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Cell publishes findings of unusual significance in any area of experimental biology, including but not limited to cell biology, molecular biology, neuroscience, immunology, virology and microbiology, cancer, human genetics, systems biology, signaling, and disease mechanisms and therapeutics.
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- The nature and function of cells
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A cell is a mass of cytoplasm that is bound externally by a cell membrane. Usually microscopic in size, cells are the smallest structural units of living matter and compose all living things. Most cells have one or more nuclei and other organelles that carry out a variety of tasks. Some single cells are complete organisms, such as a bacterium or yeast. Others are specialized building blocks of multicellular organisms, such as plants and animals.
What is cell theory?
Cell theory states that the cell is the fundamental structural and functional unit of living matter. In 1839 German physiologist Theodor Schwann and German botanist Matthias Schleiden promulgated that cells are the “elementary particles of organisms” in both plants and animals and recognized that some organisms are unicellular and others multicellular. This theory marked a great conceptual advance in biology and resulted in renewed attention to the living processes that go on in cells.
What do cell membranes do?
The cell membrane surrounds every living cell and delimits the cell from the surrounding environment. It serves as a barrier to keep the contents of the cell in and unwanted substances out. It also functions as a gate to both actively and passively move essential nutrients into the cell and waste products out of it. Certain proteins in the cell membrane are involved with cell-to-cell communication and help the cell to respond to changes in its environment.
cell, in biology, the basic membrane-bound unit that contains the fundamental molecules of life and of which all living things are composed. A single cell is often a complete organism in itself, such as a bacterium or yeast. Other cells acquire specialized functions as they mature. These cells cooperate with other specialized cells and become the building blocks of large multicellular organisms, such as humans and other animals. Although cells are much larger than atoms, they are still very small. The smallest known cells are a group of tiny bacteria called mycoplasmas; some of these single-celled organisms are spheres as small as 0.2 μm in diameter (1μm = about 0.000039 inch), with a total mass of 10−14 gram—equal to that of 8,000,000,000 hydrogen atoms. Cells of humans typically have a mass 400,000 times larger than the mass of a single mycoplasma bacterium, but even human cells are only about 20 μm across. It would require a sheet of about 10,000 human cells to cover the head of a pin, and each human organism is composed of more than 30,000,000,000,000 cells.
A cell is enclosed by a plasma membrane, which forms a selective barrier that allows nutrients to enter and waste products to leave. The interior of the cell is organized into many specialized compartments, or organelles, each surrounded by a separate membrane. One major organelle, the nucleus, contains the genetic information necessary for cell growth and reproduction. Each cell contains only one nucleus, whereas other types of organelles are present in multiple copies in the cellular contents, or cytoplasm. Organelles include mitochondria, which are responsible for the energy transactions necessary for cell survival; lysosomes, which digest unwanted materials within the cell; and the endoplasmic reticulum and the Golgi apparatus, which play important roles in the internal organization of the cell by synthesizing selected molecules and then processing, sorting, and directing them to their proper locations. In addition, plant cells contain chloroplasts, which are responsible for photosynthesis, whereby the energy of sunlight is used to convert molecules of carbon dioxide (CO2) and water (H2O) into carbohydrates. Between all these organelles is the space in the cytoplasm called the cytosol. The cytosol contains an organized framework of fibrous molecules that constitute the cytoskeleton, which gives a cell its shape, enables organelles to move within the cell, and provides a mechanism by which the cell itself can move. The cytosol also contains more than 10,000 different kinds of molecules that are involved in cellular biosynthesis, the process of making large biological molecules from small ones.
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Specialized organelles are a characteristic of cells of organisms known as eukaryotes. In contrast, cells of organisms known as prokaryotes do not contain organelles and are generally smaller than eukaryotic cells. However, all cells share strong similarities in biochemical function.
Cells contain a special collection of molecules that are enclosed by a membrane. These molecules give cells the ability to grow and reproduce. The overall process of cellular reproduction occurs in two steps: cell growth and cell division. During cell growth, the cell ingests certain molecules from its surroundings by selectively carrying them through its cell membrane. Once inside the cell, these molecules are subjected to the action of highly specialized, large, elaborately folded molecules called enzymes. Enzymes act as catalysts by binding to ingested molecules and regulating the rate at which they are chemically altered. These chemical alterations make the molecules more useful to the cell. Unlike the ingested molecules, catalysts are not chemically altered themselves during the reaction, allowing one catalyst to regulate a specific chemical reaction in many molecules.
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Biological catalysts create chains of reactions. In other words, a molecule chemically transformed by one catalyst serves as the starting material, or substrate, of a second catalyst and so on. In this way, catalysts use the small molecules brought into the cell from the outside environment to create increasingly complex reaction products. These products are used for cell growth and the replication of genetic material. Once the genetic material has been copied and there are sufficient molecules to support cell division, the cell divides to create two daughter cells. Through many such cycles of cell growth and division, each parent cell can give rise to millions of daughter cells, in the process converting large amounts of inanimate matter into biologically active molecules.
Learn about the basic unit of life, the cell, and its structure, functions, and diversity. Explore the similarities and differences between animal cells, plant cells, and bacterial cells, and the organelles, molecules, and processes that make them function.
The cell is the basic structural and functional unit of all forms of life. Every cell consists of cytoplasm enclosed within a membrane; many cells contain organelles, each with a specific function. The term comes from the Latin word cellula meaning 'small room'. Most cells are only visible under a microscope.
Learn about the history and theory of cells, the basic units of life. Explore the diversity and functions of different types of cells, and how they are observed and studied.
- What is the main function of a typical cell in the human body?Cellular biology is a pretty in depth field, but cells basically break down sugars into usable energy, they regulate growth through cellular divisi...
- in the second paragraph, when you cut a cell in half, what do you see, and are any cells the same?When cut a cell in half you will see a cell membrane, cell wall (in some cells), cytoplasm- the jelly-like substance in the cell, mitochondria- the...
- Is it actually possible to cut a cell in half (as mentioned in the second introductory paragraph)? I...they use staining agents do dye the cell. Staining agents include Methyl Blue and Safrannin
- how many cells is an egg made of?When you say that, do you mean it in an "embryonic egg, inside of the womb" context or an egg that has been laid?
- Does number of the cells in our body always remain the same ?Not really: cells continuously die and split so that they keep getting destroyed but the body replaces them too. Also, children have fewer cells th...
- Are cells in the human body more reliant on other cells than unicellular organisms?We are looking at it on a different scale. An unicellular organism does not even have 'other cells to be reliant on' since it is unicellular. In a...
- how would that first cell survive?Most likely because of the lack of competition. If you were the only organism alive, with lots of resources around you, why wouldn't you be able to...
- are cells made out of cellsLol that's not possible! Cells are instead made out of various biomolecules and cell organelles, which are made out of various other molecules bond...
Cells are the basic units of life, with common features and functions that vary by size, shape, and function. Explore the composition, structure, and diversity of cells, and how they adapt to different environments and roles.
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Apr 28, 2017 · Learn about the basic unit of life, cells, and their characteristics, functions, and types. Compare prokaryotes and eukaryotes, and see examples of archaebacteria, bacteria, and plant cells.
Learn about the basic structure and functions of cells, the most fundamental units of life. Watch a video, read a transcript, and explore questions and comments from other learners.
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- Sal Khan
