It depends what kind of cell it is. If it is a single-celled organism, it generally lives in some body of water. Life Functions within a wide set of parameters.
Light, dark, heat, cold, acid, alkaline, conventional sources of subsistence and nutrition available, or the bottom-of-the-Sea conditions where top-side food is unavailable - all amount to the sustenance of Life.
Life's cells also abide in the lightless Ocean bottoms - at black smokers where there is neither O2 nor light - yet H2S and Life occur in abundance.
Some creatures eye-cells never encounter light and thereby give rise to eyeless creatures.
Your answer is " ... its environment. " That is, it is growing only by feeding ... upon ... well: <there cannot be any big things without the little things> all of the available things in its environment to fulfill its two aims, growth and reproduction.
The principles of Biochemistry state that all of the above steps shall be performed at maximum efficiency, a biochemistry book calls it The Molecular Logic of Living Organisms - most simply stated as the conservation of energy.
first growth (g1)phase
interphase
interphase
Interphase, in the G1 phase where it grows and grows!
All cell functions are managed from the nucleus as this is where the code of life, DNA, is kept.
cell is the functional,structural and behavioural unit of life.
Cells.
cytoplasm
cell
genetic information
The nucleus has DNA which has all the blueprints that direct the functions of each cell.
Each cell carries out various functions of life
Any single celled organism carries out the functions of life, but, if considered living, a virus is much smaller than a cell. However, viruses are only DNA and can do little except control a cell with their DNA. They do not eat, or control their own movement, nor can they reproduce without a host.
That is the nucleus. it is made of heredity material made of DNA and it carries on the functions of life.
CO2
Organelles.
cell
The cell cycle can be divided into two major periods: interphase, in which the cell grows and carries on its usual activities; and the mitotic phase, during which the nucleus divides and cytokinesis forms two cells.
The cell is the smallest unit of life capable of carrying out life functions.
Many one-celled organisms perform all their life functions by themselves. Cells in a many-celled organism, however, do not work alone. Each cell carries on it's own life functions while depending in some way on other cells in the organism.