3.7.7Additional lessons
HIV and AIDS — IB Biology HL Revision Notes & Topical Questions
5 min read 4 parts Lesson 6 of 101
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 4Transmission of HIV
The virus
- The virus Human immunodeficiency virus is a retrovirus with an RNA genome, and it cannot survive for long outside the human body.
Body fluids
- Body fluids HIV passes from person to person by direct exchange of body fluids such as blood, semen, vaginal fluid and breast milk.
Common routes
- Common routes Unprotected sex, shared needles and the transfer of blood are the main routes, and an infected mother can pass the virus to her baby.
No insect vector
- No insect vector Unlike malaria, HIV is not carried by a vector and is not spread by casual contact such as touching or sharing a room.
Prevention
- Prevention Condoms, screening of donated blood, needle exchange and drugs given to mothers during pregnancy all lower the risk of transmission.
Part 2 of 4Effect on the Immune System
Helper T cells coordinate the adaptive response, so losing them weakens the whole system.
1
The virus enters the body and infects helper T cells, using proteins on their surface membrane to attach and gain entry.
2
Inside the cell, the viral RNA is copied into DNA by reverse transcriptase, and the DNA is inserted into the host genome.
3
The infected helper T cell makes new viral particles, which are released and go on to infect other helper T cells.
4
Over months to years the number of helper T cells falls, because infected cells die and are not replaced fast enough.
5
With few helper T cells, B cells and other lymphocytes are poorly activated, and the person becomes vulnerable to infections that a healthy person would resist.
Part 3 of 4HIV and AIDS
HIV and AIDS
HIV
- HIV This is the name of the virus that infects the host.
AIDS
- AIDS Acquired immune deficiency syndrome is the group of illnesses that develop when the immune system has been badly weakened by HIV.
Opportunistic infections
- Opportunistic infections Diseases such as tuberculosis, pneumonia and some cancers cause most of the deaths, not the virus directly.
Treatment
- Treatment Antiretroviral drugs block steps in viral replication and allow many people to live a near-normal life span.
| Term | Meaning |
|---|---|
| HIV | The virus |
| HIV positive | Antibodies or virus detected in the blood |
| AIDS | Late-stage syndrome of opportunistic infections |
| Antiretroviral | Drug that interferes with viral replication |
Part 4 of 4Exam Checklist & Tips
3.7.7 – Key Points for the Exam
- Retrovirus A virus with an RNA genome that is copied to DNA by reverse transcriptase.
- Helper T cell The lymphocyte type targeted by HIV.
- AIDS Syndrome resulting from severe loss of immune function.
- Opportunistic infection An infection that takes hold because the immune system is weak.
- Antiretroviral A drug that slows viral replication.
Common Mistakes
- Using HIV and AIDS as if they meant the same thing;
- HIV is the virus and AIDS is the condition it can lead to.
- Saying that HIV is spread by mosquitoes or by touching an infected person.
- Claiming that antibiotics can treat HIV, since antibiotics act only on bacteria.
- Stating that HIV directly kills the patient, when death usually follows opportunistic infections.
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