Definition
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.
Animal Cells vs. Plant Cells
Animal cells and plant cells are both eukaryotic. Thus, they both have a defined nucleus and other membrane-bound organelles. However, animal and plant cells also have some fundamental differences.
Animal cells, unlike plant and fungi cells, do not have a cell wall. Instead, multicellular animals have other structures that provide support to their tissues and organs, such as skeleton and cartilage. Additionally, animal cells also lack chloroplasts found in plant cells. Chloroplasts are specialized organelles that trap energy from the sun and use it as fuel to produce sugars in a process called photosynthesis.
Additionally, while plant cells tend to have a large, central vacuole, animal cells lack this feature. Some animal cells do have small vacuoles, but their function is to assist in the storage and transport of large molecules.
Animal Cell Structure
Animal cells have a variety of different organelles that work together to allow the cell to perform its functions. Each cell can be thought of as a large factory with many departments, like manufacturing, packaging, shipping, and accounting. Different organelles represent each of these departments.
There are lots of different animal cells that each carry out specialized functions. Therefore, not every animal cell has all types of organelles, but in general, animal cells do contain most (if not all) of the following organelles. Additionally, some organelles will be highly abundant in certain cells and not others.
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