What is a Ribosome? A Ribosome is a cluster of proteins and nucleic acids that constructs proteins in a cell. They are found in the cytoplasm of a cell or on the endoplasmic reticulum and in both animal and plant cells. Endoplasmic reticulum is a network of membranes within a cell’s cytoplasm that produce a variety of molecules. It is found in both animal and plant cells. Structure Ribosome: : consists of two subunits (a smaller and larger subunit) each of which contains RNA and proteins Endoplasmic Reticulum: •Smooth ER- looks like tubes and it acts as a storage organelle. •Rough ER- looks very bumpy and has ribosomes attached to it. They are very important in the synthesis and packaging of proteins. Functions: Ribosome: They are responsible for organizing and assembling amino acids to form proteins. Endoplasmic Reticulum: Creates a variety of different molecules and operates as a transport system.