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From Wikipedia

Organelle

In cell biology, an organelle (ɔrɡəˈnɛl) is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer.

The name organelle comes from the idea that these structures are to cells what an organ is to the body (hence the name organelle, the suffix -elle being a diminutive). Organelles are identified by microscopy, and can also be purified by cell fractionation. There are many types of organelles, particularly in eukaryotic cells. Prokaryotes were once thought not to have organelles, but some examples have now been identified.

History and terminology

In biology, organsare defined as confined functional units within anorganism. 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.

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 form of organulum, the diminutive of latinorganum). From the context, it is clear that he referred to reproduction related structures of protists. 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. Thus, the original definition was limited to structures of unicellular organisms.

It would take several years before organulum, or the later term organelle, became accepted and expanded in meaning to include subcellular structures in multicellular organisms. Books around 1900 from Valentin Häcker, Edmund Wilson and Oscar Hertwig still referred to cellular organs. Later, both terms came to be used side by side: Bengt Lidforss wrote 1915 (in German) about "Organs or Organells".

Around 1920, the term organelle was used to describe propulsion structures ("motor organelle complex", i.e., flagella and their anchoring) and other protist structures, such as ciliates. Alfred Kühn wrote about centrioles as division organelles, although he stated that, for Vahlkampfias, the alternative 'organelle' or 'product of structural build-up' had not yet been decided, without explaining the difference between the alternatives.

In his 1953 textbook, Max Hartmann used the term for extracellular (pellicula, shells, cell walls) and intracellular skeletons of protists.

Later, the now-widely-used definition of organelle emerged, after which only cellular structures with surrounding membrane had been considered organelles. However, the more original definition of subcellular functional unit in general still coexists.

In 1978, Albert Frey-Wyssling suggested that the term organelle should refer only to structures that convert energy, such as centrosomes, ribosomes, and nucleoli. This new definition, however, did not win wide recognition.

Examples

While most cell biologists consider the term organelle to be synonymous with "cell compartment", other cell biologists choose to limit the term organelle to include only those that are DNA-containing, having originated from formerly-autonomous microscopic organisms acquired via endosymbiosis.

The most notable of these organelles having originated from endosymbiontbacteria are:

Other organelles are also suggested to have endosymbiotic origins, (notably the flagellum - see evolution of flagella).

Under the more restricted definition of membrane-bound structures, some parts of the cell do not qualify as organelles. Nevertheless, the use of organelle to refer to non-membrane bound structures such as ribosomes is common. This has led some texts to delineate between membrane-bound and non-membrane bound organelles. These structures are large assemblies of macromolecules that carry out particular and specialized functions, but they lack membrane boundaries. Such cell structures include:

Eukaryotic organelles

Eukaryotes are one of the structurally complex cell type, and by definition are in part organized by smaller interior compartments, that are themselves enclosed by lipid membranes that resemble the outermost cell membrane. The larger organelles, such as


From Yahoo Answers

Question:

Answers:Lysosomes are organelles that carry the cell's digestive enzymes. Lysosomes have to be membrane bound. This is because of the enzymes. The digestive enzymes in the cell break down and "recycle" the unneeded materials in the cell. If the enzymes were allowed to float freely within the cytoplasm, the digestive enzymes would "break down" and recycle the entire cell- they're that strong. When the lysosomes are membrane bound, they can only break down something that comes into it. This protects the cell from being digested by their own enzymes.

Question:On my science homework, there is a riddle that goes: Since I contain many enzymes, I can digest an injured cell; And can break down a large molecule Into a smaller one as well. Help , please ! (:

Answers:The Lysosome!

Question:Name 5 organelles contained in animal cells and their function

Answers:the cell membrane: - cell-cell recognition - separate cyctoplasm from outside enviroment - absorbtion of ions - maintain different conc of ions in and out of the cell by diffusion, facilitated diffusion, osmosis, endocytosis and active transport. - prevent viruses and bacteria from entering cell - enables phagocytosis (cell "eating") and pinocytosis (cell "drinking") - allows disposal of waste material (when secretory vesicles fuse with membrane to secrete material) - attaches cell to other cells through desosomes, gap junctions, and tight junctions - Increase surface area for exchange of substances using microvilli golgi body or golgi apparatus: - receives protiens from endoplasmic reticulum at the 'cis' face - packages and modifies proteins for export froom the 'trans' face - synthesis of secretory polysaccharides - formation of lysosomes - addition of material to cell membrane (enlargement) Lysosomes: - digestion of ingested particles (taken in by endocytosis) - disposal of defunct or surplus organelles (autophagy) - cell death (autolysis) Endoplasmic Reticulum: - provide large surface area for chemical reactions - form intracellular transport system - post-translational modifications of proteins synthesised at the ribosomes - synthesis of lipids and steroids - detoxication - storage and release of calcium ions Mitochondria - synthesis of ATP (Adenosine triphosphate) - Heat production (55% of energy released from the reactions in the mitochondria is given off as heat) Hope i helped you. that's to my knowledge, i'm a bio student =))

Question:Ok I really suck at this sort of thing could you please help me out? 1 Organelles found only in animals cells, which move chromosomes apart during mitosis and meiosis: 2 Sites of protein synthesis: 3 Site of transcription of RNA and assembly of ribosomes: 4 A selectively permeable membrane that controls absorption or release of substances in and out of the cell: 5 The 'powerhouse' of the cell responsible for energy production: 6 The digestive organelles, which produce enzymes to aid disposal of foreign bodies. 7 Greatly expanded surface area for biochemical reactions: 8: Thick cellulose structure that gives strength and rigidity to plant fells: 9 Production site of cellular secretions: 10 Sacks that act as storage depots for water, waste products 11 Contains the DNA Any and all help appreciated! Thanks in advance!

Answers:1. Centrosome 2. Ribosome 3. Rough Endoplasmic Reticulum 4. Plasma Membrane 5. Mitochondria 6. Lysosome 7. Smooth Endoplasmic Reticulum 8. Cell Wall 9. Golgi Apparatus (and Secretory Vacuoles) 10. Vacuole 11. Nucleus

From Youtube

Digestive Enzymes, Nutrition and Your Health :Nutrition by Natalie Information about Digestive Enzymes Digestive Enzymes are enzymes that specifically work in the digestive system to facilitate the digestion, absorption, and transportation of nutrients. They also work to promote timely elimination of digestive waste products that are not of use to the body. Without enzymes, our cells would not get adequate nutrition and we would not survive. Enzymes function as catalysts to enhance and dramatically speed up biochemical reactions that occur in every one of our cells. They are only activated in water, so staying hydrated is very important for enzymes to work effectively. Enzymes must be present to ensure proper digestion of nutrients, energy production, metabolism, transportation of fluid to cells, and elimination of toxins among many other functions. Enzymes exist in foods to help our body's breakdown what we eat. Raw, uncooked foods are the only foods that contain enzymes. Since the majority of our diets are cooked foods, we significantly limit the enzymes available in our food for digestion, thus putting more stress on our digestive systems. Some supplemental enzymes should be taken with food to enhance digestion and absorption of nutrients, whereas other supplemental enzymes should be taken on an empty stomach to support circulation, decrease inflammation, support our immune systems and combat stress. Imbalances in these factors have been scientifically proven to be associated with or the cause of numerous diseases ...

Enzymes for Digestion and Health Part 2 :www.takebackyourhealth.com What Enzymes Do Enzymes are complex protein molecules that are found in every cell in your body. Enzymes can become activated, and are capable of specific tasks such as, the production of energy or exchange of oxygen, and carbon dioxide, when we breathe. They are able to transfer energy to other molecules, making it easier for them to be produced, and utilized by the body, creating a domino effect, and therefore, speeds up all bodily functions. Our body contains 1300 different enzymes that break down nutrients, rebuild cells, and cause the body to function disease-free. The digestive system transforms food into energy for the body's use by breaking down complex proteins, fats and carbohydrates into smaller, simpler, and more usable forms. Without this transformation, digestion and assimilation of nutrients is difficult to impossible. Your health is more overtaxed, and abused by excesses of processed foods, and stimulants baked flour, dairy, and, caffeine, soft drinks, sugar, and alcohol. Digestion begins with the sight and smell of food that stimulates the secretion of enzymes. The tasting and chewing allows saturation of the salivary enzyme, amylase, which breaks down the starch to glucose when chewing potato or bread. The pH drops to an acid range as low as four or five. The upper portion of the stomach called the fundus continues to use amylase and other enzymes for predigestion. The stomach contents are then passed through the pyloric valve ...