3.6.7Additional lessons
HIV and AIDS — IB Biology SL Revision Notes & Topical Questions
5 min read 5 parts Lesson 76 of 142
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 5The Virus and Its Target
HIV
- HIV Human immunodeficiency virus is a retrovirus with RNA as its genetic material and an outer envelope.
Target cells
- Target cells It infects helper T cells, which carry the surface receptor that the virus binds to.
Reverse transcriptase
- Reverse transcriptase This viral enzyme makes DNA from the viral RNA once inside the host cell.
Provirus
- Provirus The viral DNA inserts into the host genome, where it can lie inactive before it is switched on.
Part 2 of 5From Infection to AIDS
HIV is the virus and AIDS is the syndrome that can develop years later.
1
The virus binds to a helper T cell, enters it and uses reverse transcriptase to make DNA copies of its genes.
2
The viral DNA is integrated into the host chromosome and later directs the production of new virus particles.
3
New viruses leave the cell, often destroying it, and infect other helper T cells.
4
As helper T cells decline, the immune system cannot activate B cells and cytotoxic T cells properly.
5
AIDS is diagnosed when the immune system is so weakened that opportunistic infections and some cancers appear.
Part 3 of 5Transmission and Prevention
Routes of transmission
- Routes of transmission HIV passes in body fluids through sexual contact, contaminated blood or needles, and from mother to child.
Not spread by
- Not spread by HIV is not spread by casual contact such as handshakes, sharing food or mosquito bites.
Prevention
- Prevention Safe sex, screening of donated blood, sterile needles and treating pregnant women reduce transmission.
Treatment
- Treatment Antiretroviral drugs block viral enzymes, such as reverse transcriptase, and keep the virus at very low levels.
| Term | Meaning |
|---|---|
| HIV | The virus |
| AIDS | The syndrome caused by a severely weakened immune system |
| Opportunistic infection | An infection that takes hold because immunity is low |
Part 4 of 5Why HIV Is Hard to Control
Why HIV Is Hard to Control
Mutation
- Mutation The virus mutates rapidly, so its antigens change and drugs may become less effective.
Latency
- Latency Viral DNA can remain hidden in the host genome without producing virus.
Attacks immunity
- Attacks immunity Destroying helper T cells damages the very system that would fight it.
Part 5 of 5Exam Checklist & Tips
3.6.7 – Key Points for the Exam
- Retrovirus A virus with an RNA genome that uses reverse transcriptase to make DNA.
- Helper T cell The lymphocyte that HIV infects, needed to coordinate the immune response.
- AIDS Acquired immunodeficiency syndrome, the late stage of HIV infection.
- Opportunistic infection An infection that occurs because the immune system is weakened.
Common Mistakes
- Using HIV and AIDS as if they were the same; HIV is the virus and AIDS is the syndrome.
- Saying HIV is a bacterium treated with antibiotics.
- Stating HIV attacks red blood cells or B cells directly; its main target is helper T cells.
- Claiming people can catch HIV from toilet seats or mosquito bites.
Last updated:
\n