Textbook Notes: Viruses Flashcards
What is a virus?
A microscopic parasite, much smaller than bacteria.
What are viruses made up of?
Viruses consist of a protein coat or capsid, surrounding a core of nucleic acid. In some viruses the nucleic acid is DNA, in others it is RNA.
What are the functions of the different parts of a virus?
The outer layer (capsid) (protein coat) - to gain entry to a host cell by manipulating the surface membrane of the host cell.
Nucleic acid - …..
How do viruses reproduce?
Viruses do not “reproduce” as such, they replicate.
Viruses cannot reproduce on their own - all the raw materials, energy and enzymes provided are from the host cell.
- Virus attaches itself to the outside of the host cell and injects it’s genetic material in it.
- The viral DNA/RNA replicates inside the host cell.
- Viral DNA takes over the host cell’s functioning, causing it to make protein coats.
- Viral particles are assembled. Identical copies of the virus are formed.
- Host cell bursts open, releasing copies of the virus. These are now ready to attack other host cells and make more copies.
Types of viruses are…
Human warts (papillioma)
Cold (rhino) virus - infects human resp. tract
Rabbit Calicvirus - only affects rabbits.
How do viruses move?
They rely on external sources to move - wind, rain, cough, blood.
What life processes do viruses carry out? How?
They do not respirate.
Sensitivity - they do not respond to the environment.
Cells - they are not made up of cells.
Excretion - viruses do not produce anything as a product.
Nutrition - they cannot obtain nutrients. They rely on the host cell to gain energy.
Reproduction - they do not “reproduce” as such, but instead replicate. The structure allows it to make copies of itself. (through host cells).
What is active immunity?
Immunity provided by the body.
What is mutation? How does it occur? What does it lead to?
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Describe how disease in plants occurs. How is it treated?
Most plant diseases are fungal or viral. Viral diseases can cause abnormal growth rather than killing the host plant; fungal diseases cause death of tissue and sometimes the whole plant. Fungal diseases can be controlled by spraying with fungicides that kill the fungus, and burning any affected plant tissue to destroy the spores.
What are some of the body’s defences to pathogens?
Skin acts as a waterproof protection.
If microbes enter by chance, body removes them through coughing and sneezing reflexes.
Stomach acid (HCl) kills microbes (low pH, strong).
Cilia, (microscopic hairs in the nostrils) trap microbes.
Sweat has (micro) amounts of antiseptics).
Tears wash away microbes.
Mucus traps microbes as well.
What is passive immunity?
Immunity where antibodies are externally introduced to the body. Produced outside the body but used inside by different means.
e.g: when a mother breastfeeds, child gets the immunity from it’s mother.
when a child is vaccinated, passive immunity is short-lived. It will work in the body until the antibody is used up.
What is a vaccine?
Vaccination involves the introduction into the body of a weakened (attenuated) pathogen or one that has been killed but can still stimulate antibody production. This means the immune system remembers the infection and knows how to prevent it/fight it.
Explain how the immune system provides term protection against disease.
When a pathogen/toxin enters our body, white blood cells will recognise it as a foreign body. An immune response will send off antibodies which will get rid of the infection.
Once infection is over antibodies remain in the body and special WBC called the “memory cells” which are “armed” and “ready” protect the body against any further pathogenic entry.
What are some ways in which the body is able to recognise that a pathogen has entered?
Fever. Body naturally tries to increase the temperature to kill the pathogens.
Inflammation. Glands fill with plasma (liquid part of blood) to support the immune system.
