Animal cells are the basic unit of life in organisms of the kingdom Animalia. They are eukaryotic cells, meaning that they have a true nucleus and specialized structures called organelles that carry out different functions. Animal cells do not have plant-specific organelles like cell walls, which support the plant cell, or chloroplasts, the organelle that carries out photosynthesis.
Overview of Animal Cells
Animals, plants, fungi, and protists are all made up of at least one eukaryotic cell. In contrast, bacteria and archaea are made up of a single prokaryotic cell.
All cells are surrounded by a cell membrane (also called a plasma membrane). The cell membrane is the boundary that separates the inside of the cell from the outside of the cell. The plasma membrane encloses all the cell components, which are suspended in a gel-like fluid called the cytoplasm. The cytoplasm is the location of the organelles.
Eukaryotic cells are distinguished from prokaryotic cells by the presence of a defined nucleus and other membrane-bound organelles, such as the mitochondria, endoplasmic reticulum, and Golgi apparatus. Prokaryotic cells do not have a defined nucleus (instead, a region of the cytoplasm – called the nucleotide – holds the genetic material). They also lack membrane-bound organelles.
Animals are all multicellular, meaning multiple cells work together to form the whole organism. In complex organisms, such as humans, these cells can be highly specialized to perform different functions. As such, they often look and function very differently from one another, even though they are all human cells.