Answer: Animal cell's shape and structure are determined by the cytoskeleton.
What is the cytoskeleton?
The cytoskeleton is present in all animal cells, prokaryotic (bacterial) cells contain a very rudimentary version of it, while plant cells do not have one at all. It consists of several types of large molecules that provide physical support to the cell as well as internal transport along its length for organelles like endoplasmic reticulum (ER), mitochondria, vacuoles, etc. The three main components are microtubules, intermediate filaments and microfilaments which give rise to different structures within the cell. Microtubules are long cylindrical tubes made up of two protein subunits (alpha and beta tubulin) that form a hollow tube. These are the main components of the cytoskeleton, they provide support to the cell while also having transport capacity for organelles like endoplasmic reticulum (ER), mitochondria, vacuoles, etc. Microtubules are dynamic structures which means their state is constantly changing i.e., growing, shrinking or moving around depending on requirements of the cell.
