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    How HIV Infects Helper T Cells

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    This solution will review the basics of viruses and discuss the process that occurs when a helper T cell is infected by the HIV virus. It includes a glossary to aid in understanding of the technical terms, that occur in a first year introductory college biology class.

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    First, let me review the basics about viruses. Viruses are merely a piece of RNA or DNA, depending upon the type of virus, that is surrounded by a protein coat. They have a very small genome and cannot replicate this genetic material on their own. They cannot reproduce outside of a host cell, therefore they are not considered a living thing.

    1.The HIV virus enters a helper T cell and attaches to a specific receptor located on the surface of the T cell membrane, CD4 + fusin. It works much like enzymes do because the CD4 receptor is a certain shape. When this happens the virus and the cell membrane fuse and the core of the virus enters the cell.

    2. At this point, the viral RNA and the core proteins are released into the cytoplasm. RNA is transcribed into DNA, via the enzyme reverse transcriptase. The viral DNA, which is double stranded, is transported to the nucleus and integrated by another enzyme, into the host cell DNA. The viral DNA can remain dormant in the DNA of the host cell for many years. At some point, HIV DNA is converted by RNA Polymerase into 2 splices of RNA of unequal length.

    3.The short piece of HIV RNA is transferred into the cytoplasm and the golgi apparatus to be used to create the protein coat and non core proteins of the new virus. The longer piece of viral RNA will become the RNA core of the virus. Transcription and translation have been altered for the survival of the virus.

    4. The new virus forms from the RNA core and the proteins. This new virus buds off the host cell and infects another cell.

    Cell death from an HIV infection is thought to occur in two ways. Infected cells succumb to the damage done by viral reproduction. Another idea is that HIV infection causes apoptosis to occur at an inappropriate time, in the cell cycle. Eventually, the person develops AIDS because the number of healthy T cells is reduced.

    Although there is no cure yet, certain drugs can prolong the person's life. The drug AZT works by inhibiting the enzyme reverse transcriptase, so that the HIV virus cannot transcribe the RNA into DNA. Another class of drugs used are protease inhibitors. These drugs prevent assembly of the HIV proteins into the finished product.


    Helper T Cell: A type of T cell that secretes proteins that help activate the immune system.

    CD4 + Fusin: The receptor protein on the helper T cell where the HIV virus binds to the host cell.

    Reverse Transcriptase: The enzyme which converts the RNA into DNA.

    RNA Polymerase: The enzyme which transcribes the DNA codons into the appropriate RNA codons, in protein synthesis.

    Apoptosis: Programmed cell death.

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    Campbell, Neil et al. (2005)Biology 7th edition, ch 43, San Francisco, CA. Pearson Benjamin Cummings.

    This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!

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