Week 6: Virology Flashcards
Viruses are microscopic _________ that can infect ______, and are neither ______ nor _______.
Organisms, hosts, prokaryotic, eukaryotic
Viruses are made of a small piece of _____ material (______ or _____) inside of a protective shield (_______)
Genetic, DNA, RNA, capsid
Why do viruses need to infect a host?
Cannot replicate their own DNA/RNA, proteins, and must hijack the host cellular mechanisms to perform these functions. Are metabolically inert.
What are five methods of viral entry into the host?
- droplet (ex. nose)
- trans-placental
- oral
- direct (injection)
- sexual
What is the basic structure of a non-enveloped virus?
Nucleic acid within a capsid, made of individual capsomeres.
What is the structure of an enveloped virus?
Non-enveloped PLUS an envelop made of lipids, glycoproteins, and matrix peoteins.
What are the 3 mechanisms of RNA virus hijacking? Give an example for each mechanism.
- direct: viral genome acts like mRNA ex. rubella.
- viral RNA is transcribed by viral RNA polymerase to act like mRNA ex. influenza
- reverse transcription ex. HIV
How is viral DNA hijacked into cellular DNA?
Infected cells are ‘forced’ to translate viral mRNA to make viral proteins. DNA is forcibly inserted into genome. ex. herpes
What are the 4 steps of infection & replication?
- attachment & penetration
- uncoating & replication
- assembly
- release
What are the two methods of penetration?
- endocytosis
- receptor/virus fuse with cell membrane and enter
What occurs during ‘uncoating?’
Envelope/capsid is shed, viral nucleic acids are released
What occurs during assembly?
Replicated nucleic acids are assembled with proteins for new capsid
Describe lytic infection.
Replication and release via cell lysis.
Describe persistent infection.
Replication of virus, cell lives and continues to slowly release viral particles.
Describe latent infection.
Virus remains ‘quiet,’ replication takes place when a signal triggers release from latency
Prokaryotes are _______ with no _____, only genomic DNA in a single “_______.” They have _____ that carry DNA, and a cell membrane coated by a ____ ______ and ____ layers.
Bacteria, nucleus, chromosome, plasmids, cell wall, lipid.
Eukaryotes have several ________ in a membrane-bound _______. Their translation takes place on ________, have many _______, and has a single plasma ______.
chromosomes, nucleus, ribosomes, organelles, membrane
What are three examples of eukaryotes?
Protozoa, fungi, vertebrates
How big are bacteria (exception?)? What are two interesting characteristics?
10x smaller than RBC (except bacillus anthracis).
1. most abundant organisms
2. most tolerant of environmental conditions
What are the 3 main classes (by shape) of bacteria? Describe.
Cocci (grape)
Bacilli (hotdog)
Spirochetes (string)
What are the three arrangements of cocci? Describe.
Diplococci (pairs)
Streptococci (chains)
Staphylococci (clusters)
What is special about facultative anaerobes? How are obligate aerobes different?
Facultative = can grow with or without oxygen.
Obligate = NEED oxygen to grow to perform aerobic metabolism
Describe anaerobes. Obligate anaerobes?
Do not need oxygen and make up most gut and vaginal flora. Obligate anaerobes can NOT have oxygen to prosper.
Where does gram staining bind to on a cell wall? What does the cell wall provide for bacteria?
Peptidoglycan. Provides protection and is an essential role in cell division.
Gram negative cell walls have two layers outside of their _________ layer: a ________ space and an outer membrane composed of __________ and _________.
Peptidoglycan, periplasmic, lipoproteins, lipopolysaccharide
What is lipopolysaccharide?
LPS is an endotoxin and strong stimulant of innate immunity
Which type of bacteria (positive or negative) is harder to kill?
Gram negative is harder to kill (with antibiotics). This is because, although they have a thinner peptidoglycan wall, there are two additional layers on top of their cell wall that strengthen their immunity.
What are the 5 major functions of plasma membranes?
- selective permeability
- electron transport/oxy phosphorylation
- excretion
- enzymes
- receptors
What fiber is only present in gram positive bacteria?
Techoic acid.
How does catalase act as a defense enzyme in bacteria?
WBC will produce hydrogen peroxide to kill bacteria. Catalase breaks down hydrogen peroxide and subverts immune cells.
How do bacteria utilize coagulase?
Forms a clot around bacteria to protect it from immune cells.
Describe the 4 phases of the bacterial growth curve.
Lag = vigorous activity, cells don’t divide
Log = rapid cell division
Stationary = nutrient depletion/toxic products
Death = decline in bacteria
Bacteria adapt to their environment by controlling ________ __________. How does this happen?
Gene expression. Change the amount of mRNA transcription.
What do plasmids and bacteriophages do?
These are extra-chromosomal DNA elements that replicate independent of genomic DNA, allow exchange between different types of bacteria.
Many plasmids contain __________ genes that encode ______ and ______. What does this accomplish?
Virulence, enzymes, toxins. Help bacteria overwhelm host tissues & immunity, obtain nutrients. Explains why bacteria is drug-resistant sometimes.
What is the physical representation of streptococcus in its 3 strains?
A-hemolytic = green (partial hemolysis)
B-hemolytic = clear, complete hemolysis
Y-hemolytic = no hemolysis
Fungi are _________ that have both a _________ and _________. What are the two types of fungi and their characteristics?
Eukaryotes, nucleus, organelles. Branches filamentous = hyphae, a mass is known as mycelium. Yeasts = single-celled spheres.
Fungi absorb nutrients from the environment, making them ___________. Infections that fungi cause can be acquired from the ____________ or normal __________.
Heterotrophic, environment, flora.
All fungal species have _________ reproductive processes. How does reproduction differ between branched filamentous and yeasts?
Asexual. Branched filamentous = release spores, which can cause infection. Yeasts = division or budding.
What type of infection do filamentous fungi cause?
Superficial/cutaneous mycosis. Ex. athlete’s foot or vagina candidiasis
What type of infection do yeasts cause??
Deep myosis (involvement with internal organs).
What are signs/symptoms of candida spp.?
Colonize mucous membranes, causing yeast infections, or “thrush.” Burning/itching, pH normal.
Protozoa are ______, ______-celled animals that typically contain __________ on their cell structure. They can occur as free living organisms or as ________, and reproduce through _______ _______.
Eukaryotic, single, flagella, parasites, binary fission.
Helminths are multicellular ________ that parasite organs, especially ____. They have ______ reproduction, but the _____ ________ is specifically designed to combat their penetration. What are 2 forms of transmission?
Worms, GI, sexual, intestinal mucosa.
1. swallowing infective stages ex. eggs/larvae
2. larvae penetrating skin
What are the three outcomes of viral infection?
Lytic = kills cell
Persistant = uses & leaves
Latent = dormant until activated via stress, autoimmune, etc.
What are differences in plasma membranes in prokaryotes vs. eukaryotes?
Eukaryotes = single PM, yeast have chitin
Prokaryotes = peptidoglycan layer (gram neg-pos)
How is the plasma membrane different in bacteria (prokaryotes) than eukaryotes?
No mitochondria in prokaryotes, PM performs ETC & oxidative phosphorylation. Also excretes hydrolytic exoenzymes.
What do hydrolytic exoenzymes do?
Helps bacteria digest food outside of their cell body.
What do bacteriophages do?
A virus that infects prokaryotic cells.
What are the three unique ways that bacteria can perform metabolic processes?
- anaerobic respiration
- fermentation
- no mitochondria, PM replacesch
What do group A streptococci cause? What type of hemolysis do they cause?
Strep, fever, necrotizing tissue. Beta-hemolytic (completely lyses)
Describe giardia.
“Beaver fever” are found in untreated water, cause diarrhea.
What type of bacteria is typically found in animal feces?
Protozoan species called toxoplasma gondii. Has NS effects.
What do group B streptococci cause? What type of hemolysis do they cause?
Vaginal/intestinal flora. Beta hemolytic (completely lyses).
What do type D streptococci cause? What type of hemolysis do they cause?
UTIs, endocarditis. Gamma (none) or alpha (partial) hemolytic.
