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Cell Organelles
Cell Organelles
23
Biology
12th Grade
11/12/2008

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Term
TIGHT JUNCTIONS
Definition
They prevent the passage of molecules and ions through the space between cells. So materials must actually enter the cells (by diffusion or active transport) in order to pass through the tissue. Found in animal cells.(Tight junctions are composed of a branching network of sealing strands, each strand acting independently from the others. Therefore, the efficiency of the junction in preventing ion passage increases exponentially with the number of strands)
Term
GAP JUNCTIONS
Definition
a specialized intercellular connection between certain animal cell-types. It directly connects the cytoplasm of two cells, which allows various molecules and ions to pass freely between cells.(A notable use of gap junctions is in the electrical synapse found in some neurons.)
Term
LEUKOPLAST/LEUCOPLAST
Definition
They lack pigments, so they are not green. They are located in roots and non-photosynthetic tissues of plants. They provide a wide range of biosynthetic functions, incl. the synthesis of fatty acids, many amino acids, etc. Some can be specialized for bulk storage of starch, lipid, or protein
Term
LEUKOPLAST/LEUCOPLAST
Definition
They lack pigments, so they are not green. They are located in roots and non-photosynthetic tissues of plants. They provide a wide range of biosynthetic functions, incl. the synthesis of fatty acids, many amino acids, etc. Some can be specialized for bulk storage of starch, lipid, or protein
Term
CHLOROPLAST
Definition
organelles in plant cells and eukaryotic algae that conduct photosynthesis. They absorb light and use it with water and carbon dioxide to produce sugars. They capture light energy to conserve free energy in the form of ATP
Term
Smooth Endoplasmic Reticulum
Definition
Functions: allows increased surface area for the action or storage of key enzymes and the products of these enzymes. Functions in several metabolic processes including synthesis of lipids and steroids, metabolism of carbohydrates, regulation of calcium concentration, drug detoxification, attachment of receptors on cell membrane proteins, and steroid metabolism. Structure: It consists of tubules and vesicles that branch forming a network. Found in: Animals and plants. In eukaryotes.
Term
Rough Endoplasmic Reticulum
Definition
Function: It plays a central role in the synthesis and export of proteins and glycoproteins. Structure: a complex network of membranes which is present throughout the cell and which is continuous with the outer membrane of the nuclear envelope. Found in: animals and plants. in eukaryotes.
Term
LYSOSOMES
Definition
STRUCTURE: A membrane-bounded sac of hydrolytic enzymes that the cell uses to digest macromolecules. These enzymes work best in an acidic environment, at about pH 5. This internal environment is maintained by pumping H+ from the cyostol into the lumen of the lysosome. They are found in plant and animal cells. FUNCTION: It basically provides a space where the cell can digest macromolecules safely, without the destruction that would occur if hydrolytic enzymes roamed freely.
-Uses phagocytosis to enclose food in a vacuole that pinches off internally from the plasma membrane. This food vacuole fuses with a lysosome, hydrolytic enzymes digest the food, and food is then returned to the cyostol as nutrients for the cell.
-It can get rid of wastes – digesting old organelles (autophagy).
-Macrophages, in humans, defend the body by destroying bacteria and other invaders.
-Programmed cell destruction (lysosomes carry this out).
SPECIAL NOTES: Pompe's disease: liver damaged by accumulation of glycogen that lysosomes aren't breaking down. Tay-Sachs Disease: lipid-digesting enzyme is missing and brain becomes impaired by accumulation of lipids.
Term
MITOCHONDRION
Definition
Found in most eukaryotes. STRUCTURE: Mitochondrion is enclosed in an envelope of two membranes, each a phospholipid bilayer with a unique collection of embedded proteins. The outer membrane is smooth, but the inner membrane is convoluted, with infoldings called cristae. The inner membrane divides the mitochondrion into two internal compartments: intermembrane space and the mitochondrial matrix. Cristae give the inner mitochondrial membrane a large SA that enhances the productivity of cellular respiration. FUNCTION: The mitochondrion is the site of cellular respiration. Some of the metabolic steps of CR occur in the matrix. Other proteins that function in CR, including the enzyme that makes ATP, are built into the inner membrane.
Term
CILIA
Definition
A short cellular appendage specialized for locomotion, formed from a core of nine outer doublet microtubules and two inner single microtubules ensheathed in an extention of plama membrane.
Term
FLAGELLA
Definition
a long cellular appendage specialized for locomotion, formed from a core of nine outer doublet microtubules and two inner single microtubules, ensheathed in an extention of plasma membrane.
Term
cytoplasm/cytosol
Definition
the cytoplasm plays a mechanical role, i.e. (example) to maintain the shape, the consistency of the cell and to provide suspension to the organelles. it's also a storage place for chemical substances indispensable to life. Vital metabolic reactions take place here, for example anaerobic glycolysis and protein synthesis.
Term
Capsule
Definition
very large organelle in some prokaryotic cells, such as cells of bacteria. it is a layer that lies outside the cell wall of bacteria. this layer is disease-causing. this layer is well organized and not easily washed off. It is usually composed of polysaccharides, but could be composed of other materials (e.g., polypeptide in B. anthracis). because the capsule helps to protect bacteria against phagocytosis, the capsule is considered a virulence factor
Term
Cytoskeleton
Definition
Cellular ‘skeleton’ that maintains cell shape, protects cell, and plays a roll in transport and cell division. Dynamic structure made up of microfilaments, intermediate filaments, and microtubules Eukaryotic and prokaryotic.
Term
microtubule
Definition
move vesicles, granules, organelles like mitochondria, and chromosomes via special attachment proteins part of cytoskeleton eukaryotes, prokaryotes
Term
EXTRACELLULAR MATRIX
Definition
function: In biology, the extracellular matrix (ECM) is the extracellular part of animal tissue that usually provides structural support to the animal cells in addition to performing various other important functions. The extracellular matrix is the defining feature of connective tissue in animals.ECM can serve many functions, such as providing support and anchorage for cells, segregating tissues from one another, and regulating intercellular communication.
structure:
Extracellular matrix includes the interstitial matrix and the basement membrane.[1] Interstitial matrix is present between various animal cells (i.e., in the intercellular spaces). Gels of polysaccharides and fibrous proteins fill the interstitial space and act as a compression buffer against the stress placed on the ECM.[2] Basement membranes are sheet-like depositions of ECM on which various epithelial cells rest
-only in animal cells
Term
PLASMODESMATA
Definition
function: Plasmodesmata (singular, plasmodesma) are small channels that directly connect the cytoplasm of neighboring plant cells to each other, establishing living bridges between cells. Similar to the gap junctions found in animal cells, the plasmodesmata, which penetrate both the primary and secondary cell walls (see Figure 1), allow certain molecules to pass directly from one cell to another and are important in cellular communication.
structure:The plasmodesmata is structured in an entirely different configuration than the animal cell gap junction because of the thick cell wall. Due to the presence of plasmodesmata, plant cells can be considered to form a synctium, or multinucleate mass with cytoplasmic continuity. Accordingly, the tiny channels have caused a significant amount of debate among scientists regarding cell theory, some suggesting that the cells of higher plants are not really cells at all since they are not physically separated or structurally independent from one another.omewhat cylindrical in shape, plasmodesmata are lined with the plasma membrane so all connected cells are united through essentially one continuous cell membrane. A majority of plasmodesmata also contain a narrow tube-like structure called the desmotubule, which is derived from the smooth endoplasmic reticulum of the connected cells.
-only in plant cells
Term
Nucleoid
Definition
function : serves as he genetic center for prokaryotes
structure: clump of genetic material (can be organized a little bit, see description above
found in prokaryotes only
special notes:A genophore is the DNA of a prokaryote. This is commonly referred to as a prokaryotic chromosome. The term chromosome is misleading for a genophore because the genophore lacks chromatin
the nucleoid contrasts with the nucleus in eukaryotes
Structure: In prokaryotes, the nucleoid (meaning nucleus-like) is an irregularly-shaped region within the cell of prokaryotes where the genetic material is localized.[1] The genome of prokaryotic organisms generally is a circular, double-stranded piece of DNA, of which multiple copies may exist at any time. The length of a genome widely varies, but generally is at least a few million base pairs
Term
Mesosome
Definition
function:unclear/unknown
structure:folded invaginations in the plasma membrane of bacteria that are produced by the chemical fixation techniques used to prepare samples for electron microscopy.
seen in "fixed cells"(of bacteria??idk)
no special notes
Term
Perioxysome
Definition
cell organelle in eukaryotes, contain many enzymes (catalase, D-amino acid oxidase) which breakdown and remove toxic substances as well as breakdown fatty molecules.
Term
Vacuole
Definition
space or cavity in cell cytoplasm, used for storage, containment of food, water, unwanted/dangerous substances. In plants, vacuole contains cell sap (water, enzymes, ions, salts, etc) and through turgor helps maintain structure of plant cell. In animals, vacuole helps in endocytosis and exocytosis by acting as a medium of transport.
Term
Desmosome
Definition
-Function: cell structure specialized for cell-to-cell adhesion. A type of junctional complex, they are localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes. BASICALLY THEY CONNECT CELLS TOGETHER
-Structure: Molecular complexes of the adhesion proteinsdesmoglein and desmocollin. These proteins are attached to intracellular keratin cytoskeletal filaments
-Found in: Epithelial cells (skin cells)
-Special Note: When desmosomes aren't working correctly, skin cells pull apart and create blisters! (Kooool.lol)
Term
Vesicle
Definition
-Structure: a small bubble of liquid within cell (looks like an intertube)
-Function: Used mainly for storage and transport of materials within a cell
-Found in:???(Im pretty sure its all cells though)
-Special Note: The vesicle is separated from the cytosol by at least one lipid bilayer. If there is only one lipid bilayer, they are called unilamellar vesicles; otherwise they are called multilamellar.
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