Biology 2382B Midterm: Cell Bio 2382 Midterm 2 Notes.pdf
2 May 2014
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Microtubules are 25 nm in diameter, and very long. Microtubules make up things such as flagella, that"s why it is much longer than a cell. Made up of tubulin: a polymer of alpha and beta tubulin. Almost always exist as alpha-beta dimer (110 kda; both alpha and beta monomers are 55 kda each) Alpha-beta dimer is the basic subunit, you build things with it. When things get taken apart, they get taken apart at this dimer level. Dimers can polymerize (can grow a chain) Protofilament: dimers that are formed end to end. Will have alpha on one end, beta on the other (hence polarity) Bunch of protofilaments can come together to form a hollow tube (which is 25 nm in diameter; up to 100 m long; Hollow tube also has polarity; they all have protofilaments that have alpha on one end, beta on the other end. Alpha end is called the minus end; beta is plus end.
