34 terms

Chapter 20

viruses and prokaryotes
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virus[es]
non-living particles that aren't in a domain, latin for poison
nonliving particle made up of proteins, nucleic acids, and sometimes lipids. viruses can reproduce only by infecting living cells
capsid
protein coat around a virus, protects the virus. some viruses have another membrane over the capsid [lipid envelope]
tobacco mosaic virus
first virus to be discovered
viral reproduction
viruses have to get into a cell to survive. viruses reproduce only inside a living host cell. to enter a host cell, most viruses have proteins on their surface membrane or capsid that binds to receptor proteins on the cell. trick the cell to take in virus, or just genetic material, once in cell, viral genes are eventually expressed and may destroy the cell.
most viruses infect only a specific type of cell.
bacteriophage
viruses that infect bacteria, DNA virus
parts: head with dna inside, and capsid around it, a collar, sheath, base plate, and tail fibres which attach to the cell.
lytic infection
virus enters a bacterial cell, makes copies of itself, and causes the cell to burst/lyse.
1. attachment- the bacteriophage attaches to the cell wall
2. entry of phage DNA and degradation of host DNA
3. bacterial chromosome is broken apart
4. phage DNA directs production of lots of new viruses.
5. cell is lysed and new copies of the bacteriophage are released.
lysogenic infection
host cell is not immediately taken over, viral nucleic acid is inserted into host cell's DNA, copies along with host DNA without damage, viral DNA multiplies with host cells
1. virus inserts DNA into bacterium
2. the viral DNA inserts itself into the bacterial chromosome, where it is called a prophage
3. the prophage may replicate with the bacterium for many generations
4. the prophage cam exit the bacterial chromosome and enter a lytic cycle.
prophage
bacteriophage DNA that becomes embedded in the bacterial host's DNA [see lysogenic infection]
RNA viruses
70% of all viruses are RNA viruses
1. the common cold [rhino virus]
the capsid also enters inside the cell w/the RNA
2. human immunodeficiency virus (HIV)
retrovirus, when enters cell, like lysogenic infection, may remain inactive for many cell cycles before making new viruses and damaging the hosts. once activated, begins to destroy system of the body that would normally fight infection.
RNA -> DNA -> RNA -> Protein
RNA mutates more easily b/c its less stable.
reverse transcriptase
more varieties and its harder to combat, it can hide inside your DNA
viruses and cells
we think viruses came from cells, they can't have been first b/c they need cells to reproduce
they are non-living, even though have characteristics of living things.
viruses have continued to evolve alongside the cells they infect.
prokaryotes
unicellular organisms that lack a nucleus. they are classified as bacteria or archaea, two of the three domains of life.
eubacteria
more common, peptidoglycan in cell walls, came first
archaebacteria
generally live in harsh conditions, no peptidoglycan, genes more closely related to eukaryotes.
name means ancient bacteria, but didn't come first, but they have not changed much over time.
shapes of prokaryotes
bacilli- rod-shaped, plural bacillus
cocci- spherical, coccus
spirilla- spiral or corkscrew shape, spirillum
can be part of their names, like pneumococcus bacteria
modes of nutrition
see chart
typical bacterial structure
see chart
modes of metabolism
-obligate aerobes
[obligatory oxygen]
require oxygen for ATP
cellular respiration
-obligate anaerobes
oxygen is poisonous, fermentation
-facultative anaerobes
cellular respiration or fermentation. usually choses one because it makes 18x more ATP
prokaryotes don't have mitochondria like eukaryotes so use cell membrane for respiration
growth, reproduction, recombination of prokaryotes
binary fission- asexual reproduction, in which one cell splits into two. grows so nearly doubled in size, replicates DNA and divides in half, producing two identical cells.
endospore- spore that forms inside of prokaryotes, thickened harder layer around chromosome and some cytoplasm for protection, later released, highly resistant to changes in the environment, very protective.
thick internal wall that encloses the DNA and a portion of the cytoplasm. can remain dormant for a while, lets survive harsh conditions.
example- anthrax bacillus, can do this, causes death, could it be in a bomb to go off? would it survive?
mutations
bacteria reproduce quickly, more chance of mutations, could cause bacteria to evolve.
conjugation
cytoplasmic bridge forms b/t two bacterial cells, form of sexual reproduction
exchange genetic information by this, hollow bridge forms b/t two bacterial cells, genetic material, usually plasmid, moves from one cell to the other. plasmids have genes that let bacteria survive somewhere that would otherwise be fatal. increases genetic diversity among prokaryotes.
***transduction
prokaryote picks up a naked piece of DNA, crossing-over occurs, maybe will get stuff from new DNA
***transduction
virus mistakenly transfers a piece of bacterial DNA from one bacteria to another, mistake, not meant to happen, but virus doesn't spread.
importance of prokaryotes
decomposers, producers, nitrogen fixers [change nitrogen gas into ammonia, on roots of legumes as like fertilizers], humans use for food production and in medicines.
pathogen
infectious agent [microbe] or microorganism that causes disease in plants or animals
disease mechanisms [of bacterial diseases]
1. damaging host tissue [like in tuberculosis, where destroys lots of tissue in lungs, and can enter a blood vessel and travel elsewhere]
2. releasing toxins [diptheria, tetanus] in respiratory, nervous system can be meningitis, penumonia, streptococcus [chain], staphococcus [cluster]
controlling bacteria
-physical removal [washing hands]
-disinfectants [purell]
-food storage [refrigerator]
-food processing [heat up bacteria]
-sterilization by heat [medical instruments]
preventing bacterial disease
vaccine-weakened or dead form of the pathogen or inactivated form of the toxin is put into you, body makes reserve of antibodies to attack in the future, memory cells and antibodies if you get the disease a second time
treating bacterial diseases
antibiotics-only work against bacteria, block function of enzymes, only work against living things.
viral disease mechanisms
1. directly destroying living cells
2. affecting cell processes in ways that affect homestasis [ex-common cold, chicken pox]
preventing viral diseases
washing hands, vaccines, cover mouth
treating viral diseases
anti-viral drugs [attack viral enzymes]
but can't use antibiotics
emerging disease
a disease that first shows up in a population also a disease that is no longer controllable
superbugs
from overuse of antibiotics/antiviral drugs, pathogen we can't control, is not affected by drugs.
prions
protein infectious particles
misshapen proteins, can make more and cause other proteins to become misshapen when they bump into them. discovered in mad cow disease, mostly neurological and brain things.
spreads from just touching other proteins, and protein shape determines function.
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