Single Cell

A single cell can carry out many function.

A single cell with its numerous components and organelles can be so complete that it is able to function as a complete organism!

Examples of such unicellular organisms (or organisms that are made up of ONE cell only) are protozoa, bacteria, viruses, and certain types of algae and fungi.

In fact, most microorganisms are usually unicellular in nature.

The following table, show how and where the living process are carried out in each of the unicellular organisms;

Living process	Paramecium	Amoeba
a) Respiration	Diffusion through its cell membrane	Diffusion through its cell membrane
b) Excretion of excess water	Contractile vacuole	Contractile vacuole
c) Reproduction	Mitosis (cell division of nucleus) - binary fission	Mitosis (cell division of nucleus) - binary fission
d) Growth	Synthesis of new cytoplasm and organelle	Synthesis of new cytoplasm and organelle
e) Response to environment	Taxis - whole cell moves toward favourable stimuli and away from unfavourable stimuli	Taxis - whole cell moves toward favourable stimuli and away from unfavourable stimuli
f) Locomotion	Pseudopodia	Cilia
g) Nutrition (eating)	Phagocytosis, digestion in food vacuoles and lysozymes	Ingestion through oral groove, digestion in food vacuoles and egestion through its anal pore