Hi!
The shape and size of a cell is indeed related to its function. For example, the nerve cells are elongated in shape and are thin and dainty. This helps in transmitting the signals easily. Furthermore, the dendrites at the ends help transmit the messages to more than one other nerve cell so the message can reach either the brain or the spinal cord faster. The thin shape also helps keep the message on a straight path and keeps the message from getting confused or mixed up with other messages being transmitted so as to insure the direct and immediate receiving of all the messages.
We can also take the exampla of a simple animal cell. An animal cell does not have a cell wall. This makes it easy for it to move around the body. The red blood cells are also good examples of such a cell. It is round in shape so that it holds larger amounts of haemoglobin ( which contains oxygen ) for transportation all around the body.
Hope this helps !
