Science, Tech, Math › Science The Cell What Are Cells? Print This is a colored transmission electron micrograph (TEM) of an Escherichia coli bacterium in the early stages of binary fission, the process by which the bacterium divides. Credit: CNRI/Getty Images Science Biology Cell Biology Basics Genetics Organisms Anatomy Physiology Botany Ecology Chemistry Physics Geology Astronomy Weather & Climate By Regina Bailey Regina Bailey Biology Expert B.A., Biology, Emory University A.S., Nursing, Chattahoochee Technical College Regina Bailey is a board-certified registered nurse, science writer and educator. Her work has been featured in "Kaplan AP Biology" and "The Internet for Cellular and Molecular Biologists." Learn about our Editorial Process Updated on August 21, 2019 Life is both wonderful and majestic. Yet for all of its majesty, all organisms are composed of the fundamental unit of life, the cell. The cell is the simplest unit of matter that is alive. From the unicellular bacteria to multicellular animals, the cell is one of the basic organizational principles of biology. Let's look at some of the components of this basic organizer of living organisms. Eukaryotic Cells and Prokaryotic Cells There are two primary types of cells: eukaryotic cells and prokaryotic cells. Eukaryotic cells are called so because they have a true nucleus. The nucleus, which houses DNA, is contained within a membrane and separated from other cellular structures. Prokaryotic cells, however, have no true nucleus. DNA in a prokaryotic cell is not separated from the rest of the cell but coiled up in a region called the nucleoid. Classification As organized in the Three Domain System, prokaryotes include archaeans and bacteria. Eukaryotes include animals, plants, fungi and protists (ex. algae). Typically, eukaryotic cells are more complex and much larger than prokaryotic cells. On average, prokaryotic cells are about 10 times smaller in diameter than eukaryotic cells. Cell Reproduction Eukaryotes grow and reproduce through a process called mitosis. In organisms that also reproduce sexually, the reproductive cells are produced by a type of cell division called meiosis. Most prokaryotes reproduce asexually and some through a process called binary fission. During binary fission, the single DNA molecule replicates and the original cell is divided into two identical daughter cells. Some eukaryotic organisms also reproduce asexually through processes such as budding, regeneration, and parthenogenesis. Cellular Respiration Both eukaryotic and prokaryotic organisms get the energy they need to grow and maintain normal cellular function through cellular respiration. Cellular respiration has three main stages: glycolysis, the citric acid cycle, and electron transport. In eukaryotes, most cellular respiration reactions take place within the mitochondria. In prokaryotes, they occur in the cytoplasm and/or within the cell membrane. Comparing Eukaryotic and Prokaryotic Cells There are also many distinctions between eukaryotic and prokaryotic cell structures. The following table compares the cell organelles and structures found in a typical prokaryotic cell to those found in a typical animal eukaryotic cell. Cell Structure Prokaryotic Cell Typical Animal Eukaryotic Cell Cell Membrane Yes Yes Cell Wall Yes No Centrioles No Yes Chromosomes One long DNA strand Many Cilia or Flagella Yes, simple Yes, complex Endoplasmic Reticulum No Yes (some exceptions) Golgi Complex No Yes Lysosomes No Common Mitochondria No Yes Nucleus No Yes Peroxisomes No Common Ribosomes Yes Yes Eukaryotic and Prokaryotic Cell Structures Cite this Article Format mla apa chicago Your Citation Bailey, Regina. "The Cell." ThoughtCo, Apr. 5, 2023, thoughtco.com/what-are-cells-373361. Bailey, Regina. (2023, April 5). The Cell. Retrieved from https://www.thoughtco.com/what-are-cells-373361 Bailey, Regina. "The Cell." ThoughtCo. https://www.thoughtco.com/what-are-cells-373361 (accessed September 5, 2024). copy citation We Care About Your PrivacyWe and our 100 partners store and/or access information on a device, such as unique IDs in cookies to process personal data. You may accept or manage your choices by clicking below, including your right to object where legitimate interest is used, or at any time in the privacy policy page. These choices will be signaled to our partners and will not affect browsing data.We and our partners process data to provide:Store and/or access information on a device. Use limited data to select advertising. Create profiles for personalised advertising. Use profiles to select personalised advertising. Create profiles to personalise content. Use profiles to select personalised content. Measure advertising performance. 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