Biology Cellular Organelles
Terms
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- Prokaryotic cells
- The procaryotic cell has no well defined nucleus or organelles. Its genetic material is concentrated in the cytosol or cytoplasmic region, but is not seperated from the rest of the cell by a membrane
- Eukaryotic cells
- In contrast to prokaryotic cells, eukaryotic cells have a well defined, membrane bound nucleus. Eukaryotic cells also have numerous membrane bound organelles. In other words, the nuclear (genetic) material is enclosed by a nuclear membrane.
- Cytoplasm
- the entire region between the nucleuss and the membrane bounding the cell, the cell membrane/plasma membrane. It consists of a semifluid medium called the cytosol, in which are located organelles of a specialized form an function, and most of them are absent from prokaryotic cells.
- Cell membrane
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Structure: a double layer (bilayer) of phospholopids. Embedded in this lipid bilayer or attached to its surfaces are diverse proteins; (a) integral : embedded in the lipid bilayer(b) peripheral: attached to the surface Cholesterol and unsaturated hydrocarbon tails in the phospholipids affect the membrane fluidity.
Function: The cell membrane is selectively semipermeable and regulates what gets into and what leaves the cell. Each membrane has a unique composition of lipids and proteins that are suited to the membrane's function(s), which include transport, enzymatic activity, signal transduction, intercellular joining, cell-cell recognition, and attachment to the cytoskeleton and extracellular matrix (ECM). - Nucleus
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Structure: Double-membrane bound structure that contains most of the genes that controlof the eukaryotic cell. The membrane seperates the nucleus and its genetic material from the cytosol. Genetic material most commonly in the long-thin form; chromatin.
Function: To regulate and control cellular activities. - Nuclear Membrane
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Structure: A double-Membrane, each a lipid bilayer with associated embedded proteins. Covered with nuclear pores, openings that allowing materials into the nucleus, as well as for allowing materials to pass out of the nucleus.
Function: To contain and support the nuceoplasm (nuclear sap) and to act as a barrier that seperates the nuclear material from the cytosol. - Nucleolus
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Structure: A roughly spherical mass of densely stained granules and fibers which are attached to part of the chromatin. Sometimes more than one in a cell; found only in non-dividing cells
Function: Site of ribosome synthesis. the ribosomes are synthesized and assembled here and then pass through the nuclear pores. Also the site of RNA synthesis. - Ribosomes
- Structure: Made up of two subunits, one large and one small, which are constructed from protein and RNA. In eukaryotes, these subunits are constructed in the Nucleolus. Two types of ribosomes; free and bbound ; free ribosomes are suspended in the cytosol and bound ribosomes are attached to the outside of the endoplasmic reticulum.
- EndoPlasmic Reticulum
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Structure: A membaneous maze so extensive that it accounts for more than half of the total membrane of eukaryotic cells. Consists of a nR seperates its internal space, the cisternal space, from the cytosol. The ER is continuous with the nuclear membrane. There are two distinct, though connected, regions of ER that differ in ribosomes whereas rough ER appears rough through the electron microscope because of its attached Robosomes.
Function: Both smooth and rough ER perform important functions, the most important of which are protein synthesis in rough ER and the transport of intracellular products and enzymes by the smooth ER - Golgi Apparatus/Complex
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Structure: A series of flattened membraneous sacs, cisternae, that look like a stack of pancakes. A cell may have several of these Stacks.
Function:The golgi apparatus serves as a manufacturing, warehousing, sorting and shipping site for intracellular products. It is here that the products of the ER are modified, stored then sent ot other destinations. Theu are especially extensive in cells specialized for secretion. - Lysosome
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Structure: A membrane bound sac of hydrophilic enzymes that the cell uses to digest marcomolecules. There are lysosomal enzymes that hydrolyze proteins, polysaccharides, fats and nucleic acids - all themajor types of macromolecules. These enzymes work best in an acidic environment, at about pH5.
Function: To destroy varous cellular organelles that have outlived their usefulness as well as to destroy and digest material ingested via endocytosis. Lysosomes are also responsible for the autodigestion of cells if, for reasons still not understood, enough of the various types of enzymes are released.