What is the smallest part of the body that is said to be alive?

Hint: Living organisms are made up of multiple components that work together to carry out the biological functions. Various organ systems are formed with the association of different organs that synchronize to perform a function. Similarly organs are formed by different tissues of same origin and function. Tissues are formed by the association of similar cells.

Complete answer:
The smallest part of any living organism’s body that is alive are the cells. It is the most basic structural and functional unit of any organism. Cells are the only component that can exist on its own. All the living organisms are composed of at least one cell, and all the new cells arise from this pre-existing cell. All the vital biological functions of the organisms take place within the cells. The information regarding the cell division is also stored within the cells. Thus cells function as the basic building blocks that aggregate to form a complete living organism. All the functions of the body are regulated at the cellular level. The cell is composed of three basic components, cell membrane, cytoplasm and the nucleus. There are differences in the structures of animal and plant cells.

Figure: Basic structure of a cell

Note:
There are two types of cells namely: prokaryotic and eukaryotic. Eukaryotic cells are well defined cells that have a well defined nucleus in it. These types of cells are found in all of the higher organisms and microscopic organisms such as fungi and protists such as amoeba. Prokaryotic cells are the primitive cells that are devoid of a well defined nucleus as well as other properly developed membrane bound organelles that are present in several bacteria.