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Its made up of Icosohedral capsid which is is made up of capsomere proteins.

It has envelope of a single phospholipid lipid bilayer

It also has reverse transcriptase, opposite of RNA polymerase which takes a strand of RNA and creates a strand of DNA. The viral RNA acts as a template strand.

On the membrane it has receptors called GP120 which are glycoprotien. All cell membranes have glycoproteins. The CD4 receptors are complementary to GP120.

HIV bind to the CD4 receptors on the cell surface, the CD4 recpeptors on the cells attach to the glycoprotein GP120 on the virus surface. The virus fuses into the membrane of the cell, enters by fusion. The capsid is digested by protease to release RNA. This exposes the RNA and by using reverse transcriptase to make a complementary DNA strand. DNA polymerase forms double stand of DNA which integrates into the DNA of T-helper cells, by entering through nuclear pores. This breaks off as the T-helper cell is lysed.

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HIV leads to death?

The Viral RNA enters the host cell, Viral DNA is made from the viral RNA usig reverse transcriptase.

The viral DNA will incorporate itself in to the host cell, DNA using DNA integrase.

Then viral RNA and protiens will be produced.

These can infect other cells and also destruct other cells because T-killer cells by lysed.

 Lowers the number of T-helper cells which weakens the immune system of the person so they wil be vulnerable to other disease e.g. TB.

T-helper cells activate T-killer cells and B-lymphocyte cells.

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HIV Phases

The Acute Phase: HIV virus has a receptor GP120, which attaches to a receptor CD4 on the membrane of a typr of white blood cell called a HELPER T Cell.

The HIV rapidly infects Helper T cells and the virus population increases quickly. So Helper T cell falls rapidly. This phase end when the killer T cells begin to recognise infected Helper T cells and kill them, slows the replication of the virus.

The Chronic Phase: Lasts for many years, the virus continues to repplicate, but the killer T cells keep the numbers in check. However, the immune system is weakened other bateria and viruses are more likely to infect the person.

The Disease Phase: Numbers of virus increases the number of Helper T cell falls so the immune system gets weaker and weaker. A second pathogen infects the person can cause opportunistic infection which cannot be fought off. Ther Person DIES quickly from the secondary infection. 

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Evolution of HIV

HIV mutates very quickly, once inside he body the viral antigens change. The immune system can't keep face with the changes. HIV attacks Helper T cells, low numbers of Helper T cell, the immune system cannot communicate and HIV can survive in the body. 

  • HIV weakens the immune system to increase its chance of survival
  • HIV stays in the body for years, so it can spread all over the body
  • HIV specifically targets Helper T cells 
  • HIV spreads by sexual contact, so it can easily spread.
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Mycobacterium Tuberculosis

It is inhaled into the lungs in form as droplets of water and mucus from an infected person. TB reproduces in the lungs, bacteria produces toxin, the damage lung tissue cause coughing, increases transmission of disease. The body launches immune response to TB, histamine release and inflammation occus. The Macrophages enter the lungs in large numbers, the macrophages engluf the TV bacteria in large numbers which forms a mass of tissue called granuloma. Insode the granuloms straves the oxygen, which kills the bacteria. When the bacteria is killed the lungs will heal!


TB bacteria may survive inside the macrophages as the cell walls of the bacterium are thick and contain a waxy layer which the bacteria is resistant to the macrophage enzymes. Meaning the Bacterium may survive and reproduce inside macrophage for many years without an infection. When the imnmune system is weakened by malnutrition, or another disease such as HIV, the TB bacterium may break out and re-infects the body. The bacyeria reproduces rapidly, but the body cannot destroy many that quickly. Therefore Damaged lungs leads to DEATH!

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Evolution of TB

TB is spread by drople infection meaning its very effective as this can spread easily and quickly.

TB specifically target the epithelial cells meaning when you inhale the bacteria it will enter the epithelial cells much quicker.

TB weaken the immune system to increase its chance of survival.

TB has the ability to stay in the body for years, so it can spread when ever it becomes active.

TB survives inside the macrophages and can e dormant until the immune system is really weak, then TB bacterium will infect.

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