Objective Questions Unit 2 Flashcards
Describe the structure of an enveloped virus in detail including the composition of each part. What is the average range of viral sizes?
Nucleic Acid Core: DNA or RNA
Capsid: Protein coat protecting the genetic material
Envelope: Lipid membrane surrounding the capsid, aiding entry into host cells.
Matrix Proteins: Proteins connecting the envelope to the capsid, aiding structure and viral assembly.
Envelope Glycoproteins: proteins embedded in the envelope, often with carbohydrate attachments
Size range: 20 to 300 nanometers (nm) in diameter
Describe the structure of a naked virus in detail including the composition of each part. What is the average range of viral sizes?
- Nucleic Acid Core: DNA or RNA, single or double-stranded.
- Capsid: Protein shell for protection and attachment, made of capsomeres.
- No Envelope: No lipid membrane, making them more resilient to harsh environments.
- Size range: 20 to 400 nanometers (nm) in diameter
What structures do bacteria have that viruses don’t?
Cell wall
Cell membrane
Cytoplasm
Ribosomes
Flagella (sometimes present)
(Step 1) Describe, in detail, the lytic replication of T4 phage
- Attachment: The T4 phage, with its tail fibers, specifically binds to receptors on the surface of the E. coli cell, initiating the infection process
(Step 2) Describe, in detail, the lytic replication of T4 phage
- Entry and Uncoating: the tail sheath/tail tube of the phage goes through the bacterial cell membrane, allowing the phage DNA to be injected into the host cytoplasm; Leaves its protein coat on the outside of the cell
(Step 3) Describe, in detail, the lytic replication of T4 phage
- Synthesis: the phage DNA takes control of the host cell’s machinery, initiating the synthesis of early phage proteins, including enzymes needed for DNA replication.
(Step 4) Describe, in detail, the lytic replication of T4 phage
- Assembly: Newly synthesized phage components, including heads, tails, and tail fibers, are assembled into complete virions. Capsomeres assemble around the genetic information as well as any proteins it brings inside the capsid
(Step 5) Describe, in detail, the lytic replication of T4 phage
- Maturation and release: After assembly the host cell wall is lysed (broken open) by phage-encoded lysozyme, releasing the phages to infect new bacterial cells.
(Step 1) Describe, in detail, the lysogenic replication of Lambda phage
- Attachment: The Lambda phage attaches to specific receptors on the surface of the E. coli cell using its tail fibers
(Step 2) Describe, in detail, the lysogenic replication of Lambda phage
- Entry: The phage injects its linear DNA into the bacterial cell, while the capsid remains outside. The injected DNA circularizes to prevent degradation
(Step 3) Describe, in detail, the lysogenic replication of Lambda phage
- Integration (Prophage Formation): The circularized phage DNA integrates into the bacterial chromosome using a phage-encoded enzyme called integrase. Once integrated, the phage DNA is now called a prophage and is dormant within the bacterial chromosome
(Step 4) Describe, in detail, the lysogenic replication of Lambda phage
- Replication: When the host cell divides, it replicates its own DNA along with the integrated prophage DNA. Each daughter cell receives a copy of the prophage.
(Step 5) Describe, in detail, the lysogenic replication of Lambda phage
- Induction: Under certain conditions (such as stress, UV radiation, or chemical exposure), the prophage can be excised from the host genome and enter the lytic cycle. The viral DNA then begins to replicate, produce viral proteins, and ultimately lead to the assembly of new virions, followed by cell lysis
Transduction Definition
The process by which a virus transfers genetic material from one cell to another
Generalized Transduction Definition
Any bacterial gene can be transferred from one bacterium to another;
Results from an error during the assembly of phage where the piece of bacterial DNA accidentally gets packaged into the phage capsid
Specialized Transduction Definition
Only specific bacterial genes located near the phage integration site are transferred;
In lysogenic phase the phage goes through induction (from a stress) and tries removing itself from the chromosomes, it accidentally takes parts of the host chromosome with it
How does Generalized transduction and specialized transduction benefit a bacterium?
Generalized:
increase genetic diversity
enables recipient to potentially gain new traits (ex. antibiotic resistance)
enhances adaptability allowing them to better survive in changing environments
Specialized:
provide recipient bacteria with advantageous traits closely linked to those genes (near it)
enables bacteria to rapidly acquire essential functions (virulence factors) enhances their competitiveness and survival
(Step 1) Describe, in detail, HIV life cycle
- Attachment: HIV uses its envelope glycoproteins (gp120) to attach to CD4 receptors on the surface of T-helper cells (CD4+ T cells). The virus also interacts with co-receptors (CCR5 or CXCR4) to facilitate entry
(Step 2) Describe, in detail, HIV life cycle
- Entry/Fusion: Once gp120 binds to CD4-CCR5 conformational change happens that allow a fusion portion of the gp120 to allow it to enter the host (endocytosis)
(Step 3) Describe, in detail, HIV life cycle
- Uncoating: gp41 helps cell membrane fuse with the endosome membrane, viral capsid is removed, releasing the viral RNA and enzymes (such as RT) into the host cell’s cytoplasm. Also releases genetic information and integrase (protein)
(Step 4) Describe, in detail, HIV life cycle
- Synthesis (of DNA): Reverse transcriptase synthesizes the dsDNA from the +ssRNA template
(Step 5) Describe, in detail, HIV life cycle
- Integration: Once synthesized it enters through the nuclear pore and integrase (protein) is brought with it and this protein allows it to insert itself into the host chromosome, now it is called a provirus (Proviruses are permanently stuck in the host chromosome)
(Step 6) Describe, in detail, HIV life cycle
- Synthesis (of RNA): The integrated proviral DNA is transcribed into viral mRNA using the host’s RNA polymerase.
+ssRNA will be used as a genome for virus,
will be translated on free ribosomes
and some will be one large protein that has information to make the RT
some of the RNA will be translated through the secretory pathway, the RER, Golgi apparatus, and transport vesicles;
those are the spike proteins that will end up on the cell surface
(Step 7) Describe, in detail, HIV life cycle
- Release: Released through exocytosis (genetic information as well as large proteins)
(Step 8) Describe, in detail, HIV life cycle
- Assembly/Maturation: Once it’s outside of the cell, assembly and maturation occurs. The protease will cut the large protein into individual proteins, such as RT, integrase, capsid proteins will house the two RNA’s that will be part of the genetic information for HIV
Compare & contrast release of enveloped virus vs. naked virus
Enveloped viruses release via budding (less damaging to host cells); Enveloped viruses acquire their lipid membrane from the host
Naked viruses release via lysis (causing cell death); Naked viruses lack this structure and rely on host cell rupture for release
Define latency
A state in which a virus remains dormant within a host cell, not causing active infection or symptoms, but can reactivate under certain conditions.
Why do you think that it is difficult to treat viral disease?
Treating viral diseases is challenging because viruses rely on host cells for replication, making it difficult to target them without harming the host’s cells
Additionally, viruses often mutate rapidly, leading to variations that can evade the immune system and resist antiviral treatments
Briefly explain how a virus could potentially cause cancer.
Name a cancer-related virus & the specific cancer associated with it.
(Viruses that cause cancer: Oncoviruses;)
Viruses can potentially cause cancer by integrating their genetic material into the host cell’s DNA, disrupting normal cell regulation and promoting uncontrolled cell division
HPV (DNA virus): causes cervical cancer
How does culturing a bacteriophage compare with that of culturing an animal virus?
Bacteriophages require bacteria for culture and can be observed more quickly through plaque formation
Animal viruses need living animal cells, making the culturing process more complex and time-consuming
What is a viroid?
A small, infectious RNA molecule that can cause diseases in plants by disrupting their normal cellular processes
What is a prion?
An infectious agent composed entirely of misfolded proteins that can induce abnormal folding in normal proteins, leading to neurodegenerative diseases in animals and humans.
Are viroid’s and prions considered alive?
Viroids and prions are not considered alive;
Viroids can replicate within host cells but lack the features typical of living organisms
Prions cause disease by inducing other proteins to misfold; they also lack the characteristics of life
Compare & contrast virus, viroid and prion
Similarities: All three are acellular entities that can cause disease
Differences:
Virus is composed of: Nucleic acid (DNA or RNA), protein capsid, some lipids (envelope); Virus is the only one that can replicate but it needs a host cell
Viroid is composed of: RNA only
Prion is composed of: Proteins only
Virus is biggest, than viroid, than prion
What is the composition of a prion?
Proteins
What three diseases are caused by prions?
Creutzfeldt-Jakob disease (CJD)
Bovine Spongiform Encephalopathy (BSE)
Kuru
How do scientists think that prions “replicate”?
Scientists think prions replicate by inducing normal proteins to misfold into the abnormal prion shape;’
p-Prp converts c-Prp into p-Prp through a process called templating
How can prions be inactivated outside of the body?
Heat Treatment: Autoclaving at high temperatures (134°C or 273°F) for at least 30 minutes can destroy prions
Chemical Disinfectants:
-Bleach at 1-2% concentration can reduce prion infectivity
-Phenolic compounds may also be effective
Incineration: Burning contaminated materials at high temperatures (above 600°C or 1112°F) ensures complete destruction of prions.
UV Radiation: High doses of UV light can help inactivate prions, though it’s less practical for all materials.
Proteolytic Enzymes: Some enzymes that break down proteins can reduce prion levels, but may not eliminate infectivity completely
Physical Disruption: Methods like grinding or sonicating contaminated materials can help, but usually need to be followed by heat or chemical treatment.
What is the Classification of Covid-19?
Family Coronaviridae, genus Betacorona virus
What is the structure of Covid-19?
- +ssRNA
- Enveloped, helical capsid
(Step 1) What is the steps of synthesis of Covid-19?
- Attachment to ACE2 receptor (heart, gut, lungs, kidneys, testis, brain)
(Step 2) What is the steps of synthesis of Covid-19?
- Entry via receptor mediated-endocytosis
(Step 3) What is the steps of synthesis of Covid-19?
- Synthesis of genome requires RNA dependent RNA polymerase
(Step 4) What is the steps of synthesis of Covid-19?
- Viral protein synthesis via host ribosomes (free and RER)
(Step 5) What is the steps of synthesis of Covid-19?
- Maturation
(Step 6) What is the steps of synthesis of Covid-19?
- Release via exocytosis
What is the classification of RSV (respiratory syncytial virus)?
Family Paramyxoviridae, genus Pneumovirus
What is the structure of RSV (respiratory syncytial virus)?
- -ssRNA (nonsegmented)
- Enveloped with helical capsid
(Step 1) What is the steps of replication for RSV (respiratory syncytial virus)?
- Attachment: Attach to the cells surface glycoprotein
(Step 2) What is the steps of replication for RSV (respiratory syncytial virus)?
- Entry/Uncoating: Membrane fusion or endocytosis (entry/uncoating)
(Step 3) What is the steps of replication for RSV (respiratory syncytial virus)?
- Synthesis: Brings in RNA dependent RNA polymerase
-Transcribes genes to make nonstructural proteins, coat proteins
-Replication of genome
(Step 4) What is the steps of replication for RSV (respiratory syncytial virus)?
- Translation: Translation on cell free ribosomes (nonstructural, coat), RER for envelope proteins
(Step 5) What is the steps of replication for RSV (respiratory syncytial virus)?
- Release: Budding (gains envelope from CM)
What is the classification of Influenza?
Family Orthomyxoviridae
Types: 4 (A,B,C,D)
(Seasonal caused by Human Influenza A & B virus)
What viral surface proteins are the Influenza A subtypes based on?
Hemagglutinin (H)
and
Neuraminidase (N)
What is the structure of Influenza?
*Enveloped, helical capsid
* -ssRNA (has 8)
*Must bring in RNA dependent RNA polymerase (because its -ssRNA)
(Step 1) What are the steps of replication for Influenza?
- Attachment: Recognize host cell by binding to sialic acid
(Step 2) What are the steps of replication for Influenza?
- Entry/Uncoating: (enter host nucleus) occurs via receptor mediated endocytosis
-Uncoats inside cytoplasm;
releasing the genome as well as the RNA dependent RNA polymerase
-Capsomeres, RNA dependent RNA polymerase made off free ribosomes
(Step 3) What are the steps of replication for Influenza?
- Synthesis: Envelope proteins will be made through the secretory pathway; RER, Golgi, transport vesicle, cell membrane
(Step 4) What are the steps of replication for Influenza?
- Assembly and maturation
(Step 5) What are the steps of replication for Influenza?
5: Release: releases through budding
What is the classification for Monkey Pox (mPox)?
Family Poxviridae (related to smallpox) genus: Orthopoxvirus
What is the structure of Monkey Pox?
- dsDNA (linear 197 kilobases)
- Nucleocapsid (oblong)
- Enveloped
Where does replication happen for Monkey Pox?
In the cytoplasm;
using their own RNA or DNA polymerase, only thing they’re using from the host is the ribosomes
(Step 1) What are the steps of replication for Monkey Pox?
- Attachment: attachment to some glycoprotein on the cell surface (may be similar to smallpox: laminin or heparin sulfate)
(Step 2) What are the steps of replication for Monkey Pox?
- Entry/Uncoating: Outer envelope breaks apart, inner envelope fuse (hemi fusion) w/ CM or endocytosis occurs
Uncoating occurs in the cytoplasm
(Step 3) What are the steps of replication for Monkey Pox?
- Synthesis: DNA dependent RNA polymerase transcribes genes for mRNA
-make proteins (DNA dependent DNA polymerase, DNA dependent RNA polymerase, capsid) using cells free ribosomes
-make proteins (envelope proteins) using cells RER to be transported via cell’s secretory pathway
- (RER -> Golgi -> transport vesicles -> CM
(Step 4) What are the steps of replication for Monkey Pox?
- Maturation
(Step 5) What are the steps of replication for Monkey Pox?
- Release: exits via exocytosis by fusing with CM (gain envelope for virion)
6: An agricultural microbiologist wants to stop the spread of a viral infection of a crop like TMV (Tobacco mosaic virus) . Is stopping viral attachment a viable option? Why or why not?
No, plant viruses need to enter through a wound of some sort made by an insect or instrument
How does a plant virus, like TMV, get from one plant cell to another in this multicellular organism?
The Plasmodesmata;
what is connecting them
What is the size range for a bacterial cell, virus, viroid, and prion?
Bacterial cell: 200 - 555,000 nm
Virus: 10 - 800 nm
Viroid: 2 - 130 nm
Prion: 5 nm
Is it a living thing? (bacterial cell, virus, viroid, and prion)
Bacterial cell: yes
Virus: no
Viroid: no
Prion: no
What are the structural components of each? (bacterial cell, virus, viroid, and prion)
Bacterial cell: Cell structures, genome
Virus: Nucleic acid (DNA or RNA), protein capsid, some lipids (envelope)
Viroid: RNA only
Prion: Proteins only
Can it replicate? (bacterial cell, virus, viroid, and prion)
Bacterial cell: yes
Virus: with a host cell
Viroid: no
Prion: no
Can it grow? (bacterial cell, virus, viroid, and prion)
Bacterial cell: yes
Virus: no
Viroid: no
Prion: no
Does it respond to environmental stimuli? (bacterial cell, virus, viroid, and prion)
Bacterial cell: yes
Virus: some
Viroid: no
Prion: no
Does it metabolize ? (bacterial cell, virus, viroid, and prion)
Bacterial cell: yes
Virus: no
Viroid: no
Prion: no
What is the CA, AT, and MOT of Bacterial Meningitis?
CA: Streptococcus pneumoniae, Neisseria meningitidis
AT: Bacterium (B)
MOT: Person to person, respiratory
What is the CA, AT, and MOT of Listeriosis?
CA: Listeria monocytogenes
AT: Bacterium (B)
MOT: Ingestion of contaminated food
What is the CA, AT, and MOT of Botulism?
CA: Clostridium botulinum
AT: Bacterium (B)
MOT: Ingestion of contaminated food
What is the CA, AT, and MOT of Tetanus?
CA: Clostridium tetani
AT: Bacterium (B)
MOT: contamination of wounds (soil, endospores)
What is the CA, AT, and MOT of Viral meningitis?
CA: Enterovirus
AT: Viral (V)
MOT: Respiratory (saliva, mucus, spit)
What is the CA, AT, and MOT of Polio?
CA: Poliovirus
AT: Viral (V)
MOT: Respiratory, contaminated food or water
What is the CA, AT, and MOT of Rabies?
CA: Lyssavirus
AT: Viral (V)
MOT: bite of infected animal
What is the CA, AT, and MOT of Trachoma?
CA: Chlamydia trachomatis
AT: Bacterium (B)
MOT: bacteria from genitalia transferred to eyes or nose (e.g. in childbirth)
What is the CA, AT, and MOT of Bacterial conjunctivitis
CA: Haemophilus influenzae
AT: Bacterium (B)
MOT: Person to person by hands from respiratory tract
