lecture 6

lecture 6 - BIOL 213 17.1 The Viruses Our understanding of...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
BIOL 213 Microorganism- Immunology 17.1 The Viruses • Our understanding of disease, genetics, and some of the characteristics of life has come from the study of viruses. • Viruses are extremely small and noncellular and are not included in the classification of living organisms. • Viruses consist of two primary structures. – An outer capsid – An inner core of either DNA or RNA 17.1 The Viruses (cont.) • The outer membrane of some animal viruses may include an outer membrane envelope with spike-shaped glycoproteins. • This outer membrane is a piece of the host’s plasma membrane which also contains viral proteins. • The interior of the virus also contains a variety of proteins. 17.1 The Viruses (cont.) 17.1 The Viruses (cont.) • The debate over whether viruses are living organisms has focused on several facts. – Viruses are obligate intracellular parasites, meaning that they can only reproduce inside a living cell. – Viruses can be synthesized chemically in the laboratory. – Viruses have a genome that is subject to mutation and controls viral reproduction. Viral Reproduction • Viruses are specific to a particular host cell. • Once inside the host, the viral genome takes over the cell and uses the host’s enzymes, ribosomes, tRNA, and ATP to synthesize new viral particles.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
• A bacteriophage (or phage) is a virus that reproduces in a bacterium. • There are two possible cycles of phage reproduction. – A lytic cycle – A lysogenic cycle Reproduction of Bacteriophages (cont.) • The lytic cycle has five stages. – Attachment – Penetration – Biosynthesis – Maturation – Release • The attachment stage involves the attachment of the capsid molecule to the receptor on the surface of the host cell. Reproduction of Bacteriophages (cont.) • Penetration is the stage during which a viral enzyme breaches the bacterial cell wall so that the viral DNA can be injected. • During the biosynthesis stage, the virus deactivates all host genes not needed for viral reproduction and initiates the synthesis of viral components. Reproduction of Bacteriophages (cont.) • The assembly of new viral particles occurs during maturation. • During the release stage, viral lysozymes rupture the bacterium to release the new virus particles. • The lytic cycle causes the death of the host bacteria. Reproduction of Bacteriophages (cont.) • In the lysogenic cycle, the host cell may not immediately lyse because the phage is latent. • After attachment and penetration, integration occurs as the viral DNA becomes incorporated into the host DNA. • This latent viral DNA is called a prophage. Reproduction of Bacteriophages (cont.) • The prophage is replicated along with the host DNA and is passed along to all daughter cells. • Daughter cells with a prophage are
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/24/2008 for the course BIO 213 taught by Professor Lee during the Winter '08 term at Cal Poly.

Page1 / 16

lecture 6 - BIOL 213 17.1 The Viruses Our understanding of...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online