Viruses Obligate intracellular parasites meaning they need to live within a host cell But that s a bit different with viruses because they aren t actually alive It s only purpose is to make more viruses Why aren t viruses living Because they are not cellular they can only replicate inside a host cell there is no ATP generating system they have no ribosomes they contain only one nucleic acid and has no metabolism In talking about viruses sizes there is no standard shape or size Ebola is a somewhat unusually large viruses at 970 nm Virus Components Every virus has a capsid and nucleic acid o Capsids made up of individual protein units called capsomeres They protect the nucleic acid and are responsible for the virus s shape o Viruses can contain double strand DNA single strand RNA double strand RNA or single strand RNA There are a lot of double stranded DNA viruses like in living cells Herpes is an example Not many viruses are single strand DNA One example is B19 or the Fifth disease This is also sometimes called the Slapped Face Syndrome Rotaviruses are examples of double strand RNA viruses They are common in children main symptoms include a lot of diarrhea Single strand RNA viruses are probably the most common Examples include rhinovirus flu virus and rabies o Some viruses also have an envelope which is made of membrane material that will fuse with the cell membrane of a host releasing the inside of the virus into the cell Virus specificity animal plant and bacterial viruses bacteriophages or phages Even within these specifications many viruses are specific to a single species o The bacteriophage It acts like a big old syringe that injects genetic material into the host cell Viral replication Viruses do not produce toxins They affect their host by replicating o 1 the virus particle or virion attaches to host cell o 2 Particle enters the cell and uncoats its DNA o 3 The DNA will coat for RNA which will code for viral proteins o 4 These early proteins will make new DNA copies with will make more RNA which will code for even more proteins specifically capsid proteins o 5 The proteins come together and mature into new virions o 6 The new viruses exit the cell o What happens to the host cells it lyses the virus leaves without killing it or the cell continues to produce the viruses until it dies or the virus leaves o When enveloped viruses mature within their host they will bud out fo the cell or steal a portion of the cell membrane to make its new envelope The Lytic Cycle is what we call the portion of viral replication that ends in the lysing of the cell specific example given was the cycle of t even bacteriophages which all infect E Coli Note bacterial viruses will always lyse it s host Lysogeny or the Lysogenic cycle Lamba another E Coli infecting virus does something different than the T evens o Lysogenic cycle begins the same way the phage injects DNA which forms it s own little ring next to the bacteria s DNA o In this case the viral DNA integrates itself into the bacterial chromosome becoming a prophage Now when this lysogenized cell reproduces all the new cells will have inactive virus DNA in them that can become active initiating the lytic cycle and lyse them at any moment the odds of the lytic cycle taking the lysogenic cycle is 1 in a million The odds of the lysogenized cells or any of it s following generation initiating the lytic cycle are also 1 in a million Lysogenic Conversion when the lysogenic cycle imparts a new characteristic to the lysogenic cell o An example is the bacteria that produces botulinum toxin scarlet fever toxin and diphteria toxin only does so when its been lysogenized to produce these toxins o VIRUSES DO NOT PRODUCE TOXINS They just get their host cell to do it for them o The genetic changed introduced into the host can cause some pretty deadly results I didn t write down any examples Some crazy cool variations on the virus o Oncogenic Virus those that cause cancer Its nucleic acid becomes part of the host cell leading to the loss of control of the cell s growth and reproduction This isn t the same of lysogeny because lysogeny only takes place within bacteria This is in relation to multicellular organisms o Preventing viral infections get the vaccination Controlling an already present virus treat the symptoms until your antibodies catch up and kick the virus out o Viroids not even true viruses They are just naked RNA with no protein coat or cellular structure Potato Spindle Tuber Disease is an example o Prions infectious naked proteins or proteinaceous infectious particles They almost always affect neurological functions Prion diseases include Scrapie Kuru associated with cannibalism and is contracted by eating brains Disease Chronic Wasting Disease if you see a deer stumbling around kinda drunkenly don t fucking eat it Mad Cow Disease or Bovine Spongiform encephalopathy Creutzfeldt Jakob Disease the human variant of Mad Cow There is a proposed mechanism for how a prion works PrPc is on the surface of our brain cells and prions are a mutated version of these guys PrPSc It reacts and converts the normal proteins on your brain cells and they get taken up by the cell where they accumulate and kill the cell Enzymes and Energy Enzymes all enzymes are proteins but not all proteins are enzymes They are catalysts in spontaneous reactions spontaneous reactions ONLY o For example lactose a disaccharide is made up of glucoses and galactose It ll take a year for lactose to break down into those two on its own Enzymes will speed up the process o Note Catalytic RNA can speed up reactions as well But they are producing ribozymes not enzymes o Some other components of enzyme based reactions Cofactor required by some enzymes for activity Coenzyme an organic cofactor like Vitamin B Remember we define organic as made of hydrocarbons Factors that influence enzymatic activity temperature pH substrate concentration among others o For most enzymes used by multicellular organisms like us human body temperature is usually optimal temperature o Optimal pH depends on the part of the body it is working in o When an enzyme is exposed to temps beyond the optimal it will become denatured and probably won t be able to return to a function form ATP and Energy ATP or adenosine triphosphate is the energy currency of the cell o What about PEP phosphoenolpyruvate It has approximately twice the energy of ATP and is an intermediate for glycolysis It costs too much energy to make it o The