Raw Material
UNIT 9: VIRUSES, VIROIDS, & PRIONS
Lesson 1 – Characteristics of Viruses
Depending on their characteristics, viruses may or may not kill the host cell. Viruses are too small to be seen with a light microscope and cannot be cultured outside their hosts. Viruses and Bacteria Compared. | Bacteria | Viruses | | Typical Bacteria | Rickettsias/Chlamydias | | Intracellular Parasite | No | Yes | Yes | Plasma Membrane | Yes | Yes | No | Binary Fission | Yes | Yes | No | Pass through Bacteriological filters | No | No/ Yes | Yes | Possess both DNA & RNA | Yes | | No | ATP-Generating Metabolism | Yes | Yes /No | No | Ribosomes | Yes | Yes | No | Sensitive to Antibiotics | Yes | Yes | Yes |
There are viruses that infect invertebrates, vertebrates, plants, protists, fungi, and bacteria. Viruses that infect bacteria are called bacteriophages, or phages.
The nucleic acid of a virus is protected by a protein coat called the capsid. Each capsid is composed of protein subunits called capsomeres. In some viruses, the capsid is covered by an envelope, which usually consists of some combination of lipids, proteins, and carbohydrates. Depending on the virus, envelopes may or may not be covered by spikes, which are carbohydrate-protein complexes that project from the surface of the envelope. Some viruses attach to host cells by means of spikes. Viruses may be classified into several different morphological types on the basis of their capsid architecture. * Helical Viruses
Resemble long rods that bay be rigid or flexible. The viral nucleic acid is found within a hollow, cylindrical capsid that has a helical structure. The virus that causes rabies is a helical virus. * Polyhedral Viruses
The capsid is in the shape of a polyhedron with 20 triangular faces and 12 corners. An example is the poliovirus. * Enveloped Viruses
Capsid covered by an envelope. Usually a roughly spherical virus. When helical or polyhedral viruses are enclosed
Lesson 1 – Characteristics of Viruses
Depending on their characteristics, viruses may or may not kill the host cell. Viruses are too small to be seen with a light microscope and cannot be cultured outside their hosts. Viruses and Bacteria Compared. | Bacteria | Viruses | | Typical Bacteria | Rickettsias/Chlamydias | | Intracellular Parasite | No | Yes | Yes | Plasma Membrane | Yes | Yes | No | Binary Fission | Yes | Yes | No | Pass through Bacteriological filters | No | No/ Yes | Yes | Possess both DNA & RNA | Yes | | No | ATP-Generating Metabolism | Yes | Yes /No | No | Ribosomes | Yes | Yes | No | Sensitive to Antibiotics | Yes | Yes | Yes |
There are viruses that infect invertebrates, vertebrates, plants, protists, fungi, and bacteria. Viruses that infect bacteria are called bacteriophages, or phages.
The nucleic acid of a virus is protected by a protein coat called the capsid. Each capsid is composed of protein subunits called capsomeres. In some viruses, the capsid is covered by an envelope, which usually consists of some combination of lipids, proteins, and carbohydrates. Depending on the virus, envelopes may or may not be covered by spikes, which are carbohydrate-protein complexes that project from the surface of the envelope. Some viruses attach to host cells by means of spikes. Viruses may be classified into several different morphological types on the basis of their capsid architecture. * Helical Viruses
Resemble long rods that bay be rigid or flexible. The viral nucleic acid is found within a hollow, cylindrical capsid that has a helical structure. The virus that causes rabies is a helical virus. * Polyhedral Viruses
The capsid is in the shape of a polyhedron with 20 triangular faces and 12 corners. An example is the poliovirus. * Enveloped Viruses
Capsid covered by an envelope. Usually a roughly spherical virus. When helical or polyhedral viruses are enclosed