Unit 5: Bacteria & Viruses Flashcards
What are the 3 components of a virus
Core of DNA or RNA
capsid
potential envelope
What is a capsid
A protein coat surrounding the core
What do capsid proteins do
They bind to the cell and “tricks” the cell into letting it inside
What is an envelope
Lipid bilayer that makes it easier for viruses to fuse to host cell
bacteriophage
Virus that attacks bacteria
Can any virus attack any cell
No, viruses have specific proteins on their capsids that allows them to only attack specific cells
What are the 2 types of viral infection
Lytic and lysogenic
What are the steps to a lytic infection
- Phage DNA enters
- New phage DNA and proteins are synthesized into phages, duplication
- Cell breaks open, phages released
- Phages attach to a new host cell and inject DNA
What are the steps to a lysogenic infection
- Phage DNA enters
- Phage DNA and bacterial chromosome combine, becomes a prophage
- Bacterium reproduces, prophage is copied and transmitted
- Many cell divisions produce a colony of bacteria infected with prophage or the prophage exits and initiates a lytic cycle
prophage
Viral DNA in the host DNA
What are retroviruses, what specific enzyme do they have
Viruses that contain RNA as genetic material
contains reverse transcriptase
What is reverse transciptase
An enzyme that transcribe RNA into DNA
Why do retroviruses have high rates of mutation
They lack replication error-checking mechanisms, cannot correct mutations as they occur
Can retroviruses remain dormant
yes
What are 2 things a virus and a cell have in common
Contains genetic material
has the ability to evolve
What is a virus dependent on a cell for
Growth
reproduction
obtaining and using energy
responding to the envrionment
What are the 2 types of vaccines
A preparation of pathogens introduced into the body to build immunity
or
mRNA introduced that codes for proteins on the virus that builds immunity
Can viruses be grown in nutrient agar like bacteria?
Viruses cannot be grown like bacteria because they require a host cell in order to grow
Why do antibiotics work on bacteria and not against viruses?
Antibiotics attack the cell wall, viruses don’t have cell walls so they aren’t effected
What are the 6 components of bacteria
Cell wall
cell membrane
genetic information
ribosomes
capsule
flagellum
what purpose does the capsule serve
Mucous layer that protects against infection and allows adhesion
What type of genetic material do bacteria have
A circular chromosome of DNA
where is the genetic information found in bacteria
nucleoid
what are plasmids
small circular rings of DNA, carries only a few genes
What are the 2 types of plasmids
F-plasmids and R-plasmids
F-plasmid
codes for the production of pili
R-plasmid
codes for antibiotic resistance
How do bacteria reproduce
Binary fission
binary fission
Bacteria copies its DNA then splits in half, producing 2 daughter cells
How often does binary fission occur
20min - 3 hours
What are the 3 prokaryote adaptation to increase genetic variation
Transduction
transformation
conjugation
transduction
Phages carry prokaryotic genes from one host cell to another
Describe the process of transduction
- Phage injects DNA into host cell
- Phage enzymes degrade host DNA
- Cell synthesizes new phages that incorporate phage DNA and some host DNA by accident
- Transducing phage (phage with host DNA) injects donor DNA into new host cell
- Donor DNA incorporated into host cell chromosome
transformation
Bacteria take up DNA from surrounding environment
Conjugation
Bridge forms between 2 bacterial cells by pili and genetic info is passed on
Operon
Set of genes and the switches that control the expression of those genes
When does gene regulation occur in prokaryotes
During transcription
Negative Gene regulation
Ability to turn off gene expression
Positive Gene Regulation
Ability to initiate and/or amplify gene expression
Repressible Operon
Always on unless the repressor is activated
What type of operon is the TRP operon
Negative gene regulation, repressible operon
Inducible operon
Always off until repressor is deactivated
What type of operon is the lac Operon
Negative gene regulation, inducible
What is an allosteric protein
A protein that changes shape and activity when bound to a molecule
What happens when tryptophan binds to the repressor protein and the subsequent product
It turns the repressor protein on by changing the shape of the enzyme, it then connects to the operator, resulting in gene expression being turned off
corepressors
Molecules that bind to repressor proteins
What does the lac operon produce
B-galactosidase aka enzymes that break down lactose
What does the trp operon produce
tryptophan
What happens when lactose binds to the repressor protein
The repressor protein becomes inactive and detaches from the operator, allowing for transcription and gene expression to occur
what is the inducer in the lac operon
Allolactose, a form of lactose
What pathways are inducible and repressible enzymes usually used for?
Inducible, catabolic
repressible, anabolic
What does CAP bind to?
cAMP
Is CAP a repressor or activator protein?
activator
What happens when there is a high level of cAMP
CAMP binds with CAP and that complex binds to the promoter region which enhances RNA Polymerase binding, increases transcription
If lactose levels are high, what is the glucose concentration
low
What are the 3 common shapes of bacteria
Cocci
bacilli
spirilla
What are the 2 types of cell walls in bacteria
Gram Positive and Gram Negative
Can all bacteria move?
no
Why can bacteria move
Some move with the aid of their flagella
Others move by lashing, snaking, or spiraling forward
What are the 4 types of Metabolism
Chemoheterotrophs
photoheterotrophs
photoautotrophs
chemoautotrophs
Chemoheterotrophs
Organisms that take in organic material to obtain energy
Photoheterotrophs
Photosynthetic and needs to take in organic material
Photoautotrophs
Photosynthetic Bacteria
