Viruses

• viruses are tiny structures that consist of only a protein coat inside which is either a strand of nucleic acid - either DNA or RNA
• they can only be viewed under an electron microscope as they are so small
• viruses are obligate parasites so they can only replicate when in a host cell
• viruses are not cells because they do not have membranes or any cell organelles - they are not included in any of the 5 kingdoms of living things
• viruses are on the border between living and non-living things
• living features - have nucleic acid and a protein coat and can replicate and pass on genetic information
• non-living factors - the only have one type of nucleic acid, do not contain any organelles and cannot reproduce, respire or feed
• a virus contains a protein coat called a capsid - they also contain a single strand of either DNA or RNA - but not both
• classified on their shape - rod shaped, round and complex