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Micro Test 3

Question Answer
What are the three non-living members of pathogens? Viruses
Viroid Infectious DNA
What is the name of the type of viruses that infect prokaryotic cells? Bacteriophages
Prions Infectious proteins
What type of parasites are viruses? Obligate intracellular
What is the size of phages in relation to their host? 100-1000x smaller
What type of genetic material do viruses have? RNA, DNA, ss,ds, or linear
Nucleocapsid Some nucleic acid polymer (DNA or RNA) and the capsid enveloped by an envelope
What makes up the capsid? Repeating proteins called capsomers
Envelope Lipid bilayer derived from the host membrane
How does the envelope assist in binding to the host cell? It contains glycoprotein which are recognized by the host cell
What is a naked virus? Contains only the nucleic acid and capsid, no envelope
What are matrix proteins? Proteins that lie between the envelope and the capsid
Draw a nucleocapsid Drawing
Two main types of symmetry Helical
What is the extracellular form of the virus called? Virion
Helical symmetry The capsomeres arrange in a helix through a spontaneous process called self assembly
What virus is known to have helical symmetry Tobacco mosaic
What restricts the number of viral proteins that can be encoded? The small size of the genomes
What determines the length of a helical virus? The length of the nucleic acid sequence
What determines the width of a helical virus? Size of the capsomeres
Why is icosahedral symmetry the most efficient? Greatest volume inside and requires the smallest number of capsomeres to build the structure
The axis of symmetry inside a icosahedral can divide the structure into what kinds of segments? 5 fold
3 fold
2 fold
What is an example of an icosahedral virus? HPV
Do viruses carry out metabolic process? No. They are metabolically inert
Why do viruses use enzymes? 1.Contains a lysozyme like enzyme that make a hole in the peptidoglycan to allow entry
2.neuraminidase is used to destroy proteins of the host tissues to allow liberation of the virus
3. RNA viruses carry rna dependent RNA pol. (RNA replicases)
How do retroviruses use enzymes? Use reverse transcriptase to go directly from DNA to DNA
What are the basic steps of viral replication 1.find a host and attach 2.inject (entry)3.modulate host expression 4.replicate 5. Transc/trans of viral proteins 6. Assemble 7.exit
How can a virus modulate host expression? 1.Shut off all the host gene expression so it can use the machinery for itself
2.Totally degrade the host DNA using endonucleases
Stages for lytic phages 1.Attatchment mediated by the tail fibers
2.Entry by tail contraction
3.Transc/transl (reduce host gene expression)
What stages make up the latent period of viral replication? Ecplise and maturation
Replication cycle of lytic phages 1. Attachment
2. Penetration
3. Synthesis of viral nucleic acid and protein
4. Assembly and packaging
5. Lysis and release of new virions
What occurs during the eclipse phase? The viral genome and proteins are replicated and translated
What occurs during the maturation phase? The newly synthesized viral nucleic acids and coats assemble and the number of infectious viroins inside the cell rises dramatically
What are some example of viral receptors? Macros, glycoproteins, or lipoproteins, flagella, and pili
What is a specific phage thag binds to e.coli? T4
What is the receptor for the T4 phage? Carbs in the LPS layer of gram – bacteria
What is the difference for icosahedral binding and filamentous phages? Icosahedral phages bind to the side of the receptor and filamentous phages bind at the tip
T4 penetration mechanism The tail fibers attach to polysaccharides on the surface of e.coli. The tail fibers retract allowing the talk to come into direct contact with the cell wall via the tail pins. The T4 lysozyme makes a hole in the peptidoglycan layer and the tail contract
Where does a T4 phage get it's replication machinery? It encodes or it's own 8 piece set of replication machinery
What is unique about the T4 genome? Expresses circular permutation
What is circular permutation? Each copy of the viral genome contains the same set of genes but they are arranged in a different order
Concatamer The entire genome is first replicated, then genomic units are joined end to form a concatamer
When the concatamer is cut it isn't cut at specific sequences, it's just cut enough to fill the a phage head. What is this called? Headful packaging
Flaw of headful packaging There is typically an excess of about 3-6kb
What are the 3 major sets of proteins that the T4 genome encodes? Early proteins, middle proteins, late proteins
Early proteins Synthesis enzymes
Unique T4 base
T4 replisome enzymes
Proteins that modify the host RNA pol
Middle and late genes RNA pol modifying proteins
Virion structural and release proteins
Does a T4 encode it's own RNA pol? No. It modifies the host
How do you shut off host transcription? A phage encode anti sigma factor binds to host RNA pol sigma factor, making it unable to recognize the host promoter
Does capsid and tail assembly recquire energy? No. It is spontaneous
Genome packaging Proheads are assembled
A packaging motor is assembled at the opening of the prohead
DSDNA is pumped in using ATP
The DNA and scaffolding proteins are discarded
There are other assembly steps and then the packaging motor is discarded
What components make up a prohead? Scaffolding proteins
Portal proteins
When new phages have been assembled, how do they cause the cell to lyse? The virion encodes for a pair of late enzymes to breach the cytoplasmic membrane and peptidoglycan layer, once this occurs, the cell breaks through osmotic lysis
Temperate viruses Establish long term stable relationships with the host
Examples of temperate phages Lambda and P1
Temperate viruses are associated with lysogeny. What is this? Replication of the viral genome in synchrony with the host
What is the difference between the P1 genome and the lambda genome in lysogeny? For the lambda genome, it integrates into the host cell
The p1 genome exist as plasmid
What controls the state of lysogeny? A phage encoded repressor protein is usually synthesized at low levels in the cell
What happens if the phage repressor is inactivated or synthesis is halted? The prophage will move into the lytic cycle by excision of the host DNA
How is lambda integrase used for the lysogenic cycle? It recognizes the phage and bacterial genome attachment sites
How are viruses classified? By the structure of their genome
Acute infection Rapid onset of symptoms with quick resolution
Persistent infection Long lasting
Chronic virus Type of persistent infection there there is continuous low level production Where you can even be asymptomatic
Examples of a chronic infection Hepatitis b
Latent infection Periods of infection, then periods remaining silent (ex cold sores)
What is a silent viral genome called? Provirus
What are the potential results of an animal virus infection? Lysis
Main steps of an animal virus life cycle 1. Membrane fusion
3. Replication
4. Release
Membrane fusion process Attatch to receptors
Viral envelope fuses with the membrane and the nucleocapsid is released into the cytoplasm
Uncoat the nucleic acid
How does endocytosis accomplish membrane fusion?
Endocytosis is reduced by the envelope fuses with the endosome
What triggers the release of the capsid in endocytosis? pH change
How do DNA viruses replicate? They use the host machinery
Double stranded DNA virus Use the same type of replication as the host
Types of single strand DNA viruses + Or-
– DNA replication Must be converted to + ssrna before it can be translated to protein
+ssdna replication Can be directly converted to protein
How do enveloped viruses release? Budding off of the plasma membrane or ER
Extrusrion of a virus 1. Glycoprotein spikes insert into the membrane
2. Matrix proteins coat the inside
3. Extrusion
4. New viruses released
What is an example of a DNA tumor virus Polyomavirus SV40
Polyomavirus features Cancer inducing
Why is SV40 important? All molecular processes were figured out from this virus
Used to grow the polio vaccine
Does SV40 use it's own replication machinery or machinery from the host? Host. It's too small to encode it's own
What are the two types of hosts SV40 can infect
What occurs in a permissive host? New virion and lysis
Nonpermissive host Integrated into the host DNA and has a loss of growth inhibition causing transformation
Herpesvirus (all very latent) Large group of viruses that cause many diseases in humans
Example of some herpes viruses Epstein Barr-mono
Varicella Zoster-chicken pox
HSV1-8-cold sore
After the virus fuses with the membrane and the nucleocapsid is released, where does it go? The nucleus
What three classes of mRNA are produced from herpes viruses? Immediate early
Delayed early
Immediate early Encode regulatory proteins that stimulate the synthesis of delayed early proteins and primase so it can't start replication
Delayed early proteins Encode specific DNA pol and DNA binding protein
Late proteins Encode structural proteins
What does replication of the herpes virus result in? Concatamers
How does the enveloping process of the herpes virus differ from other enveloped viruses? The envelope for the herpes virus is added through the budding through the nuclear membrane
HSV latency Establish lifelong latency in the sensory neurons as an episome
Adenovirus Large group of icosahedral, naked, linear, dsDNA viruses
What do adenoviruses cause? Mild respiratory infections in humans
Where does the DNA replicate for the adenovirus? Nucleus
What is unique about adenovirus replication? It doesn't make a lagging strand due to a covalently bound cytosine attached to the 5' end of their DNA that acts as a primer
Sequence of events following infection of the adenovirus The nucleocapsid is released into the nucleus where and early genes are transcribed using the host RNA pol.
What are the first transcription products of the adenovirus? The terminal protein and the viral DNA pol.
What are the products of the initial replication of the adenovirus? A completed DS genome and a single – DNA strand.
What happens to the -ssDNA after it has been replicated?
Cyclizes by means of its terminal repeats and a complimentary +sense is synthesized from it's 5' end
RNA viruses usually contain what type of RNA strand? Single strand
Where do RNA viruses replicated? Cytoplasm
Lysogenic conversion Presence of a prophage changes the phenotype of the host
Examples of bacteria effected by lysogenic conversion. C. Diphtheriae
S. Pyogenes
Three main ways to defend against phages 1. Altering receptors
2. Restriction enzymes
Altering receptors as a defense mechanism S. Aureus makes protein A
How do restriction enzymes degrade DNA? Recognize specific sequences and cut them
What kind of RNA pol do RNA viruses use? RNA dependent RNA pol that they encode for
What are the hosts of polio? Humans and primates
Polio size Very small
What is produced from the direct translation of polio RNA? Autocatalytic poly protein
Polyprotein Single protein that can cleave itself into multiple pieces
Where does polio replication occur? Cytoplasm
VPg protein Picked up by both the pos and neg strands and functions a as primer for RNA synthesis
What aspect of a eukaryotic cell is the VPg synonymous to? 5'cap
How are corona viruses different than the polio virus? Corona is larger and uses a different replication mechanism
What unique physical characteristics do corona viruses have? Club shaped glycoprotein spikes
What RNA virus has the largest genome? Corona
Corona translation Only the portion of the genome encoding the helicases is directly synthesized
The other section issues as a template for negative strands which are then translated to coronal proteins
Where is the corona viruse assembled? Golgi
What's unique about – strand RNA viruses? They're complimentary to the mRNA
Influenza traits Enveloped, pleomorphic, segmented virus
What does it mean for a virus to be segmented? Multiple independent RNA pieces that are synonymous to chromosomes
What are the two important influenza surface proteins? Hemagglutinin
Hemagglutinin Highly immunogenic (causes a response of the immune system)
Antibodies against it prevent the virus from entering the cell
Causes clumping of red blood cells
Neuraminidase Breaks down sialic acid component of the host membrane
Antigenic shift Segments of the RNA genome from 2 different strains infecting the same cell are reassorted
What is the product of antigenic shift? Hibrid virions that have different surface proteins unrecognized by the immune system
Antigenic drift Results in different strains
What flu strains can infect humans H1,H2,H3 and N1,N2
How many total HA and NA strands are there? 16 HA, 9 NA
What causes antigenic drift? Minor mutations
What results in pandemic viruses? Antigenic shift
Why are pigs the devil? Pigs have receptors of both avian and human strains so if both infect the same cell then all the segments get jumbled and picked up so there is a new virion that can infect humans
Tropism Ability of a virus to infect a host or tissue
2,3 and 2,6 SA acid confirmations 2,3-lower in humans and birds
2,6-upper in humans
Pigs have both on 1 epithelial cells
What is an example of a double stranded RNA virus? Reovirus
Where does replication of the reovirus occur? In the host cytoplasm within the nucleocapsid because the host has enzymes that recognize ds rna as foreign
The first step in reovirus replication Sythesize + sense rna from – using the viral encoded RNA replicase
What is the biggest cause of diarrhea in infants? Reovirus
What supplies the nucleotides for RNA synthesis of the reovirus? Host cell
What model of replication does the reovirus use? Conservative (only off of the minus strand)
What caps the newly synthesized reovirus mRNAs? Methylated nucleotide
Primitive control in reoviruses Most mRNA molecules encode for 1 protein, but 1 specific mRNA encodes for 2 and sometimes a ribosome missed the start codon of the first gene and travels to the second one.
Reovirus primitive control Molecular mistake
Retroviruses Contain developed virions with two identical copies of the RNA genome
Reverse transcriptase Makes DNA from RNA
Three major enzymatic activities of reverse transcriptase 1. Reverse transcription
2. Ribonuclease activity (degrade RNA strand)
3. DNA pol. (Make DNA from SSDNA)
Viral trna Functions as a primer for reverse transcriptase
What is the product of reverse transcriptase? DSDNA with terminal repeats that allow for integration into the host host chromosome
Where does HIV integrate? Outermost shell of the nucleus because of a short life of viral integrase
If the retrovirus genes are induced, how can they appear? As virions of genomic RNA or as retroviral proteins
What genes do all retroviruses have? Gag,pol,env
Gag 5' end and encodes for structural proteins and protease
Pol gene Splices postranslationally to yield gag, reverse transcriptase, and integrase
Env protein Makes envelope and can only be made after the full mRNA has been cleared of the gag and pol regions
Prion Mutated version of a protein that is found normally
PrPc Normal protein seen in brain tissue
PrPcs Change purely in confirmation that causes scarpie
Plaques Aggregated of the PrPcs protein resulting in cell death
Structure of PrPcs Flat pleated beta sheets
How are prions transmitted Eating the entire animal, contact with contamitaned medical equipment (electrode, HGH transfusion)
Inherited prion disease Genetic CJD
Fatal familial insomnia
Sporadic prion disease Sporadic CJD
Random mutation with memory loss, depression, motor skill loss, and finally a coma
Chronic wasting disease Weightless
Blank face
How is chronic wasting disease transmitted? Animal to animal contact through saliva or feces
Protozoa characteristics Eukaryotic
Lack cell walls
Usually not pathogens
Moist environment
Support the endosymbiont theory
Two easily converted life stages of the protozoa Trophozoite
Trophozoite Mobile feeding form that is more active
Cyst Dormant stage with little metabolism and the vessel for infection
Diplomomads Contain two nuclei and mitosomes and a reduced mitochondria and lack the electron transport chain and the ability to carry out the citric acid cycle
Mitosomes Where they carry out glycolisis and fermentation
What type of cell walls does the cyst form have? Chitin
What's an example of a diplomomad? Giardia intestinalis (most common waterborne disease)
Symptoms of giardia intestinalis Diarrhea, indigestion, abdominal pain, rotton egg stool
Who carries giardias? Bevers and muskrats
Life cycle of giardias Ingested from contaminated food/water/hands
Once in the intestine, they uncyst and replicate through binary fission, then they recyst and are passed through the stool
Where is giardia common? Up north and by rivers
Parsbasilida characteristics Single nucleus and lack mitochondria
Have a parabasal body
Can't produce cyst
Parabasal body Supports the Golgi
Example of parsbasilida Trichomomas vaginalis
How do you get trichomomas vaginalis? Intimate contact or sauna
Symptoms of trichomoma vaginalis Foul smelling discharge
Painful urination.
Euglenozoa Unicellular flagellates with kinetoplastids
Chemotrophs and phototrophs
Kinetoplastids Single large mitochondria and are responsible for rapid changes of surface proteins so the body can't respond
Example of euglenozoa Trypanosoma cruzi (Chaga's disease)
Symptoms of Chaga's disease Romanas sign (swollen eye)
Chronic indeterminate (heart arithmea)
How do you get trypanosoma cruzi? Triatoma bug (kissing bug) feces
T. Cruzi life cycle 1.Tryoanosomes are ingested by the kissing bug when it feeds on an infected human 2. Flsgellated parasites develope in the midgut of the bug 3. Become ineffective in hindgut 4. Bite/scratch 5. Travel in blood some burst out and some infect other cells
Form of trypanosome that replicates through binary fission and has no flagella Amastigote
When does t. Cruzi become infectious again? When it is flagellated and ingested by the kissing bug
Where do you see Chagas The South (started in Brazil)
What is another example of a euglenozoa? Trypanosoma brucei
Characteristics of trypanosoma brucei Transmitted by the glossina tsetse fly
Symptoms of trypanosoma brucei Inflammation of the brain and spinal chord which results in a slow loss of nervous system and African sleeping sickness
Aveolates Characterised by sacs under the cytoplasm for osmotic balance
Example of aveolates Ciliates, dinoflaggelates, and apicomplexans
Ciliate characteristics Cilia
Have a macronucleus and a micronucleus
What type of genes are regulated by the macronucleus? Basic functions such as growth and feeding
What is regulated by the micronucleus? Sexual genes
What is an example of a ciliate? Balantidium coli
What does balantidium coli cause? Balantiasis
What is a symptom of balantidium and how do you get it? Perforated colon
Contaminated food and water
Dinoflagellate characteristics Unicellular
Photosynthetic pigments
Cellulose plates
Two flagellum
Toxic dinoflaggelates Gonyaulax
Pfiesteria piscicida
What causes red tide? Gonyaulax
What causes paralytic shellfish poisoning? Pfiesteria piscicida
Ampicomplexan characteristics Cause severe human diseases
Nonmotile adult stage
Uptake of nutrients through the plasma membrane
Derived from secondary endosymbiosis
Apicomplex Allows burrowing through the host
Sporozoan Switch between sexual and asexual reproduction
What are apicoplast? Degenerate chloroplasts that can't use photosynthesis but catalyze fatty acid, isoprenoid, and heme biosynthesis
What is one disease caused by ampicomplexans? Malaria
What species causes malaria? Plasmodium
What are the symptoms of malaria? Fever, anemia, renal failure
What is the incubation period for malaria? 2 weeks
Paroxysm cycle Between fever and not fever (cold:immature parasites grow, hot:fever destroys mature parasites)
How is malaria transmitted? Anopheles mosquitos
Malaria in humans
Injects saliva, travels to liver in kupffer cells to hide from immune system and infected cells become sticky
Mosquito and malaria Mosquito bites someone with malaria and malaria sex occurs when it's warm. A fertilized cell migrates to the outer lining of the mosquitoes stomach and forms a cyst
How to amoebozoa move? Pseudopodia
How do you contract an amoeba? Ingested through contaminated water
What insects carry amoebas? Roaches or flies
Example of an amoebozoa Entamoeba histolytica
Entamoeba histolytica traits Chitin-shelled cysts
Symptoms of an amoeba Invasive amebic dysentery (diarrhea with bloody stool, occasionally leave the intestine and go to the brain)
Entamoeba histolytica life cycle Ingested frim contaminated food or water integrate into the 4 forms, move to the colon, form cyst, pass
Form of plasmodiun cell that can reproduce Gametocyte
Form of plasmodiun cell that first goes to the liver Sporozoites
Form of plasmodiun cell that infects red blood cell Merazoite
What's the difference between a yeast and a mold?
Yeast are unicellular molds are filamentous
What does it mean to be saprophytic? Absorbs nutrients from decaying material
Components of fungal cell walls Ergosterol and chitin
Fungal structures Hyphae
Fruiting bodies
Hyphae characteristics Tubular cell walls that surround the membrane from which sexual spores are produced
Occasionally more than nucleus can be found in a hyphae cell forming nuclear divisions without the formation if cross walls. This condition is known as… Coenocytic
Hyphae form together to form a tuft called the… Mycelium
Haustoria What parasitic fungi use to penetrate the host membrane
Condida Asexual spores that can be pigmented and give the mycelium a dusty appearance
Fruiting bodies Structure containing millions of spores that can be dispersed
Fungi reproduction 1. + and – end fuse to make a dikaryon
2. Nuclei fuse
3. Meiosis produces haploid spores
4. Spores divide through mitosis
Dikaryon count N+n
Fungal habitats Can withstand higher salt, sugar, and acid concentrations than bacteria
Grow at 20-30°C
Medical relevance Allergic or asthmatic reaction to spores
Mycosis-growth on the body
Ingested toxins
GTA fungal monitoring Apergillus monitors presence of aflotoxin in wheat
Chytridiomycetes characteristics Soil/fresh water
Flagellated mobile spores
Temperature sensitive
Example of a chytridiomycete Batrachochytrium dendrobatidis
Dendrobatidis symptoms Grows under the skin of frogs and inhibits respiration
How many amphibians are at risk for debdobatidis? 1/3 (tracked from South America to Texas)
Zygomycetes Responsible for food spoilage
Use zygospores for sexual
Example of a zygomycete Rizopus stolonifer
Ascomycetes (sac fungi) Most common and diverse
Beer and bread
Like sugar
Faculative anerobe
Example of an ascomycete Saccharomyces cerevisiae, Candida, histoplasma
Mating in s. Cerevisae 1.A and alpha types fuse to make diploid zygotes in the presence of hormones
2. Form a diploid cell that goes through meiosis forming a 4n ascus.
3. 4 ascospores form resulting in 4 haploid cells
Examples of candidiasis Vulvovaginal candidiasis
Diaper rash
What does it mean for Candida to be opportunistic? Infection happens only if the host is compromised
What causes histoplasmosis? Histoplasma capulatum
Histoplasma characteristics Dimorphic:yeast in 1 temp, mold in another
Symptoms of rhizopus Swelling of face region
Where is histoplasma mold located? Soil, Bird and bat droppings
Histoplasmosis symptoms Usually just flu like symptoms but can cause pulmonary problems
When does histoplasmosis transition to yeast? 37°C
Basidiomycetes Mushrooms and toadstools
What phase do basiodiomycetes spend most of their time? Haploid mycelium
When do basidiocytes become mushrooms? During their sexually reproductive phase with rapid development of the fruiting body
Mushrooms fruiting body Basidiocarp
Basidiomycete examples Amanita muscari
Muscari Doing shrooms
Cyptococcus Can grow as a yeast when inhaled
First causes pneumonia but can hurt those immunocompromised
What are helminths? Macroscopic worms
Another name for cestodes Tapeworms
Cestode traits Flat ribbon bodies
No digestive tract
Eggs are produced at the end of the cestode and then break off
What absorbs the nutrients from the host in tapeworms? Cuticle
How do cestodes attatch to the GI track? Scolex
Proglottid Segmented region with male and female reproductive parts
Example of tapeworms Taenia
Symptoms of tapeworms Weightloss
Who gets tapeworms? Poor rural areas
Taenia solium life cycle 1. Pig eats eggs
2. Eggs hatch and move to form muscle cyst
3. Human injest in undercooked meat
4. Excyst and attatch to intestine via scolex
5. Form proglottids which are passed
Another name for nematodes Round worms
Nematode characteristics Round, unsegmented, tapored, have own digestive tract, parasite of every vertebrate
How do you diagnose a tapeworm? Stool
Example of a nematode Enterobius vermicularis
What is enterobius vermicularis? A pinworm that causes enterbiasis
Symptoms of enterbiasis Irritability
Sleep deprivation
How is enterbiasis spread? Butt scratching
Who gets enterbiasis? Kids
Ascaris characteristics Produce over 200,000 eggs a day
Largest and most common nematode
Free living in soil and water
Symptoms of ascariasis Inability to gain weight
Ruptured capillaries
How is ascariasis spread? Feces
Who gets ascariasis Tropical places
What is the general term for a nematode infection? Filariasis
Bsncrofti traits Filariasis that exhibits periodicity and causes elaphantiasis
Another name for trematodes Flukes
Symptoms of bancrofti Nocturnal cough
Excess fluid
Trematodes traits Can live decades in a host
Flat and leaf shaped with suckers
Life cycle with more than one host
What kind of flukes can there be? Blood, liver, and lung
Infectious trematodes Schistosoma mansoni
Schistosoma traits Found in fresh water
Burrow through feet
Swimmers itch
Schistosoma symptoms Belly swelling
Another name for schistosomiasis Snail fever
What is the larval form of schistosoma? Cercaria
Schistosoma life cycle