Animation of cell organelles by Drew Berry and Etsuko Uno, wehi.tv Nucleus, cytoskeleton (actin and microtubules), cytoplasm, golgi and vesicles, endoplasmic reticulum, plasma membrane.
This biology video tutorial provides a basic introduction into cell structure. It also discusses the functions of organelles such as the nucleus, ribosomes, mitochondria, chloroplasts, etc.
Here is a list of topics:
1. Introduction to the cell
2. The nucleus - the cell's command center
3. The Nucleolus - production of ribosomes
4. Chromatin & DNA
5. Smooth ER vs Rough ER
6. Lysosomes & Intracellular Digestion
7. The Golgi Body
8. The Mitochondria - Cellular Respiration & ATP
9. The cytoplasm
10. The Cytoskeleton
11. Microtubules, Microfilaments, & Intermediate Filaments
12. Centrioles
13. Cilia & Flagella
14. Animal Cells and Plant Cells
15. Vacuoles - a storage organelle
16. The Chloroplasts - Photosynthesis
17. The Cell Wall of a Plant
18. The Cell Membrane & Selective Permeability
n this video you can quickly and easily learn everything you need to know about the basic animal cell.
The individual cell is the unit of structure of all living things. An entire organism may consist of a single cell which is called Unicellular or many cells which is called Multicellular. In human beings and other multicellular organisms, the cells tend to be organized in specific ways. A group of like cells performing a particular function is referred to as a Tissue. An organ is a discrete structure composed of several different tissues together. Organ = several different tissues together. An organ system is a group of organs together performing an overall function. Ie. integumentary, muscular, skeletal, nervous,circulatory, lymphatic, respiratory, endocrine, urinary/excretory, reproductive and digestive The individual organism is the combination of all of these things as a discrete and separate entity. THE MAJOR COMPONENTS OF A "TYPICAL" ANIMAL CELL. Cell Membrane. The cell membrane surrounds and separates the cell from its environment. The cell membrane allows certain material to pass through it as they enter or leave the cell. Nucleus, Within the cell is the nucleus. The nucleus plays a central role in the cell. Information is stored in the nucleus and distributed to guide the life processes and functions of the cell. Within the nucleus is the chromatin material, made up of a protein DNA. At the time of cell division, this chromatin material is aggregated into individual structures known as chromosomes. Each chromosome has a set of specific genes, basic unit of heredity which are passed from parents to their children, which determine all of the physical and chemical characteristics of the body, which represent its structure and function. The nucleus also contains a nucleolus which is a structure that creates ribosomes. Ribosomes – are granular particles which make protein, they are known as the “protein factories” in the cell. They are composed mainly of nucleic acids which help make the protein needed for many cell functions. They can float freely in the cell or attach to the endoplasmic reticulum. Protoplasm, The major substance of the cell is known as protoplasm. It is a combination of water and a variety of materials dissolved in the water. Outside the cell nucleus, protoplasm is called Cytoplasm. Inside the cell nucleus, protoplasm is called Nucleoplasm. Organelles, Within the cytoplasm, certain structures are called organelles, organelles means Little Organs. These little organs have unique jobs to perform. These organelles include structures such as the: Endoplasmic Reticulum, Various kinds of Vacuoles, Golgi Apparatus, Mitochondria and Centrioles
In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name organelle comes from the idea that these structures are parts of cells, as organs are to the body, hence organelle, the suffix -elle being a diminutive. Organelles are either separately enclosed within their own lipid bilayers (also called membrane-bound organelles) or are spatially distinct functional units without a surrounding lipid bilayer (non-membrane bound organelles). Although most organelles are functional units within cells, some functional units that extend outside of cells are often termed organelles, such ascilia, the flagellum and archaellum, and the trichocyst.
In biology organs are defined as confined functional units within an organism. The analogy of bodily organs to microscopic cellular substructures is obvious, as from even early works, authors of respective textbooks rarely elaborate on the distinction between the two.
In the 1830s, Félix Dujardin refuted Ehrenberg theory which said that microorganisms have the same organs of multicellular animals, only minor.
Credited as the first to use a diminutive of organ (i.e., little organ) for cellular structures was German zoologist Karl August Möbius (1884), who used the term organula (plural of organulum, the diminutive of Latinorganum). In a footnote, which was published as a correction in the next issue of the journal, he justified his suggestion to call organs of unicellular organisms "organella" since they are only differently formed parts of one cell, in contrast to multicellular organs of multicellular organisms.
While most cell biologists consider the term organelle to be synonymous with cell compartment, a space often bound by one or two lipid bilayers, some cell biologists choose to limit the term to include only those cell compartments that contain deoxyribonucleic acid (DNA), having originated from formerly autonomous microscopic organisms acquired via endosymbiosis.
Under this definition, there would only be two broad classes of organelles (i.e. those that contain their own DNA, and have originated from endosymbiotic bacteria):
plastids (e.g. in plants, algae, and some protists).
Other organelles are also suggested to have endosymbiotic origins, but do not contain their own DNA (notably the flagellum – see evolution of flagella).
A second, less restrictive definition of organelles is that they are membrane-bound structures. However, even by using this definition, some parts of the cell that have been shown to be distinct functional units do not qualify as organelles. Therefore, the use of organelle to also refer to non-membrane bound structures such as ribosomes is common and accepted. This has led many texts to delineate between membrane-bound and non-membrane bound organelles. The non-membrane bound organelles, also called large biomolecular complexes, are large assemblies of macromolecules that carry out particular and specialized functions, but they lack membrane boundaries. Many of these are referred to as "proteinaceous organelles" as there many structure is made of proteins. Such cell structures include:
The mechanisms by which such non-membrane bound organelles form and retain their spatial integrity have been likened to liquid-liquid phase separation.
Eukaryotic cells are structurally complex, and by definition are organized, in part, by interior compartments that are themselves enclosed by lipid membranes that resemble the outermost cell membrane. The larger organelles, such as the nucleus and vacuoles, are easily visible with the light microscope. They were among the first biological discoveries made after the invention of the microscope.
Not all eukaryotic cells have each of the organelles listed below. Exceptional organisms have cells that do not include some organelles that might otherwise be considered universal to eukaryotes (such as mitochondria). There are also occasional exceptions to the number of membranes surrounding organelles, listed in the tables below (e.g., some that are listed as double-membrane are sometimes found with single or triple membranes). In addition, the number of individual organelles of each type found in a given cell varies depending upon the function of that cell.
The cell wall is composed of peptidoglycan and is rigid, provides shape to the cell, helps to keeps the organelles inside the cell, and does not let the cell burst due to changes in osmotic pressure.
Mitochondria and plastids, including chloroplasts, have double membranes and their own DNA. According to the endosymbiotic theory, they are believed to have originated from incompletely consumed or invading prokaryotic organisms.
Prokaryotes are not as structurally complex as eukaryotes, and were once thought not to have any internal structures enclosed by lipid membranes. In the past, they were often viewed as having little internal organization, and lack cellular compartments; but slowly, details are emerging about prokaryotic internal structures. An early false turn was the idea developed in the 1970s that bacteria might contain cell membrane folds termed mesosomes, but these were later shown to be artifacts produced by the chemicals used to prepare the cells for electron microscopy.
However, there is increasing evidence of compartmentalization in at least some prokaryotes. Recent research has revealed that at least some prokaryotes have microcompartments, such as carboxysomes. These subcellular compartments are 100–200 nm in diameter and are enclosed by a shell of proteins. Even more striking is the description of membrane-bound magnetosomes in bacteria, reported in 2006.
The bacterial phylum Planctomycetes has revealed a number of compartmentalization features. Planctomycetes have an intracytoplasmic membranes that separates the cytoplasm into paryphoplasm (an outer ribosome-free space) and pirellulosome (or riboplasm, an inner ribosome-containing space). Membrane-bound anammoxosomes have been discovered in five Planctomycetes anammox genera. In the Planctomycetes Gemmata obscuriglobus, a nucleus-like structure surrounded by lipid membranes has been reported.
(A) Electron micrograph of Halothiobacillus neapolitanus cells, arrows highlight carboxysomes. (B) Image of intact carboxysomes isolated from H. neapolitanus. Scale bars are 100 nm.
Study the interdependence of a cell's nucleus, ribosomes, endoplasmic reticulum, and Golgi apparatus
Learn about the different cell organelles, including the mitochondrion, the nucleus, the ribosome, and others.
Organelle, any of the specialized structures within a cell that perform a specific function (e.g., mitochondria, ribosomes, endoplasmic reticulum). Organelles in unicellular organisms are the equivalent of organs in multicellular organisms. The contractile vacuole of protozoans, for example, extracts fluid wastes from the cell and eliminates them from the organism, as does the kidney in larger organisms.
Nucleus
Nucleus
Nucleus; animal cell.
A micrograph of animal cells, showing the nucleus (stained dark red) of each cell.
Known as the cell’s “command center,” the nucleus is a large organelle that stores the cell’s DNA (deoxyribonucleic acid). The nucleus controls all of the cell’s activities, such as growth and metabolism, using the DNA’s genetic information. Within the nucleus is a smaller structure called the nucleolus, which houses the RNA (ribonucleic acid). RNA helps convey the DNA’s orders to the rest of the cell and serves as a template for protein synthesis.
Ribosomes
Ribosomes
Ribosomes are the protein factories of the cell. Composed of two subunits, they can be found floating freely in the cell’s cytoplasm or embedded within the endoplasmic reticulum. Using the templates and instructions provided by two different types of RNA, ribosomes synthesize a variety of proteins that are essential to the survival of the cell.
Endoplasmic reticulum
Endoplasmic reticulum
The endoplasmic reticulum (ER) is a membranous organelle that shares part of its membrane with that of the nucleus. Some portions of the ER, known as the rough ER, are studded with ribosomes and are involved with protein manufacture. The rest of the organelle is referred to as the smooth ER and serves to produce vital lipids (fats).
Golgi apparatus
Golgi apparatus
If the proteins from the rough ER require further modification, they are transported to the Golgi apparatus (or Golgi complex). Like the ER, the Golgi apparatus is composed of folded membranes. It searches the protein’s amino acid sequences for specialized “codes” and modifies them accordingly. These processed proteins are then stored in the Golgi or packed in vesicles to be shipped elsewhere in the cell.
Chloroplasts
Chloroplasts
In plants and some algae, organelles known as chloroplasts serve as the site of photosynthesis. Chloroplasts contain a pigment known as chlorophyll, which captures the sun’s energy to transform water and carbon dioxide into glucose for food. Chloroplasts allow autotrophic organisms to meet their energy needs without consuming other organisms.
Mitochondria
Mitochondria
The “powerhouses” of the cell, mitochondria are oval-shaped organelles found in most eukaryotic cells. As the site of cellular respiration, mitochondria serve to transform molecules such as glucose into an energy molecule known as ATP (adenosine triphosphate). ATP fuels cellular processes by breaking its high-energy chemical bonds. Mitochondria are most plentiful in cells that require significant amounts of energy to function, such as liver and muscle cells.
