A virus to attack human cells depend on the membrane?
415464
Viruses need to be inside of a  host cell (human, bacteria, plant etc.) to reproduce. So to get inside the host they have surface proteins (sticking out of a lipid bilayer-just like most mammalian cells) that are able to trick the host cell into letting it inside, that's where it does the damage to the host. ---To simplify the virus needs to have a Protein Coating that is similar to the Protein Receptors on its host cell in order to infect it.---
47489
YES. An infected person's tear film, like other body fluids, DOES contain the virus.
1109408
There very well could be. I found this article to be really fascinating. Here's an excerpt\n\nAlligators and crocodiles, like humans, have a natural defence system against invading bacteria, viruses and fungi, which involves a group of proteins called the complement system.\n\nWhen Dr Merchant exposed the alligator blood to pathogens such as HIV, West Nile Virus and E Coli, it started to kill them.\n\n"It turns out that this complement system is much more effective than ours. \n\n"But there is really no clinical utility because I can't isolate them from alligators and inject them into your veins because your body would recognise that it was not human."\n\nInstead, he hopes to be able find something in the crocodile and alligator blood that can be mimicked in a drug, and has begun to look at white blood cells - the cells that flock to fight invading pathogens.\n\nWhite blood cells make and release tiny proteins to fight the infection and Dr Merchant believes that, if he can isolate these from the animals, it might point a way to making new antibiotics and antiviral drugs for humans.
403247
Essentially the first question is right, but human viruses are very clever in that several coat layers are used. for example HPV, HSV (herpes).  Viruses are just proteins and DNA, nothing more.  They don't contain organelles, they don't reproduce independantly, they don't fulfill many life functions.
297340
Most times the projections are what allow the virus to bind and then enter a host cell.  They can also be used to mediated membrane fusion and cell to cell spead of the virus.
771971
Cell membrane, or phospholipid bi-layer.
376744
Different viruses target different cells. This can be due to specific antigens (markers) on the cells or receptors.  Also Viruses known as retroviruses contain RNA inside them and RNA reverse trancriptase than when inserted into a cell can integrate into the cells own DNA. Thus, using the viruses as a factory to produce more viruses or other effects in the neighboring cells.
775996
They can be.  Some viruses are harder to kill then others.  I f viruses can't be killed, we would die of a simple cold.  Some viruses  are like roaches,  You could smash the ones you find, but they breed faster than you could kill them.  Others, like Herpes are attacked by our bodies defense until the virus is under control.  The remaining viruses hided where our defenses can't attack or find them.  When our defenses weekend, they come out again.  Others are like HIV.  Your body can kill them, but if the virus are able to make a foothold in our body, it attacks our immune system, therefor our body can't kill them anymore.
693283
I don't know off the top of my head, but try looking here. It has loads of good and useful virology info.\nhttp://www-micro.msb.le.ac.uk/
103750
Its virus and spread from infection with unsafe sex and infected blood exchange/ transmission from infected person.
6888
First off jamesmusik84's is completely wrong. Please don't consider any of it. The second answer is along the right path, except I have no idea what the reference to antibiotic is suggesting and some viruses have RNA genomes but many more have DNA genomes. And as far as bacteria go, both RNA and DNA are present inside there cells.\n\nSo, the answer to your question. Let's start this way: Bacteria are small single-celled organisms. Unllike eukaryotic cells (like the ones that make up animals, plants, fungi and many single-celled organisms such as yeasts) which package their genetic material (DNA) in membrane structures called nuclei, bacteria (which are also referred to as prokaryotes) don't have a nucleus. Bacteria also don't have other organelles which are found in eukaryotes, such as endoplasmic reticulum, mitochandria, chloroplasts, golgi bodies, etc. But like eukaryotes, bacteria do have an outer lipid membrane.\n\nSo, you can think of bacteria of little fluid filled sacs. Along with eukaryotic, bacteria are an example of "cells" which are the smallest unit of living things on earth.\n\nViruses, on the other hand, do not have an outer membrane. They don't the capacity to make their own proteins. They don't have the capacity ot replicate or metabolize on their own -- of which bacteria (and eukaryotes) do. It's for this reason that we don't consider viruses "living" things. Viruses have to "infect" a cell -- injecting its genetic material inside -- and use the cell's metabolic machinery to reproduce.\n\nViruses are essentially small protein "capsules" that have a piece of genetic information packaged inside. Because viruses are required to infect a cell to propogate themselves, they are classified as obligate intra-cellular pathogens.\n\nViruses tend to only infect specific cell types. Some infect bacteria. Some infect plants. Others infect animals. The specificity of what a virus can infect is goes beyond whether they can infect bacteria, plants or animals. Usually viruses have to infect a very specific animal, plant or bacteria. And even in the case of viruses that infect animals and plants, not only do the infect specif animals, they are usually limited to a few cell types whithin that animal.\n\nTake HIV for example: to the best of my knowledge HIV only infects humans (i.e. the "H" in HIV -- Human Immunodeficiency Virus). But it doesn't just infect any human cell. HIV only infects white blood cells -- specifically a class of white blood cells called T cells (there are many other "classes" of white blood cells including such things as B cells, NK cells, neutrophils, basophils, eosinophils and macrophages).\n\nI hope this sheds some light on the matter.
139320
My understanding is that the virus has to have a way into the bloodstream.  If you have a cut in your mouth, for example, that is how the virus could travel from the semen into your bloodstream
1001099
sometimes, depending on the matter, there can be viruses.
1025133
animals get infected by viruses...some viruses can infect both human & animals...some will show deffernt symptoms in animals than in human...some viruses show symptoms in human but they don't in animals so animals are called in this case: carriers...\nas for common cold:there are different serotypes each infect & show symptoms in different species..\nwhy do a virus infect a species not a nother??if this is what U mean: it depends on the outer structure of the virus, there are diferent types of receptors on the outer structure (envelope or wall...etc..)that will be attached to it's maching place in the cell it attackes....then the infection will begin...if the place on cell doesn't mach : no infection will be done..
915822
Viruses themselves are not alive. Most virologists consider them non-living, as they do not meet all the criteria of the generally accepted definition of life. They are similar to obligate intracellular parasites as they lack the means for self-reproduction outside a host cell, but unlike parasites, viruses are generally not considered to be true living organisms. Among other factors, viruses do not possess a cell membrane or metabolise on their own.\n\ncompter viruses are not alive either.
445823
Most of these have deadly viruses. You have to be exceedingly careful.
116848
Some viruses ('phages') can be used to insert certain genes into the living cell. This isn't a standard procedure in any way, but it's becoming more and more studied...