Viruses.docx

Viruses Viruses are tiny microorganisms consisting of nucleic acid surrounded by a protein coat. Viruses can be rod shaped, spherical or complex. Viruses are obligate parasites, meaning they have to live in or on a different organism, causing it harm, to survive. (16) Viruses cannot be included in T...

Viruses Viruses are tiny microorganisms consisting of nucleic acid surrounded by a protein coat. Viruses can be rod shaped, spherical or complex. Viruses are obligate parasites, meaning they have to live in or on a different organism, causing it harm, to survive. (16) Viruses cannot be included in The Five Kingdom system because they are non-cellular and do not carry out any metabolic reactions on their own. Virus Replication Attachment A virus attaches to the host cell. Proteins on the virus match up with receptor sites on the host wall or membrane. This is why viruses are often specific to one host cell Entry The virus forms a hole in the host cell and the viral nucleic acid is squeezed out of its protein coat into the host cell. The protein coat is left outside the cell. In animal cells, the protein coats also enter, but are digested Synthesis The host nucleic acid is made inactive. The viral nucleic acid uses the host’s organelles to produce new viral nucleic acid and protein coats Assembly New viruses are assembled inside the host cell Release The new viruses are released when the host cell bursts Vaccines - Vaccines can be made from viruses and then used to treat the diseases they cause - The virus is either killed, weakened, or a similar less virulent virus is used to infect the patient - The patient’s immune system responds by producing antibodies against the virus - Later contact with the virus causes an immune response so the virus is destroyed before it can cause any symptoms - The patient is then immune to the disease - The human papillomavirus (HPV) that causes warts and cervical cancer has been used to create a vaccine that successfully prevents cervical cancer of this type Benefits of Viruses - Control of bacterial infections: Bacteriophages can be used to kill harmful bacteria. In this way they may help reduce infections by antibiotic resistance bacteria. - Genetic engineering: Used as vectors to transfer genes from one organism to another. Disadvantages of Viruses Viruses can cause disease and death to humans, animals, and plants. - Human: Chicken pox, shingles, cervical cancer - Plant: tobacco mosaic virus and sugar beet virus