IB Biology A2.3 Notes

This page contains our IB Biology notes for A2.3. By reading each one of these notes, you will fully cover the content for IB Biology 'Viruses'.

All Topic 2 Sub-topics (HL)A2.1: Origins of cells A2.2: Cell Structure (HL)A2.2: Further cell structure (HL)A2.3: Viruses B2.1: Membranes And Transport (HL)B2.1: Further membranes and transport B2.2: Organelles & Compartmentalisation (HL)B2.2: Further organelles B2.3: Cell Specialisation (HL)B2.3: Further cell specialisation (HL)C2.1: Chemical signalling C2.2: Neural Signalling (HL)C2.2: Further neural signalling D2.1: Cell Division (HL)D2.1: Cell cycle (HL)D2.2: Gene expression D2.3: Water Potential (HL)D2.3: Further water potential

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Chapters

1. Viruses

2. Viral Life cycles

3. Viral Origin and Evolution

4. Influenza

5. HIV

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Viruses

Viruses are inert and acellular pathogens that infect other organisms. Whilst there are many types of viruses with variable shapes and appearances, they are similar in structure and share the following features:

Small fixed size
Protein capsids
No cytoplasm
Genetic material as either DNA or RNA
Few or no enzymes

Further to this, some viruses are enveloped in host cell membrane. This is advantageous because it can:

Facilitate viral entry into the host cell
Evade immune system recognition
Protect the genetic material

You are not expected to know examples of enveloped and unenveloped viruses, but examples of viruses you need to be aware of include:

Bacteriophage λ
Coronavirus
HIV

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