9+2 arrangement

 The 9 + 2 arrangement refers to how the microtubules are organised in structures such as the flagella and cilia. It has 9 pairs of microtubules situated on the outside that are bound together and 2 pairs of microtubules in the middle that are not bound together. Attached to these doublet pairs, consisting of both microtubules in a fused pair, are dynein arms. These are motor proteins that create mechanical work energy from chemical energy aquired from ATP hydrolysis enabling movement along microtubules.