Meet the HIV virus

This schematic shows shows a graphic representation of the structure of an HIV viron. A viron is a single virus particle. The actual "active" chemical molecules are the two ribbonlike copies of RNA protected inside the green capsid core shell, along with two copies of a protein molecule (the black balls labeled "protease, polymerase, RNAse, integrase"). The protein molecules have several functions once the virus penetrates into the hf DNA, the material that genes are made from. Once inside the host T cell, the major one being to jump-start the process of viron replication.

RNA is a mirror image of T cell, the "black ball" protein goes to work making multiple copies of viral DNA out of the two strands of viral RNA. This process is called "reverse transcription" because it is the opposite of what usually happens in normal cells. Generally, normal DNA molecules (the natural genes of the body) code for multiple copies of mirror image RNA which then goes fourth into the cell body to make protein molecules useful to the cell.

Instead, this new viral DNA creates more viral RNA. The new copies of viral RNA now hijack the host cell's "ribosomes", which are little protein factories that construct protein according to the instructions encoded in the viral RNA. The new viral proteins are then organized into new virons which then escape the host cell taking with them an envelope of the host cell's own membrane as a protective envelope along with two copies of the newly manufactured RNA. 

In the lower left of this electron micrograph you can see a new viron budding off the membrane of an infected T cell.  If you look closely, you can also see that the cell membrane of the T cell is composed of two very thin parallel lines.  These lines are actually two interlaced molecules of phospholipids (called a bilayer) which is the common construction of all cellular membrane structure.  Note that when the viron buds off, it removes some of this host membrane structure for its own protection.  Within each viron, now encapsulated in its own stolen cellular membrane, lives the capsid which is a virus manufactured protein sheathe which houses the core viral RNA.

The image to the right shows the structure of a natural cell membrane. It is composed of a pair of phospholipid chains which are arranged in such a way that the lipid portions face each other thereby avoiding contact with the aqueous (water based) surrounding medium. For a better understanding of this structure, click on the image. 

In the schematic at the top of the page, the red envelope is actually the stolen cell membrane. The purple molecules lining it are a viral protein which stabilizes the membrane. The dumbbell shaped molecules projecting outward from the membrane are specially manufactured "sugar" molecules called glucopolysacharides which are responsible for recognizing the correct host cell membrane and then attaching to it so it can begin the process of entering another host cell. 

HIV is in a broad category called "retroviruses" because it contains RNA as the infective molecule instead of DNA which is the stuff of other "normal" viruses. The prefix "retro" means "reverse" and is a reference to the reverse transcription mentioned above. 

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