Exam 1 Review:  Chapter 3 - Cell Organelles & Cytoskeleton

ribosomes - The submicroscopic rounded, non-membrane-bound particles (cell organelles) composed of several strands of ribosomal RNA = rRNA and ribosomal proteins which are found in the cytoplasm of living cells, some are found free in the cytoplasm, some associated with the cytoplasmic surface of the nuclear membrane or the cytoplasmic surface of the rough endoplasmic reticulum (RER) membrane; some are also found within the mitochondria; they serve as the site of assembly for peptides, polypeptides and proteins encoded by messenger RNA = mRNA from the DNA blueprint.  [For more information of the process of protein synthesis at the ribosome, see translation.]

endoplasmic reticulum = ER - A complex membrane-bound cell organelle which consists of a network of interconnected membranous channels and compartments (cisternae) of various shapes which are continuous with both the nuclear envelope and the Golgi apparatus located within the cytoplasm of cells which are involved in the synthesis, modification, and transport of cellular materials.

cisternae - Any of the membrane-bound internal compartments of the network of interconnected channels and sac-like vesicles of various shapes which comprise the endoplasmic reticulum.

rough ER - A cell organelle with a network of  membranous channels and compartments (cisternae) of various shapes which are continuous with both the nuclear envelope and the Golgi apparatus; it always has ribosomes which are attached to the cytoplasmic face of the channels which synthesize proteins for storage in vesicles and perhaps export from the cell.

smooth ER - A cell organelle with a network of  membranous channels and compartments (cisternae) of various shapes which are continuous with both the nuclear envelope and the Golgi apparatus; ribosomes are not attached to the cytoplasmic face of the channels; this organelle may be involved in the synthesize of non-proteins (carbohydrates, lipids, small organic molecules, e.g., signal molecules) for export from the cell or it may be a location for membrane-bound enzymes involved in certain aspects of cellular metabolism.

Golgi complex = Golgi body = Golgi apparatus - A cytoplasmic cell organelle, present in most cells, which is composed of a network of stacked membranous vesicles; the organelle functions in the packaging and export of materials formed at the endoplasmic reticulum.

lysosomes - Any of the membrane-bound cytoplasmic organelles of most cells which contain various hydrolytic enzymes (proteases, lipases, nucleotidases, etc., synthesized at the RER and packaged by the Golgi apparatus) which function in intracellular digestion by merging with a phagosome and are suspected of contributing to aging when they become "leaky;" these structures are often large enough to be seen in the light microscope; they are especially prominent in leukocytes, and liver and kidney cells.

peroxisomes - Any of the membrane-bound cytoplasmic organelles of most cells which contain various redox = oxidation-reduction enzymes, e.g., catalase and oxidase (synthesized at the RER and packaged by the Golgi apparatus), which catalyze the production and breakdown of hydrogen peroxide; these structures are too small to be seen in the light microscope.

mitochondria - The spherical or elongated cytoplasmic organelles, bounded by a double membrane, found in nearly all eukaryotic cells which contain DNA & RNA (genetic materials), ribosomes, and many enzymes important for cell metabolism, including those responsible for the oxidation of nutrient molecules to ATP (usable chemical energy).  nickname - the "powerhouse of the cell."

cristae membranes - Any of the inward projections or folds of the inner membrane of a mitochondrion; they are the locations for a variety of membrane-bound redox = oxidation-reduction enzymes and the ATP synthetases important for the production of ATP from the final oxidation of nutrient molecules.

matrix (mitochondrial) - The interior of the mitochondrion, housed within the inner = cristae membrane, which is a gelatinous mass of materials including DNA & RNA (genetic materials), ribosomes, and many dissolved enzymes important for cell metabolism, including those responsible for the further oxidation of nutrient molecules, specifically in the conversion of pyruvate molecules to acetate groups which are fed to the Kreb's cycle = citric acid cycle = tricarboxylic acid cycle to liberate CO2, H2O, and various metabolic intermediate energy transfer compounds which will contribute to ATP synthesis in pathways housed in the cristae membranes.

cellular respiration - The oxidative process occurring within living cells by which the chemical energy of organic molecules is released in a series of metabolic steps with the production of ATP, some occurring in the cytoplasm and some within the mitochondria, involving the consumption of oxygen and the liberation of carbon dioxide and water; it is generally divided into two stages:  (1) anaerobic glycolysis in the cytoplasm followed by (2) the citric acid cycle and oxidative phosphorylation at the electron transport chain in the mitochondria.  aka - aerobic respiration

cytoskeleton - The collection of various cytoplasmic protein fibers, including actin and microtubules, which give shape to the cell and may contribute to the movement of the cell or the movement of components of the cell within the cytoplasm.  [For more images of the cytoskeleton.]

 
The image below shows the actin fibers in a cow endothelial (blood vessel) cell. The yellow colored strings are the polymerized form of the protein and the red color indicates the presence of the single protein units. The image below shows the microtubules in a cow endothelial cell.

microfilaments - Any of the minute contractile protein fibers, actin, located throughout the cytoplasm of cells and functioning primarily in maintaining the shape and structural integrity of a cell; they may contribute to changes in cell shape in those cells capable of changing their shape.

microtubules - The cylindrical hollow cytoskeletal protein complexes (structures) which are distributed throughout the cytoplasm of eukaryotic cells, providing structural support and assisting in cellular locomotion, internal transport and forming the spindle apparatus at cell divisions.

intermediate filaments - Any of the group of five types of minute contractile protein fibers, including keratin, larger in diameter than actin but smaller than microtubules, which located throughout the cytoplasm of most cells and function primarily in maintaining the shape and structural integrity of a cell; they may contribute to changes in cell shape in those cells capable of changing their shape.

flagella - The special cell organelle consisting of microtubules in a 9 + 2 array, surrounded by cell membrane, which beat in a back-and-forth motion, powered by ATP hydrolysis, to achieve movement; in humans, this organelle is found only on mature sperm cells = spermatozoa; they are large enough to be seen in the light microscope.

cilia - The microscopic hairlike processes, membrane-bound cell surface organelles containing an internal cytoskeleton of microtubules, extending from the plasma cell membrane and capable of rhythmical motion; they act in unison to produce an oar-like motion which moves the surrounding medium, usually a mucous secretion, along the surface of a tubular organ such as the respiratory tree or the uterine tube; these structures are barely large enough to be seen in the light microscope as an indistinct "brush border."

centrosomes - The small regions of cytoplasm adjacent to the nucleus which contain the centrioles and serves to organize microtubules; they are observed in those cells which will complete the cell cycle and divide by mitosis or meiosis, at which time each one will divide into two portions and move to organize the two poles of the mitotic or meiotic spindle.

centrioles - The two cylindrical, non-membrane bound cell organelles which are composed of nine triplet microtubules and form the asters during mitosis and meiosis; they are only observed in those cells which will complete the cell cycle and divide by mitosis or meiosis.

 


List:

9. ten cellular organelles and their function(s).

Cellular Organelle Function(s)
ribosome site of cytoplasmic protein synthesis
endoplasmic reticulum = ER
[2 kinds:  rough ER & smooth ER ]
site of synthesis of proteins for export from the cell [rough ER]
site of synthesis of non-protein materials for export from the cell and site of many membrane-bound enzyme pathways [smooth ER]
Golgi complex site of packaging in vesicles of materials synthesized at the ER for export from the cell
lysosome storage vesicle for various digestive enzymes
peroxisome site of many membrane-bound oxidative enzyme pathways, e.g., pathway for hydrogen peroxide catabolism
mitochondrion site of final aerobic metabolism of nutrients ["aerobic respiration"] to produce useful chemical energy [ATPs]
flagellum provides cellular motility [only for sperm cells in human males]
cilium provides motion to a fluid covering the external face of a cell, .e.g., to move mucous secretions up the respiratory tree
centrioles site of organization of spindle apparatus for mitosis and meiosis
cytoskeleton gives shape to cell and may participate in movement of organelles within cells


10. three examples of inclusions.

          glycogen granules - lipid droplets - pigment granules - cytoplasmic crystals

14. the four cell organelles a protein synthesized for export would pass through on the way out of the cell in the correct sequence.

          ribosome - rough ER (rough endoplasmic reticulum) - Golgi apparatus - secretory vesicle

Sketch and Label:

 6. the component parts of a mitochondrion.