Virus
Viruses
• Too small to see with a light microscope
Chapter 10: Viruses
Lecture Exam #3 Wednesday, November 22nd (This lecture WILL be on Exam #3)
• Visible with electron microscopy
• Not cells: no nucleus, organelles, or cytoplasm • Obligate intracellular parasites
• Can only reproduce inside a living cell
Dr. Amy Rogers Office Hours: MW 9-10 AM
• Viruses are on the border between living & nonliving things • Have either DNA or RNA, never both • Often cause death of the host cell
• Genus/species names not used in viral classification
Compenents of a virus
(lipid bilayer)
Viral components: Nucleic Acid
• Viral genomes can be either DNA or RNA • This genome, once inside a host cell, directs synthesis of new viral proteins, and also replication of new viral genomes • Viral genomes come in all kinds:
• Single- or double-stranded, RNA or DNA • Linear or circular • One piece or segmented (in several fragments)
(protein)
(DNA or RNA)
(glycoproteins)
Viral components: Capsid
• A protein shell that surrounds & protects the nucleic acid • Determines the shape of the virus • Made up of many subunits called capsomeres
• Capsomeres may be all the same, or virus may have several different proteins in its capsid • Composition & arrangement of capsomeres is characteristic of each virus (use for identification)
Viral components: Envelope
• Not all viruses have an envelope
• Enveloped virus: has one • Naked virus: does NOT have an envelope
• Envelope is a Lipid bilayer membrane
• acquired from a host cell membrane when virus “buds” (plasma membrane) or passes through a membrane-bound organelle (such as the nucleus) • Composition of envelope resembles that of the cell membrane from which it came
• Some envelopes have spikes
• Glycoproteins (proteins bound to carbohydrates) that stick out from the envelope • Spikes often are important for attachment to host cells
1
Viral components: Envelope
Enveloped viruses: Advantages
•
• Too small to see with a light microscope
Chapter 10: Viruses
Lecture Exam #3 Wednesday, November 22nd (This lecture WILL be on Exam #3)
• Visible with electron microscopy
• Not cells: no nucleus, organelles, or cytoplasm • Obligate intracellular parasites
• Can only reproduce inside a living cell
Dr. Amy Rogers Office Hours: MW 9-10 AM
• Viruses are on the border between living & nonliving things • Have either DNA or RNA, never both • Often cause death of the host cell
• Genus/species names not used in viral classification
Compenents of a virus
(lipid bilayer)
Viral components: Nucleic Acid
• Viral genomes can be either DNA or RNA • This genome, once inside a host cell, directs synthesis of new viral proteins, and also replication of new viral genomes • Viral genomes come in all kinds:
• Single- or double-stranded, RNA or DNA • Linear or circular • One piece or segmented (in several fragments)
(protein)
(DNA or RNA)
(glycoproteins)
Viral components: Capsid
• A protein shell that surrounds & protects the nucleic acid • Determines the shape of the virus • Made up of many subunits called capsomeres
• Capsomeres may be all the same, or virus may have several different proteins in its capsid • Composition & arrangement of capsomeres is characteristic of each virus (use for identification)
Viral components: Envelope
• Not all viruses have an envelope
• Enveloped virus: has one • Naked virus: does NOT have an envelope
• Envelope is a Lipid bilayer membrane
• acquired from a host cell membrane when virus “buds” (plasma membrane) or passes through a membrane-bound organelle (such as the nucleus) • Composition of envelope resembles that of the cell membrane from which it came
• Some envelopes have spikes
• Glycoproteins (proteins bound to carbohydrates) that stick out from the envelope • Spikes often are important for attachment to host cells
1
Viral components: Envelope
Enveloped viruses: Advantages
•