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Cell Biology Test 4
Ch. 7,15,18
70
Biology
Undergraduate 3
04/19/2013

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Term
7 Glycocalyx
Definition
the cell coat- formed from carbohydrate projections from the plasma membrane & mediates cell to cell and cell to substratum interactions
Term
7 The extracellular matrix (ECM)
Definition
an organized network beyond the plasma membrane - plays role in stermining shape and activities of the cell
Term
7 Basement membrane
Definition
ECM... a cont. sheet that underlies epithelial tissue and surrounds blood vessels. - maintian cell attchm. - substratum for cell migration - barrier to macromolecules
Term
7 Collagens
Definition
Fibrous gycoproteins found only in the ECM.
Most abundant protein in the body
provide high tensile strength
types of collagen speciffic to parts on the body
ALL COLLAGENS ARE A TRIMER OF POLYPEPTIDE CHAINS WOUND AROUND EACH OTHER
PROVIDE INSOLUABLE FRAMEWORK THAT DETERMINES MECHANICAL PROPERTIES OF THE MATRIX
disease: epidermolysis bullosa
Term
7 Proteogycans
Definition
protein polysaccharide complex, with the core protein attached to glycosaminoglycans (GAGs)
- have repeating disaccharide structure
-Neg charged gags attract cation which attracts water forming gel
Term
7 Fibronectin (Fn)
Definition
a linear array of distinct polypeptides giving it a modular structure
-each polypeptide is about 30Fn modules
Fn modules are found in other proteins too
-FB HAS BINDING SITES FOR OTHER COMPONENTS OF THE ECM
-FB IS ONE COMPONENT THAT GUIDES MIGRATING CELLS DURING EMBRYOGENESIS
Term
7 Laminins
Definition
ECM
Extracellular glycoproteins consisting of three polypeptide cahins inked by disulfide bonds
-HELP CELL MIGRATION DURING DEVELOPMENT
-COMPONENTS OF BASEMENT MEMBRANES
Term
7 Glycoproteins
Definition
are proteins that contain oligosaccharide chains (glycans) covalently attached to polypeptide side-chains.
Term
7 polysacarides
Definition
are long carbohydrate molecules of monosaccharide units joined together by glycosidic bonds(binds carbohydrtes to another molecule).
Term
7 Integrins
Definition
family of membrane proteins composed of heterodimers with alpha beta subunits
-major role in integrating extracellular and intracellular environments/signals.
Role in ADHESION TO CELLS TO THEIR SUBSTRATUM OR OTHER CELLS
-linkage between integrins and their ligand mediates adhesion between cells and their enviroment
-binding of proteins to integrins is facilitated by tripeptde rgd
-integrins cytoplasmic domans contain binding sites for cytoplasmic proteins
-make connection between ECM and the cytoskeleton
Term
7 Focal Adhesions
Definition
scattered, discrete sites for CELL ADHESION TO THEIR SUBSTRATUM IN VITRO
-MAY ACT AS A SENSORY STRUCTURE
-ARE ALSO IMPLICATED IN CELL LOCOMOTION
*key proteins Actin, integrin
Term
7 Hemidesmosomes
Definition
cell to surface BASAL ATTACHMENTS OF EPITHELIAL CELLS TO THE BASEMENT MEMBRANE IN VIVO
-contain a dense plaque with filaments consisting of keratin
-KERATIN FILAMENTS ARE LINKED TO THE ECM BY MEMBRANE-SPANNING INTEGRINS
*key proteins Keratin and integrin
Term
7 DESMOSOMES
Definition
disk shaped in cell to cell interaction
-**contain cadherins that link the two cells across a narrow gap
-** Cadherins of demosomes have different domain structures: desogleins and desmocollins
*keyproteins desoglein and desmocollin (cadherins)
Term
7 Focal Adhesions vs. Hemidemosomes
Definition
FA: outside of the cell in substrate in vitro
Inetgrins connect inner to outer cell surface
Actin filaments represent internal structures

HemiD: Outside of cell in substrate in vivo
Integrins connect inner to outter cell surface
Keratin filaments represent internal structures
Term
7 selectins
Definition
FAMILY OF INTEGRAL MEMBRANEGLYCOPROTEINS THAT BIND TO SUGARS ON THE SURFACE OF THE CELLS
-contain a small cytoplasmic domain, a single membrane-spanning domain, and a large extracellular segment
Three types:
E-endothelial cells
P-on platlets and endothelial cells
L-on leukocytes
Term
7 lectins
Definition
sugar binding proteins
Term
7 immunoglobin superfamily (IgSF)
Definition
most proteins are involved in immune functions.
-most igSF molecules mediate interaction of lymphocytes with cells required for immune response
-contain fibronectin like domains (FnIII)
Term
7 cadherins
Definition
glycoproteins tbat mediate ca2+ dependent cell-cell adhesion
-transmit signals from ECM to the cytoplasm
-mediate many of the changes in adhesive contacts during embryonic deleopment through the epithelial-mesenchymal transition (EMT)
Term
7 cadherins and the EMT
Definition
Migration from one location to another is associated with the loss if cadherin expression, allowing cadherin decficent cells to eliminate their connections with adjacent cells. and become neural tubes
Term
7 inflammatory responses
Definition
- recruitment of leukocytes to site of injury
- NEUTROPHILS ATTAH P- and E-Selectins
-Neutrophils start to "roll" along wall of vessels
Term
7 The role of cell adhesion in inflammation
Definition
- as neutrophils interact with inflamed venule endotheliium, platelet activating factor (PAF) is displayed
-PAF sends a signal to invrease the binding activity of some integrins
-Activated integrins casue neutrophils to stop rolling and adhere firmly the wall of vessel
Term
7 Mestastis
Definition
The spread of a tumor to other parts of the body
Term
7 Mestastic cell properties
Definition
-are less adhesive
-able to penetrate several barriers
-able to invade normal tissues
Term
7 The role of cell adhesion in metastasis
Definition
DURING GROWTH AND DEVELOPMENT OF A TUMOR THERE IS LODD OF E-CADHERIN LEADING TO LESS ADHESION
-CHANGES IN NUMBERS AND TYPES OF CELL-ADHESION MOLECULES PROMOTE METATASIS
Term
7 Adherens Junctions
Definition
**form belts near apical surface called Junctional Complex
**cells of an adherens junction held together by calcium-dependent linkages (eg cadherins)
*Key proteins : actin, cadherins
Term
7 Transmembrane signaling
Definition
the transer of information across the plasma membrane
-** Integrins and cadherins can transmit signals from the extracellular environment to the cytoplasm
Term
7 Tight Junctions
Definition
*specialized contacts between epithelial cells
-*located at the very apical end of the junctional complex between adjacent cells
-*serve as a barrier to the free diffusion of water and solutes from the extracellular compartment
-some are permeable to specffic ions or solutes
-form the blood-brain barrier
**keyproteins:occudin and claudin
Term
7 Occludins
Definition
proteins found in TJs
Term
7 Claudins
Definition
form the major structural component of TJs and in the differnce in selective permaiblity
Term
7 gap junctions
Definition
**sites between animal cells for intercellular communication
- composed entirely of the membrane protein connexin which are organized into a connexon
-gj intercellular communincation allows the passage of low-weight molecules
-**allow integration of activites of cells into a finctional unit
-**compatibility differences between connexins either promote or prevent communication between different cells
*key protein: connexin
Term
7 Cell walls
Definition
provide plants protection against mechanical abrasion, pathogens, and osmotic stress
-the fibrous componet is cellulose
-cellulose is organized into microfibrils, (provide cell wall rigidity)
-matrix contans HEMICEEULOSES, PECTINS, and PROTEINS
-arrise as a ceel plate that forms between plasma membrane and daughter cells
-the walls of growing cells are PRIMARY WALLS and allow fexibility that the SECONDARY WALLS in mature cells lack
Term
7 Plasmodesmata
Definition
**cytoplasmic channels passing through cell walls of adjacent plant cells
-lined by plasma membrane
-contain a central structure (desmotuble)
-serve as sites of cell-cell communincation
Term
15 Extra cellular messenger molecules
Definition
*transmit messages between cells
Term
15 Autocrine signaling
Definition
the cell receptor is on its surface that respond to the messenger
Term
15 paracrine signaling
Definition
messenger molecules travel short distances through extracellular space
Term
15 endocrine signaling
Definition
messenger molecules reach their target cell through the blood stream
Term
15 receptors
Definition
*Recieve the message
-some receptors generate an intracellular second messenger through an enzyme called an EFFECTOR.
-other surface receptors recruit proteins to their intracellular domains
Term
15 Signaling Pathways in signal transduction
Definition
consits of a series of proteins
- each protein in a pathway alters the conformation of the next protein
- protein conformation is usually altered by phosphorylation ( adding a phosphate group to another molecule)
-target proteins ultimately receive a message to alter cell activity
Term
15 extracellular messengers include...
Definition
-small molecules like amino acids and their derivatives
-gases such as NO and CO
-Eicosanoids,(lipids derived form fatty acids)
-peptides and proteins
Term
15 Types of Receptors
Definition
- steroid hormone receptors (NR)
-**G-protein coupled recpetors (GPCRs)
-** Receptor protein-tyroine kinases RTKs
-ligand gated channels
-B and T receptors
Term
15 GPCRs
Definition
g prtoein coupled receptors are numerous and have seven trans-membrane domain and interact with G proteins
Term
15 Signal Transduction by G protein-coupled receptors
Definition
-Ligand binding on the extracellular domain changes the intracellular domain
-affinity for g proteins increases, and the receptor binds G protein intracellularly
-GDP is exchanged for GTP on the G protein, activating the G protein
-one ligand-bound receptor can activate many g proteins
Term
15 Termination of response in G protein couples receptors
Definition
-Densensitization- by blocking active receptors turning on additonal G proteins
-G protein couldped receeptor kinase GRK -activates a GPCR via phosphorylation
-proteins called arrestins compete with G proteins to bind GPCRs
-Termination of the response is accelerated by regulators of G protein signaling RGS
Term
15 Bacterial toxins
Definition
target GPCRs and Gproteins
Term
15 Cyclic AMP cAMP
Definition
is a 2nd messenger which amplify the response of the ligand
Term
15 DAG diaglycerol
Definition
activates protein kinase C which phosphorylates serine and threnine residues on target proteins
Term
15 phosphorylated phosphoinositides
Definition
form lipid-binding domains called PH domains
a derivative is Phosphoinositides (PI)
Term
15 IP3 receptor
Definition
-one is calcium channel located at the surface of the smooth endoplasmic reticulum
-binding of ip3 opens the channel and allows ca2+ ions to diffuse out
Term
15 Regulation of blood glucose level
Definition
- **different stimuli acting on the same target may induce the same response
-** glucagon and epinephrine bind to different receptors on the same cell
-both hormones stimulate glucoses breakdown and inhibit synthesis
-**cAMP is activated by the G protein of both hormone receptors (convergence)
-Responses are amplified by signal cascades
Term
15 other aspects of cAMP signal Transduction
Definition
-some PKA molecules phosphorylate nuclear proteins
-phosphorlayted transcription facttors regulate gene expression
-phosphatases halt the reaction cascade
-cAMP is produced as long as the external stimuli is present
Term
15 role of GPCRs in sensory Preception
Definition
-rhodopsin is a photosensitive protein for black and white vision that is also a GPCRs
-sveral color recptors are GCPRs
-oderant receptors in the nose are gcprs
-taste receptors for bitter and sweet are gpcrs
Term
15 loss of function mutation
Definition
result in nonfunctional signal pathways
retinitis pigmentosa:lacks ability to activate g protein
Term
15 gain of function mutation
Definition
creates a constituively activated G protein (bengin tumors,asthma blood pressure and hiv)
Term
15 Protein-tyrosine kinases
Definition
phosphorylate tyrosine residues on target proteins.
-regulate cell growth, division, differentiation, survival, and migration.
Term
15 receptor protein- tyrosine kinases (RTKs)
Definition
cell surface receptors of the protein-tyrosine kinase family
Term
15 receptor dimerization
Definition
-results from ligand binding
-protein kinase activity is activated
.tyrosine kinase phosphorylates another subunit of the receptor (autophosphorylation).
. RTKs phosphorylate tyrosines within phosphotyrosine motifs
Term
15 Phosphotyrosine-Dependent Protein-Protein Interactions
Definition
**Phoosphorylated tyrosines bind effector proteins that have SH2 domains and PTB (Phosphotyrosine Binding) domains
Term
15 SH2 and PTB domain Proteins include
Definition
-adaptor proteins that bind other proteins
-docking proteins that supply receptors with other tyrosine phosphorylation sites
-signaling enzymes (kinases) that lead to changes in the cell
-transcription factors
Term
15 The Ras Map kinase pathway
Definition
-** ras Gprotein embedded in the membrane by a lipid group
-Ras is active when bound to gtp and inactive when bound to GDP
-ras can have GTPase activity
Term
15 Accesory proteins in ras-map kinase pathway
Definition
GAPs- shortenn the active time of Ras
GEFs-stimulate the exchange for GDp to GTP
GDIs-inhibit GDP
Term
15 Ras-MAP kinase cascade
Definition
a cascade of enzymes resulting in activating transcription factors
Term
15 adapting map kinase to transmit different tyeps of information
Definition
-end results differ in different cells/ situations
-specificity of the MAP kinase response due to differences in the types of kinases participating and differences in spatial organization of components
Term
15 signaling by the the insulin receptor
Definition
-insulin regulates blood glucose levels by increasing cellular uptake of glucose
-The insulin receptor is a proteintyrsine kinase
.) autophosphorylated receptor is a protein-tyrosine kinase
.) IRSs bind proteins with SH2 domains, which activate downstream signal molecules.
.) SH2 domain-containg proteins are kinases that phosphorylate a lipid, PI3 kinase
Term
15 Glucose Transport
Definition
-PKB regulates glucose uptake by GLUT4 transporters
.) GLUT4 transporters reside in intracellular membrane vesicales
.)Vesicles fuse with the mebrane in response to ligand binding to the IR
-Diabetes mellitus is caused by defects insulin signaling and type 2 diabetes is caused by gradual insensitivity to insulin
Term
15 Insulin signaling and lifespan
Definition
- lifespan increased with insulin decreases; shows high levels and increased insulin sensitivity
Term
Signaling pathways in Plants
Definition
-plants lack cyclic nucleotides and RTKs
-plants have protein kinases what phosphoylate histidine residues
>downstream cascade simlar to Map kinase cascade
>target of the cascade is usually transcription factors
Term
Cytoplasmic calcium levels
Definition
are determined by events within a membrane
-calcium levels control cistol beacause it is pumped out into the extracellular space and the membrane is highly permeable to the ion
-calcium channels can be transiently opened by action potentiality or calcium itself
-**calcium binds to calcium binding proteins like calmodulin which afffects other proteins
Term
Regulating calcium concentration in plant cells
Definition
-cytosolic calcium changes in response to sever stimuli, including light, pressure, gravity, and hormones
-Calcium signaling aids in decreasing turgor pressure in guard cells
Term
Signaling pathways can converge, diverge, and cross talk as follows...
Definition
-**Signals form unrelated receptors can converge to activate a common effector
-**identical signals can diverage to activate a variety of effectors
-**signals can be passed back and forth between pathways as a result of crosstalk
Term
Convergence
Definition
- GPCRs, receptors tyrosine kinases, and integrins bind to different ligands but they all can lead to a docking site for Gbr2
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