Because they were created to do so.
All living organisms use energy to carry out daily functions
organelles
Cells.
Many things need bacteria to carry out their daily life functions. This includes humans, other animals, and some species of plants.
organells
the smallest function of life are cells.
The word you are looking for is "metabolize." It refers to the process by which living organisms obtain and utilize energy from their surroundings to carry out life functions and processes.
yes
cell
Nothing that we know of can survive the heat generated on surface of stars, therefore, no. Planets could carry life forms.
The smallest units that carry out the functions of life are cells. Cells are the basic structural and functional units of all living organisms. They perform essential functions such as energy production, protein synthesis, and replication.
A one-celled organism is the smallest organism that can carry out all functions of life. Two examples would be a paramecium (Protista kingdom), and Cyanobacteria (Eubacteria kingdom).