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| cooperative assemblies of cells found in multicellular organisms |
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| gives supportive tissues their strength; provides one way to bind cells together |
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| link cells together in the flexible, mobile tissues of animals; present in most epithelial tissue; classified according to function; some provide tight seals the prevent leakage of molecules across epithelia, some provide strong mechanical attachments, some provide for intimate chemical communication |
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| self-renewing undifferentiated cells; plays a role in tissue renewal and repair |
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| the strength of plant tissue; formed like boxes that enclose, protect, and constrain the shape of each of its cells; extracellular matrix |
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| long fibers interwoven with other polysaccharides and structural proteins bonded together to form a complex structure that resists compression and tension |
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| extracellular matrix is plentiful and carries the mechanical load |
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| found in all multicellular animals; come in many varieties; constitutes 25% of total protein mass in mammals; chief proteins in bone, tendon, and skin |
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| connective-tissue cells that manufacture and inhabit the matrix; skin, tendon, etc.; makes both collagen and other organic components of the matrix |
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| an extracellular matrix protein that provides linkage to bare collagen |
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| a receptor protein that spans the cell's plasma membrane; passively transmits stress to the cell to the sturdy cytoskeleton |
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| extracellular proteins linked to GAGs; resists compression and serve as space-fillers; extremely diverse |
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| Glycosaminoglycans (GAGs) |
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| a special class of complex negatively charged polysaccharides; strongly hydrophillic; tend to adopt highly extended conformations, occupying a huge volume relative to their mass; easily form gels at low concentrations |
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| the majority of cell types in the body of a vertebrate; cells are joined together side by side to form multicellular sheets |
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| surface of a cell that is free and exposed to the air or to interstitial fluid |
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| surface of a cell that rests on some other tissue to which it is attached |
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| a tough sheet of extracellular matrix composed of a specialized type of collagen and various other macromolecules; supports the basal surface of the epithelium |
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| seals neighboring cells together so that water-soluble molecules cannot easily leak between them |
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| transmembrane proteins to which adherens junctions and desmosomes are built around; a molecule in one cell binds directly to an identical molecule in a neighboring cell; requires Ca++ to be present in the extracellular medium |
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| each cadherin molecule is tethered inside its cell via several linker proteins to actin filaments; often forms a continuous adhesion belt around each of the interacting epithelial cells, located near the apical ends just below the tight junctions |
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| a different set of cadherin molecules achor inside each cell and connect to intermediate filaments (keratins) |
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| externally, integrins bind to the extracellular matrix protein laminin in the basal lamina; inside the cell, they are linked to keratin filaments, creating a structure that looks superficially like half a desmosome |
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| appears as a region where the membranes of two cells lie close together and exactly parallel with a very narrow gap of 2-4 nm between them; this gap is filled via connexons |
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| functional counterpart of gap junctions found in plants; minute communicating channels that are connected to the cytoplasms of adjacent plant cells and span the intervening cell walls (in plants, these cause the cytoplasm to be continuous from one cell to the next) |
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| a class of signal molecules that serve to keep the stem cells and precursor cells at the base of each intestinal crypt in a proliferative state |
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| Embreyonic Stem Cells (ES Cells) |
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| cells that, under the right conditions, can be kept proliferating indefinitely in culture and still retain unrestricted developmental potential |
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| the cloning of entire multicellular animals |
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| an elaborate technique for generating personalized ES cells rather than cloning an entire animal; the process is similar to reproductive cloning at first, but the embryo is never transplanted into a uterus for further development; these cells can be grafted back into the original donor without immunological rejection |
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| Induced Pluripotent Stem Cells (iPS Cells) |
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| the insertion of 3 genes (Oct3/4, Sox2, and Klf4) into fibroblasts converts them into cells essentially the same as ES cells, including the ability to differentiate in diverse ways and to contribute to any tissue; the conversion rate of fibroblasts is low and there is some safety concerns about implanting derivatives of virus-infected cells into patients; process is not currently in use in humans |
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disease of tissue renewal; arise from violations of the basic rules of social cell behavior; defined by 2 properties;
1. proliferate in defiance of normal constraints
2. invade and colonize territories normally reserved for other cells |
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| results from mutations that interfere with the accurate replication and maintenance of the genome and thereby increase the mutation rate itself |
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| only one gene copy needs to be mutated to cause trouble, resulting in this |
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| both gene copies must be lost or inactivated before an effect is seen |
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| the corresponding normal form of an oncogene |
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| slowly expands to accommodate cell growth in multicellular plants |
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| swelling pressure; the driving source of the stretching of the primary cell wall |
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| forms once growth of the cell stops and the wall no longer needs to expand; rigid; produced either by thickening the primary wall or deposition of new layers with a different composition underneath the old ones |
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| polysaccharide; most abundant organic macromolecule on earth; synthesized on the outer surface of the cell by enzyme complexes embedded in the plasma membrane |
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| a highly cross-linked network deposited within the matrix to make the cell more rigid and waterproof; found in woody plants |
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| the ropelike collagen superhelix is ordered into polymers; thin cables 10-300nm in diameter |
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| the precursor form of collagen that cells make to prevent the assembly of the cohesive aggregates inside the cell prior to exocytosis |
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| enzymes that cut off the terminal domains of procollagen to allow assembly after the molecules emerge into the extracellular space |
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| Leucocyte Adhesion Deficiency |
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| people lacking the integrins on WBCs that allows the cells to crawl out of the blood vessels at sites of infection; sufferers undergo repeated bacterial infections |
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| a protein that provides adhesive sites for integrin molecules in the plasma membrane of epithelial cells |
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| proteins that form tight junctions; arranged in strands along the lines of the junction to create the seal |
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| the type of binding where proteins on one cells plasma membrane directly binds to proteins on a neighboring cells plasma membrane |
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| the type of intermediate filament found in epithelia |
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| protruding ends of many identical protein complexes that lie in the plasma membranes of the two apposed cells; forms channels across the two plasma membranes and are aligned end-to-end so as to create narrow passageways that allow inorganic ions and small water-soluble molecules to move directly from the cytosol of one cell to the cytosol of another |
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| Three Key Factors That Maintain The Organization of Tissues |
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1. cell communication
2. selective cell-cell adhesion
3. cell memory |
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| akin to macrophages; slowly eats away at old bone |
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| akin to fibroblasts; new bone matrix is deposited by these |
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| Terminally Differentiated Cells |
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| cells that are unable to divide; RBCs, surface epidermal cells, absorptive and goblet cells of gut lining |
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| Proliferating Precursor Cells |
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| generates the replacements for terminally differentiated cells; derived from stem cells |
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| cells that retain unrestricted developmental potential (stem cells) |
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| the nucleus of an unfertilized egg cell is sucked out and replaced by a nucleus from a regular diploid cell. the diploid donor cell can be taken from a tissue of an adult individual. the embryo begins development in a culture medium until it is transplanted into the uterus of a foster mother, where it grows normally; genetically the same as the donor cell, except for some of the cytoplasmic mitochomdria |
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| cells that proliferate abnormally but to not invade inappropriate territories; can usually be removed cleaning and completely via surgery |
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| a tumor is cancerous only if it has the ability to invade surrounding tissue |
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| the statistical analysis of human populations that is used to look for factors that correlate with disease incidence |
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| Key Behaviors of Cancer Cells |
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Definition
1. reduced dependence on signals from other cells for their growth, survival, and division.
2. less prone than normal cells to undergo apoptosis.
3. can often proliferate indefinitely (due to reactivation of an inactive telomerase).
4. genetically unstable with a greatly increased mutation rate
5. abnormally invasive; lack specific cell adhesion molecules that hold normal cells in their proper place.
6. survive and proliferate in foreign tissues to form secondary tumors |
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| Adenomatous Polyposis Coli (APC) |
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| inactivation of this gene causes early onset of colorectal cancer |
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| a proto-oncogene; gene regulatory protein; activated by an extracellular signal to promote transcription; if mutated, the cell can proliferate without this signal, or will repress apoptosis |
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| the G1 checkpoint mechanism protein; a transcription regulator that activates the transcription of P21; can induce apoptosis if DNA damage is too severe to be repaired; mutants in this gene are found in 1/2 of all human cancers |
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| a tumor suppressor gene; mutations causing inactivation of this gene allows the cell to progress through the G1 checkpoint in the absence of growth factors |
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