Biology / Unit 9 Bio 1903 short lesson, about 20 seconds
Four Capsid Shape Classes
Captions available
The idea
Viral capsids fall into four shape classes: helical, icosahedral, enveloped, and head-and-tail, built from repeating protein subunits called capsomeres.
In practice
Tobacco mosaic virus is helical, poliovirus is icosahedral, and bacteriophage T4 combines an icosahedral head with a helical tail.
Where people slip
Capsid shape alone predicts neither a virus's disease nor its host species— it only helps sort viruses into families.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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