Unit 2 test Flashcards
(24 cards)
Why are viruses not considered living
- Not made up of cells
- Only capable of 1 living function ie. reproduction & only with living cell
- outside the cell, viruses are lifeless chemicals.
list the 6 characteristics of living organisms
- composed of cells
- growth and development
- able to reproduce
- respond and adapt to their environment
- obtain and use energy
- produce wastes.
What is capsid
Protein coat for protection
What is core
Nucleic acid either DNA or RNA
What are the spikes that help the virus attach to its specific host cell called
Receptor sites.
What is an envelope
In only some viruses- surrounds the capsid and is derived from the host cell as the virus is released.
What shapes do viruses come in and give examples
filaments- Ebola
spherical- HIV, COVID, Smallpox, SARS, influenza.
Geometrical-Adenovirus and Bacteriophage T4
How are viruses classified as
- the organisms they infect
-what type of host cells and the range for ex. HIV infects WBC and the cold infects respitory cells. - The structure
+size and shape of capsid
+ The nucleic acid DNA or RNA
+ If it has envelop or not.
Why can’t viruses reproduce by themselves?
- Lack specific enzymes and ribosomes
- They don’t have enough energy needed to synthesise their parts.
What happens in the attachment phase of the lytic cycle
- Virus attaches to host cell using its receptor sites
- injects its core (DNA) in the host cell
What happens in the synthesis phase of the lytic cycle
- Viral DNA stops host protein synthesis
- Host ribosomes produce viral protein
- Viral DNA is also replicated 100’s of times using cell machinery
What happens in the assembly phase of the lytic cycle
- Capsid surrounds viral DNA core
- 100’s of virus particles are put together in the cytoplasm of the host cell
What happens in the Release phase of the lytic cycle
- Viruses produce enzymes to burst host cell
- 100’s of viruses are released
- These viruses infect neighbouring cells.
What is Virulent
Viruses that reproduce with the lytic cycle are called virulent
What is the special enzyme that changes RNA to DNA called
reverse transcriptase
What are RNA viruses called
Retroviruses.
Why are retroviruses especially lethal.
Because the viral DNA produced by this enzyme can splice into the host chromosome and stay dormant for months or years.
What are 3 examples of retroviruses?
AIDS, Genital herpes and cold sores
Where did viruses come from
Came from detached fragments of genetic material & proteins from living cells.
Why are viral diseases difficult to
- There is no drug that can kill virus in the body.
- Some virus might be in a lysogenic cycle and be dormant like HIV
- some viruses are oncoviruses.-cause cells to become cancerous
What are ways to protect from getting the virus in the first place
Vaccines: Only true protection against viruses are vaccines.
-people are given weakend or dead version of the virus, that way your immune system builds up proper antibodies and wbc
Antiviral agents: Drugs given after infection to slow the reproduction of the virus baiscly gives your immune system a head start.
What happens in viral vector gene therapy
- viral core is removed & desired human gene is added
- virus is mixed with living cells
- virus attaches to human host cell & injects the human gene.
- oncolytic virus used in targeted cancer treatment.
Why can’t AIDS survive outside a body
because glycoprotein membrane around its capsid dries out
How can AIDS spread
- blood to blood
- secretions
- breast milk.
