MIC 203 Exam 1 Practice Flashcards

Comprehensive practice question-and-answer flashcards covering Chapters 1 through 4 for MIC 203 Exam 1 based on Dr. Williams' Study Guide.

What are the cellular status and key features of bacteria?

Bacteria are prokaryotic, unicellular organisms that lack a membrane-bound nucleus and may be pathogenic or nonpathogenic.

How do archaea differ cellularly and clinically from bacteria?

Archaea are prokaryotic and unicellular like bacteria, but they are distinct from bacteria, many live in extreme environments, and there are no currently established human pathogens.

What distinguishes viruses and prions from cellular microorganisms?

Viruses and prions are acellular. Viruses contain DNA or RNA inside a protein coat (sometimes with an envelope) requiring a host cell, whereas prions are infectious proteins with no nucleic acid.

What is the difference between resident microbiota and transient microbiota?

Resident microbes persist routinely at body sites, whereas transient microbes are temporary and more readily removed through hygiene.

What defines an opportunistic pathogen?

An opportunistic pathogen causes disease when host defenses are weakened, a microbial community is disrupted, or the organism enters a vulnerable site.

Define mutualism, commensalism, and parasitism in host-microbe relationships.

Mutualism is a relationship where both organisms benefit; commensalism is where one organism benefits while the host has no apparent benefit or harm; parasitism is where the microbe benefits while harming the host.

What is the correct order of the taxonomic hierarchy from broadest to most specific?

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

What are the correct formatting rules for binomial nomenclature?

Capitalize the genus, lowercase the species epithet, and italicize both in print (or underline both separately when handwritten). After first use, abbreviate the genus (e.g., Escherichia coli becomes E. coli).

How did Louis Pasteur's swan-neck flask experiment disprove spontaneous generation?

Pasteur used a swan-neck flask that allowed air in but trapped dust and microbes in the bend, keeping broth sterile until contaminated and supporting biogenesis.

What are Koch's four classic postulates?

1. The suspected pathogen is associated with diseased hosts and absent from healthy hosts. 2. Isolate the pathogen and grow it in pure culture. 3. Introduce the cultured organism into a healthy susceptible host and reproduce the disease. 4. Re-isolate the same organism from the experimentally infected host.

What are the building blocks and cellular importances of carbohydrates?

Carbohydrates consist of monosaccharides forming disaccharides and polysaccharides. They provide immediate energy, storage, and structures such as cellulose, chitin, peptidoglycan, lipopolysaccharide, glycocalyx, and agar.

What are the four levels of protein structure?

Primary structure is the amino acid sequence; secondary structure includes alpha helices and beta sheets; tertiary structure is the full shape of one chain; quaternary structure combines multiple chains.

How do DNA and RNA differ in sugar composition and nitrogenous bases?

DNA contains deoxyribose sugar and bases A, T, G, and C; RNA contains ribose sugar and bases A, U, G, and C.

Define genotype and phenotype.

Genotype is the genetic makeup of an organism; phenotype is an observable characteristic influenced by gene expression and environment.

What are the Five I's of microbiology laboratory procedures in correct order?

Inoculation, Incubation, Isolation, Inspection, and Identification.

How do pure, mixed, and contaminated cultures differ?

A pure culture contains only one species or strain; a mixed culture contains two or more identified species; a contaminated culture contains unwanted organisms.

What are the physical properties and origin of agar?

Agar comes from red algae, is not digested by most microbes, melts near $100^\text{o}\text{C}$, and solidifies near $42^\text{o}\text{C}$.

What is the difference between selective and differential media?

Selective media contain agents that inhibit some microbes while favoring others; differential media permit several organisms to grow but reveal visible differences such as colony color, medium color change, hemolysis, or gas.

Why is MacConkey agar classified as both a selective and differential medium?

MacConkey agar is selective because it inhibits many Gram-positive bacteria, and differential because it distinguishes growing Gram-negative bacteria by lactose fermentation (producing pink colonies).

What visual changes define alpha, beta, and gamma hemolysis on blood agar?

Alpha hemolysis causes partial breakdown with greenish discoloration; beta hemolysis produces complete clearing; gamma indicates no hemolysis.

How is total magnification calculated on a light microscope?

Total magnification equals ocular magnification multiplied by objective magnification (for example, a $10\times$ ocular with a $100\times$ objective equals $1000\times$ total magnification).

Why is immersion oil required when using the $100\times$ objective lens?

Immersion oil reduces refraction and light loss between the slide and the $100\times$ oil objective, improving resolution.

How do Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) differ?

TEM passes electrons through thin sections to reveal internal ultrastructure and viruses, whereas SEM scans electrons over the surface to produce detailed three-dimensional appearing surface views.

What are the four reagents used in the Gram stain sequence in order?

1. Crystal violet primary stain 2. Iodine mordant 3. Alcohol or acetone decolorizer 4. Safranin counterstain.

What are the final colors of Gram-positive and Gram-negative bacteria after a properly performed Gram stain?

Gram-positive bacteria appear purple, while Gram-negative bacteria appear pink or red.

What feature of the cell wall causes acid-fast organisms to retain carbolfuchsin?

Carbolfuchsin is retained after acid-alcohol decolorization because of a lipid-rich envelope containing mycolic acids.

What does a positive acid-fast stain indicate clinically, and what are its limits?

It raises clinical concern for mycobacterial disease such as Mycobacterium tuberculosis, but a positive smear does not establish exact species identity or antimicrobial susceptibility.

What is the primary function of a bacterial endospore?

An endospore is a dormant survival structure formed during unfavorable conditions that resists heat, drying, radiation, and chemicals; it is not a reproductive structure.

How do coccus, bacillus, vibrio, spirillum, and spirochete cell shapes differ?

Coccus is spherical; bacillus is a rod; vibrio is a curved rod; spirillum is a rigid spiral; spirochete is a flexible corkscrew.

What are the major structural differences between Gram-positive and Gram-negative cell envelopes?

Gram-positive envelopes have a thick peptidoglycan layer, contain teichoic acids, and lack an outer membrane. Gram-negative envelopes have a thin peptidoglycan layer, lack teichoic acids, and possess an outer membrane containing LPS and porins.

Why are antibiotics that target peptidoglycan synthesis ineffective against Mycoplasma?

Mycoplasma naturally lacks a cell wall (using membrane sterols for stability), so drugs directed only at peptidoglycan synthesis lack a target.

What sub-units form the bacterial $70\text{S}$ ribosome?

The $30\text{S}$ small subunit and $50\text{S}$ large subunit combine to form the bacterial $70\text{S}$ ribosome.

What is Lipid A, and how does it trigger host systemic inflammation?

Lipid A is the lipid anchor of outer membrane lipopolysaccharide (LPS). Recognition via CD14 and TLR4–MD-2 triggers inflammatory mediators (TNF, IL-1, IL-6), which in excess can cause vasodilation, capillary leakage, hypotension, and DIC.

What are the steps of biofilm formation?

Attachment $\rightarrow$ community growth and matrix formation $\rightarrow$ maturation $\rightarrow$ dispersal.

How do prokaryotic and eukaryotic cytoplasmic ribosomes compare?

Prokaryotic cytoplasmic ribosomes are $70\text{S}$, whereas eukaryotic cytoplasmic ribosomes are $80\text{S}$.

What evidence supports the endosymbiotic theory for mitochondria and chloroplasts?

Mitochondria and chloroplasts retain circular DNA, contain bacterial-type ribosomes, and divide independently in a manner resembling bacterial division.

What is the eukaryotic pathway for a secreted protein from gene to secretion?

DNA transcription in nucleus $\rightarrow$ mRNA export through nuclear pores $\rightarrow$ translation on rough ER ribosomes $\rightarrow$ transport vesicle $\rightarrow$ Golgi modification and sorting $\rightarrow$ secretory vesicle delivery or secretion.

How do yeast and mold forms of fungi differ?

Yeasts are unicellular fungi that typically reproduce by budding; molds are multicellular filamentous fungi that grow as hyphae forming a mycelium network.

What caused the hepatocellular injury in the maize exposure clinical case involving Aspergillus flavus?

Ingestion of food contaminated with aflatoxin (a mycotoxin produced by A. flavus), which causes acute hepatocellular injury without requiring fungal invasion of host tissue.

What are the roles of the trophozoite and cyst stages in protozoa?

The trophozoite stage is active, feeding, and motile for growth and tissue interaction; the cyst stage is a dormant protective form that supports survival outside the host and transmission via food or water.

Which protozoan parasite discussed in lecture lacks a cyst stage?

Trichomonas vaginalis lacks a cyst stage and is transmitted through intimate contact.

Define definitive host, intermediate host, and transport host in parasitic helminth life cycles.

A definitive host supports sexual maturity and reproduction; an intermediate host supports larval or developmental stages; a transport (paratenic) host carries the parasite without further development.

What are the steps of the pinworm (Enterobius vermicularis) transmission cycle?

Eggs are swallowed $\rightarrow$ larvae hatch in intestine $\rightarrow$ adults mature and mate $\rightarrow$ female moves to perianal area and lays eggs $\rightarrow$ itching contaminates fingers $\rightarrow$ eggs are ingested.