MCBM 1- (10) Microtubules Questions
and Answers 100% Correct
What are microtubules made up of? - ANSWER - -alpha and beta tubulin = dimer.
-dimers come together to form a protofilament
-13 protofilaments = microtubule.
Discuss polarity in regards to structure of microtubules. What is positive and negative? Where
are they found? What end grows? - ANSWER - Alpha is the (-), Beta is the (+) end. Although
there is no chemical polarity, this is said to be polar.
All beta tubulins are at the top, all of the alpha tubulins are at the bottom.
The Beta (+) end grows while the (-) end is non growing.
Discuss tubulin and its relationship to GTP. - ANSWER - Alpha and beta tubulin are always
bound to a GTP or a GDP.
Depolymerization: takes off dimer
GTP tubulin has a high affinity for the plus end of a microtubule.
When the dimer is bound to a GTP, it has a high affinity for for other dimers with GTP. When it
loses a phosphate and turns into a GDP, it loses its affinity and falls off. This goes on and on in
an attempt to balance.
Why are microtubule based cancer drugs effective? - ANSWER - Because microtubules play
such an important role in cell division, they are targeted.
Taxanes: Stabilizes microtubules. In interphase, they are not allowed to depolymerize so
spindles cannot be formed.
and Answers 100% Correct
What are microtubules made up of? - ANSWER - -alpha and beta tubulin = dimer.
-dimers come together to form a protofilament
-13 protofilaments = microtubule.
Discuss polarity in regards to structure of microtubules. What is positive and negative? Where
are they found? What end grows? - ANSWER - Alpha is the (-), Beta is the (+) end. Although
there is no chemical polarity, this is said to be polar.
All beta tubulins are at the top, all of the alpha tubulins are at the bottom.
The Beta (+) end grows while the (-) end is non growing.
Discuss tubulin and its relationship to GTP. - ANSWER - Alpha and beta tubulin are always
bound to a GTP or a GDP.
Depolymerization: takes off dimer
GTP tubulin has a high affinity for the plus end of a microtubule.
When the dimer is bound to a GTP, it has a high affinity for for other dimers with GTP. When it
loses a phosphate and turns into a GDP, it loses its affinity and falls off. This goes on and on in
an attempt to balance.
Why are microtubule based cancer drugs effective? - ANSWER - Because microtubules play
such an important role in cell division, they are targeted.
Taxanes: Stabilizes microtubules. In interphase, they are not allowed to depolymerize so
spindles cannot be formed.
