Chapter 3 virus and subvirus
Chapter 3 virus and subvirus
Section 1 Virus structure Euvirus: at least contains two components- nucleic acid and proteIn Subvirus: molecular pathogen includes: viroid(类病毒)— independent infectious RNA only virusoid(拟病毒)— non-independent infectious RNA only prion(朊病毒)—— protein only
Section 1 Virus structure Euvirus ：at least contains two components—— nucleic acid and protein Subvirus：molecular pathogen includes： viroid（类病毒） ——independent infectious RNA only virusoid（拟病毒）——non-independent infectious RNA only prion（朊病毒）——protein only
1. definitions Viruses are obligate intracellular parasites which can only be viewed with the aid of an electron microscope They vary in size from approximately 20-200 nm. In order to persist in the environment they must be capable of being passed from host to host and of infecting and replicating in susceptible host cells
Viruses are obligate intracellular parasites which can only be viewed with the aid of an electron microscope. They vary in size from approximately 20-200 nm. In order to persist in the environment they must be capable of being passed from host to host and of infecting and replicating in susceptible host cells. 1. definitions
A virus particle has thus been defined as a structure which has evolved to transfer nucleic acid from one cell to another a The nucleic acid found in the particle is either DNA or RNA, is single-or double-stranded and linear or segmented. In some cases the nucleic acid may be circular
A virus particle has thus been defined as a structure which has evolved to transfer nucleic acid from one cell to another. The nucleic acid found in the particle is either DNA or RNA, is single- or double-stranded and linear or segmented. In some cases the nucleic acid may be circular
The simplest of virus particles consists of a protein coat(sometimes made up of only one type of protein which is repeated hundreds of times which surrounds a strand of nucleic acid
The simplest of virus particles consists of a protein coat (sometimes made up of only one type of protein which is repeated hundreds of times) which surrounds a strand of nucleic acid
More com plicated viruses have their nucleic acid surrounded by a protein coat which is further engulfed in a membrane structure, an envelope consisting of virally coded glycoproteins derived from one of several regions within the infected cell during the maturation of the virus particle. The genetic material of these com plex viruses encodes for many dozens of virus specific proteins
More complicated viruses have their nucleic acid surrounded by a protein coat which is further engulfed in a membrane structure, an envelope consisting of virally coded glycoproteins derived from one of several regions within the infected cell during the maturation of the virus particle. The genetic material of these complex viruses encodes for many dozens of virus specific proteins
the complete fully assembled virus is termed the virion. It may have a glycoprotein envelope which has peplomers(包膜粒) projections, spike突起,刺突) which form a ' fringettg'around the particle. The protein coat surrounding the nucleic acid is referred to as the capsid. The capsid is composed of morphological units or capsomers(衣壳粒). The type of capsomer depends on the overall shape of the capsid but in the case of icosahedral capsids the capsomers are either pentamers or hexamers(五邻体或六邻体).The combined nucleic acid-protein complex which comprises the genome is termed the nucleocapsid (t 衣壳), which- is often enclosed in a core withinthe virion
The complete fully assembled virus is termed the virion. It may have a glycoprotein envelope which has peplomers (包膜粒)(projections, spike突起,刺突) which form a ‘fringe边缘’ around the particle. The protein coat surrounding the nucleic acid is referred to as the capsid . The capsid is composed of morphological units or capsomers（衣壳粒）. The type of capsomer depends on the overall shape of the capsid, but in the case of icosahedral capsids the capsomers are either pentamers or hexamers（五邻体或六邻体）. The combined nucleic acid-protein complex which comprises the genome is termed the nucleocapsid（核 衣壳）, which is often enclosed in a core within the virion
Structure of the virus Nucleic acid (DNA or RNA) nucleocapsid Viron Capsid (protein) Envelope (glycoprotein)
Nucleic acid （DNA or RNA） nucleocapsid Viron Capsid （protein） Envelope （glycoprotein） Structure of the virus
(a) b Fig(a unenveloped/helical (tobacco mosaic virus):(b)unenveloped/icosahedral (adenovirus);(c)enveloped/helical (paramyxovirus):(d)enveloped/icosahedral (herpesvirus)
Fig. (a) unenveloped/helical (tobacco mosaic virus): (b) unenveloped/icosahedral (adenovirus); (c) enveloped/helical (paramyxovirus): (d) enveloped/ icosahedral (herpesvirus)
Surface tubules Outer envelope Core envelope Core fibriles Lateral body Palisade layer )