Viruses Flashcards
(22 cards)
What are Viruses?
____non-living____ particles that __use_____ the metabolic machinery of ___living_____ cells to __reproduce_____
They are ____obligate parasites___________ (can’t function without a host cell)
Viruses, because they were so __small____ were not identified until the invention of the electron microscope in 1934. Viruses are measured using a unit called the ____nanometer______ (nm) which is one 100,000,000th of a meter
To get an idea of how small viruses are: ____5000____ flu viruses fit on the head of a pin
Very small (10-400nm) ____non-living_____ particles
__Not cellular_______ (no cellular structures) to carry out life processes
___Dependent______ on a host cell’s machinery for ___survival_____ and ___reproduction________
They are infectious particles consisting of a nucleic acid (DNA or RNA)
Viruses are non-living because:
Unable to ___reproduce______ on their own
Unable to ____move____ independently
Do not react to ___stimuli_______
Lack cell structures
No Cytoplasm, organelles or cell membranes
Do not ____metabolize______ food
Host Range:
Some viruses can only _infect______ one species while others can infect multiple species
Can be ___broad_____ (multiple species or cells)
Can be ___narrow_____ (one species or cell)
Proteins on surface of virus match with proteins on the surface of the host cells
Lock and Key
Viral Structures:
Not as complex as ____living____ things
They consist of:
Genetic Material (either ___DNA_____ or ____RNA___)
Protective Protein Coat (called a __Caspid________)
Shapes:
Helical
Polyhedral -
Spherical with envelope
Bacteriophage (head and tail structure)
Bacteriophages:
Also known as __Phages______
They infect ____bacteria____ cells
Most other types of viruses enter the ___host_____ cell, phages do __not_____
They inject their ___DNA_____ into the bacteria and their protein capsule remains ____outside_____ of the cell
Virus Classification:
Viruses can be classified according to their:
__size____ and ___shape_____ of capsid
___shape____ and ___strucutre_____ of virus
___Genetic______ material (DNA or RNA)
___Reproduction________ method (lysogenic vs. lytic)
Type(s) of ________ the virus causes
Virus Classification: Genetic Material
Viruses with __DNA_______
Single or ___double______ stranded DNA with a capsid
Examples of DNA viruses include ____chickenpox________, smallpox, ___herpes_____, mononucleosis
Viruses with __RNA________
___single____ stranded RNA with a capsid
Examples of RNA viruses include Human Immunodeficiency Virus (HIV), __Influenza________, Rabies, ____Ebola________
Virus Classification: two types of Reproduction
Lysogenic Cycle
Lytic Cycle
Lysogenic Cycle
Virus injects __DNA_____ into host cell’s chromosomes and becomes ____dormant_______
When the viral DNA has joined the host DNA, this is referred to as ___provirus_______
Lytic Cycle:
Virus injects DNA into host DNA
Viral DNA __hijacks______ host and uses it to ___replicate____ new viruses
Lyctic Cycle process
A) Attachment to receptor site - proteins in virus tail specifically fits the structure of the bacterial wall - specific virus -hose infections.
B) Penetration- virus injects genetic material and infects the host cell.
C) Multiplication- GENETIC MATERIAL OF VIRUS BREAKS UP DNA OF THE HOST CELL AND PRODUCES COPIES OF VIRAL GENETIC MATERIAL AND PROTEIN ASPIDS.
D) Assembly - Viral genetic material and capsid are assembled into new viruses.
E) Lysis- release of new viruses that infect neighboring cells and host cell dies.
Lysogenic Cycle process
Viral DNA is ____combined____________with host DNA and forms a ____provirus___________
(does not interfere with normal function)
Viral DNA can ____replicate____________ along with the host cell’s DNA for many _______generations______
Virus is _______reactivated___________ by stress, infection, UV light
Re-entry into the ___lytic cycle_____________
Examples: _____cold sore, chicken pox shingles_______________________________________________________
comparison between lyctic cycle and lysogenic cycle:
lyctic cycle:
Usually ___shorter_____ time
Cell does not ___divide___ after viral infection
Cells are __infected______ on at a time
Results in cell __death______
Lysogenic Cycle:
Usually takes ___longer_____
Viral DNA is passed on to all daughter cells
Requires an environmental stimulus to begin __lytic_____ cycle
Once the lytic cycle begins, it results in cell ___death_______
How are Viruses Transmitted?
___oral_____ transmission
___trans-placental_________ transmission
___sexual_______ transmission
____animal____ or ___insect___ bite
Direct inoculation
____droplet____ transmission
Why are they Bad?
Infects plants and destroys farmer’s __crops_______.
Infects animals and humans and causes many ___diseases_____ through the __lytic cycle_______. E.g. Covid-19, SARS, influenza, chicken pox, common cold
___smyptoms______ are produced by ____desctruciton_____ of ___cells______ and ____tissues_____.
Can ____hide_____ in the __DNA_______ of an organism (lysogenic cycle) and can be transmitted to another person ___unkowingly______. E.g. HIV, hepatitis
Have the ability to __mutate_______ and change their outer appearance, making them difficult to ___treat______.
Why are they Good?
They are ___smaller______than a living cell, so viruses can be used as ___vectors______ to carry __good_______ genes into diseased cells. This is called __gene thereapy_______ and is a method used to treat some __genetic disorders_______ such as diabetes and cystic fibrosis.
What two ways can viruses be Beneficial?
Genetic Therapy
Chemotherapy Drugs
Genetic Therapy
Viruses can enter specific cells and___insert_____ their DNA . Therefore, they can be used to deliver ___drugs_____ or _genes________ to target cells .
They place ___drugs______ inside virus capsules or ____replace_____ the DNA
This can also be used to create __genetically________ ___modified________ organisms or plants
Chemotherapy Drugs
Use virus capsule to deliver drugs to __treat________ tumour cells
How do we Treat Viruses
Viruses cannot be treated with ___antibiotics_______, because antibiotics act to kill certain types of ___bacteria________ cells
Some viruses are “treated” __premtively________ with __vaccines________, made from ____dead or weakened__________ virus particles
How Vaccines Work:
Our __immune________ system is made up of white blood cells and __antibodies_____
The white blood cells seek out ___foreging______ invaders and __kill_______ them
Once destroyed, the antibodies produce an antibody for that ____specific_______ virus
This allows the body to _recognize_________ that infectious agent more quickly often avoiding more serious ____infection_______
