Disease: Viruses | A-level Biology | OCR, AQA, Edexcel

The Immune System: B and T Cells in a Snap! Unlock the full A-level Biology course at http://bit.ly/2YOOzOx created by Adam Tildesley, Biology expert at SnapRevise and graduate of Cambridge University. The key points covered of this video include: 1. Introduction to Viruses 2. Structure of Viruses 3. Structure of HIV Introduction to Viruses A virus is a type of pathogen. Viruses are non living and are particles which means they are just a collection of molecules. Viruses can only replicate inside living host cells.Viruses have to enter the cells of the host they infect in order to survive. They hijack the host cell protein production machinery to replicate. After reproducing in the host the new virus particles burst out of the host cell and kill it. This process is how viruses infect the host and cause disease. Structure of Viruses Viruses are very different to bacteria. Viruses do not have any organelles because they are not cells. They cannot make their own proteins because they do not have ribosomes. Viruses have genetic material which can be either DNA or RNA. The virus genetic material is enclosed inside a protein coat called a capsid. On the viral membrane surface viruses have attachment proteins which allow the virus to attach to host cells. These attachment proteins are viral antigens. We can summarize the differences between bacteria and viruses. Structure of HIV The human immunodeficiency virus (HIV) is a virus that infects humans and causes acquired immune deficiency syndrome (AIDs). HIV has a lipid envelope. HIV has RNA as its genetic material. HIV has an enzyme called reverse transcriptase which generates DNA from the HIV RNA. HIV is called a retrovirus because it generates DNA from RNA using reverse transcriptase. This DNA generated will then integrate into the host cell DNA. This will result in the generation of new HIV particles using host cell machinery. Summary Viruses are non-living particles Viruses can only replucate inside living host cells Viruses have no organelles Viruses have genetic material which is either DNA or RNA The viral genetic material is enclosed in a protein coat called a capsid Viruses have attachment proteins which allow them to attach to host cells