Sub-cellular structure

Each cell contains smaller parts called sub-cellular structures. Their structures suit particular jobs, and the cell works because these jobs are connected. For example, genetic instructions in the nucleus can be used to make proteins at ribosomes, while respiration in mitochondria transfers the energy needed for cell activities.

A cell is the basic structural unit of a living organism. It contains sub-cellular structures, each suited to a particular function. Their arrangement is not arbitrary: genetic information must be stored, proteins must be produced, energy must be released and the movement of substances must be controlled.