What are microtubules and plastids?

Microtubules, being part of the cytoskeleton... help a cell maintain its shape.

Microtubules typically radiate outwards from the centre of the cell; a place called an MTOC or microtubule organizing centre. They are involved in kinetichore and spindle formation during mitosis. On...

Microtubules are one of the components of the cytoskeleton.

a small, double-membraned organelle of plant cells and certain protists, occurring in several varieties, as the chloroplast, and containing ribosomes, prokaryotic DNA, and, often, pigment. by Garrett...

All chloroplasts are plastids because chloroplasts are plastids containing chlorophyll. But, all plastids are not chloroplasts because only those plastid that contains chlorophyll are chloroplasts.