Learn A-Level Biology: HIV and AIDS

Introduction

• Topic: Structure, replication, and symptoms of HIV/AIDS
• Instructor: Mr. IK
• Purpose: Understanding the biological mechanisms of HIV and the effects of AIDS

Viral Structure

• Viruses: Not considered living cells, require host cells for replication
• Medicine Challenges:
  • Difficult to treat due to necessity of destroying host cells to eliminate viruses
  • Antibiotics ineffective against viruses due to lack of common bacterial structures (e.g., cell walls, organelles)

Structure of HIV

• Core Components:
  • RNA: Genetic material
  • Reverse Transcriptase: Enzyme required for replication
• Protein Capsid: Outer protein coat
• Envelope: Derived from the host cell membrane (lipid membrane)
• Protein Attachments: Facilitate attachment to helper T cells

HIV Replication Process

1. HIV Transportation:
   • Transported in the blood
   • Targets helper T cells (a type of white blood cell)
2. Attachment:
   • Protein attachments on HIV bind to CD4 proteins on helper T cells
3. Fusion and Entry:
   • HIV membrane fuses with helper T cell membrane
   • Releases reverse transcriptase and RNA into the cell
4. Replication:
   • Reverse transcriptase converts viral RNA to DNA
   • DNA integrates into the host cell's nucleus
   • New HIV particles are produced, leading to destruction of helper T cells

Symptoms of HIV/AIDS

• HIV Symptoms (initial weeks):
  • Flu-like symptoms: Fever, rash, swollen glands
  • Linked to destruction of helper T cells
• AIDS Symptoms:
  • Occurs when significant destruction of helper T cells interferes with the immune system
  • Vulnerability to infections and cancer
  • Death usually results from the compromised immune system, not the virus itself

Summary

• Replication: Viruses replicate inside host cells; antibiotics are ineffective
• HIV Structure: Comprised of RNA core, reverse transcriptase, capsid, host-derived envelope
• Disease Progression:
  • HIV positive: Presence of HIV
  • AIDS: Extensive destruction of helper T cells affecting immune function

Additional Resources

• Website for Practice: Visit misterich.com for practice questions on this topic
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