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UCSB ChE 170
Cell and Molecular Biology for Engineers (Fa 10)
218
Chemical Engineering
Undergraduate 4
12/04/2010

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Term
Action Potential
Definition
Rapid, transient, self-propagating electrical signal in the plasma membrane of a cell such as a neuron or muscle. A nerve impulse.
Term
Activator
Definition
A protein that binds to a specific regulatory region of DNA to permit transcription of an adjacent gene
Term
Active Transport
Definition
Movement of a molecule across a membrane driven by ATP hydrolysis or another form of metabolic energy
Term
Adaptation
Definition
Adjustment of sensitivity of a cell or organism following repeated stimulation. Can allow a response even when there is a high background level of stimulation
Term
Adenosine Triphosphate (ATP)
Definition
Nucleoside triphosphate composed of adenine, ribose, and three phosphate groups that is the principal carrier of chemical energy in cells. The terminal phosphate groups are highly reactive in the sense that their hydrolysis, or transfer to another molecule, is accompanied by the releas of a large amount of free energy.
Term
Adenylyl Cyclase
Definition
Enzyme that catalyzes the formation of cyclic AMP from ATP. An important component of some intracellular signaling pathways
Term
Affinity
Definition
How tightly a given molecule bonds
Term
Allosteric
Definition
Describes a protein that can exist in two or more conformations depending on the binding of a molecule (a ligand) at a site other than the catalytic site.  Proteins composed of multiple subunits often display a cooperative response to lingand binding, because the binding of a ligand to one subunit facilitates the binding of ligands to the other subunits.
Term
Alpha Helix
Definition
Common structural motif of proteins in which a linear sequence of amino acids folds into a right-handed helix stabilized by internal hydrogen bonding between back-bone atoms
Term
Amino Acid
Definition
Organic molecule containing both an amino group and a carboxyl group
Term
Amphipathic
Definition
Having both hydrophobic and hydrophilic regions, as in a phospholipid or a detergent molecule
Term
Anabolism
Definition
Reaction pathways by which large molecules are made from smaller ones. Biosynthesis.
Term
Antibody
Definition
Protein produced by B lymphocytes in response to a foreign molecule or invading organism. Binds to the foreign molecule or cell extremely tightly, thereby inactivating it or marking it for destruction.
Term
Antigen
Definition
Molecule that provokes the production of specific neutralizing antibodies in an immune response
Term
Antiport
Definition
Type of coupled transporter that transports two different ions or small molecules across a membrane in opposite directions, either simultaneously or in sequence.
Term
Archea
Definition
One of the two divisions of procaryotes, often found in hostile environments such as hot springs or concentrated brine
Term
Bacteria
Definition
Commonly used name for any procaryotic organism, but more precisely refers to the eu********, the "true ********," one of the three major domains of life. Most are single-celled organisms. Some species of ******** cause disease
Term
Base Pair
Definition
Two nucleotides in an RNA or a DNA molecule that are specifically pared by hydrogen bonds - for example, G with C, and A with T or U
Term
Beta Sheet
Definition
Folding pattern found in many proteins in which neighboring regions of the polypeptide chain associate side by side with each other through hydrogen bonds to give a rigid, flattened structure
Term
Binding Site
Definition
Region on the surface of a protein, typically a cavity or groove, that is complementary in shape to, and forms multiple noncovalent bonds with, a second molecule (the ligand)
Term
Ca2+/Calmodulin-Dependeint Protein Kinase (CaM-kinase)
Definition
Enzyme that phosphorylates target proteins in response to an increase in Ca2+ ion concentration, through its interaction with the Ca2+ binding protein calmodulin
Term
Calmodulin
Definition
Small Ca2+ binding protein that modifies the activity of many target enzymes and membrane transport proteins in response to changes in Ca2+ concentration
Term
Cancer
Definition
Disease caused by abnormal and uncontrolled cell division resulting in localized growths, or tumors, which may spread throughout the body
Term
Catabolism
Definition
General term for the enzyme-catalyzed reactions in a cell by which complex molecules are degraded to simpler ones with release of energy. Intermediates in these ********* reactions are sometimes called *******ites
Term
Cell Cortex
Definition
Specialized layer of cytoplasm on the inner face of the plasma membrane. In animal cells it is an actin-rich layer responsible for cell-surface movements.
Term
Cell Junction
Definition
Specialized region of connection between two cells or between a cell and the extracellular matrix
Term
Cell Signaling
Definition
The molecular mechanisms by which cells detect and respond to external stimuli and send messages to other cells
Term
Cell Wall
Definition
Mechanically strong fibrous layer deposited by a cell outside its plasma membrane. Prominent in most plants, bacteria, algae, and fungi, but not present in most animal cells
Term
Cellulose
Definition
Structural polysaccharide consisting of long chains of covalently linked glucose units. It provides tensile strength in plant cell walls.
Term
Centromere
Definition
Constricted region of a mitotic chromosome that holds sister chromatids together; also the site on the DNA where the kinetochore forms and then captures microtubules from the mitotic spindle
Term
Centrosome (Cell Center)
Definition
Centrally located organelle of animal cells that is the primary microtubule-organizing center and separates to form the two spindle poles during mitosis. In most animal cells it containes a pare of centrioles.
Term
Channels
Definition
An aqueous pore in a lipid membrane, with walls made of protein, through which selected ions or molecules can pass
Term
Chloroplast
Definition
Specialized organelle in algae and plants that contains chlorophyll and in which photosynthesis takes place
Term
Cholesterol
Definition
Lipid molecule with a characteristic four-ringed steroid structure that is an important component of the plasma membranes in animal cells
Term
Chromatin
Definition
Complex of DNA, histones, and nonhistone proteins found in the nucleus of a eucaryotic cell
Term
Chromosome
Definition
Long threadlike structure composed of DNA and associated proteins that carries the genetic information of an organism. Especially visible when plant and animal cells undergo mitosis or meiosis.
Term
Clathrin
Definition
Protein that makes up the coat of one type of transport vesicle. Vesicles coated in this bud from the Golgi apparatus on the outward secretory pathway and bud from the plasma membrane on the inward endocytic pathway
Term
Coated Vesicle
Definition
Small membrane-enclosed organelle with a cage of proteins (the coat) on its cytosolic surface. It is formed by the pinching off of a protein coated region of membrane
Term
Codon
Definition
Sequence of three nucleotides in a DNA or messenger RNA molecule that represents the instruction for incorporation of a specific amino acid into a growing polypeptide chain.
Term
Collagen
Definition
Fibrous protein rich in glycine and proline that is a major component of the extracellular matrix and connective tissues. Exists in many forms: type I, the most common, is found in skin, tendon, and bone; type II is found in cartilage; type IV is present in basal laminae and so on.
Term
Combinatorial Control
Definition
Describes the way in which groups of proteins work together in combination to control the expression of a single gene
Term
Condensation Reaction
Definition
Type of chemical reaction in which two organic molecules become linked to each other by a covalent bond with concomitant removal of a molecule of water
Term
Connective Tissue
Definition
Tissues such as bone, tendons, and the dermis of the skin, in which extracellular matrix is plentiful and carries the mechanical load
Term
Coupled Transporter
Definition
Membrane transport protein that carries out transport in which the transfer of one molecule depends on the simultaneous or sequential transfer of a second molecule
Term
Cyclic AMP
Definition
Nucleotide generated from ATP in response to hormonal stimulation of cell-surface receptors. Acts as a signaling molecule by activating protein kinase A; it is hydrolyzed by a phosphodiesterase
Term
Cyclic-AMP-dependent Protein Kinase
Definition
Enzyme that phosphorylates target proteins in response to a rise in intracellular cyclic AMP concentration
Term
Cytokine
Definition
Small protein made and secreted by cells that acts on neighboring cells to alter their behavior. Act via cell-surface receptors.
Term
Cytoplasm
Definition
Contents of a cell that are contained within its plasma membrane but, in the case of eucaryotic cells, outside the nucleus
Term
Cytoskeliton
Definition
System of protein filaments in the cytoplasm of a eucaryotic cell that gives the cell shape and the capacity for directed movement. Its most abundent components are actin filiments, microtubules, and intermediate filiments.
Term
Cytosol
Definition
Contents of the main compartment of the cytoplasm, excluding membrane-enclosed organelles such as the ER and mitochondria. The cell fraction remaining after membranes, cytoskelital components, and other organelles have been removed.
Term
Denature
Definition
To cause adramatic change in the conformation of a protein or nucleic acid by heating it or by exposing it to chemicals. Usually results in the loss of biological function.
Term
Diacylglycerol (DAG)
Definition
Lipid produced by the cleavage of membrane inositol phospholipids in response to extracellular signals. Composed of two fatty acid chains linked to glycerol, it serves as a membrane-located signaling molecule to help activate protein kinase C.
Term
Differentiation
Definition
Process by which a cell undergoes a progressive change to a more specialized and usually easily recognized cell type
Term
Disulfide Bond
Definition
Covalent linkage formed between two sulfhydryl groups on cysteins. Common way to join two proteins or to link together different parts of the same protein in the extracellular space.
Term
DNA
Definition
Double-stranded polynucleotide formed from two separate chains of covalently linked deoxyribonucleotide units. It serves as the cell's store of genetic information that is transmitted from generation to generation.
Term
DNA Methylation
Definition
The enzymatic addition of methyl groups to cytosine bases in DNA. Methylation generally turns off genes by attracting proteins that block gene expression
Term
Dynein
Definition
Member of a family of large motor proteins that undergo ATP-dependent movement along microtubules. Responsible for the bending of cilia.
Term
Electrostatic Interaction
Definition
Interaction involving formal electric charges
Term
Endocytosis
Definition
Uptake of material into a cell by an invagination of the plasma membrane and its internalization in a membrane-bounded vesicle
Term
Endoplasmic Reticulum (ER)
Definition
Labrinthine, membrane-enclosed compartment in the cytoplasm of eukaryotic cells, where lipids and secreted and membrane-bound proteins are made
Term
Endosome
Definition
Membrane-enclosed compartment of a eukaryotic cell through which endocytosed material passes on its way to the lysosomes
Term
Endrocrine Signaling
Definition
Signaling involving hormone movement over long distances
Term
Enzyme-coupled Receptor
Definition
Transmembrane receptor proteins that activate an intracellular enzyme in response to ligand binding to the extracellular part of the receptor
Term
Epigenetic Inheritance
Definition
Inheritance that is superimposed on the information that is inherited in the DNA sequence itself. Often, information in the form of a particular type of chromatin structure (eg a certain pattern of histone modification or DNA methylation)
Term
Epithelial Tissue
Definition
Close packed cells covering the surface of the body
Term
Eucaryote
Definition
Living organism composed of one or more cells with a distinct nucleus and cytoplasm. Includes all forms of life except archaea, bacteria and viruses.
Term
Exocytosis
Definition
Process by which most molecules are secreted from a eukaryotic cell. These molecules are packaged in membrane-enclosed vesicles that fuse with the plasma membrane, releasing their contents to the outside
Term
Extracellular Matrix
Definition
Complex network of polysaccharides (such as glycosaminoglycans or cellulose) and proteins (such as collagen) secreted by cells. A structural component of tissues that also influences their development and physiology.
Term
Extracellular Signal Molecule
Definition
Any molecule present outside the cell that can elicit a response inside the cell when the molecule binds to a receptor protein. Some signal molecules, such as steroid hormones, can enter cells and act on internal receptors embedded in the plasma membrane and exposed on the cell surface
Term
Fatty Acid
Definition
Compound such as palmitic acid that has a corboxylic acid attached to a long hydrocarbon chain. Used as a major source of energy during metabolism and as a starting point for the synthesis of phospholipids.
Term
Fibroblast
Definition
Common cell type found in connective tissue that secretes an extracellular matrix rich in collagen and other extracellular matrix macromolecules. Migrates and proliferates readily in wounded tissue and in tissue culture.
Term
Fibronectin
Definition
Extracellular matrix protein that binds to integrins on cell surfaces, helping cells to adhere to the matrix
Term
Fibrous Protein
Definition
A protein with an elongated shape. Typically one such as collagen or intermediate filament protein that is able to associate into long filamentous structures.
Term
Free Energy Transduction
Definition
The use of free energy of one source in order to drive another reaction
Term
G protein
Definition
One of a large family of GTP-binding proteins composed of three different subunits that are important intermediaries in intracellular signaling pathways. Usually activated by the binding of a hormone or other ligand to a transmembrane receptor
Term
Gene
Definition
Region of DNA that controls a discrete hereditary characteristic of an organism, usualy responsible for specifying a single protein or RNA molecule
Term
Gene Expression
Definition
The process by which a gene makes its effect on a cell or organism by directing the synthesis of a protein or an RNA molecule with a characteristic activity
Term
Genome
Definition
The total genetic information carried by a cell or an organism (or the DNA molecules that carry this information)
Term
Gibbs Free Energy
Definition
Energy that can be extracted from a system to do useful work, such as driving a chemical reaction
Term
Glucose
Definition
Six-carbon sugar that plays a major role in the metabolism of living cells. Stored in polymeric form as glycogen in anial cells and as starch in plant cells.
Term
Glycolipid
Definition
Membrane lipid molecule with a short carbohydrate chain atached to a hydrophobic tail
Term
Glycoprotein
Definition
Any protein with one or more covalently linked oligosaccharide chains. Includes most secreted proteins and most proteins exposed on the outer surface of the plasma membrane.
Term
Glycosylation
Definition
The addition of a sugar to a protein
Term
Golgi Apparatus
Definition
Membrane-enclosed organelle in eukaryotic cells where the proteins and lipids made in the ER are modified and sorted for transport to other sites
Term
G-protein-coupled Receptor (CPCR)
Definition
Cell-surface receptor that associates with an intracellular trimeric GTP-binding protein (G protein) after receptor activation by an extracellular ligand. These receptors are sevenpass transmembrane proteins
Term
GTP-binding Protein
Definition
An allosteric protein whose conformation and activity are determined by its association with either GTP or GDP. Includes many proteins involved in cell signaling, such as Ras and G proteins
Term
Guanosine Triphosphate (GTP)
Definition
Major nucleoside triphosphate used in the synthesis of RNA and in some energy-transfer reactions. Also has a special role in microtubule assembly, protein synthesis, and cell signaling.
Term
Histone
Definition
One of a group of abundant basic proteins, rich in arginine and lysine, that are associated with DNA in chromosomes to form nucleosomes
Term
Homologous Recombination
Definition
Genetic exchange between a pair of identical or very similar DNA sequences, typically located on a pair of homologous chromosomes. A similar process is used to repair double-strand breaks in DNA.
Term
Hormone
Definition
A chemical substance produced by one set of cells in a multicellular organism and transported via body fluids to target tissues on which it exerts a specific effect
Term
Hydrolysis Reaction
Definition
Cleavage of a covalent bond with accompanying addition of water, -H being added to one product of the cleavage and -OH of the other
Term
Hydrophobic Interaction
Definition
Interaction forming partial electric charges
Term
Immunoglobulin
Definition
Alternative name for an antibody (abbreviated Ig)
Term
Inositol 1,4,5-trisphosphate (IP3)
Definition
Small intracellular signaling molecule produced during activation of the inositol phospholipid signaling pathway; causes Ca2+ release from the ER
Term
Inositol Phospholipid
Definition
Minor lipid components of plasma membranes that contain phosphorylated inositol derivatives; important both for distinguishing different intracellular membranes and for signal transduction in eukaryotic cells
Term
Integrins
Definition
Family of transmemebrane proteins present on cell surfaces that enable cells to adhere to each other and to the extracellular matrix, being also involved in cell signaling
Term
Intracellular Signaling Molecule
Definition
Molecule (usu protein) that is part of the mechanism for transducing and transmitting signals inside a cell
Term
Intracellular Signaling Pathway
Definition
The set of proteins and small-molecule second-messengers that interact with each other to relay a signal from the cell membrane to its final destination in the cytoplasm or nucleus
Term
Intron
Definition
Noncoding region of a eucaryotic gene that is transcribed into an RNA molecule but is then excised by RNA splicing to produce mRNA
Term
Ion Channel
Definition
Transmembrane protein or protein complex that forms a water-filled channel across the lipid bilayer through which specific inorganic ions can diffuse down their electrochemical gradients
Term
Ion-channel-coupled Receptor
Definition
Transmembrane receptor protein or complex that forms a gated ion chanel that opens in response to the binding of a ligand to the external face of the channel
Term
Keratin
Definition
Fibrous structural protein making up the outer layer of skin, hair, nails, etc.
Term
Kinesin
Definition
A large family of motor proteins that use the energy of ATP hydrolysis to move along a microtubule
Term
Lagging Strand
Definition
One of the two newly made strands of DNA found at a replication fork. This strand is made of discontinuous lengths that are later joined covalently.
Term
Leading Strand
Definition
One of the two newly made strands of DNA found at a replication fork. This strand is made by continuous synthesis in the 5' to 3' direction
Term
Ligand
Definition
General term for a molecule that binds to a specific site on a protein
Term
Lipid
Definition
Organic molecule that is insoluble in water but dissolves readily in nonpolar organic solvents. One class, the phospho******, forms the structural basis of biological membranes.
Term
Liposome
Definition
Artificially made vesicles made of a lipid bilayer
Term
Local Mediator
Definition
Secreted signal molecule that acts at a short range on adjacent cells
Term
Lysosome
Definition
Intracellular membrane-enclosed organelle containing digestive enzymes, typically those most active at the acid pH found in these organelles
Term
MAP Kinase
Definition
Mitogen-activated protein kinase. Protein kinase that performs a crucial step in relaying signals from cell-surface receptors to the nucleus. It is the final kinase in the three-kinase sequence called the MAP kinase cascade
Term
Membrane Potential
Definition
Voltage difference across a membrane due to a slight excess of positive ions on one side and of negative ions on the other
Term
Membrane-enclosed Organelle
Definition
Any organelle in the eucaryoti cell that is surrounded by a lipid bilayer membrane, for example, the ER, Golgi, and lysosome
Term
Messenger RNA (mRNA)
Definition
RNA molecule that specifies the amino acid sequence of a protein. Produced by RNA splicing (in eucaryotes) from larger RNA molecule made by RNA polymerase as a complementary copy of DNA. It is translated into protein in a process catalyzed by ribosomes.
Term
MicroRNA (miRNA)
Definition
Small noncoding RNAs that control gene expression by base-pairing with specific mRNAs to regulate their stability and their translation
Term
Mitochondria
Definition
Membrane-enclosed organelle, about the size of a bacterium, that carries out oxidative phosphorylation and produces most of the ATP in eucaryotic cells
Term
Molecular Switch
Definition
Protein or protein complex that operates in an intracellular signaling pathway and can reversibly switch between an active and inactive state
Term
Monomeric GTPase
Definition
Small, single-subunit GTP- binding protein. Proteins of this family, such as Ras and Rho, are part of many different signaling pathways
Term
Motor Protein
Definition
Protein such as myosin or kinesin that uses energy derived from ATP hydrolysis to propel itself along a protein filament or polymeric molecule
Term
Myosin
Definition
Type of motor protein that uses ATP to drive movements along actin filaments. A large protein that forms the thick filaments of skeletal muscle. Smaller versions are widely distributed and are responsible for many actin-based movements.
Term
NAD+
Definition
Activated carrier molecule that participates in an oxidation reaction by accepting a hydride ion (H-) from a donor molecule, thereby producing ***H. Widely used in the energy-producing breakdown of sugar molecules.
Term
NADPH
Definition
A carrier molecule closely related to NADH used as an electron donor in biosynthetic pathways
Term
Neurotransmitter
Definition
Small signaling molecule secreted by a nerve cell at a chemical synapse to signal the postsynaptic cell
Term
Nitric Oxide (NO)
Definition
Small highly diffusible molecule widely used as an intracellular signal
Term
NMR Spectroscopy
Definition
Technique used for determining the three-dimensional structure of a protein; it I performed in solution without requiring a protein crystal.
Term
Nuclear Envelope
Definition
Double membrane surrounding the nucleus. Consists of outer and inner membranes perforated by nuclear pores
Term
Nuclear Lamina
Definition
Fibrous layer on the inner surface of the inner nuclear membrane formed as a network of intermediate filaments made from nuclear lamins.
Term
Nuclear Pore
Definition
Channel through the nuclear envelope that allows selected large molecules to move between the nucleus and cytoplasm
Term
Nuclear Receptor
Definition
Receptor proteins present inside a eukaryotic cell that can bind to signal molecules that enter the cell, such as steroid hormones; the complex of nuclear receptor and signal molecule subsequently acts as a transcription regulator
Term
Nucleosomes
Definition
Beadlike structural unit of a eucaryotic chromosome composed of a short length of DNA wrapped around a core of histone proteins; the fundamental subunit of chromatin
Term
Nucleotide
Definition
Nucleoside with a series of one or more phosphate groups joined by an ester linkage to the sugar moiety. DNA and RNA are polymers of this.
Term
Organelle
Definition
A discrete structure or subcompartment of a eucaryotic cell (especially one that is visible in the light microscope) that is specialized to carry out a particular function. Examples include mitochondria and the Golgi Apparatus.
Term
Osmotic Pressure
Definition
Pressure that must be exerted on the low-solute concentration side of a semipermeable membrane to prevent the flow of water across the membrane as a result of osmosis
Term
Osteoblast
Definition
Cells that make bone tissues
Term
Paracrine Signaling
Definition
Signals passing via tissues
Term
Passive Transport
Definition
The movement of a small molecule or ion across a membrane due to a difference in concentration or electrical charge
Term
Peptide Bond
Definition
Chemical bond between the carbonyl group of one amino acid and the amino group of a second amino acid - a special form of amide linkage
Term
Peroxisome
Definition
Small membrane-enclosed organelle that uses molecular oxygen to oxidize organic molecules. Contains some enzymes that produce hydrogen peroxide and others that degrade it
Term
Phagocytic Cell
Definition
A cell such as a macrophage or neutrophil that is specialized to take up particles and microorganisms by phagocytosis
Term
Phagocytosis
Definition
The process by which particulate material is engulfed by a cell.
Term
Phosphatase
Definition
Enzyme that removes a phosphate group from its substrate
Term
Phosphoinositide 3-kinase (PI 3-kinase)
Definition
Enzyme that phosphorylates inositol phospholipids in the ER in response to signals received by the cell. The phosphorylated lipids become docking sites for intracellular signaling proteins
Term
Phospholipase C
Definition
Enzyme associated with the PM that performs a crucial step in the inositol phospholipid signaling pathways
Term
Phospholipid
Definition
Type of lipid molecule used to make biological membranes. Generally composed of two fatty acids linked through glycerol phosphate to one of a variety of polar groups
Term
Phosphorylation
Definition
The covalent addition of a phosphate group to a side chain of a protein catalyzed by a protein kinase. Usually alters the activity or properties of the protein in some way.
Term
Pinocytosis
Definition
Type of endocytosis in which soluble materials are taken up from the environment and incorporated into vesicles for digestion (cell drinking)
Term
Plasma Membrane
Definition
The membrane that surrounds a living cell
Term
Polymerase
Definition
General term for an enzyme that catalyzes addition of subunits to a polymer
Term
Polysaccharide
Definition
Linear or branched polymer composed of sugars. Examples are glycogen, hyaluronic acid, and cellulose.
Term
Positive Feedback Loop
Definition
Situation in which the end product of a reaction stimulates its own production
Term
Post-Transcriptional Control
Definition
Regulation of gene expression that occurs after transcription of the gene has begun; examples are regulation of RNA splicing and other RNA processing events, and regulation of translation by microRNA
Term
Procaryote
Definition
Major category of living cells distinguished by the absence of a nucleus. Comprise the archaea and the eubacteria (commonly called bacteria), two of the three domains of life.
Term
Promoter
Definition
Nucleotide sequence in DNA to which RNA polymerase binds to begin transcription
Term
Proofreading
Definition
The process by which DNA polymerase corrects its own errors as it moves along DNA
Term
Protease
Definition
Enzyme such as trypsin that degrades proteins by hydrolyzing some of their peptide bonds
Term
Proteasome
Definition
Large protein complex in the cytosol that is responsible for degrading cytosolic proteins that have been marked for destruction by ubiquitylation or by some other means
Term
Protein Kinase
Definition
One of a very large number of enzymes that transfers the terminal phosphate group of ATP to a specific amino acid side chain on a target protein
Term
Protein Kinase
Definition
Transferrs the terminal phosphate group of ATP to a specific amino acid side chain or target protein
Term
Protein Kinase C (PKC)
Definition
Enzyme that phosphorylates target proteins in response to a rise in diacylgycerol and Ca2+ ions
Term
Protein Phosphatase
Definition
Enzyme that removes, by hydrolysis, a phosphate group from a protein, often with high specificity for the phosphorylated site
Term
Proteoglycan
Definition
Molecule consisting of one or more glycosaminoglycan chains attached to a core protein
Term
Purines
Definition
One of the two categories of nitrogen-containing ring compounds found in DNA and RNA. Examples are adenine and guanine.
Term
Pyrimidines
Definition
One of the two categories of nitrogen-containing ring compounds found in DNA and RNA. An example is cytosine.
Term
Rab Protein
Definition
A family of small GTP-binding proteins present on the surfaces of transport vesicles and organelles that serve as molecular markers identifying each membrane type. Rab proteins help to ensure that transport vesicles fuse only with the correct membrane
Term
Ras
Definition
One of a large family of small GTP-binding proteins that helps relay signals from cell-surface receptors to the nucleus
Term
Reading Frame
Definition
The set of successive triplets in which a string of nucleotides is translated into protein. An mRNA molecule is read in one of three possible of these, depending on the starting point.
Term
Receptor Protein
Definition
Protein that detects a stimulus, usually a change in concentration of a specific molecule, and then initiates a response in the cell. Cell-surface receptors, such as the acetylcholine receptor and the insulin receptor, are located in the plasma membrane, with their ligand-binding site exposed to the external medium. Intracellular receptors, such a steroid hormone receptors, bind ligands that diffuse into the cell across the plasma membrane.
Term
Receptor Serine/Threonine Kinase
Definition
Enzyme coupled receptor with an extracellular signal-binding domain and an intracellular kinase domain that phosphorylates signaling proteins on serine or threonine
Term
Receptor Tyrosine Kinase (RTK)
Definition
Enzyme coupled receptor in which the intracellular domain has a tyrosine kinase activity, which is activated by ligand binding to the receptor’s extra-cellular domain
Term
Receptor, Receptor Protein
Definition
Detects a stimulus, usu a change in concentration, and then initiates a response in the cell
Term
Receptor-Mediated Endocytosis
Definition
Mechanism of selective uptake of material by animal cells in which a macromolecule binds to a receptor in the plasma membrane and enters the cell in a clathrin-coated vesicle
Term
Regulatory DNA Sequence
Definition
DNA sequence to which a transcription regulator binds to determine when, where, and in what quantities a gene is to be transcribed into RNA
Term
Replication Origin
Definition
Site on a chromosome at which DNA replication begins
Term
Reporter Gene
Definition
Introduced gene encoding a protein whose activity is easy to monitor experimentally. It is usually joined to a regulatory sequence, which will then switch on the reporter gene in the normal context in which its own gene is usually expressed
Term
Repressor
Definition
A protein that binds to a specific regulatory region of DNA to prevent transcription of an adjacent gene
Term
Ribosomal RNA (rRNA)
Definition
Any one of a number of specific RNA molecules that form part of the structure of a ribosome and participate in the synthesis of proteins. Often distinguished by their sedimentation coefficient, such as 28S rRNA or 5S rRNA
Term
Ribosomes
Definition
Particle composed of ribosomal RNAs and ribosomal proteins that associates with messenger RNA and catalyzes the synthesis of protein
Term
Riboswitch
Definition
Short sequences within some RNAs that change their conformation when specifically bound to small molecules such as metabolites and in this way regulate transcription or translation
Term
Ribozyme
Definition
An RNA molecule possessing catalytic properties
Term
RNA
Definition
A (usually) single-stranded polynucleotide in the form of a chain of covalently linked ribonucleotide subunits. It is synthesized when an RNA polymerase copies the nucleotide sequence of DNA. RNA serves a variety of functions in cells.
Term
RNA Interference (RNAi)
Definition
Cellular mechanism activated by double-stranded RNA molecules that results in the destruction of RNAs containing a similar nucleaotide sequence. It is widely exploited as an experimental tool for preventing the expression of selected genes (gene silencing)
Term
RNA Polymerase
Definition
Enzyme that catalyzes the synthesis of an RNA molecule on a DNA template from nucleoside triphosphate precursors
Term
Rough Endoplasmic Reticulum
Definition
Region of the ER associated with ribosomes and involved in the synthesis of secreted and membrane-bound proteins
Term
Second Messenger
Definition
Small molecule formed in or released into the cytosol in response to an extracellular signal that helps to relay the signal to the interior of the cell
Term
Secondary Structure
Definition
Regular local folding pattern of a polymeric molecule in proteins, it refers to alpha helices and beta sheets
Term
Secretory Vesicle
Definition
Membrane-enclosed organelle in which molecules destined for secretion are stored prior to release. Sometimes called a secretory granule because darkly staining contents make the organelle visible as a small solid object
Term
Sequence Identity
Definition
The linear order of monomers in a large molecule, for eample amino acids in a protein or nucleotides in DNA. In general the sequence of a macromolecule specifies its precise biological information.
Term
Serine/Threonine Kinase
Definition
Enzyme that phosphorylates specific proteins on serines or thronines
Term
Side Chain
Definition
Portion of an amino acid not involved in making peptide bonds; gives each amino acid its unique properties
Term
Signal Cascade
Definition
Sequence of linked protein reactions, often including phosphorylation and dephosphorylation, that carries information within a cell, often amplifying an initial signal
Term
Signal Sequence
Definition
Amino acid sequence that directs a protein to a specific location in the cell, such as the nucleus or mitochondria
Term
Signal Transduction
Definition
Conversion of an impulse or stimulus from one physical or chemical form to another. The process by which a cell responds to an extracellular signal
Term
Small Interfering RNA (siRNA)
Definition
Short lengths of RNA produced from double-stranded RNA during the process of RNA interference. They base-pair with identical sequences in other RNAs, leading to the inactivation or destruction of the target RNA
Term
Small Messenger
Definition
Small molecule formed in or released into the cytosol in response to an extracellular signal that helps to relay the signal to the interior of the cell (second messenger)
Term
SNARE
Definition
One of a family of membrane proteins responsible for the selective fusion of vesicles with a target membrane inside the cell
Term
Sodium-Potassium Pump
Definition
Transmembrane carrier protein, found in the plasma membrane of most animal cells, that pumps Na+ out of and K+ into cell, using the energy derived from ATP hydrolysis
Term
Specificity
Definition
Selective affinity of one molecule for another that permits the two to bind or react, even in the presence of many unrelated molecular species
Term
Spectrin
Definition
Cytoskelital protein that lines the inner side of the plasma membrane
Term
Stem Cell
Definition
Relatively undifferentiated cell that can continue dividing indefinitely, throwing off daughter cells that undergo terminal differentiation into particular cell types
Term
Steroid Hormone
Definition
Lipophilic molecule related to cholesterol that acts as a hormone. Estrogen & testosterone as examples
Term
Storage Protein
Definition
Biological reserve of metal ions and amino acids; used by organisms
Term
Telomere
Definition
Structure at the ends of linear chromosomes, associated with a characteristic DNA sequence that is replicated in a pecial way. Counteracts the tendency of the chromosome otherwise to shorten with each round of replication.
Term
Transcription Factor
Definition
Term loosely applied to any protein required to initieate or regulate transcription in eucaryotes. Includes transcription regulators as well.
Term
Transcription Promoter
Definition
Region of DNA that facilitates the transcription of a particular gene
Term
Transcription Regulator
Definition
Protein that binds specifically to a regulatory DNA sequence and is involved in controlling whether a gene is switched on or off
Term
Transcription Terminator
Definition
Region of DNA that markes the end of the transcription of a particular gene
Term
Transfer RNA (tRNA)
Definition
Set of small RNA molecules used in protein synthesis as an interface (adaptor) between mRNA and amino acids. Each type of this molecule is covalently linked to a particular amino acid.
Term
Transport Protein
Definition
Protein that carries ions, small molecules or macromolecules across a biological membrane
Term
Transport Vesicle
Definition
Membrane vesicles that carry proteins from one intracellular compartment to another, for example from the ER to the Golgi
Term
Transporter
Definition
Membrane protein that transports ions or molecules across a cell membrane
Term
Tyrosine Kinase
Definition
Enzyme that phosphorylates specific proteins on tyrosines
Term
Ubiquitin
Definition
Directs proteins to the proteasome, which is an organelle in the cell that degrades and recycles unneeded proteins
Term
Unfolded Protein Response (URP)
Definition
Cellular response triggered by the accumulation of misfolded proteins in the ER. The cell produces more ER and more of the molecular machinery needed to restore proper protein folding and processing
Term
Vesicle
Definition
Small, membrane-enclosed, spherical organelle in the cytoplasm of a eucaryotic cell
Term
Vesicle Fusion
Definition
The merging of a vesicle with another vesicle or a part of a cell membrane
Term
Vesicular Transport
Definition
Transport of material between organelles in the eukaryotic cell via membrane-enclosed vesicles
Term
Voltage-Gated Channel
Definition
Membrane protein that selectively allows ions such as sodium to cross a membrane and is opened by changes in membrane potential. Found mainly in electrically excitable cells such as nerve and muscle.
Term
X-Ray Crystallography
Definition
Technique used to determine three-dimensional protein structures by analyzing the diffraction pattern of a beam of X-rays passed through a crystal of the protein.
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