Viruses Flashcards
Are viruses living or non-living
non-living
What do all viruses require to survive
A host
What are DNA and RNA and what are they made out of.
DNA and RNA are “Nucleic Acids” The building block of these nucleic acids are “nucleotides”, which consist of a phosphate (P), sugar (S) and a base (B).
What is the function of DNA and RNA in a bacterial cell
hold the key to genetic information for keeping viruses functioning and allowing for reproduction.
What are the two differences between DNA and RNA
RNA is single-stranded; DNA is double-stranded and the strands form a “double helix”
Both DNA and RNA possess four different bases; DNA has ATGC, and RNA has AUGC.
Convert from DNA to RNA:
A G T T G A C G A T G
U C A A C U G C U A G
What do viruses do with their genetic information that can be detrimental to us?
The virus inject its DNA or RNA into our cells and uses our cell’s DNA-making proteins and techniques to create more virus cells.
What are the two steps of protein synthesis?
Transcription
Translation
What are proteins made up of and what determines their shape/function?
Proteins are molecules made up of individual units called amino acids. The sequence of amino acids dictates the shape of the resulting protein and therefore the function
What are the two main functions of protein. Name them
Structural and Catalysts
Explain the structural function of proteins
Proteins can fit together and become part of a structure, like the capsid of a virus, or your hair and fingernails.
Explain the catalyst function of proteins
Proteins can speed up chemical reactions. Their shape allows chemicals to fit into their “active sites” like a lock and key. From there, the chemicals will be bonded together, or torn apart. These kinds of proteins are called enzymes.
Where does transcription occur?
in the nucleus
where does translation occur
in the ribosomes
Explain what occurs in transcription
The DNA needs to be converted into RNA (using the DNA to RNA base pairing rule
Explain what occurs in translation
The strand of RNA leaves the nucleus and joins a ribosome. It is now known as a “messenger RNA”, or mRNA. The cell “reads” the mRNA in groups of 3, called CODONS, and a transfer RNA, tRNA, with a corresponding ANTICODON, delivers its specific amino acid to the ribosome. This process continues, and the protein gets longer. Translation stops when a “stop” codon is reached. The resulting protein may be structural or an enzyme.
What are the three types of viruses
DNA, RNA, and Retrovirus
Explain what would make a virus a DNA virus
Contain DNA which will be the starting point of protein synthesis
Explain what would make a virus a RNA virus
Contain RNA, which means the first step of protein synthesis, transcription, is “skipped” and the RNA enters translation
Explain what would make a virus a Retrovirus
Contain RNA and an enzyme called “reverse transcriptase”. Reverse transcriptase converts the viral RNA “backwards” into DNA. Then protein synthesis starts at that point – the beginning.
What type of virus is most unstable/dangerous and why?
Viruses that contain RNA are more unstable as they mutate, or change the order of their bases, more often than DNA viruses do. As a result, treatment for these types of viruses may need to change more frequently, and it is more difficult to develop vaccines because there can be many different strains.
What are the lytic/lysogenic cycles?
how viruses behave and reproduce in your cells in order to cause disease.
Explain the steps of the lytic cycle
- Virus attaches to cell and inserts DNA
- Viral DNA forms a circle inside cell (at this stage the cell will either go lytic or lysogenic)
- New viral DNA and proteins are produced and assembled
- The cell burst, releasing more viral DNA and proteins
Explain the steps of the lysogenic cycle
- Virus attached to cell and inserts DNA
- Viral DNA forms a circle inside cell (at this stage the cell with either go lytic or lysogenic)
- Viral DNA inserts itself into bacterial chromosome
- Bacterium reproduces normally, replicating viral DNA with each cell division. Cell and viral DNA are reproduced many times
- Occasionally, the viral DNA separates from the bacterial chromosome, initiating a lytic cycle when enough viral DNA has been replicated.
What determines if a cell will go lytic or lysogenic?
The relative virulence, or ability to cause disease. Viruses can be very virulent and cause disease symptoms quickly and all at once, like a cold (lytic cycle) Or viruses can be temperate and remain in hiding and cause bouts of disease symptoms more slowly and over longer periods of times, like HIV or Herpes (lysogenic cycle).
How is immunity achieved?
Immunity is achieved when a pathogen enters a host, BUT that host fights it off before illness occurs.
What are humans 3 lines of defense?
- skins, acids, mucus membranes.
- white blood cells, inflammation, fever
- specific, system-wide, whole-body fight that involves specialized white blood cells called B and T cells.
Which line of defence involves immunity?
the THIRD line of defence
Why does the second line of defence involve fever? What does a fever do to the virus?
Once the phagocytes have been activated, a chemical called interleukin-1, IL-1, is released by the phagocytes and travels to the hypothalamus and resets it, increasing your temperature and causing fever.
Fever slows the reproduction rate of the pathogens, and higher temperatures cause a faster immune response to occur.
Where are B-cells and T-cells produced?
These cells are manufactured in the lymphatics system
What is the lymphatic system?
The lymphatics system consists of a network of lymph vessels that contain a fluid called “lymph”. Sometimes these vessels widen into “nodes”. When a localized infection occurs, nearby nodes swell, like tonsils in the throat.
Where do B-cells and T-cells mature?
B cells are made and mature in the Bone marrow, and are then sent into the blood. T cells are also made in the bone marrow, but they migrate to the Thymus to mature before entering the blood stream
What is an antigen? What is an antibody? Explain the relationship between the two.
Antigens are any part of an invader that triggers the production of antibodies.
Antibodies are made by people in response to an antigen. They are Y-shaped proteins whose upper “tips” differ in their shapes.
When antigens trigger the formation of antibodies, only those antibodies with the corresponding shape will be produced.
What is the cell-mediated response and which cells does it use?
The Cell-Mediated response causes T cells to destroy body cells that have already been invaded by the pathogen
What is the humoural response and which cells does it use?
The Humoral response causes B cells to produce antibodies which then attach to the antigens on the pathogen, rendering them useless.
Why does the second exposure to the same antigen evokes a faster response with a larger concentration of antibodies.
This second faster response is due to the presence of the memory B and memory T cells
What are the two types of immunity
Innate (inborn, genetic factors), Acquired (as human progresses through life)
What are the two types of acquired immunity and what do they mean
Active (own anti-bodies) and Passive (ready-made antibodies)
What are the two types of active immunity and how can you get them
Natural (exposure to infectious agents), Articfial immunization (vaccines)
What are two types of passive immunity and how can you get them?
Natural (maternal antibodies via breastmilk or placenta) or Passive (ready-made antibodies vaccines)
What does the hygiene hypothesis state?
hygiene hypothesis states that early childhood exposure to particular microorganisms protects against allergic diseases by contributing to the development of the immune system. Therefore a lack of exposure due to increased hygiene is thought to lead to defects in the establishment of immune tolerance.
