Chapter 13: Viruses - Essential structure Flashcards
1
Q
What are viruses?
A
- Acellular particles capable of infecting host cells and causing disease
2
Q
What does it mean by viruses are not free-living?
A
- they require a host cell in which to multiply
3
Q
Obligate intracellular parasites are a type of virus. What do they do?
A
- use host metabolic systems and usually disrupt normal host cell function
4
Q
What are characteristics of viruses? (5)
A
- Acellular
- do not have a plasma membrane
- contains a single type of nucleic acid (DNA or RNA)
- surrounded by a protein coat
- May or may not have additional envelope of lipids
5
Q
Do viruses have enzymes?
A
have very few of their own, but they take enzymes of their host
6
Q
In lecture, what type of viruses are more prone to degradation?
A
- envelope viruses
7
Q
What kind of organisms can viruses effect? (5)
A
- animals
- plants
- fungi
- protozoa
- bacteria
8
Q
Most viruses are specific for a single host species. What does this mean?
A
- To infect a cell, the virus must recognize features on the host cell surface
ex. some viruses recognize the fimbriae of a certain bacterial species
9
Q
What type of microscope must be used to view viruses?
A
- electron microscopes
- range from 20-1000 nm in length
10
Q
What three parts do viruses have?
A
- nucleic acid
- capsid
- envelope
note that viruses need at least 2 of these
11
Q
Can viruses have both DNA and RNA?
A
no
12
Q
What can the nucleic acid in viruses be?
A
- single stranded or double stranded
- linear or circular
- can be in several pieces - segmented
13
Q
What is the total amount of nucleic acid in a virus
A
- a few thousand to 250 000 base pairs
14
Q
How many base pairs does the E. coli chromosome have?
A
4.6 million
15
Q
What is a capsid? (2)
A
- protein coat surrounding the nucleic acid
- made up of individual proteins called capsomeres
