Question

How does the HIV virus act on target cells in the body (Unit 1: Biochemistry; Unit 2: Metabolic Process; Unit 3: Molecular Genetics; Unit 4: Homeostasis)? can you please relate to every unit... I really need help with this especially the first 2 units.

this grade 12 biology

Answer 1

Once in the body, HIV attaches to several types of white blood cells. The most important are certain helper T lymphocytes (T cells). Helper T lymphocytes activate and coordinate other cells of the immune system. On their surface, these lymphocytes have a receptor called CD4, which enables HIV to attach to them. Thus, these helper lymphocytes are designated as CD4+.

HIV is a retrovirus. That is, it stores its genetic information as ribonucleic acid (RNA). Once inside a CD4+ lymphocyte, the virus uses an enzyme called reverse transcriptase to make a copy of its RNA, but the copy is made as deoxyribonucleic acid (DNA). HIV mutates easily at this point because reverse transcriptase is prone to making errors during the conversion of HIV RNA to DNA. These mutations make HIV more difficult to control because the many mutations increase the chance of producing HIV that can resist attacks by the person’s immune system and/or antiretroviral drugs.

The HIV DNA copy is incorporated into the DNA of the infected lymphocyte. The lymphocyte’s own genetic machinery then reproduces (replicates) the HIV. Eventually, the lymphocyte is destroyed. Each infected lymphocyte produces thousands of new viruses, which infect other lymphocytes and destroy them as well. Within a few days or weeks, the blood and genital fluids contain a very large amount of HIV, and the number of CD4+ lymphocytes may be reduced substantially. Because the amount of HIV in blood and genital fluids is so large so soon after HIV infection, newly infected people transmit HIV to other people very easily.