This document summarizes the key organelles and their functions in plant and animal cells. It describes the nucleus, which contains DNA, and the nucleolus. Ribosomes build proteins throughout the cell. The endoplasmic reticulum acts as an internal transport system, with rough ER adding proteins and smooth ER building lipids. Golgi bodies package and modify materials. Lysosomes break down waste. Mitochondria generate energy. Plants also contain vacuoles for water storage, chloroplasts for photosynthesis, and a cell wall for structure and protection.