Class Notes (839,091)
Australia (1,845)
BMS1021 (6)

BMS1021:Cells, tissues and organisms: Lecture 5, 6 & 7 summaries

4 Pages

Biomedical Sciences
Course Code
John Bertram

This preview shows page 1. Sign up to view the full 4 pages of the document.
Lecture 5: Viruses: - unicellular - small in size (10-400nm) - obligate intracellular parasites - many have a limited host range - genetic material surrounded by a protein coat and potentially lipid envelope - replicate/ multiply exclusively inside the host cell - Lack complete enzyme systems, ribosomes etc. - virions = extra cellular virus particles (packaged sets of genes in transit between host cells Viruses of the same genus share these major features: • Nature of nucleic acid • Protein coat symmetry, structure • Presence or absence of an envelope Virus genomes vary according to: - Nucleic acid (DNA or RNA) - Single or double stranded - Segmented Difference between RNA and DNA: DNA • Double stranded = linear or circular • Single stranded = circular RNA • Double stranded = several linear segments • Single stranded = one or several linear segments Virion - genome is surrounded by repeating protein subunits (protomers). • Repeating subunits form a protein coat or capsid. Virions can be divided into for 4 structural classes: 1. Helical capsid structure: - Red shaped coat of repeating units - Hollow tubes with protein walls - Single protomer of capsid associate with nucleic acid 2. Icosahedral capsid structure - Have 12 vertices and 20 equilateral triangular faces - Consists of repeating units of protein (capsomers), made of protomer subunits - Whole coat is the capsid - Surrounds the core of nucleic acid & protein (nucleocapsid) 3. Enveloped viruses - Some viruses consist of icosahedral or helical nucleocapsid surrounded by envelope - Envelope is host cell-derived membrane - Envelope contains virus-encoded proteins or glycoprotein ‘spikes’ 4. Complex viruses - Mixture of shapes - No consistent symmetry (e.g. poxviruses, bacteriophage) Bacteriophage: Complex virus: A virus that infects bacteria by injection into the cell Viral reproduction: General steps of virus reproduction: 1. Attachment of virion to host and uncoating 2. Entry of viral nucleocapsid/nucleic acid 3. Synthesis of viral proteins and nucleic acids 4. Assembly of structural subunits, packaging of nucleic acid, maturation 5. Release of progeny virions (cell may lyse or may not lyse – diagram on the right shows the cycles) Host range of viruses: - Plant and animal viruses do not infect bacteria - Is restricted because of specific receptors on the c
More Less
Unlock Document

Only page 1 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.