BMS1021 Lecture Notes - Polysaccharide, Heterokont, Saprotrophic Nutrition
Document Summary
Viruses of the same genus share these major features: nature of nucleic acid, protein coat symmetry, structure, presence or absence of an envelope. 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: helical capsid structure: Single protomer of capsid associate with nucleic acid: icosahedral capsid structure. Have 12 vertices and 20 equilateral triangular faces. Consists of repeating units of protein (capsomers), made of protomer subunits. Surrounds the core of nucleic acid & protein (nucleocapsid: enveloped viruses. Some viruses consist of icosahedral or helical nucleocapsid surrounded by envelope. Envelope contains virus-encoded proteins or glycoprotein spikes": complex viruses. A virus that infects bacteria by injection into the cell. Is restricted because of specific receptors on the cells membrane.