Chapter 20: Viruses and Prokaryotes Flashcards
How complex are viruses?
Viruses are the simplest life-like structures.
True or False: It’s easier to change a simple structure, rather than complex.
True
Why aren’t viruses living?
Viruses are not living because they only reproduce they only reproduce (and they need a host to do so).
How do viruses reproduce?
Viruses reproduce only by infecting living cells.
Who demonstrated that the cause of tobacco mosaic disease was found in the liquid extracted from infected plants?
Dmitri Ivanovsky
Ivanovsky found that viruses are _______ than bacteria, and they can stay in a ____________ form.
Ivanovsky found that viruses are smaller than bacteria, and they can stay in a crystalline form.
What are viruses made of?
proteins, nucleic acids, and sometimes lipids
True or False: Viruses differ widely in terms of size and structure.
True
The protein coat surrounding a virus is called a what?
capsid
Can viruses have an additional membrane surrounding the capsid?
Yes
The simplest viruses contain only a few _____, whereas the most complex may have more than a hundred _____.
genes
What do most proteins on the capsid do?
Bind to receptor proteins on the host cell
When are the viral genes expressed?
Once the viral genes are inside the host the cell- this is also when the virus can destroy the host cell.
Viruses that infect bacteria are called what?
bacteriophages
What do bacteriophages have for protection?
A tail sheath
What happens in a lytic infection?
In a lytic infection, a virus enters a bacterial cell, makes copies of itself, and causes the cell to burst (lyse).
What is an example bacteriophage that causes a lytic infection?
Bacteriophage T4
Bacteriophage T4 has a ___ ____ inside a protein capsid that bonds to the surface of a host cell.
Bacteriophage T4 has a DNA core inside a protein capsid that bonds to the surface of a host cell.
What does the virus do once it bonds to the cell surface?
It injects its DNA into the cell.
What type of RNA does the cell make from the viral genes?
messenger RNA
The viral mRNA is translated into viral _______ that chop up the cell’s DNA.
proteins
Copies are made of _______ ____ once the viral genes control the cell.
Copies are made of nucleic acid once the viral genes control the cell.
The host cell’s metabolic system makes copies of ______ ____ and ______ ________.
The host cell’s metabolic system makes copies of nucleic acid and capsid proteins.
The viral nucleic acid and proteins are then assembled into what?
new virus particles
The virus particles are released to infect other cells when the host cell _____.
lyses
What are the names of the two cycles that the virus can go through (depending on environmental conditions)?
Lytic Cycle and the Lysogenic Cylcle
What does “lysis” mean (from the word lytic)?
destroy
True or False: Chromosomes are made of genetic material.
True
A virus that attacks bacteria is called a _____.
phage
What are the steps to the Lytic Cycle?
- virus attaches to cell and injects DNA
- viral DNA circulizes
(if continuing with lytic) - new viruses (viroids) are made
- cell lyses (releases virus)
repeat
What are the new viruses made in the Lytic Cycle called?
viroids
What are the two classifications of prokaryotes?
Bacteria and Archaea
What is the main difference between bacteria and archaea?
Materials
Prokaryotes are ___-________.
Prokaryotes are sub-cellular.
The smallest and most abundant microorganisms on Earth are ___________.
prokaryotes
Do prokaryotes have DNA?
Yes
Where is a prokaryote’s DNA found?
In the cytoplasm (it free floats)
A primitive cell (like a prokaryote) is more sophisticated than a ____, but less than a _________.
A primitive cell (like a prokaryote) is more sophisticated than a virus, but less than a eukaryote.
True or False: Prokaryotes have cell walls.
True
What are in the cell wall of a prokaryote?
Sugars and amino acids
So prokaryotes have an additional layer of protection for resistance called a what?
slime capsule
The _____________ describes the bacterial cell wall made of part sugar and part amino acid .
peptidoglycan
Are bacteria a larger group than archaea?
Yes
Some prokaryotes have ________ that they use for movement.
flagella
____ mainly serve to anchor the bacterium to a surface or to other bacteria.
pili
Archaea look very _______ to bacteria.
similar
Both archaea and bacteria ____ nuclei.
Both archaea and bacteria lack nuclei.
Do archaea have peptidoglycan?
No, the archaea membranes contain different lipids.
Archaea DNA sequences are more like those of what than those of bacteria?
eukaryotes
_____ and _________ are related more closely to each other than to ________.
Archaea and eukaryotes are related more closely to each other than to bacteria.
True or False: Many archaea live in extremely harsh environments.
True
Archaea and bacteria both are equally small, ____ _______, and have cell walls.
Archaea and bacteria both are equally small, lack nuclei, and have cell walls.
Prokaryotes are much ________ than most eukaryotic cells.
smaller
Rod-shaped prokaryotes are called what?
bacilli
Spherical prokaryotes are called what?
cocci
Spiral and corkscrew-shaped prokaryotes are called ____.
spirilla
How do prokaryotes move?
Some do not move at all.
Some are propelled by flagella.
Some glide slowly along a layer of slime-like secreted material.
Can bacteria adapt by changing shape to survive?
Yes
How do prokaryotes store the chemical energy they need?
by storing it in the form of food molecules such as sugar
True or False: Some species are able to change their method of energy capture or release depending on the conditions of their environments.
True
When a prokaryote has grown so that it has nearly doubled in size, it _________ its DNA and divides in half.
When a prokaryote has grown so that it has nearly doubled in size, it replicates its DNA and divides in half.
After the division, there are now two identical cells. What type of reproduction is this?
binary fission
What form of reproduction is binary fission?
asexual
When growth conditions become unfavorable, many prokaryotic cells form an _________.
endospore
An endospore is a a thick internal wall that encloses the what?
DNA and a portion of the cytoplasm
Can endospore remain dormant for a long period of time?
Yes
What is one of the main ways prokaryotes evolve?
Mutations
In prokaryotes, mutations are _________ by daughter cells produced by binary fission.
In prokaryotes, mutations are inherited by daughter cells produced by binary fission.
The process of prokaryotes exchanging genetic information is called what?
conjugation
During conjugation, a hollow bridge forms between two _________ _____.
bacterial cells
The genetic material, usually in the form of a ______, moves from one cell to the other.
plasmid
Many plasmids carry genes that enable bacteria to what?
survive in new environments or to resist antibiotics that might otherwise prove fatal
What does this transfer of genetic information increase?
It increases the genetic diversity in populations of prokaryotes.
_____________ bacteria are present in soil and in rotting plant material decompose complex organic molecules into simpler molecules.
Actinomycetes
How do prokaryotes supply raw materials, and thus help to maintain equilibrium in the environment?
By decomposing dead organisms
What is a type of pond bacteria that performs photosynthesis?
cyanobacteria
Food chains are dependent upon ___________ as producers of food and biomass.
prokaryotes
What do all organisms need to make protein and other molecules?
Nitrogen
Only a few kind of organisms, all of which are what, can convert N2 into useful forms?
Prokaryotes
What process converts nitrogen gas into ammonia?
Nitrogen fixation
Nitrogen-fixing bacteria and archaea provide __% of the nitrogen used by other organisms.
90
The prophage is a combination of the _____ and _________ DNA.
The prophage is a combination of the viral and bacterial DNA.
Once combined, can the two types of DNA separate?
No
In the lysogenic cycle, when the viral DNA is replicated and the host cell divides, the DNA makes a what?
copy of itself
For both daughter cells, the genetic makeup is what?
the genetic makeup is identical at the end of mitosis
If the environmental conditions allow for it, the viral DNA circularizes and then goes into the _________ ____.
lysogenic cycle
What are the steps to the lysogenic cycle?
- viral DNA integrates into host DNA
- viral DNA is replicated (host replicates own DNA)
host cell divides (mitoses) - prophage may leave host DNA to enter lytic cycle
What is the difference between the lysogenic cycle and the lytic cycle?
The lytic cycle destroys the host cell, once it uses it. The lysogenic cycle takes advantage of the host cell, but lets it live.
True or False: Both cycles are a survival mechanism, so the virus can stay “alive.”
True
In the lysogenic cycle, when the host cell divides, what part of mitosis is it?
Cytokinesis
How many times does the DNA make a copy of itself?
Each time the host cell divides
What is the difference between HIV and AIDS?
HIV is the infection. AIDS is when the patient starts showing symptoms.
An illness that can transfer from each species is called what?
zoonosis
An example of zoonosis is what?
Rabies
