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BZ 310-2
Cell Biology Exam 2
| Term | Definition |
|---|---|
| Glycocalyx | A layer on the outer surface of the plasma membrane. It contains membrane carbohydrates along with extra cellular materials that have been secreted by the cell into the external space, where they remain closely associated with the cell surface. |
| Extracellular Matrix (ECM) | An organized network of extracellular materials that is present beyond the immediate vicinity of the plasma membrane. It may play an integral role in determining the shape and activities of the cell. |
| Collagen | A family of fibrous glycoproteins known for their high tensile strength that function exclusively as part of the extracellular matrix. |
| Proteoglycan | A protein-polysaccharide complex consisting of a core protein molecule to which chains of glycosaminoglycans are attached. |
| Integrins | A superfamily of integral membrane proteins that bind specifically to extracellular molecules. |
| Focal Adhesions | The plasma membrane in the region of these contains clusters of integrins that connect the ECM to a surface by means of connections to the cytoskeleton. |
| Hemidesmosome | Specialized adhesive structure at the basal surface of epithelia that functions to attach the cells to the basement membrane. Made of plaques that contain keratin filaments that course out of the cytoplasm. |
| Selectin | A family of integral glycoproteins that recognize and bind to specific arrangements of carbohydrate groups projecting from the surface of cells. Mediate transient interactions between circulating white blood cells and vessel walls during inflammation. |
| Transmembrane Signaling | Transfer of information across the plasma membrane. |
| Gap Junctions | Site of intercellular communication between animal cells.Plasma membranes of adjacent cells are about 3nm from each other, and the gap is spanned by fine pipelines, or connexons. |
| Cell Wall | A rigid, non-living provides support and protection for the cell it surrounds. |
| Transport Vesicle | The shuttles, formed by budding from a membrane compartment, that carry materials between organelles. |
| Constitutive Secretion | Discharge of materials synthesized in the cell into the extracellular space in a continual manner. |
| Regulated Secretion | Discharge of materials synthesized in the cell that have been stored in membrane-bound secretory granules in the peripheral regions of the cytoplasm, occurring in response to an appropriate stimulus. |
| Secretory Granules | Large, densely packed membrane-bound structure highly concentrated secretory materials that are discharged into the extracellular space following a stimulatory signal. |
| Endocytic Pathway | The route for moving materials from outside the cell to compartments, such as endosomes and lysosomes, located within the cell interior. |
| Signal Sequence | Special series of amino acids located at the N-terminal portion of newly forming proteins that triggers the attachment of the protein-forming ribosome to an ER membrane and the movement of the nascent polypeptide into the ER. |
| Translocon | A protein-lined channel embedded in the ER membrane; the nascent polypeptide is able to move through the translocon in its passage from the cytosol to the ER lumen. |
| Quality Control | Methods for the cell to ensure DNA, RNA, and Proteins have their correct structure. Misfolded proteins are destroyed, RNAs with premature stops are destroyed, and abnormal DNA is repaired. |
| Coated Vesicle | Vesicles that bud from a membrane compartment typically possess a multi-subunit protein coat that promotes the budding process and binds specific membrane proteins. COPI, COPII, and clathrin are the best characterized types. |
| SNARE | Key proteins that mediate the process of membrane fusion. T versions are located in the membranes of target compartments. V versions incorporate into the membranes of transport vesicles during budding. |
| Autophagy | The destruction of organelles and their replacement during which an organelle is surrounded by a double membrane. The membrane surrounding the organelle then fuses with a lysosome. |
| Turnover | The regulated destruction of cellular materials and their replacement. |
| Vacuole | A single membrane-bound, fluid filled structure that comprises as much as 90% of the volume of many plant cells. |
| Endocytosis | Mechanism for the uptake of fluid and solutes into a cell. Can be divided into two types: bulk-phase, which is non-specific, and receptor-mediated, which requires the binding to a specific receptor. |
| Phagocytosis | Process by which particulate materials are taken into cells. Materials are enclosed within a fold of the plasma membrane, which buds into the cytoplasm to form a vesicle called a phagosome. |
| Coated Pits | Specialized domains of the plasma membrane; they serve as collection points for receptors that bind substances that enter a cell by means of endocytosis. |
| Endosome | Organelles of the endocytic pathway. Materials taken up are sorted in early ones and late ones function as destination sites of lysosomal enzymes transported from the golgi. |
| Motor Proteins | Proteins that utilize ATP to generate mechanical forces that propel the protein, as well as its attached cargo, along the cytoskeleton. 3 types Kinesin, Dynein and Myosin. |
| Kinesin | A plus end-directed motor protein that moves vesicles and other organelles along microtubules through the cytoplasm. It is a member of a family of (KRPs). |
| Processive | A term applied to proteins that are capable of moving considerable distances along their track or template without dissociating from it. |
| Dynein | An exceptionally large, cargo-carrying, multisubunit motor protein that moves along microtubules toward their minus end. This family of proteins occurs as cytoplasmic and ciliary or axonemal versions. |
| Microtubule-Organizing Centers (MTOCs) | A variety of specialized structures that exert a role in initiating microtubule formation. |
| Basal Body | A structure that resides at the base of the cilium or flagellum and which generates their outer microtubules. They are identical in structure to centrioles. Both can give rise to one another. |
| Dynamic Instability | A term that relates to the assembly/disassembly properties of the plus end of a microtubule. The term describes the fact that growing and shrinking microtubules can coexist in the same region of a cell. |
| Microtubules | Hollow, Cylindrical cytoskeletal structures, 25nm in diameter, whose wall is composed of tubulin. They are polymers assembled from α and β tubulin heterodimers that are arranged in rows, or protofilaments. |
| Intermediate Filaments | Strong, ropelike cytoskeletal fibers approximately 10 nm in diameter that, depending on the cell type may be composed of a variety of protein subunits capable of assembling into similar types of filaments. |
| Microfilaments | Solid, 8nm thick, cytoskeletal structures composed of a double-helical polymer of the protein actin. They play a key role in virtually all types of contractility and motility within cells. |
| Actin | A globular cytoskeletal protein that polymerizes to form a flexible, helical filament capable of interacting with myosin. These filaments provide mechanical support for eukaryotic cells, determine the cells shape, and enable movement. |
| Myosin | A large family of motor proteins that moves along actin-containing microfilaments. Most are +end directed. |
| Neuromuscular Junction | The point of contact of a terminus of an axon with a muscle fiber, it is the site of transmission of the nerve impulses from the axon across the synaptic cleft to the muscle fiber. |
| Transverse(T) Tubule | Membranous folds along which the impulse generated in a skeletal muscle is propagated into the interior of the cell. |
| Sarcoplasmic Reticulum | A system of cytoplasmic, Ca2+ storing SER membranes in muscle cells that forms a membranous sleeve around the myofibril. |
| Muscle Fiber | A skeletal muscle cell, referred to as this because of its highly ordered, multinucleated, cable like structure composed of hundreds of thinner, cylindrical myofibrils. |
| Allele | Alternate forms of the same gene. |
| Linkage Group | Groups of genes that reside on the same chromosome causing non-independent segregation of traits controlled by these genes. |
| Mutant | An individual having an inheritable characteristic that distinguishes it from the wild type. |
| Genetic Recombination | Reshuffling of the genes on chromosomes (thereby disrupting linkage groups) that occurs as a result of breakage and reunion of segments of homologous chromosomes. |
| Supercoiled | A molecule of DNA that has greater or fewer than 10 base pairs per turn of the helix. |
| Topoisomerase | Enzymes that are able to change the supercoiled state of the DNA duplex. They are essential in transcription and translation. |
| Pseudogene | Sequences that are clearly homologous to functional genes, but have accumulated mutations that render them non-functional. |
| Transposition | Movement of DNA segments from one place on a chromosome to an entirely different site, often affecting gene expression. |
| Transposable Element | DNA segments that take part in transposition. |
| Genetic Polymorphisms | Sites in the genome that vary with relatively high frequency among different individuals in a species population. |
| Transcription | The formation of a complementary RNA from a DNA template using RNA Polymerase 2 |
| Messenger RNA (mRNA) | The intermediate molecule between a gene and the polypeptide for which it codes. It is assembled as a complementary copy of one of the two DNA strands that encodes the gene. |
| Translation | Synthesis of proteins in the cytoplasm using the information encoded by an mRNA. |
| Ribosomal RNA (rRNA) | The RNAs of a ribosome. It recognizes and binds other molecules, provide structural support, and catalyzes the chemical reaction in which amino acids are covalently linked to one another. |
| Transfer RNA (tRNA) | A family of small RNAs that translate the information encoded in the nucleotide alphabet of an mRNA into the amino acid alphabet of a polypeptide. |
| Promoter | The site on the DNA to which an RNA polymerase molecule binds prior to initiating transcription. It contains information that determines which of the 2 DNA strands is transcribed and the site at which transcription begins. |
| Transcription Unit | The corresponding segment of DNA on which a primary transcript is transcribed. |
| rDNA | The DNA sequences encoding rRNA that are normally repeated hundreds of times and are typically clustered in one or a few regions of the genome. |
| Nucleoli | Irregular-shaped nuclear structures that function as the ribosome-producing organelles. |
| Intervening Sequence | Regions of DNA that are between coding sequences of a gene and that are therefore missing from corresponding mRNA. |
| Split Genes | Genes with intervening sequences of introns and exons. |
| Exons | Those parts of a split gene that contribute to a mature RNA product. |
| Introns | Those parts of a split gene that correspond to the intervening sequences. |
| RNA Splicing | The process of removing the intervening DNA sequences (introns) from a primary transcript. |
| Small Nuclear RNAs (snRNAs) | RNAs required for mRNA processing that are small (90-300bp) and that function in the nucleus. |
| Spliceosome | A macromolecular complex containing a variety of proteins and a number of distinct ribonucleoprotein particles that functions in removal of introns from a primary transcript. |
| Exon Shuffling | The movement of genetic modules among unrelated genes facilitated by the presence of introns; the introns act like inert spacer elements between exons. |
| Anticodon | A three-nucleotide sequence in each tRNA that functions in the recognition of the complementary mRNA codon. |
| Initiation codon | The triplet AUG, the site to which the ribosome attaches to the mRNA to assure that the ribosome is in the proper reading frame to correctly read the entire message. |
| Conventional Myosin (Myosin 2) | The protein that mediates muscle contractility as well as certain types of non muscle motility such as cytokinesis. |
| Unconventional Myosins (Myosin 1 and 3-18) | Many diverse roles including organelle transport. |
| Myofibrils | The thin, cylindrical strands found within muscle fiber cells. Each one is composed of repeating linear arrays of contractile units, called sarcomeres, that give muscle cells their striated appearance |
| Sarcomere | Contractile units of myofibrils that are endowed with a characteristic pattern of bands and stripes that give skeletal muscle cells their striated appearance. |
| RNA Polymerase 1 | The transcribing enzyme found in eukaryotic cells that synthesizes the large (28S, 18S, and 5.8S) rRNAs |
| RNA Polymerase 2 | The transcribing enzyme found in eukaryotic cells that synthesizes mRNAs and most small nuclear RNAs |
| RNA Polymerase 3 | The transcribing enzyme found in eukaryotic cells that synthesizes the various RNAs and 5s rRNAs. |
| Laminins | Extracellular glycoproteins that influence cell differentiation, migration, and adhesion. |
| Cadherins | A family of related glycoproteins that mediate Ca2+ dependant cell to cell adhesion. Join cells of similar type to one another and that they are essential for molding cells into cohesive tissues and holding them together. |
| Adherens | Serve as junctions including clusters of cadherins that connect the external environment to the actin cytoskeleton and provide a pathway for signals to be transmitted from the cell exterior to the cytoplasm. |
| Desmosomes | Contain cadherins that link two cells and are common in tissues which are subjected to mechanical stress such as cardiac muscle. |
| Plasmodesmata | Cytoplasmic channels that pass through cell walls to connect cells and that, like gap junctions of animal cells, in plants they serve in cell-to-cell communication. |
| Secretory (Biosynthetic) Pathway | Route through the cytoplasm by which materials are synthesized in the ER or golgi, modified during passage through the golgi, and transported within the cytoplasm to various destinations such as the plasma membrane, a lysosome, or a large vacuole. |
| cis Golgi network | This is the portion of the Golgi complex serves is closest to the endoplasmic reticulum and functions as a sorting station that distinguishes between proteins to be shipped back to the endoplasmic reticulum and those that are allowed to proceed out. |
| trans Golgi network | This is a sorting station of the Golgi complex where proteins are parceled into different types of vesicles heading either to the plasma membrane or to various intracellular destinations. |
| COPII-coated vesicles | Move materials from the ER forward to the ERGIC and Golgi. |
| COPI-coated vesicles | Move materials in a retrograde direction 1) from the EGRIC and Golgi back to the ER and 2) from trans Golgi back to cis Golgi. |
| Clathrin-coated vesicles | Move materials from the TGN to endosomes, lysosomes, and plant vacuoles. They also move materials from the plasma membrane to the cytoplasmic compartments along the endocytic pathway. |
| Cytoskeleton | An elaborate interactive network composed of 3 filamentous structures. These provide structural support and a framework responsible for the positioning the various organelles. |
| Topoisomerase Type 1 | Changes the supercoiled state of DNA by creating a transient break in one strand of the duplex. |
| Topoisomerase Type 2 | Makes a transient break in both strands of the DNA duplex. Another segment of the DNA molecule or a separate molecule entirely is then transported through the break and the severed strands are resealed. Requires during mitosis to disentangle DNA. |
| Shine-Dalgarno Sequence | Bacterial promoter that is responsible for identifying the precise nucleotide at which transcription begins |
| piRNAs | Small RNAs that act to suppress the movement of transposable elements in germ cells. |
| RNA interference | A process in which double-stranded RNAs lead to degradation of mRNAs having identical sequences. |
| Frameshift Mutation | A single base pair is either added or deleted from the DNA, resulting in an incorrect reading frame. |
| Nonsense Mutation | A stop codon is produced early within a gene, thereby causing premature termination of the polypeptide chain. |
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