Science Questions 4 Science Wizzes - 10 points?

1. How did biologists conclude that viruses require a host?

2. Penicillins and cephalosporins interfere with the bacterial synthesis of petitdoglycan, a large molecule that bateria use to make cell wals. Why are these drugs safe for human cells but harmful to bacterial cells?

3. During an appointment with his doctor, Ryan is diagnosed with a lung infection due to a virus. What type of anibiotic should Ryan's doctor prescribe to treat the viral infection?

4. During antibiotic treatment, a few disease-causing bacteria may be genetically less vulnerable to a particular anibiotic. What happens if these bacteria survive?

5. HIV contains an enzyme called reverse transcriptase. What do you think is the function of reverse transcriptase?

6. Explain why the envelope surronding an HIV particle is derived from the hose cell membrane.

7. The structure of the knoblike proteins on the outside of the HIV envelope can mutate, or change. Why is it difficult to creat an AIDS vaccine?

1. Viruses shown unable to replicate by themselves
2. Human cells do not have cell walls so they are not affected by the interference of their construction, unlike bacterial cells.
3. No antibiotics, as they cannot treat a viral infection.
4. The virus population will gradually become resistant due to natural selection, and therefore antibiotic resistance will result. A combination of antibiotics can help prevent this but they need to be used resonsibly.
5. Reverse transcriptase is used to construct DNA from a single strand of RNA so the virus can add its genetic information to the host.
6. Viruses lack their own intrinsic metabolism and so need to rely on the host cells ability to construct new virus particles. This is done by using its structures to synthesise protein coats for the new viruses. The virus cannot make it itself because it only contains genetic material inside a protein coat.
7. Because the different proteins, there is so many different potential targets for a vaccine that one may be effective for some individuals but not in others. The virus has such few targets to bind to anyway, but with rapid mutation, it is always changing and the vaccine would also need to be changed.

2. Humans don't have cell walls. Bacteria tend to explode without them.

3. None. Viruses are not bacteria and are not killed by antibiotics.

4. They will produce many more bacteria that are just like them, and therefore resistant to the particular antibiotic.

5. It is to copy the viral RNA genome to make a DNA copy from which RNA can be made. (Oh yeah, and as with the previous answer, so it can be integrated intot he genome.) It's called reverse transcriptase because usually DNA is transcribed into RNA and not the other way around.

6. Viruses use the host cell to make components for new viruses. The host cell membrane is handy, so why not use it? (Also, I think it may help the virus to hide from the immune system by cloaking it in a membrane that looks like "self" to the immune system, but I'm not 100% sure of that.)

7. The immune system develops antibodies to the proteins that it sees in the vaccine, but when the virus mutates to a form that wasn't in the vaccine, those antibodies will not recognize it. This sends the specific immune system back to square 1 and it has to start mounting a response all over again. So if they recieved a vaccine to one form and it mutated to a different one, they might as well not have gotten the vaccine.