History of the Cell: Discovering the Cell 1 Yesterday a Q and A simply ran over on a topic that we are star dust. It is nit amply evident from the mystery we are all in. So out of showing the tail, let there not be darkness exposed sirs.
2 Initially discovered by Robert Hooke in 1665, the cell has a rich and interesting history that has ultimately given way to many of today’s scientific advancements. 3 Robert Hook refined the design of the compound microscope around 1665 and published a book titled Micrographia which illustrated his findings using the instrument. 4 Although they are externally very different, internally, an elephant, a sunflower, and an amoeba are all made of the same building blocks. From the single cells that make up the most basic organisms to the trillions of cells that constitute the complex structure of the human body, each and every living being on Earth is comprised of cells. This idea, part of the cell theory, is one of the central tenants of biology. Cell theory also states that cells are the basic functional unit of living organisms and that all cells come from other cells. Although this knowledge is foundational today, scientists did not always know about cells. 5 The discovery of the cell would not have been possible if not for advancements to the microscope. Interested in learning more about the microscopic world, scientist Robert Hooke improved the design of the existing compound microscope in 1665. His microscope used three lenses and a stage light, which illuminated and enlarged the specimens. These advancements allowed Hooke to see something wondrous when he placed a piece of cork under the microscope. Hooke detailed his observations of this tiny and previously unseen world in his book, *Micrographia*. To him, the cork looked as if it was made of tiny pores, which he came to call “cells” because they reminded him of the cells in a monastery. 6 In observing the cork’s cells, Hooke noted in *Micrographia* that, “I could exceedingly plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular… these pores, or cells,…were indeed the first microscopical pores I ever saw, and perhaps, that were ever seen, for I had not met with any Writer or Person, that had made any mention of them before this…” 7 Not long after Hooke’s discovery, Dutch scientist Antonie van Leeuwenhoek detected other hidden, minuscule organisms—bacteria and protozoa. It was unsurprising that van Leeuwenhoek would make such a discovery. He was a master microscope maker and perfected the design of the simple microscope (which only had a single lens), enabling it to magnify an object by around two hundred to three hundred times its original size. What van Leeuwenhoek saw with these microscopes was bacteria and protozoa, but he called these tiny creatures “animalcules.” 8 Van Leeuwenhoek became fascinated. He went on to be the first to observe and describe spermatozoa in 1677. He even took a look at the plaque between his teeth under the microscope. In a letter to the Royal Society, he wrote, "I then most always saw, with great wonder, that in the said matter there were many very little living animalcules, very prettily a-moving.” 9 In the nineteenth century, biologists began taking a closer look at both animal and plant tissues, perfecting cell theory. Scientists could readily tell that plants were completely made up of cells due to their cell wall. However, this was not so obvious for animal cells, which lack a cell wall. Many scientists believed that animals were made of “globules.” 10 German scientists Theodore Schwann and Mattias Schleiden studied cells of animals and plants respectively. These scientists identified key differences between the two cell types and put forth the idea that cells were the fundamental units of both plants and animals. 11 However, Schwann and Schleiden misunderstood how cells grow. Schleiden believed that cells were “seeded” by the nucleus and grew from there. Similarly, Schwann claimed that animal cells “crystalized” from the material between other cells. Eventually, other scientists began to uncover the truth. Another piece of the cell theory puzzle was identified by Rudolf Virchow in 1855, who stated that all cells are generated by existing cells. 12 At the turn of the century, attention began to shift toward cytogenetics, which aimed to link the study of cells to the study of genetics. In the 1880s, Walter Sutton and Theodor Boveri were responsible for identifying the chromosome as the hub for heredity—forever linking genetics and cytology. Later discoveries further confirmed and solidified the role of the cell in heredity, such as James Watson and Francis Crick’s studies on the structure of DNA. 13 The discovery of the cell continued to impact science one hundred years later, with the discovery of stem cells, the undifferentiated cells that have yet to develop into more specialized cells. Scientists began deriving embryonic stem cells from mice in the 1980s, and in 1998, James Thomson isolated human embryonic stem cells and developed cell lines. His work was then published in an article in the journal *Science*. It was later discovered that adult tissues, usually skin, could be reprogrammed into stem cells and then form other cell types. These cells are known as induced pluripotent stem cells. Stem cells are now used to treat many conditions such as Alzheimer’s and heart disease. 14 The discovery of the cell has had a far greater impact on science than Hooke could have ever dreamed in 1665. In addition to giving us a fundamental understanding of the building blocks of all living organisms, the discovery of the cell has led to advances in medical technology and treatment. Today, scientists are working on personalized medicine, which would allow us to grow stem cells from our very own cells and then use them to understand disease processes. All of this and more grew from a single observation of the cell in a cork. [NATIONAL GEOGRAPHIC] 15 Cells are considered the basic units of life in part because they come in discrete and easily recognizable packages. That's because all cells are surrounded by a structure called the *cell membrane* — which, much like the walls of a house, serves as a clear boundary between the cell's internal and external environments. The cell membrane is sometimes also referred to as the *plasma membrane*. 16 Cell membranes are based on a framework of fat-based molecules called *phospholipids*, which physically prevent water-loving, or hydrophilic, substances from entering or escaping the cell. These membranes are also studded with proteins that serve various functions. Some of these proteins act as gatekeepers, determining what substances can and cannot cross the membrane. Others function as markers, identifying the cell as part of the same organism or as foreign. Still others work like fasteners, binding cells together so they can function as a unit. Yet other membrane proteins serve as communicators, sending and receiving signals from neighboring cells and the environment — whether friendly or alarming (Figure 1). 17 Within this membrane, a cell's interior environment is water based. Called *cytoplasm*, this liquid environment is packed full of cellular machinery and structural elements. In fact, the concentrations of proteins inside a cell far outnumber those on the outside — whether the outside is ocean water (as in the case of a single-celled alga) or blood serum (as in the case of a red blood cell). Although cell membranes form natural barriers in watery environments, a cell must nonetheless expend quite a bit of energy to maintain the high concentrations of intracellular constituents necessary for its survival. Indeed, cells may use as much as 30 percent of their energy just to maintain the composition of their cytoplasm. 18 What Other Components Do Cells Have? As previously mentioned, a cell's cytoplasm is home to numerous functional and structural elements. These elements exist in the form of molecules and organelles — picture them as the tools, appliances, and inner rooms of the cell. Major classes of intracellular organic molecules include nucleic acids, proteins, carbohydrates, and lipids, all of which are essential to the cell's functions. *19 Nucleic acids* are the molecules that contain and help express a cell's genetic code. There are two major classes of nucleic acids: *deoxyribonucleic acid (DNA)* and *ribonucleic acid (RNA)*. DNA is the molecule that contains all of the information required to build and maintain the cell; RNA has several roles associated with expression of the information stored in DNA. Of course, nucleic acids alone aren't responsible for the preservation and expression of genetic material: Cells also use proteins to help replicate the genome and accomplish the profound structural changes that underlie *cell division*. *20 Proteins* are a second type of intracellular organic molecule. These substances are made from chains of smaller molecules called *amino acids*, and they serve a variety of functions in the cell, both *catalytic* and structural. For example, proteins called *enzymes* convert cellular molecules (whether proteins, carbohydrates, lipids, or nucleic acids) into other forms that might help a cell meet its energy needs, build support structures, or pump out wastes. *21 Carbohydrates*, the starches and sugars in cells, are another important type of organic molecule. *Simple carbohydrates* are used for the cell's immediate energy demands, whereas *complex carbohydrates* serve as intracellular energy stores. Complex carbohydrates are also found on a cell's surface, where they play a crucial role in cell recognition. 22 Finally, *lipids* or fat molecules are components of cell membranes — both the plasma membrane and various intracellular membranes. They are also involved in energy storage, as well as relaying signals within cells and from the bloodstream to a cell's interior (Figure 2). 23 Some cells also feature orderly arrangements of molecules called *organelles*. Similar to the rooms in a house, these structures are partitioned off from the rest of a cell's interior by their own intracellular membrane. Organelles contain highly technical equipment required for specific jobs within the cell. One example is the *mitochondrion* — commonly known as the cell's "power plant" — which is the organelle that holds and maintains the machinery involved in energy-producing chemical reactions [image: A pie slice diagram shows the proportion of water to typical chemical components in a bacterial cell. Each chemical component is color-coded and is labeled by name and percent.]Conclusion Cells are the smallest common denominator of life. Some cells are organisms unto themselves; others are part of multicellular organisms. All cells are made from the same major classes of organic molecules: nucleic acids, proteins, carbohydrates, and lipids. In addition, cells can be placed in two major categories as a result of ancient evolutionary events: prokaryotes, with their cytoplasmic genomes, and eukaryotes, with their nuclear-encased genomes and other membrane-bound organelles. Though they are small, cells have evolved into a vast variety of shapes and sizes. Together they form tissues that themselves form organs, and eventually entire organisms. 24 Hence cells are not human. Humans have the value imbibed to the cells. K Rajaram IRS 22 8 23 On Tue, 22 Aug 2023 at 07:20, Markendeya Yeddanapudi < [email protected]> wrote: > > > -- > *Mar*The Ego Shackle > > > > You are not singular. You are a plural of 10,000 trillion interacting > cells, each cell a mini universe and ten times the number of cells > bacteria, all making you the functioning and living you. Emotionally you > are connected to the troposphere and cosmically to the whole universe, via > quantum entanglement. If you can see everything, atoms, particles etc, then > you confront the truth that you are not a static and unchanging ego but an > interacting phenomenon in the universe. You cannot find yourself as that > singular you is non-existent. The relational interactions among the cells > and the bacteria continuously changes, we call it ageing. We are processes > connected to the processes of nature. When you get absorbed into the > general macro processes of nature, it is called death. > > The method of education is feeling and not the Cartesian tracing of causes > and effects. The cause clusters and effect clusters continuously change; > the clusters often mix up, creating many new process flows, in the > invisible spectrum. > > When you adopt the method of feeling for education, then every aspect of > nature becomes very important. You cannot destroy nature and call it > development. > > What all you have to note is that you are actually part of the invisible > Microcosm, and that you are basically abstract. If you adopt altruism as > the basic motivation for living, then automatically you find that nature is > approving you. Nature makes you succeed. The gigantic Microcosm makes you > succeed and what we call miracles take over. You succeed in getting all > your positive wants. But your personal success must synchronize with the > success of nature in its macro march. You have to measure your success in > terms of happiness. If you make nature happy, nature will make you happy. > You don’t need complex mathematics to understand. Happiness is a positive > emotion and no emotion can be quantified. > > Create the flow of happiness in nature. You automatically become happy and > get what you need. > > YM > -- You received this message because you are subscribed to the Google Groups "Thatha_Patty" group. 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