Viruses And Bacteria Flashcards
What is a virus
A virus is a particle that causes disease in organisms and consists of a core of nucleic acids surrounded by a protein coating
How do viruses differ from unicellulaire organisms
Viruses do not have a nucleus, complex inner membrane, or organelles like mitochondria or endoplasmic reticulum
Describe the structure of a virus
Viruses have a core of nucleic acids ( DNA or RNA, not both ). They have a capsid [protein coat surrounding the nucleic acid and protect it]. Some viruses also have an envelope [protective protein coating seen in some viruses. Some are covered with spikes or carbs and proteins which allow viruses to chemically recognize and attach to the cell they infect].
What is ‘specificity of viruses’
Specificity of viruses describes how the viruses can infect so many different kinds of organisms
Eg. Plant viruses only infect plants
Many viruses infect just one host
What is host range
The number of host species a virus can infect
Viruses are dependent of living cells. Outside of living cells, viruses cannot ____, ____, ____, or ____ on their own.
Viruses are dependent of living cells. Outside of living cells, viruses cannot move, grow, reproduce, or respire on their own.
Viruses are obligate intracellular parasites. What did this mean?
A virus can only reproduce inside a host cell
Any hypothesis about viral origins must explain 4 observations. What are these?
- Viruses depend on totally on living organisms for survival
- Most viruses infect only a few hosts
- Families of viruses have genetic material that is more similar to host than other viruses
- Some viral genes are almost identical to genes of their host
Explain viral replication in the lyric cycle
This viral replication rapidly kills a host cell and makes the host cell lyse (burst).
Explain the lyric cycle in detail
The nucleic acid of a virus takes control of host cell’s activity and directs it to make more copies of the virus. When done, it kills the host cell, thus releasing new virus cells to infect more hosts.
What is a virulent phage
A phage that replicates only by a lyrics cycle
Describe the lysogenic cycle
A viral replication process in which a virus does not immediately kill a host cell. It may lay dormant, waiting to pop up when conditions are right (eg. Low immune system).
Describe the lysogenic cycle
A viral replication process in which a virus does not immediately kill a host cell. It may lay dormant, waiting to pop up when conditions are right (eg. Low immune system).
What is a prophage
The viral nucleic acid attaches to the host cell’s chromosomes. The prophage reproduces every time the chromosome reproduces until a stimulus causes it to attack the host and go through the lytic cycle.
What are two methods of defense bacteria have against phages
- Natural selection favors bacterial mutants with surface proteins that can’t be recognized
- They can identify foreign DNA and cut it up by using restriction enzymes (bacterial DNA is methylated so it isn’t cut accidentally)
What is a viral envelope
It is derived from a host cell’s plasma membrane that binds to specific receptors
What is a viral envelope
It is derived from a host cell’s plasma membrane that binds to specific receptors
What is the RNA genome
i. Retroviruses use reverse transcriptase to copy their RNA to DNA (eg. HIV)
ii. The viral DNA in the host virus genome is called a provirus
iii. Proviruses remain permanent residents of host cells
What is a retrovirus
Dangerous viruses that replicate nucleic acids in the reverse of the standard way. Rather than using DNA to make RNA, retroviruses use RNA to make DNA
What are viroids and prions
Viroids are tiny particles of pure RNA that cause disease in plants
Prions are particles of proteins that cause some diseases in animals
These are not viruses because
1. Viroids do not have protein capsids protecting the nucleic acids
2. Prions do not have nucleic acids
All members of kingdom monera are prokaryotic. What are 5 common characteristics of all prokaryots
- They do not have a nucleus
- They do not have membrane bound organelles
- They have different ribosomes than those found in eukaryots
- Almost all proks. are smaller than the smallest euks.
- Most prokaryots are single cell organisms
There are 2 groups under kingdom monera: eubacteria and archaebacteria. Give a short description of the two
Archaebacteria live in unusually harsh environments. They have different cell walls, membranes, and ribosomes than other monerans.
Eubacteria are known as the true bacteria. They have strong cell wallsto maintain shape, protect the cell, and prevent bursting in hypotonic environments
What are methanogens
Methanogens produce CH4 and live in oxygen-free environments. (Found in swamps, marshes, mammals). Used industrially to treat sewage and purify water
What are thermoacidiphiles
These live in extremely hot (60°-250°C) and acidic waters. Colonies of these glisten the edges of near boiling hot springs
What are chemosynthesizers
These use inorganic compounds as an energy source. They flourish in the deep-sea hot springs formed by volcanic vents on the ocean floor
What are extreme halophiles
These live in extremely salty conditions. They grow in water 9× saltier than sea water