IB Biology A2.3 Notes

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:

1. Small fixed size
2. Protein capsids
3. No cytoplasm
4. Genetic material as either DNA or RNA
5. Few or no enzymes

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

1. Facilitate viral entry into the host cell
2. Evade immune system recognition
3. 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:

1. Bacteriophage λ
2. Coronavirus
3. HIV