theodor schwann cell theory experiment

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cell theory

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• National Center for Biotechnology Information - PubMed Central - Cell Theory, Specificity, and Reproduction, 1837–1870
• Biology LibreTexts - Cell Theory
• Oregon State University Pressbooks - Allied Health Microbiology - Foundations of Modern Cell Theory
• Tokyo Medical and Dental University - A unifying concept: the history of cell theory
• Khan Academy - History and development of cell theory
• Thompson Rivers University - Human Biology - Discovery of Cells and Cell Theory

cell theory , fundamental scientific theory of biology according to which cells are held to be the basic units of all living tissues . First proposed by German scientists Theodor Schwann  and  Matthias Jakob Schleiden  in 1838, the theory that all plants and animals are made up of cells marked a great conceptual advance in biology and resulted in renewed attention to the living processes that go on in cells.

The history of cell theory is a history of the actual observation of cells, because early prediction and speculation about the nature of the cell were generally unsuccessful. The decisive event that allowed the observation of cells was the invention of the  microscope  in the 16th century, after which interest in the “invisible” world was stimulated. English physicist  Robert Hooke , who described cork and other plant tissues in 1665, introduced the term  cell  because the  cellulose  walls of dead cork cells reminded him of the blocks of cells occupied by monks. Even after the publication in 1672 of excellent pictures of plant tissues, no significance was attached to the contents within the cell walls . The magnifying powers of the microscope and the inadequacy of techniques for preparing cells for observation precluded a study of the intimate details of the cell contents. The inspired Dutch microscopist  Antonie van Leeuwenhoek , beginning in 1673, discovered  blood cells ,  spermatozoa , and a lively world of “animalcules.” A new world of unicellular organisms was opened up. Such discoveries extended the known variety of living things but did not bring insight into their basic uniformity. Moreover, when Leeuwenhoek observed the swarming of his animalcules but failed to observe their division, he could reinforce only the idea that they arose spontaneously.

Cell theory was not formulated for nearly 200 years after the introduction of microscopy. Explanations for this delay range from the poor quality of the microscopes to the persistence of ancient ideas concerning the definition of a fundamental living unit. Many observations of cells were made, but apparently none of the observers was able to assert forcefully that cells are the units of biological structure and function. Three critical discoveries made during the 1830s, when improved microscopes with suitable lenses, higher powers of magnification without aberration, and more satisfactory illumination became available, were decisive events in the early development of cell theory. First, the nucleus was observed by Scottish botanist  Robert Brown  in 1833 as a constant component of plant cells . Next, nuclei were also observed and recognized as such in some animal cells. Finally, a living substance called  protoplasm  was recognized within cells, its vitality made evident by its active streaming, or flowing, movements, especially in plant cells. After these three discoveries, cells, previously considered as mere pores in plant tissue, could no longer be thought of as empty, because they contained living material.

It was not until 1838 that the botanist  Matthias Jakob Schleiden, interested in plant anatomy, stated that “the lower plants all consist of one cell, while the higher ones are composed of (many) individual cells.” When the physiologist  Theodor Schwann, Schleiden’s friend, extended the cellular theory to include animals, he thereby brought about a rapprochement between botany and  zoology . The two scientists clearly stated in 1839 that cells are the “elementary particles of organisms” in both plants and animals and recognized that some organisms are unicellular and others multicellular. This statement was made in Schwann’s  Mikroskopische Untersuchungen über die Übereinstimmung in der Struktur und dem Wachstume der Tiere und Pflanzen  (1839;  Microscopical Researches into the Accordance in the Structure and Growth of Animals and Plants ). Schleiden’s contributions on plants were acknowledged by Schwann as the basis for his comparison of animal and plant structure.

Schleiden and Schwann’s descriptive statements concerning the cellular basis of biologic structure are straightforward and acceptable to modern thought. They recognized the common features of cells to be the membrane , nucleus , and cell body and described them in comparisons of various animal and plant tissues. A statement by Schleiden pointed toward the future direction of cell studies:

Each cell leads a double life: an independent one, pertaining to its own development alone; and another incidental, insofar as it has become an integral part of a plant. It is, however, easy to perceive that the vital process of the individual cells must form the first, absolutely indispensable fundamental basis, both as regards vegetable physiology and comparative physiology in general.

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Theodor Schwann (1810–1882)

Michał k. owecki.

Department of History and Philosophy of Medical Sciences, Poznań University of Medical Sciences, ul. Przybyszewskiego 37A, Poznań, Poland

Theodor Schwann (Fig.  1 ), the eminent founder of modern histology and the discoverer of the lemmocyte, was born on December 7, 1810 in Neuss, Germany, the fourth son of Elisabeth (née Rottels) and Leonard Schwann, the owner of a local bookstore. Theodor grew up in a large family—he had twelve siblings. As a child, he proved to be multi-talented and hardworking. He initially intended to study theology, but, over time, he changed his mind and chose medicine. After graduating from the Jesuit Gymnasium in Cologne in 1829, he enrolled at the University of Bonn, where, two years later, he obtained a bachelor's degree in philosophy. It was there that he first met Johannes Müller (1801–1858), an outstanding German physiologist. Schwann not only attended Müller’s lectures, but also helped the professor in laboratory research on spinal roots. Then, in the years 1831–1833, he continued his education at the University of Würzburg, where he listened to the lectures of another illustrious scientist, Johann Schönlein (1793–1864). For the final semester of his studies he moved to Berlin, following his first mentor, Müller [ 1 – 3 ]. In 1834, he passed the state medical examination and obtained the title of doctor of medicine. Schwann’s dissertation De necessitate aëris atmosphaerici ad evolutionem pulli in ovo incubato , written in Latin, discussed chicken embryo development and was inspired and supervised by Müller, who entrusted him with the position of assistant at the anatomy museum [ 2 , 3 ].

Theodor Schwann (public domain)

From the beginning of his career, Schwann was interested in the histology and physiology of the nervous system and muscle tissue. In his studies, he proved that the upper part of the esophagus is made of striated tissue, whereas the rest of the gastrointestinal tract, the uterus, pupils and bladder are constituted of smooth muscle. In the 1830s, he conducted a number of experiments in which he tried to make an objective determination of the force of muscle contraction under stimuli at varying intensities. His new methods made him a pioneer of neurophysiology and quantitative physiology. Unfortunately, he did not publish his results on his own—they were only cited in other medical journals from that period, including Müller’s Handbuch der Physiologie des Menschen and Oken’s Enzyklopädische Zeitschrift [ 3 , 4 ].

Schwann made most of his important scientific discoveries during the Berlin period (1834–1838). In 1836 he isolated the enzyme responsible for digestive processes in the stomach—and coined the name “pepsin” for this newly identified substance. A year later, he proved that yeast fermentation activated with sugar is an expression of the life processes, and that yeasts themselves are living organisms [ 3 , 5 , 6 ].

In 1838, Schwann initiated a collaboration with Matthias Schleiden. The meeting of the two scientists was to have major and far-reaching consequences: the founding of cell theory [ 7 ]. According to their new idea, a single cell was the basic structural unit of every living organism. In the same year, Schwann presented his observations in a series of short articles [ 8 ]. Then, in 1839, he published an extensive work on histology: Mikroskopische Untersuchungen über die Übereinstimmung in der Struktur und dem Wachstum der Thiere und Pflanzen (“Microscopical Researches into the Accordance in the Structure and Growth of Animals and Plants”). A substantial part of the monograph is dedicated to the microstructure of muscles and nerves. In the book, Schwann precisely described the myelinated nerve fiber. His research led to the discovery of the cell that produces the myelin sheath that envelops the axon. In honor of his contribution, this was later eponymously named the Schwann cell [ 3 , 7 , 9 ]. He also found that during embryonic development individual cells unite to form the muscle fiber [ 10 ].

Schwann’s book gained international recognition after it was printed in French (in 1842) and English (in 1847). The monograph is also worth mentioning for another reason. It was in this book that Schwann coined the term “metabolism”, signifying the totality of chemical processes in a cell. The word was introduced into scientific vocabulary for the first time in the German edition of “Microscopic Researches”, and was soon adopted worldwide [ 7 , 9 ].

Schwann’s undeniable successes led to a dynamic development in his career. In 1839, at the age of only 29, he accepted an offer of a professorship of anatomy at the University of Louvain, Belgium. He worked there for the following nine years. In recognition of his outstanding achievements, Schwann received the Copley Medal in 1845, the oldest and most prestigious award of the Royal Society of London [ 1 ]. In 1848, Schwann moved to the University of Liège, where he took over the professorship of anatomy and, after a few more years, that of physiology and embryology. He was then already world famous—in 1863 he was elected as an international member of the American Philosophical Society. Despite numerous offers of work from German universities (Munich, Giessen, Wrocław and Würzburg), he decided to stay in Belgium. He remained in Liège until the end of his career and it was there that he also spent the last years of his life, devoting himself to his hobby: photography. He retired in 1879, and, in the same year, was elected to the French Academy of Sciences and the Royal Society of London—a prestigious culmination of his distinguished career [ 1 , 2 ].

Theodor Schwann was a gentle, calm and timid man, and one who avoided conflict. He remained a bachelor until the end of his life. Even until the formal celebrations of the 40th anniversary of his university work in 1878 in Liège, he enjoyed excellent health. Shortly before his death, however, he suffered from recurrent dizziness and anxiety attacks, diagnosed as a manifestation of heart valve disease. In December 1881, he went to Cologne to visit his family for Christmas. During this stay, he suffered a stroke, as a result of which he died two weeks later, at his brother's house, on January 11, 1882. He was buried in the local cemetery, with delegates from the universities of Bonn and Liège to bid him farewell [ 1 – 3 ].

Declarations

The author states that there is no conflict of interest.

ENCYCLOPEDIC ENTRY

Cell theory.

Scientists once thought that life spontaneously arose from nonliving things. Thanks to experimentation and the invention of the microscope, it is now known that life comes from preexisting life and that cells come from preexisting cells.

Micrographia Cover

English scientist Robert Hooke published Micrographia in 1665. In it, he illustrated the smallest complete parts of an organism, which he called cells.

Photograph by Universal History Archive/Universal Images Group via Getty Images

In 1665, Robert Hooke published Micrographia , a book filled with drawings and descriptions of the organisms he viewed under the recently invented microscope . The invention of the microscope led to the discovery of the cell by Hooke. While looking at cork, Hooke observed box-shaped structures, which he called “cells” as they reminded him of the cells, or rooms, in monasteries. This discovery led to the development of the classical cell theory . The classical cell theory was proposed by Theodor Schwann in 1839. There are three parts to this theory. The first part states that all organisms are made of cells. The second part states that cells are the basic units of life. These parts were based on a conclusion made by Schwann and Matthias Schleiden in 1838, after comparing their observations of plant and animal cells. The third part, which asserts that cells come from preexisting cells that have multiplied, was described by Rudolf Virchow in 1858, when he stated omnis cellula e cellula (all cells come from cells) . Since the formation of classical cell theory , technology has improved, allowing for more detailed observations that have led to new discoveries about cells. These findings led to the formation of the modern cell theory , which has three main additions: first, that DNA is passed between cells during cell division; second, that the cells of all organisms within a similar species are mostly the same, both structurally and chemically; and finally, that energy flow occurs within cells.

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Theodor Schwann

A founding father of biology and medicine.

Thomas, Tony Abraham

Department of Continuing Medical Education, Christian Medical College, Vellore, Tamil Nadu, India

Address for correspondence: Dr. Tony Abraham Thomas, Department of Continuing Medical Education, Christian Medical College, Vellore - 632 002, Tamil Nadu, India. E-Mail: [email protected]

This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms.

Theodor Schwann is best remembered for the eponymous Schwann cell that he studied and described in his microscopic studies of nervous tissue. However, his most important contribution to science would be the fact that he was one of the founders of the 'Cell doctrine' which proposed that all living beings were made of fundamental units called cells - a foundational principle on which rests much of our understanding of biological science. Schwann was one of the first scientists to break away from vitalism to lean toward a mechanistic or physico-chemical explanation of living processes which proposed that the biological processes in cells and living beings could be explained by physical and chemical phenomena. He was also involved in describing the physiology of bile and the enzyme pepsin which furthered our understanding of the physiology of digestion. His contributions to biology and medicine has paved the way for the emergence and blooming of several fields of study such as microbiology, pathology, histology and the principle of antibiotics.

INTRODUCTION

Although most well known for the Schwann cell that bears his name, Theodore Schwann, the German physiologist, has a number of discoveries and accomplishments to his credit. He was one of the early scientists at the dawn of biology as we know it today, involved in clarifying our understanding of the basic and fundamental principles of cellular life, its structure, and its physiology. The “cell doctrine” which proposed that all living beings were made of fundamental units called cells was one such foundational principle on which rests much of our understanding of biological science and Schwann was one of the founders of this fundamental principle. He was also involved in the microscopic study of muscle and nerve cells, blood vessels and the physiology of digestion, making several pathbreaking discoveries during his lifetime, thus laying the foundation for the emergence of other branches of science.

EARLY LIFE AND CHILDHOOD

Theodor Schwann [ Figure 1 ] was born at Neuss near Dusseldorf in Prussia (modern-day Germany) on December 7, 1810. His father was a goldsmith and was involved later in the printmaking business. In his childhood, young Theodor was known to have been involved in constructing little machines in his childhood, no doubt having inherited a practical mechanical bent of mind from his father. After completing his school studies in the Jesuit College of Cologne, he came under the tutorship of Johannes Müller at the University of Bonn in 1829. Müller was a pioneer in comparative anatomy and physiology, especially known for his experimental methods and he was to have a significant impact in shaping his protégé. Schwann assisted him in his experiments in physiology and was inspired to pursue a medical career. He had his clinical training in Würzburg and went on to the University of Berlin to study once again under his mentor Müller who had now been appointed as Professor in Anatomy and Physiology at the university. Schwann's thesis work focused on the necessary role of oxygen in the development of the chicken embryo, and he obtained his MD degree in 1834. Following this, he continued assisting Müller in his physiology experiments, and the 4 years spent under his supervision laid the foundation for the remarkable scientific advances that he would pioneer. 1 2 3

SCHWANN CELL

Schwann was particularly interested in the cellular structure of muscle and nerve tissues, and this led to his discovery and description of the Schwann cells and the role it played in providing the envelope covering nerve fibers called the Schwann cell sheath (which later came to be known as the myelin sheath). The myelin sheath is a characteristic feature of myelinated nerve fibers in the central nervous system, and its presence has implications on the speed of conductivity of nerve impulses besides other functions. He was also an initiator of work on muscle cell contractility and established the first tension-length diagram. 1 2 3 This work was then carried on by Du Bois-Reymond and Helmholtz and paved the way for the development of the field of neuromuscular physiology.

In 1836, while investigating the physiology of digestive processes with Müller, he isolated a chemical substance that was responsible for digestion in the stomach. This enzyme, which he named pepsin, was the first enzyme to be prepared from animal tissue. 4 5

VITALISM AND SPONTANEOUS GENERATION DISCREDITED

The prevalent understanding of life and biological processes at that time was based on a theory called “Vitalism.” According to this theory, “living organisms are fundamentally different from nonliving entities because they contain some nonphysical element or are governed by different principles than are inanimate things.” 6 7 This principle that gives life was known as the “vital spark” or “energy,” which was considered nonphysical. Schwann was one of the first scientists to break away from vitalism to lean toward a mechanistic or physicochemical explanation of living processes which proposed that the biological processes in cells and living beings could be explained by physical and chemical phenomena without the need for a nonphysical entity. The experimental work of Schwann using yeast cells also paved the way for the discrediting of “spontaneous generation” as a theory to explain the genesis of living processes. In the process, he also described the nature of the yeast cell.

CELL DOCTRINE

Schwann was also one of the founders of the cell doctrine, which would revolutionize biology and provide the basis for understanding all of biology and biological processes. A German botanist named Matthias Jakob Schleiden [ Figure 2 ] had discovered in 1837, that there were fundamental units called cells in plants, and this agreed with the findings of Müller and his protégé Schwann who had found similar cells in their microscopic studies. The exchange of ideas between Schwann and Schleiden was thought to have taken place over a dinner when Schwann realized that he had seen cellular structures in his microscopic studies of animal nervous tissue (notochord), similar to the one his colleague was describing in plant tissues. 1 2 3 Schwann connected the dots and realized that cells were the “elementary units of life” for both plants and animals and went on to describe this in his work titled “Microscopical Researches into the Accordance in the Structure and Growth of Animals and Plants” which was published in German in 1839 and later translated into English in 1847 by the Sydenham Society. This finding was confirmed by many other scientists and led to the understanding that all living organisms were composed of fundamental units called cells and products derived from cells.

In a scientific milieu that breathed the air of vitalism, this was a revolutionary concept that would have far-reaching consequences. Later, in 1857, Rudolf Virchow a pathologist, built on this doctrine and set forth the maxim, “ Omnis cellula e cellula”- that every cell arises from another cell. By 1860, the cell doctrine was established and would go on to open up avenues for new research like the “germ theory” by Pasteur and blooming of the streams of microbiology, cell biology, histology, infectious diseases, and pathology. This doctrine also paved the way to other discoveries that developed our understanding of cellular processes that underlie the physiology of health and disease.

LATER ACADEMIC LIFE

In 1838, Schwann was appointed to the chair of Anatomy at the Université Catholique de Louvain in Belgium where he served for 9 years and during this period wrote a paper describing the physiological role of bile in digestion based on his experiments in dogs. After this, he went on to join the University of Liége in the year 1848, as a professor in Anatomy and Physiology. This latter aspect of his academic life was not marked by the prodigious amount of work and discoveries that marked his earlier tenure in Berlin though he continued to remain in touch with academic science and was involved in perfecting experimental techniques and instruments that aided these experiments. 1 2 3 5

Theodor Schwann was a devout Catholic and was known to be a gentle soul. In his later years, he grappled with the philosophical and theological implications of his discoveries, and this was to lead to life in isolation, fraught with existential questions which he discussed in several publications and in a treatise. 5 The debate is far from over and even today scientists, philosophers and theologians continue to grapple with these issues and the new areas of ignorance opened up by every surge of knowledge. Schwann died in Cologne on January 11, 1882, 3 years after his retirement.

Despite the relative scientific penury of his later years, there is no doubt that Schwann was a tremendous force in the advancement of our understanding of the basic tenets and principles of biological science. The cell doctrine, in particular, was a revolutionary step forward, and the impact of that alone is still felt in the modern age, in the various branches of Biology and Medicine that we study today. The germ theory of Pasteur, the growth of histology and pathology, principles of antisepsis, and production of antibiotics are only some of the numerous applications that emerged from this doctrine which has contributed tremendously to human health and relief from pain.

Paul Ehrlich who was awarded The Nobel Prize in Physiology or Medicine in 1908 for his work on immunity had this to say of Schwann at his Nobel Lecture – “The history of the knowledge of the phenomena of life and of the organized world can be divided into two main periods. For a long time anatomy, and particularly the anatomy of the human body, was the alpha and omega of scientific knowledge. Further progress only became possible with the discovery of the microscope. A long time had yet to pass until through Schwann the cell was established as the final biological unit. It would mean bringing coals to Newcastle were I to describe here the immeasurable progress which biology in all its branches owes to the introduction of this concept of the cell concept. For this concept is the axis around which the whole of the modern science of life revolves.” 8

Theodor Schwann was a giant in his field, and the ripples that Schwann initiated will no doubt continue in the years to come, spawning new research in medicine and in our understanding of biological life.

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Cell doctrine; Schwann cell; Theodor Schwann

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3.2 Foundations of Modern Cell Theory

Learning objectives.

By the end of this section, you will be able to:

• Explain the key points of cell theory and the individual contributions of Hooke, Schleiden, Schwann, Remak, and Virchow
• Explain the key points of endosymbiotic theory and cite the evidence that supports this concept
• Explain the contributions of Semmelweis, Snow, Pasteur, Lister, and Koch to the development of germ theory

While some scientists were arguing over the theory of spontaneous generation, other scientists were making discoveries leading to a better understanding of what we now call the cell theory . Modern cell theory has two basic tenets:

• All cells only come from other cells (the principle of biogenesis).
• Cells are the fundamental units of organisms.

Today, these tenets are fundamental to our understanding of life on earth. However, modern cell theory grew out of the collective work of many scientists.

The Origins of Cell Theory

The English scientist Robert Hooke first used the term “cells” in 1665 to describe the small chambers within cork that he observed under a microscope of his own design. To Hooke, thin sections of cork resembled “Honey-comb,” or “small Boxes or Bladders of Air.” He noted that each “Cavern, Bubble, or Cell” was distinct from the others ( Figure 3.5 ). At the time, Hooke was not aware that the cork cells were long dead and, therefore, lacked the internal structures found within living cells.

Despite Hooke’s early description of cells, their significance as the fundamental unit of life was not yet recognized. Nearly 200 years later, in 1838, Matthias Schleiden (1804–1881), a German botanist who made extensive microscopic observations of plant tissues, described them as being composed of cells. Visualizing plant cells was relatively easy because plant cells are clearly separated by their thick cell walls. Schleiden believed that cells formed through crystallization, rather than cell division.

Theodor Schwann (1810–1882), a noted German physiologist, made similar microscopic observations of animal tissue. In 1839, after a conversation with Schleiden, Schwann realized that similarities existed between plant and animal tissues. This laid the foundation for the idea that cells are the fundamental components of plants and animals.

In the 1850s, two Polish scientists living in Germany pushed this idea further, culminating in what we recognize today as the modern cell theory. In 1852, Robert Remak (1815–1865), a prominent neurologist and embryologist, published convincing evidence that cells are derived from other cells as a result of cell division. However, this idea was questioned by many in the scientific community. Three years later, Rudolf Virchow (1821–1902), a well-respected pathologist, published an editorial essay entitled “Cellular Pathology,” which popularized the concept of cell theory using the Latin phrase omnis cellula a cellula (“all cells arise from cells”), which is essentially the second tenet of modern cell theory. 5 Given the similarity of Virchow’s work to Remak’s, there is some controversy as to which scientist should receive credit for articulating cell theory. See the following Eye on Ethics feature for more about this controversy.

Eye on Ethics

Science and plagiarism.

Rudolf Virchow, a prominent, Polish-born, German scientist, is often remembered as the “Father of Pathology.” Well known for innovative approaches, he was one of the first to determine the causes of various diseases by examining their effects on tissues and organs. He was also among the first to use animals in his research and, as a result of his work, he was the first to name numerous diseases and created many other medical terms. Over the course of his career, he published more than 2,000 papers and headed various important medical facilities, including the Charité – Universitätsmedizin Berlin, a prominent Berlin hospital and medical school. But he is, perhaps, best remembered for his 1855 editorial essay titled “Cellular Pathology,” published in Archiv für Pathologische Anatomie und Physiologie , a journal that Virchow himself cofounded and still exists today.

Despite his significant scientific legacy, there is some controversy regarding this essay, in which Virchow proposed the central tenet of modern cell theory—that all cells arise from other cells. Robert Remak, a former colleague who worked in the same laboratory as Virchow at the University of Berlin, had published the same idea 3 years before. Though it appears Virchow was familiar with Remak’s work, he neglected to credit Remak’s ideas in his essay. When Remak wrote a letter to Virchow pointing out similarities between Virchow’s ideas and his own, Virchow was dismissive. In 1858, in the preface to one of his books, Virchow wrote that his 1855 publication was just an editorial piece, not a scientific paper, and thus there was no need to cite Remak’s work.

By today’s standards, Virchow’s editorial piece would certainly be considered an act of plagiarism, since he presented Remak’s ideas as his own. However, in the 19th century, standards for academic integrity were much less clear. Virchow’s strong reputation, coupled with the fact that Remak was a Jew in a somewhat anti-Semitic political climate, shielded him from any significant repercussions. Today, the process of peer review and the ease of access to the scientific literature help discourage plagiarism. Although scientists are still motivated to publish original ideas that advance scientific knowledge, those who would consider plagiarizing are well aware of the serious consequences.

In academia, plagiarism represents the theft of both individual thought and research—an offense that can destroy reputations and end careers. 6 7 8 9

Check Your Understanding

• What are the key points of the cell theory?
• What contributions did Rudolf Virchow and Robert Remak make to the development of the cell theory?

Endosymbiotic Theory

As scientists were making progress toward understanding the role of cells in plant and animal tissues, others were examining the structures within the cells themselves. In 1831, Scottish botanist Robert Brown (1773–1858) was the first to describe observations of nuclei, which he observed in plant cells. Then, in the early 1880s, German botanist Andreas Schimper (1856–1901) was the first to describe the chloroplasts of plant cells, identifying their role in starch formation during photosynthesis and noting that they divided independent of the nucleus.

Based upon the chloroplasts’ ability to reproduce independently, Russian botanist Konstantin Mereschkowski (1855–1921) suggested in 1905 that chloroplasts may have originated from ancestral photosynthetic bacteria living symbiotically inside a eukaryotic cell. He proposed a similar origin for the nucleus of plant cells. This was the first articulation of the endosymbiotic hypothesis , and would explain how eukaryotic cells evolved from ancestral bacteria.

Mereschkowski’s endosymbiotic hypothesis was furthered by American anatomist Ivan Wallin (1883–1969), who began to experimentally examine the similarities between mitochondria, chloroplasts, and bacteria—in other words, to put the endosymbiotic hypothesis to the test using objective investigation. Wallin published a series of papers in the 1920s supporting the endosymbiotic hypothesis, including a 1926 publication co-authored with Mereschkowski. Wallin claimed he could culture mitochondria outside of their eukaryotic host cells. Many scientists dismissed his cultures of mitochondria as resulting from bacterial contamination. Modern genome sequencing work supports the dissenting scientists by showing that much of the genome of mitochondria had been transferred to the host cell’s nucleus, preventing the mitochondria from being able to live on their own. 10 11

Wallin’s ideas regarding the endosymbiotic hypothesis were largely ignored for the next 50 years because scientists were unaware that these organelles contained their own DNA. However, with the discovery of mitochondrial and chloroplast DNA in the 1960s, the endosymbiotic hypothesis was resurrected. Lynn Margulis (1938–2011), an American geneticist, published her ideas regarding the endosymbiotic hypothesis of the origins of mitochondria and chloroplasts in 1967. 12 In the decade leading up to her publication, advances in microscopy had allowed scientists to differentiate prokaryotic cells from eukaryotic cells. In her publication, Margulis reviewed the literature and argued that the eukaryotic organelles such as mitochondria and chloroplasts are of prokaryotic origin. She presented a growing body of microscopic, genetic, molecular biology, fossil, and geological data to support her claims.

Again, this hypothesis was not initially popular, but mounting genetic evidence due to the advent of DNA sequencing supported the endosymbiotic theory , which is now defined as the theory that mitochondria and chloroplasts arose as a result of prokaryotic cells establishing a symbiotic relationship within a eukaryotic host ( Figure 3.7 ). With Margulis’ initial endosymbiotic theory gaining wide acceptance, she expanded on the theory in her 1981 book Symbiosis in Cell Evolution . In it, she explains how endosymbiosis is a major driving factor in the evolution of organisms. More recent genetic sequencing and phylogenetic analysis show that mitochondrial DNA and chloroplast DNA are highly related to their bacterial counterparts, both in DNA sequence and chromosome structure. However, mitochondrial DNA and chloroplast DNA are reduced compared with nuclear DNA because many of the genes have moved from the organelles into the host cell’s nucleus. Additionally, mitochondrial and chloroplast ribosomes are structurally similar to bacterial ribosomes, rather than to the eukaryotic ribosomes of their hosts. Last, the binary fission of these organelles strongly resembles the binary fission of bacteria, as compared with mitosis performed by eukaryotic cells. Since Margulis’ original proposal, scientists have observed several examples of bacterial endosymbionts in modern-day eukaryotic cells. Examples include the endosymbiotic bacteria found within the guts of certain insects, such as cockroaches, 13 and photosynthetic bacteria-like organelles found in protists. 14

• What does the modern endosymbiotic theory state?
• What evidence supports the endosymbiotic theory?

The Germ Theory of Disease

Prior to the discovery of microbes during the 17th century, other theories circulated about the origins of disease. For example, the ancient Greeks proposed the miasma theory , which held that disease originated from particles emanating from decomposing matter, such as that in sewage or cesspits. Such particles infected humans in close proximity to the rotting material. Diseases including the Black Death, which ravaged Europe’s population during the Middle Ages, were thought to have originated in this way. In the 11th Century, Persian physician Ibn Sina (sometimes referred to as Avicenna) proposed that tuberculosis was likely spread by people's breath when in close proximity. Arab physician Ibn Zuhr, writing in about 1155, documented that the common skin condition scabies was caused by tiny mites that bored into the skin. Though scabies mites are about half a millimeter long (and therefore not technically microscopic) and their skin tunnels are often visible, Ibn Zuhr 's discovery gave more evidence that unseen substances or creatures caused diseases.

In 1546, Italian physician Girolamo Fracastoro proposed, in his essay De Contagione et Contagiosis Morbis , that seed-like spores may be transferred between individuals through direct contact, exposure to contaminated clothing, or through the air. We now recognize Fracastoro as an early proponent of the germ theory of disease , which states that diseases may result from microbial infection. However, in the 16th century, Fracastoro’s ideas were not widely accepted and would be largely forgotten until the 19th century.

In 1847, Hungarian obstetrician Ignaz Semmelweis ( Figure 3.8 ) observed that people who gave birth in hospital wards staffed by physicians and medical students were more likely to suffer and die from puerperal fever after childbirth (10%–20% mortality rate) than were people in wards staffed by midwives (1% mortality rate). Semmelweis observed medical students performing autopsies and then subsequently carrying out vaginal examinations on living patients without washing their hands in between. He suspected that the students carried disease from the autopsies to the patients they examined. His suspicions were supported by the untimely death of a friend, a physician who contracted a fatal wound infection after a postmortem examination of a woman who had died of a puerperal infection. The dead physician’s wound had been caused by a scalpel used during the examination, and his subsequent illness and death closely paralleled that of the dead patient.

Although Semmelweis did not know the true cause of puerperal fever, he proposed that physicians were somehow transferring the causative agent to their patients. He suggested that the number of puerperal fever cases could be reduced if physicians and medical students simply washed their hands with chlorinated lime water before and after examining every patient. When this practice was implemented, the maternal mortality rate in people cared for by physicians dropped to the same 1% mortality rate observed among people cared for by midwives. This demonstrated that handwashing was a very effective method for preventing disease transmission. Despite this great success, many discounted Semmelweis’s work at the time, and physicians were slow to adopt the simple procedure of handwashing to prevent infections in their patients because it contradicted established norms for that time period.

Around the same time Semmelweis was promoting handwashing, in 1848, British physician John Snow conducted studies to track the source of cholera outbreaks in London. By tracing the outbreaks to two specific water sources, both of which were contaminated by sewage, Snow ultimately demonstrated that cholera bacteria were transmitted via drinking water. Snow’s work is influential in that it represents the first known epidemiological study, and it resulted in the first known public health response to an epidemic. The work of both Semmelweis and Snow clearly refuted the prevailing miasma theory of the day, showing that disease is not only transmitted through the air but also through contaminated items.

Although the work of Semmelweis and Snow successfully showed the role of sanitation in preventing infectious disease, the cause of disease was not fully understood. The subsequent work of Louis Pasteur , Robert Koch , and Joseph Lister would further substantiate the germ theory of disease.

While studying the causes of beer and wine spoilage in 1856, Pasteur discovered properties of fermentation by microorganisms. He had demonstrated with his swan-neck flask experiments ( Figure 3.4 ) that airborne microbes, not spontaneous generation, were the cause of food spoilage, and he suggested that if microbes were responsible for food spoilage and fermentation, they could also be responsible for causing infection. This was the foundation for the germ theory of disease.

Meanwhile, British surgeon Joseph Lister ( Figure 3.9 ) was trying to determine the causes of postsurgical infections. Many physicians did not give credence to the idea that microbes on their hands, on their clothes, or in the air could infect patients’ surgical wounds, despite the fact that 50% of surgical patients, on average, were dying of postsurgical infections. 15 Lister, however, was familiar with the work of Semmelweis and Pasteur; therefore, he insisted on handwashing and extreme cleanliness during surgery. In 1867, to further decrease the incidence of postsurgical wound infections, Lister began using carbolic acid (phenol) spray disinfectant/antiseptic during surgery. His extremely successful efforts to reduce postsurgical infection caused his techniques to become a standard medical practice.

A few years later, Robert Koch ( Figure 3.9 ) proposed a series of postulates (Koch’s postulates) based on the idea that the cause of a specific disease could be attributed to a specific microbe. Using these postulates, Koch and his colleagues were able to definitively identify the causative pathogens of specific diseases, including anthrax, tuberculosis, and cholera. Koch’s “one microbe, one disease” concept was the culmination of the 19th century’s paradigm shift away from miasma theory and toward the germ theory of disease. Koch’s postulates are discussed more thoroughly in How Pathogens Cause Disease .

• Compare and contrast the miasma theory of disease with the germ theory of disease.
• How did Joseph Lister’s work contribute to the debate between the miasma theory and germ theory and how did this increase the success of medical procedures?

Clinical Focus

After suffering a fever, congestion, cough, and increasing aches and pains for several days, Barbara suspects that she has a case of the flu. She decides to visit the health center at her university. The PA tells Barbara that her symptoms could be due to a range of diseases, such as influenza, bronchitis, pneumonia, or tuberculosis.

During her physical examination, the PA notes that Barbara’s heart rate is slightly elevated. Using a pulse oximeter, a small device that clips on her finger, he finds that Barbara has hypoxemia—a lower-than-normal level of oxygen in the blood. Using a stethoscope, the PA listens for abnormal sounds made by Barbara’s heart, lungs, and digestive system. As Barbara breathes, the PA hears a crackling sound and notes a slight shortness of breath. He collects a sputum sample, noting the greenish color of the mucus, and orders a chest radiograph, which shows a “shadow” in the left lung. All of these signs are suggestive of pneumonia , a condition in which the lungs fill with mucus ( Figure 3.10 ).

• What kinds of infectious agents are known to cause pneumonia?

Jump to the next Clinical Focus box. Go back to the previous Clinical Focus box.

• 5 M. Schultz. “Rudolph Virchow.” Emerging Infectious Diseases 14 no. 9 (2008):1480–1481.
• 6 B. Kisch. “Forgotten Leaders in Modern Medicine, Valentin, Gouby, Remak, Auerbach.” Transactions of the American Philosophical Society 44 (1954):139–317.
• 7 H. Harris. The Birth of the Cell . New Haven, CT: Yale University Press, 2000:133.
• 8 C. Webster (ed.). Biology, Medicine and Society 1840-1940 . Cambridge, UK; Cambridge University Press, 1981:118–119.
• 9 C. Zuchora-Walske. Key Discoveries in Life Science . Minneapolis, MN: Lerner Publishing, 2015:12–13.
• 10 T. Embley, W. Martin. “Eukaryotic Evolution, Changes, and Challenges.” Nature Vol. 440 (2006):623–630.
• 11 O.G. Berg, C.G. Kurland. “Why Mitochondrial Genes Are Most Often Found in Nuclei.” Molecular Biology and Evolution 17 no. 6 (2000):951–961.
• 12 L. Sagan. “On the Origin of Mitosing Cells.” Journal of Theoretical Biology 14 no. 3 (1967):225–274.
• 13 A.E. Douglas. “The Microbial Dimension in Insect Nutritional Ecology.” Functional Ecology 23 (2009):38–47.
• 14 J.M. Jaynes, L.P. Vernon. “The Cyanelle of Cyanophora paradoxa : Almost a Cyanobacterial Chloroplast.” Trends in Biochemical Sciences 7 no. 1 (1982):22–24.
• 15 Alexander, J. Wesley. “The Contributions of Infection Control to a Century of Progress” Annals of Surgery 201:423-428, 1985.

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• Published: May 1999

A unifying concept: the history of cell theory

• Paolo Mazzarello 1  

Nature Cell Biology volume  1 ,  pages E13–E15 ( 1999 ) Cite this article

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After the first observations of life under the microscope, it took two centuries of research before the 'cell theory', the idea that all living things are composed of cells or their products, was formulated. It proved even harder to accept that individual cells also make up nervous tissue.

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A nomenclature consensus for nervous system organoids and assembloids

CAJAL enables analysis and integration of single-cell morphological data using metric geometry

Integrated intracellular organization and its variations in human iPS cells

Kircher, A. Scrutinium Physico-medicum Contagiosae Luis Quae Dicitur Pestis (Bauerianis, Leipzig, 1658).

Google Scholar  

Winsor, M. P. Swammerdam, Jan in Dictionary of Scientific Biography vol. 13 (ed. Gillespie, C.) 168–175 (Scribner, New York, 1980).

Dobell, C. Antony van Leeuwenhoek and His "Little Animals" (Dover, New York, 1960).

Wolpert, L. Curr. Biol. 6 , 225–228 ( 1995).

Article   Google Scholar  

Singer, S. A Short History of Biology (Clarendon, Oxford, 1931 ).

Westfall, R. S. Hooke, Robert in Dictionary of Scientific Biography Vol. 7 (ed. Gillespie, C.) 481–488 (Scribner, New York, 1980).

Mayr, E. The Growth of the Biological Thought (Belknap, Cambridge, MA, 1982).

Spallanzani, L. Opuscoli di Fisica Animale e Vegetabile (Società Tipografica, Modena, 1776).

Pasteur, L. A. Ann. Sci. Nat. (part. zool.) 16 , 5– 98 (1861).

Fontana, F. Traité sur le Vénin de la Vipère sur les Poisons Américains sur le Laurier-cerise et sur Quelques Autres Poisons Végetaux (Firenze, 1781).

Brown, R. Trans. Linnean Soc. Lond. 16 , 685– 742 (1833).

Schleiden, M. J. Arch. Anat. Physiol. Wiss. Med. 13 , 137– 176 (1838).

Schwann, T. Mikroskopische Untersuchungen über die Übereinstimmung in der Struktur und dem Wachstum der Tiere und Pflanzen (Sander'schen Buchhandlung, Berlin, 1839).

Harris, H. The Birth of the Cell (Yale Univ. Press, New Haven, 1998).

Garnier, C. Bibliogr. Anat. 5 , 278–289 (1897).

Benda, C. Arch. Anat. Physiol. 73 , 393–398 (1898).

Golgi, C. Boll. Soc. Med. Chir. Pavia 13 , 3– 16 (1898); partial transl. Geller Lipsky, N. J. Micros. 155 , 3–7 (1989).

Flemming, W. Zellsubstanz, Kern und Zelltheilung (FCW Vogel, Leipzig, 1882).

Deiters, O. F. K. Untersuchungen über Gehirn und Rückenmark des Menschen und der Säugetiere (Braunschweig, Vieweg, 1865).

Kölliker, A. Handbuch der Gewebelehre des Menschen 5th edn (Engelmann, Leipzig, 1867).

Shepherd, G. M. Foundations of the Neuron Doctrine (Oxford Univ. Press, New York, 1991).

Mazzarello, P. La Struttura Nascosta. La Vita di Camillo Golgi (Cisalpino–Monduzzi, Bologna, 1996); transl. Buchtel, H. & Badiani, A. The Hidden Structure. The Life of Camillo Golgi. (Oxford Univ. Press, Oxford, in the press).

His, W. Abhandl. Math. Phys. Class. Konigl. Sach. Gesell. Wissench. Leipzig 13 , 147–209 (1897).

His, W. Abhandl. Math. Phys. Class. Konigl. Sach. Gesell. Wissench. Leipzig 13 , 477–513 (1897).

Forel, A. Arch. Psych. 18 , 162–198 (1887).

Waldeyer-Hartz, H. W. G. Deutsch. Med. Wochensch. 17 , 1352– 1356 (1891).

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Theodor Schwann (1810-1882)

Theodor Schwann was born in Neuss, Germany. He studied medicine in Berlin, and after graduation went on to do an assistantship in anatomy. In 1838, Schwann and Matthias Jakob Schleiden (1804-1881) developed the "cell theory." Schwann went on and published his monograph Microscopic Researches into Accordance in the Structure and Growth of Animals and Plants in 1839. In the monograph, Schwann identified the common features of all cells - plants and animals, and he illustrated many different cell types. Although Schwann did change the definition of cell by stressing the internal cellular components, he believed incorrectly that cells could arise from assembly of cellular fluids. In 1839, Schwann was appointed Professor of Anatomy at the University of Louvain. In 1848 he moved to Li�ge where he taught physiology and comparative anatomy.

• Description

Theodor Schwann redefined the cell as a living unit.

theodor schwann, matthias jakob schleiden, cell theory, comparative anatomy, animals and plants, cellular components, monograph,

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Cell Theory

Our understanding of cells dates back to the discovery of the microscope, which led to the formulation of the cell theory.

Cell Theory in Timeline

• Cell discovery began in the 1600s when a Dutch shopkeeper, Antony van Leeuwenhoek , discovered simple lenses and used them to visualize single-celled organisms, which he collectively termed ‘animalcules.’
• The discovery of a compound optical microscope by Hans and Zacharias Janssen in 1590 made it even easier to observe and study cells.
• In 1665, an English scientist, Robert Hooke , observed a thin slice of cork under a microscope and published his observation in the book ‘Micrographia.’ He noticed small, box-like structures resembling the cells of a monastery and coined the term ‘cell.’ However, Hooke’s observations were limited to dead plant material, and he could not fully comprehend the significance of what he had seen.
• In the early 19th century, Matthias Schleiden , a German botanist, studied plant tissues and proposed that all plants are composed of cells. He postulated that cells were the fundamental building blocks of plants, responsible for their growth and development. Schleiden’s work laid the foundation for the idea that cells play a vital role in the structure and function of living organisms.
• Around the same time, Theodor Schwann , a German physiologist, conducted extensive studies on animal tissues. He observed that animal tissues were also composed of cells, similar to what Schleiden had discovered in plants. Schwann concluded that all living organisms, plants, and animals, were made up of cells. This realization was a crucial step toward the formulation of the cell theory.

The image below shows a detailed timeline that led to the discovery of cell and the cell theory:

The Three Parts of the Cell Theory

According to the conclusions made by Schleiden and Schwann in 1838, it was proposed that:

• All living things are composed of one or more cells.
• The cell is the structural and functional unit of all living things.

However, Schleiden’s theory of spontaneous cell formation was later disapproved by Rudolf Virchow in 1855. He instead stated, ‘Omnis cellula e cellula,’ meaning ‘All cells only arise from pre-existing cells.’ which is included as the third part of the cell theory.

Thus, combining the contributions of Schleiden, Schwann, and Virchow, the traditional cell theory has three tenets. It states that:

• All organisms are composed of one or more cells
• The cell is the structural and functional unit of all living things
• All cells only arise from pre-existing cells

Modern Cell Theory

Since the formation of classical cell theory, further studies on cells with the advancement of microscope have led to the formation of the modern cell theory, which has three main additions:

• Genetic material (DNA) is passed on from one cell to another during cell division
• All cells have the same basic chemical composition
• Energy flow occurs within cells

Why is the Cell Theory Important

Cell theory transformed scientists’ understanding of living organisms’ makeup, providing a unifying framework for studying the different life forms. Its significance lies in its ability to guide research, enable medical advancements, shed light on evolutionary relationships, drive biotechnological innovations, and contribute to ecological and environmental studies.

The cell theory has transformed our understanding of biology by recognizing the cell as the fundamental unit of life. It continues to shape scientific progress in numerous fields.

• Cell Theory – Nationalgeographic.org
• Cell Theory: A Core Principle of Biology – Thoughtco.com
• Studying Cells – Cell Theory – Bio.libretexts.org
• Cell Theory – Sciencedirect.com
• Cell Theory, Specificity, and Reproduction, 1837–1870 – Ncbi.nlm.nih.gov
• History of Cell Biology – Bitesizebio.com

Article was last reviewed on Thursday, July 27, 2023

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Cell theory.

1. Cell Theory

Close your eyes and picture a brick wall. What is the wall's basic building block? It is a single brick. Like a brick wall, cells are the building blocks that make up your body.

Your body has many kinds of cells, each specialized for a specific purpose. Just as we use a variety of materials to build a home, the human body is constructed from many cell types.

Each of these cell types plays a vital role during the body's growth, development, and day-to-day maintenance. Despite their enormous variety, however, cells from all organisms—even ones as diverse as bacteria, onion, and human—share certain fundamental characteristics.

The discovery of cells involved several individuals over many years. In the 1600s, Dutch shopkeeper Antony van Leeuwenhoek used a microscope (an instrument used to view very small objects) to observe the movements of single-celled organisms, which he collectively termed “animalcules.” In the 1665 publication Micrographia , experimental scientist Robert Hooke coined the term “cell” for the box-like structures he observed when viewing cork tissue through a lens. In the 1670s, van Leeuwenhoek discovered bacteria and protozoa. Later advances in lenses, microscope construction, and microscopy techniques enabled other scientists to see some components inside cells.

By the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory , which states that one or more cells comprise all living things, the cell is the basic unit of life, and new cells arise from existing cells. Rudolf Virchow later also made important contributions to this theory.

Recall that a scientific theory is a scientific explanation for something that has been thoroughly tested. The cell theory resulted from the work of several scientists who came up with these three points that they believed explain the characteristics of cells through various types of testing, experiments, and observations.

term to know Cell Theory A theory that states all living things are made of cells, cells are the smallest unit of life, and all cells come from preexisting cells.

2. Basic Characteristics of All Cells

Asset Name: HB52

• A plasma membrane (also called the cell membrane), which encloses all of the cell parts. It is the membrane that surrounds the outer body of the cell and controls what can enter and exit the cell;
• Cytoplasm , which is the jelly-like fluid that supports the contents of the cell and is found between the plasma membrane and the nucleus;
• DNA , which is the genetic material of the cell. All cells contain some sort of genetic information that allows the cell to function and reproduce;
• Ribosomes , which are organelles that synthesize proteins.

terms to know Plasma Membrane The membrane that surrounds the outer body of the cell and controls what can enter and exit the cell. Also called, cell membrane . Cytoplasm The jelly-like fluid that supports the contents of the cell—found between the plasma membrane and the nuclear envelope. DNA A large molecule that contains all of an organism's genetic information. Ribosome A cell organelle responsible for synthesizing proteins.

3. Eukaryotic and Prokaryotic Cells

Cells fall into one of two broad categories: prokaryotic and eukaryotic. We classify only the predominantly single-celled organisms Bacteria and Archaea as prokaryotes (pro- = “before”; -kary- = “nucleus”). Animal cells, plants, fungi, and protists are all eukaryotes (eu- = “true”).

Eukaryotic cells are cells where the DNA is contained in a nucleus. Our body cells are considered eukaryotic because they all contain a nucleus.

Another characteristic of eukaryotic cells is that they, like all cells, have a plasma membrane. This is the outer layer of the cell that encloses all of the cell organelles . The organelles in a eukaryotic cell are contained within a membrane and are referred to as membrane bound.

The plasma membrane of our cells is made up of a lipid bilayer, which is composed of two layers of phospholipids. That lipid bilayer is what makes up the plasma membrane of your cells and helps to control what goes into and what can come out of the cell. All the free space within the cell is the cytoplasm.

Generally, eukaryotic cells are more complex than prokaryotic cells and they contain more organelles (for example, mitochondria, ribosomes, endoplasmic reticulum, and the Golgi apparatus).

Prokaryotic cells do contain DNA, as all cells contain DNA. However, the difference between a prokaryotic cell and a eukaryotic cell is that in a prokaryotic cell, the DNA is not contained within a nucleus. It still has the plasma membrane, which is the outer layer of the cell, and it still has cytoplasm. You'll notice in the prokaryotic cell that there are some ribosomes as well, which help to make proteins for the cell.

Overall, prokaryotic cells are a little bit less complex than eukaryotic cells and generally smaller in size.

Asset Name: HB54

terms to know Eukaryotic Cells Type of cell that holds all of its genetic information (DNA) inside of a membrane-bound nucleus. Organelle A small, organized structure within a cell. A ribosome is an organelle found within both prokaryotic and eukaryotic cells; a nucleus is an organelle found within eukaryotic cells, but not prokaryotic cells. Prokaryotic Cells Type of cell that does not contain a nucleus.

summary In this lesson, you learned about the basic elements of cell theory , which states that all things are made of cells, cells are the smallest unit of life, and all cells come from preexisting cells. You then explored the basic characteristics of all cells , and learned that all cells have a plasma membrane, DNA, and cytoplasm. Finally, you examined the similarities and differences between eukaryotic and prokaryotic cells , including that eukaryotic cells are generally bigger and more complex than prokaryotic cells and have membrane-bound organelles, including DNA contained in a nucleus.

A theory that states all living things are made of cells, cells are the smallest unit of life, and all cells come from preexisting cells.

The jelly-like fluid that supports the contents of the cell—found between the plasma membrane and the nuclear envelope.

A large molecule that contains all of an organism's genetic information.

Type of cell that holds all of its genetic information (DNA) inside of a membrane-bound nucleus.

A small, organized structure within a cell. A ribosome is an organelle found within both prokaryotic and eukaryotic cells; a nucleus is an organelle found within eukaryotic cells, but not prokaryotic cells.

The membrane that surrounds the outer body of the cell and controls what can enter and exit the cell. Also called, cell membrane .

Type of cell that does not contain a nucleus.

A cell organelle responsible for synthesizing proteins.

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