All organisms must perform life-sustaining metabolic processes in order to survive.
In unicellular organisms, of these processes are performed by that makes up the organism.
In multicellular organisms, of these processes are performed by that makes up the organism.

Explanation:

Unicellular organisms or single celled organisms that are made up only of one cell. Hence the name.Unicellular organisms are further divided into Prokaryotic and Eukaryotic organismsExamples of prokaryotic organisms are bacteria and Eukaryotic are protozoa and unicellular algae, however many eukaryotes are multi cellular as well.These organisms have to carry out life sustaining metabolic processes for their survival.These processes are metabolism, homeostasis and reproduction. Metabolism is important as it involves conversion of food into energy for cellular processes. Homeostasis for maintaining a constant internal physical and chemical conditions and reproduction is by cell division. Multi cellular organisms as the name says unlike unicellular organisms consists of more than one cells.Examples of multi cellular organisms are animals, land plants etc.,Metabolic process in multi cellular organisms is a broad category of processes happening for these organisms which involves chemical reactions and pathways that happen at organismal state, transporting substances between the cells.