Animal cells are the basic building blocks of all animals. They are eukaryotic cells, meaning they have a defined nucleus that contains genetic material. Animal cells are typically round or irregular in shape and lack a rigid cell wall, which allows for greater flexibility. They contain various organelles, such as mitochondria for energy production and ribosomes for protein synthesis. These cells are surrounded by a plasma membrane that regulates what enters and exits the cell. Animal cells also have lysosomes, which help break down waste materials, and endoplasmic reticulum, which assists in the production and transport of proteins and lipids. Together, these components enable animal cells to perform essential functions for life.