Most viruses vary in diameter from 20 nanometres (nm 0.0000008 inch) to 250–400 nm the largest, however, measure about 500 nm in diameter and are about 700–1,000 nm in length. The genomes of Mimiviruses and Pandoraviruses, which are some of the largest known viruses, range from 1 to 2.5 Mb (1 Mb = 1,000,000 base pairs of DNA). The protein and nucleic acid constituents have properties unique for each class of virus when assembled, they determine the size and shape of the virus for that specific class. Penetrating the membrane are additional proteins that determine the specificity of the virus to host cells. Some viruses have more than one layer of protein surrounding the nucleic acid still others have a lipoprotein membrane (called an envelope), derived from the membrane of the host cell, that surrounds the nucleocapsid core. The nucleic acid and proteins of each class of viruses assemble themselves into a structure called a nucleoprotein, or nucleocapsid. The amount and arrangement of the proteins and nucleic acid of viruses determine their size and shape. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!ĭissect the anatomy of icosahedral, rod-shaped, and bacteriophage virus structures in electron micrographs See all videos for this article.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more. Demystified Videos In Demystified, Britannica has all the answers to your burning questions.This Time in History In these videos, find out what happened this month (or any month!) in history.#WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find.Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives.Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.
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