Describe how cells differ from viruses in the following aspects: size and life cycle
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Viruses are much smaller than cells. They are around .02 - .2 micrometers, or 20 - 200 nanometers.
Red and white blood cells - 20 micrometers (20,000 nanometers).
Virus cycle consists of search for a host, absorption, entry, uncoating, gene transcription and replication (Viral DNA to RNA, or RNA to DNA to RNA in retroviruses), maturation, and release from the host cell. Virion infects host cell, injecting its DNA, inserts itself into the host cell's chromosome. Viral portion (Pro-virus) is copied along with host cell chromosomes during cell division. This is called the Lysogenic cycle. The pro-virus can/eventually will break down a host's DNA and uses that material to produce many more viral particles. Then the 100-200 new viruses break out, usually destroying the host cell. This is called the Lytic cycle.
Cell cycle consists of Growth, Mitosis (Nuclear division) and Cytokinesis (Division of cytoplasm). Growth is Interphase (G1, S - DNA replicates, and G2). Mitosis (M-phase) is broken down into Prophase, Metaphase, Anaphase, and Telophase.
Big difference is that cells are self-producing and viruses are not. This is sometimes what differentiates what is living and non-living. Other differences are manner and speed of reproduction: Viruses reproduce exponentially more (100-200 in lytic cycle) than cells (which merely double in cell division). Time: generally about the same (12-24 hours in mammals), not counting the time it takes virions to find a host, but the viruses reproduce exponentially so they're more prolific.
Size: On the whole viruses are much smaller than bacteria. Most animal viruses and all plant viruses are invisible under the light microscope. Some of the smaller viruses are only 200 A in diameter. Viruses have a very simple structure. They consist of a nucleic acid core surrounded by a protein coat. In this respect they are differ from typical cells which are made up of proteins, carbohydrates, lipids and nucleic acid.
Life cycle: Two types of life cycles are possible in viruses. Some viruses multiply as soon as they enter the host cell, resulting in lysis or breakdown of the host cell. In the other type of life cycle the viruses do not cause lysis of the host cell in the usual way. The viral chromosome becomes integrated with the host chromosome and is called a prophage.
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