The Cell - Structure and Organelles

Core concept

Mitochondria are often called the 'powerhouse of the cell' because they convert nutrients into usable energy (ATP) through cellular respiration, and cells with higher energy needs (like muscle cells) contain more mitochondria. The endoplasmic reticulum helps transport materials within the cell and assists in protein/lipid synthesis, while ribosomes, found on the endoplasmic reticulum or free in the cytoplasm, are the sites where proteins are actually manufactured based on genetic instructions from the nucleus.