Recap questions chapter 7b

• What is autoimmunity?

• You are blood type O- what blood type can you receive?

• What blood type is the universal donor?

• What must be given to transplant patients following their operation? Explain why.

Higher Human Biology

VirusesChapter 8

Viruses

Learning Intentions:- What are viruses?- What is viral structure?- How do viruses reproduce?- What is a retrovirus?

What are viruses?

• Living micro-organism (just!)• Only living characteristic is the fact that they reproduce• Form crystalline structures which is typical of non-living

things

• Obligate parasites because they need another living cell (host) in order to reproduce.

• Host cell is destroyed therefore viruses always associated with disease

• Viruses target specific cells- poliomyelitis virus targets nerve cells- hepatitis virus targets liver cells

• Smaller than bacteria

What is the structure of a virus?

• Viruses are not cells• Contain a nucleic acid (DNA or RNA) that carries the info

required for multiplication• Surrounded by protein coat (capsid)• Many different types

Herpes Simplex Virus The Cold Sore

Bacteriophage Virus

How do viruses reproduce?

See cut out

• A virus is inactive outside the host and can be dormant for a long time outside and inside the host cell

• It depends on the host for:- nucleotides to make viral nucleic acids- amino acids to make viral protein- ATP for energy

History and Prevention of Viruses Small Pox Virus Small Pox blisters

Cow Pox Virus Cow Pox blisters

History and Prevention of Viruses cont’d

• Edward Jenner discovered that those who had suffered from cow pox were immune to small pox

• This was the start of artificially acquired active immunity

• Polio vaccine was the first to be used- contained dead virus at first- improved by using attenuated virus (nucleic acid destroyed by heat/chemical treatment)

• Small pox now totally eradicated• Polio almost total eradication

What is a retrovirus?

(The virus that is not so fashionable!)

• Virus that contains RNA• Uses reverse transcription in order to produce viral RNA

within host cell• Retrovirus contains enzyme reverse transcriptase which is

injected into host cell along with the RNA• Virus escapes host by budding• Example Human Immunodeficiency Virus (HIV)

Human Immunodeficiency Virus

• Lambda phage