STRAIGHTERLINE MICROBIOLOGY (2025) EXAM QUESTIONS AND ANSWERS (elaborated) WITH COMPLETE SOLUTIONS

Cell walls are not typically possessed by ______.

protozoa

The two major groups of helminths are the ______ and the ______.

roundworms; flatworms

Which of the following is not true of conjugation?

a. Involves direct contact between cells

b. Transfers genes for drug resistance

c. Transfers genes for enzymes and adherence molecules

d. Involves the action of bacteriophage

e. The donor retains a copy of the transferred genes

Involves the action of bacteriophage

Which of the following properties is likely to be found in a pioneer colonizer of a biofilm on an artificial joint implant?

Surface structures for attaching to tissue

A bacterium is inoculated into a tube of thioglycollate and incubated. After incubation, turbidity appears throughout, top to bottom, with the greatest turbidty at the very top. This bacterium would be called a(n) ______.

facultative anaerobe

An organic nutrient that cannot be synthesized by the organism and must be provided is called a(n) ______.

growth factor

Humans can see objects as small as 0.1 mm. Leeuwenhoek's best microscope could magnify objects to 300X. Which of the following would be invisible using Leeuwenhoek's microscope?

Poliovirus, 30 nm

Which of the following is not associated with every virus?

a. Envelope

b. Capsomeres

c. Capsid

d. Nucleic acid

e. Genome

Envelope

A diagram of the three domains (Bacteria, Archaea, Eukarya) proceeding from the Last Universal Common Ancestor would show Archaea

branching off the Domain Eukarya.

During aerobic cellular respiration, the final electron acceptor is ______.

oxygen

The endosymbiotic theory has been developed to explain the emergence of ______.

eukaryotes

Which of the following is a unique characteristic of viruses that distinguishes them from the other major groups of microorganisms?

a. Cause human disease

b. Lack a nucleus

c. Cannot be seen without a microscope

d. Contain genetic material

e. Lack cell structure

Lack cell structure

What type of mutation alters the base but not the amino acid being coded for?

Silent

The eukaryotic cell organelle that most resembles a bacterial cell is the ______.

mitochondrion

Koch's postulates are criteria used to establish that

specific microbe is the cause of a specific disease

The study of evolutionary relationships among organisms is called ______.

phylogeny

Starch is the primary storage food for all of the following except ______.

animals

What is the maximum number of electrons in the second energy shell of an atom?

8

A nutrient medium that has all of its chemical components identified and their precise concentrations known and reproducible is termed ______.

defined

The correct microbiological term for the sample of specimen that is put into a nutrient medium to produce a culture is ______.

inoculum

The bacterium Neisseria gonorrhoeae causes the sexually-transmitted infection gonorrhea. Although it can be isolated from the vagina, there are numerous normal biota in that location as well. To generate a pure culture of this pathogenic bacterium, the best choice is a(n) ______.

selective medium

A fat is called _____ if all carbons of the fatty acid chain are single-bonded to 2 other carbons and 2 hydrogens.

saturated

Caring for patients infected with a new virus requires safety precautions for medical personnel. Choosing appropriate procedures is an example of a(n) ______ process.

deductive

All of the following are diameters of cells that would be resolved in a microscope with a limit of resolution of 0.2 µm except ______.

0.1 µm

A pure culture contains

only one identified species of microorganism.

Microorganisms are best defined as organisms that

are too small to be seen with the unaided eye

All cells contain

ribosomes for protein synthesis.

The process of sporangium formation and endospore maturation requires 6-8 hours. What is most likely to result if the temperature of the environment was raised to 100°C about 2 hours after the process started?

The endospore would not form properly because it is not yet heat resistant.

Which of the following is not a characteristic of bacteria?

Organelles termed mitochondria are the site of ATP production.

The process of dissolving the envelope and capsid to release the viral nucleic acid is ______.

uncoating

A saprobe differs from a parasite in that

a saprobe derives nutrients from dead plants and animals, but a parasite derives nutrients from living plants and animals.

You apply the acid-fast stain method to a patient's specimen, an aspirate from the lungs. Microscopic examination reveals a large number of bright pink-red bacillus-shaped bacteria in the smear. Which statement is true?

The patient has tuberculosis.

Select the statement that most accurately describes the action of antimicrobial drugs today.

Antiviral drugs often result in toxic side effects due to their inhibition of host cell activity.

Viruses attach to their hosts via ______.

host glycoproteins

Which organelle contains cristae where enzymes and electron carriers for aerobic respiration are found?

Mitochondrion

A protozoan cyst differs from a helminth egg in that

the cyst can germinate to form the organism but the egg must be fertilized.

Mycobacterium and Nocardia are distinguished from other bacteria by the ______ stain.

acid-fast

The simple microscopes used by the earliest practitioners of microscopy contained which of the following?

Magnifying lens

The three cell types discussed, eukaryotes, archaea, and bacteria, all derived from ______.

the last universal common ancestor

A scientist who studies the influence of microbes in the formation of caves is called a(n) ______.

geomicrobiologist

Which of the following is a correct description of a component of the ATP molecule?

Sugar: ribose

The valence number is the

number of electrons in the outermost orbital

Which of the following statements is incorrect regarding protein structure?

The interaction between various R groups of amino acids determines the primary structure of a protein.

The sum total of all the microbes in a certain environment is termed the ______.

microbiome

How are viroids transmitted?

Plant seeds

Viral spikes

are always present on enveloped viruses

All of the following structures contribute to the ability of pathogenic bacteria to cause disease except ______

inclusions

The production of antibiotics is a form of antagonism called ______.

antibiosis

In a close relationship, a change in one partner that results from a change in the other partner is termed ______.

coevolution

The phase of the bacterial growth curve that shows the maximum rate of cell division is the ______.

exponential phase

When whole cells or large molecules in solution are engulfed by a cell, this endocytosis is specifically termed ______.

phagocytosis

Enzymes that are only produced when substrate is present are termed ______.

induced enzymes

Sulfa drugs like Bactrim, given for bacterial infections, inhibit bacteria by blocking folic acid synthesis. The precursor molecule of folic acid is para-amino benzoic acid (PABA). Interestingly, PABA has a structure very similar to a sulfa drug. If a sulfa drug is present, the bacterial enzyme will bind the sulfa drug because of structural similarity. This is an example of ______.

competitive inhibition

The unknown bacterium that you are testing makes the enzyme phenyalanine deaminase, as indicated by the results of a phenylalanine test. This enzyme facilitates the removal of a/an ______ group from the organic compound so it can be converted into an intermediate compound for the Krebs cycle

amino

The term used to describe all of the chemical reactions within a cell is ______.

metabolism

Each of the following are electron carriers except ______.

FADP

The antiparallel arrangement within DNA molecules refers to

one helix strand that runs from the 5' to 3' direction and the other strand runs from the 3' to 5' direction

A screening system called the _______ test is used for detecting chemicals with carcinogenic potential.

Ames

The following pertain to ribosomes during protein synthesis except

they contain codons within their rRNA molecules.

Eukaryotic chromosomes differ from bacterial chromosomes because only eukaryotes have

a. histone proteins.

b. chromosomes in a nucleus.

c. several to many chromosomes.

d. elongated, not circular, chromosomes.

e. All of the choices are correct

All of the choices are correct.

The process of forming glucose from various metabolic intermediates is called ______.

gluconeogenesis

In the cell, energy released by electrons is often used to phosphorylate ______.

adp

The movement of substances from higher to lower concentration across a semipermeable membrane via a specific protein carrier but without energy expenditure is called ______.

facilitated diffusion

The movement of molecules from an area of high concentration to an area of lower concentration is called ______.

diffusion

The phase of the bacterial growth curve in which the rate of multiplication equals the rate of cell death is the ______.

stationary phase

An irregular cluster of spherical bacterial cells is termed ______.

staphylococcus

Amoebic dysentery is most commonly contracted through

the fecal-oral route from contaminated food or water.

The outcome of the Gram stain is based on differences in the ______.

cell wall

Endosymbiosis of cyanobacteria is widely accepted as an explanation for the development of chloroplasts. The presence of endosymbiotic cyanobacteria provided a cell with the advantage of ______.

photosynthesis

Uncoating of viral nucleic acid

a. does not occur in bacteriophage multiplication.

b. involves enzymatic destruction of the capsid.

c. occurs during penetration in the multiplication cycle.

d. occurs before replication.

e. All of the choices are correct.

e. All of the choices are correct.

Which of the following does not indicate microbe involvement in energy and nutrient flow?

Thermal hot springs warmed by heat from earth's interior

What would be the valence number of electrons in the sulfur (S) atom? Its atomic number is 16.

6

A reducing medium contains

substances that remove oxygen.

You need to determine if a pure culture of bacteria is gram-positive or gram-negative, but you've just spilled your only solution of crystal violet so you can't do a Gram stain. You decide to try a lysozyme treatment on a sample of each culture and then examine the samples under the microscope. The expected result is

gram-positives will lyse and appears as debris; gram-negatives will be unaffected.

Which of the following is a traditional human use of microorganisms?

Baking bread

A common method for cultivating viruses in the lab is to use in vitro systems called _____ cultures.

cell

Which scientific field is involved in the identification, classification, and naming of organisms?

Taxonomy

If a codon for alanine is GCA, then the anticodon is ______.

CGU

A microbiologist must culture a patient's feces for intestinal pathogens. Which of the following components would likely be present in a selective medium for this purpose?

Bile salts

Which of the following bacteria is not closely related to the others?

a. Salmonella bongori

b. Salmonella enterica subsp. arizonae

c. Salmonella enterica subsp. indica

d. Salmonella enterica subsp. enterica

Salmonella bongori

All of the following are monosaccharides except ______.

a. glucose

b. glycogen

c. fructose

d. deoxyribose

glycogen

FAD, NADP, NAD, and coenzyme A are all carriers of ________.

Both hydrogens and electrons are correct.

A bacterium that you isolated from pond water appears to use light for energy. Based upon this information, you inoculate the organism into fresh media, infused with lots of carbon dioxide. Even after incubation at the correct temperature (of pond water), the organism is not growing. Your best explanation of what might have happened is

there was no sulfur compound added to the medium, that could be used as an electron donor.

All bacterial cells have ______.

chromosome

Gene regulation can involve a protein repressor that blocks ______ from initiating transcription.

RNA polymerase

The bacterium Neisseria gonorrhoeae causes the sexually-transmitted infection gonorrhea. Although it can be isolated from the vagina, there are numerous normal biota in that location as well. To generate a pure culture of this pathogenic bacterium, the best choice is a(n) ______.

selective medium

Which of the following is not true about enzymes?

The correct answer is: Enzymes have high-energy bonds between phosphates.

In order to replicate within a host cell, a virus with a genome comprised of single-stranded positive-sense RNA

must use its genomic strand as a template to make copies of negative-sense RNA for packaging

Enzymes are

proteins that function as catalysts

Basic dyes are

attracted to the acidic surface of bacterial cells

The term 'recombinant organism' refers to

an organism that expresses proteins coded for by genes that originated in a different organism.

In Griffith's experiments with Streptococcus pneumoniae, rough nonencapsulated streptococci were converted into smooth encapsulated streptococci in the presence of the heat-killed smooth encapsulated streptococci. Which microbial process had Griffith identified?

Transformation

Chloroplasts are composed of membranous sacs called ______ that carry chlorophyll. Surrounding these sacs is a ground substance called ______.

thylakoids; stroma

The division of microbes termed the Mendosicutes have a cell wall type best described as ______.

archaeal

A halophile would grow best in ______.

salt lakes

One technique for staining bacteria for viewing under the microscope is called the Gram stain. In this technique, alcohol is used as a decolorizer because it degrades the outer membrane found in some bacteria. What chemical component of the cell does alcohol affect?

lipid

An important mineral ion found in the cytochrome pigments of cellular respiration is ______.

iron