has B-1,4 linkages

Modified glucose molecules like NAG and NAM are essential for:

Bacterial cell well biosynthesis

Glycosidic bonds form through:

Dehydration between monosaccharides

Which of the following are two products of the light-dependent reactions?

NADPH and ATP

EMB agar is an example of which of the following?

a selective medium, a differential medium, and a complex medium

A conjugated protein composed of a lipid and a polypeptide would be classified as a:

Lipoprotein

Which method distinguishes bacterial species based on protein mass spectra?

MALDI-TOF

Amphipathic molecules are critical for biological membranes because they:

Orient into bilayers that isolate internal cell environments

If a bacterial strain can metabolize only D-glucose but not L-glucose, this demonstrates:

Optical isomer discrimination

The products of B-oxidation feed directly into which metabolic pathway?

Krebs cycle

Which of the following must occur in a fermentative pathway to allow glycolysis to continue?

NADH must be reoxidized to NAD+

Which functional group is involved in the fermentation of peptide bonds?

Carboxyl and amino

What is the primary purpose of the transition (bridge) reaction?

To convert pyruvate into acetyl-CoA for entry into the Krebs cycle

Which pathway is used when a microbe requires nucleotides and amino acids more than ATP?

Pentose phosphate pathway (PPP)

Which of the following is produced during substrate-level phosphorylation in glycolysis?

ATP

In a redox reaction, the molecule that gains electrons is:

Reduced

Which best describes an apoenzyme?

An enzyme lacking its required cofactor or coenzyme

Where does oxidative phosphorylation occur in prokaryotes?

Cytoplasmic membrane

Why does FADH2 produce fewer ATP than NADH during electron transport

It donates electrons later in the ETS, pumping fewer protons

What is the main function of photosystem II?

Initiation of electron flow and ATP generation

What does the pressence of a ‘halo’ around colonies on blood agar indicate?

Hemolytic activity

A microbiologist inoculates a flask of nutrient broth with a smaller number of Bacillus subtillis cells and incubates it at 37 degrees C. After 12 hours, the culture reaches stationary phase. Which of the following best explains why bacterial cells in this phase are less susceptible to antibiotics that inhibit peptidoglycan synthesis?

Cells in stationary phase are not actively dividing, so peptidoglycan synthesis is minimal

A previously unknown bacterial isolate grows evenly throughout a thioglycolate tube. Genetic analysis reveals it lacks catalse but produces superoxide dimutase (SOD). Which classification best fits this organism?

Aerotolerant anaerobe

Which of the following genes would not likely be encoded on a plasmid?

Gene encoding enzymes for glycolysis

Which of the following scenarios would most likely lead to plasmolysis in a gram-negative bacterium?

Sudden exposure to a medium with 10% NaCl

During which phase of the bacterial growth curve would you expect the highest metabolic uniformity and susceptibility to antibiotics?

Log phase

A bacterial culture has a doubling time of 1 hour. You start with 1,000 cells at 8 AM. Assuming ideal conditions and no cell death, approximately how many cells with be present at 12:00 PM?

16,000

Which type of RNA catalyzes peptide bond formation during translation?

rRNA

If a prokaryotic cell were treated with a topoisomerase inhibitor, it would likely:

Lose its ability to package DNA

Why does DNA polymerization proceed in the 5’-3’ direction, but not in the reverse?

The 5’ phosphate of the incoming dNTP can be hydrolyzed to drive bond formation

If a DNA region has a high GC content, how would this affect DNA denaturation

More energy would be required to disrupt hydrogen bonding

If a mutation alters the structure of a tRNA anticodon loop, which process is most likely to fall?

Proper base pairing with mRNA codon

If a prokaryote lacks a functional DNA gyrase, what cellular process would be most impaired?

DNA replication under topological stress

What is a psychrophile?

An organism that thrives at extremely low temperatures

Which class of lipid includes ring structures and functions as hormones?

Steroids

Why are phospholipids considered amphipathic?

They contain both hydrophobic and hydrophilic heads

Which enzyme is not typically found in obligate anaerobes?

Superoxide dismutase and catalase

A dehydration synthesis reaction involves:

Removal of water to link monomers

A microbiologist uses a Petroff-Hausser chamber to count bacteria and reports 1.2 × 10^6 cells/mL. What is the main limitation of this approach if the researcher wants to evaluate the effectiveness of an antibiotic?

It counts live and dead cells indiscriminately

Which feature is shared by both enveloped and non-enveloped viruses?

Protein capsid

Why do jams and dried meats often not require refrigeration to prevent spoilage?

Low water activity

Why type of bond links nucleotides in a single strand of DNA?

Phosphodiester bond

Which of the following is found at the 3’ end of a DNA strand?

Hydroxyl group