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| the initial fiber secreted by plant cells when they first form |
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| stout, cable-like structures of cellulose that make up the primary cell wall |
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| gelatinous polysaccharides that fill the space between microfibrils |
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| the force exerted against the wall as incoming water increases the cell's volume |
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| disrupt hydrogen bonds that cross-link the microfibrils in the wall, allowing them to slide past one another |
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| an additional layer of material between the plasma membrane & the primary cell wall secreted by plants as they mature & stop growing |
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| a complex polymer that forms an exceptionally rigid network in the secondary cell wall of wood cells |
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| extracellular matrix (ECM) |
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Definition
| fiber composite secreted by animal cells for structural support |
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| the cable-like protein that dominates the fibrous component of animal ECM |
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| gel-forming substances that consist of protein cores with many large polysaccharides attached to them; found in the matrix that surrounds collagen/other fibrous components |
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| similar cells that function as a unit |
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| membrane proteins that bind to extracellular proteins |
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| ECM crosslinking proteins |
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| intercellular connections are the basis of _____ |
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| a tissue that forms external & internal surfaces |
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| a cell-cell attachment composed of specialized proteins in the plasma membranes of adjacent animal cells |
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| cell-cell attachments particularly common in animal epithelial cells & certain muscle cells |
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| cells begin to aggregate based on their origin, adhering to other cells of the same tissue type |
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| a protein produced by an immune response that binds specifically to a unique molecule type, often another protein |
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| 3 steps for how researchers tested the hypothesis that cell-cell adhesion takes place via interactions between membrane proteins |
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Definition
1. isolate the membrane proteins from a certain cell type; produce pure preparations of each protein
2. inject one of the membrane proteins into a rabbit; the rabbit's immune system cells respond by creating antibodies to the membrane protein, which is recognized as being foreign; purify these antibodies; repeat this procedure for the other membrane proteins that were isolated; in this way, obtain a large collection of antibodies - each of which binds specifically to one (& only one) type of membrane protein
3. add one antibody type to a mixture of dissociated cells from a tissue & observe whether the cells reaggregate normally; repeat this experiment with each of the other antibody types |
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Definition
| the attachment molecules in desmosomes |
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| 2 general categories of how cells respond to exchange of information |
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Definition
1. signals may alter which proteins are produced & which are not by regulating gene expression
2. signals may activate or deactivate particular proteins that already exist in the cell - often those involved in metabolism, membrane transport, secretion, & the cytoskeleton |
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| connect adjacent cells in most animal tissues |
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| plasmodesmata (plasmodesma) |
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Definition
| connections where the plasma membrane & the cytoplasm of the two cells are continuous |
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| 2 independent compartments into which tissues in plant cells are separated by the plasma membrane |
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1. symplast: a continuous network of cytoplasm connected by plasmodesmata
2. apoplast: the region outside the plasma membrane |
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| information-carrying molecules that can act on distant target cells & are secreted into bodily fluids |
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| auxin: chemical structure, received where, function |
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Definition
| small organic compound; plasma membrane; changes in long axis of plant body |
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| brassinosteroids: chemical structure, received where, function |
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| steroid; plasma membrane; plant cell elongation |
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| estrogens: chemical structure, received where, function |
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Definition
| steroid; inside cell; development of female characteristics in animals |
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| ethylene: chemical structure, received where, function |
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Definition
| C2H4 (gas); plasma membrane; fruit ripening, aging |
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| FSH: chemical structure, received where, function |
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Definition
| glycoprotein; plasma membrane; egg maturation, sperm production in animals |
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| insulin: chemical structure, received where, function |
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Definition
| protein, 51 amino acids; plasma membrane; glucose uptake in animal bloodstream |
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| prostaglandins: chemical structure, received where, function |
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Definition
| modified fatty acid; plasma membrane; variety of functions in animal cells |
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| systemin: chemical structure, received where, function |
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Definition
| peptide, 111 amino acids; plasma membrane; plant defenses against herbivores |
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| thyroxine (T4): chemical structure, received where, function |
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| modified amino acid; inside cell; metabolism in animals |
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| 2 important points about signal receptors |
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Definition
1. receptors are dynamic
2. receptors can be blocked |
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| a protein that changes shape & activity after binding to a signaling molecule |
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Definition
| the conversion of a signal from one form to another |
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| how are G-protein-coupled receptors initiated? |
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Definition
| initiate the production of intracellular or "second" messengers that then amplify the signal |
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| how are enzyme-linked receptors initiated? |
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Definition
| trigger the activation of a series of proteins inside the cell through the addition of phosphate groups |
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| 3 steps for lipid-soluble signals being processed directly |
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Definition
1. arrival of signal; steroid hormone diffuses across plasma membrane into cell
2. signal reception; hormone binds to receptor, inducing conformational change
3. direct signal response; hormone-receptor complex binds to DNA, inducing change in gene expression |
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| 4 steps for lipid-insoluble signals requiring transduction |
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Definition
1. signal reception
2. signal transduction from extracellular signal to intracellular signal
3. signal amplification (in most cases)
4. signal response; for example, specific proteins are activated that induce changes in gene expression |
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Definition
| enzymes that activate or inactivate other proteins by adding a phosphate group to them |
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| cyclic guanosine monophosphate (cGMP) |
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Definition
| opens ion channels; activates certain protein kinases |
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Definition
| activates certain protein kinases |
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| inositol triphosphate (IP3) |
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Definition
| opens calcium channels to transport stored calcium ions |
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| cyclic adenosine monophosphate (cAMP) |
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Definition
| activates certain protein kinases |
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Definition
| binds to a receptor called calmodulin; Ca 2+/calmodulin complex then activates proteins |
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| 5 steps for receptor tyrosine kinases (RTKs) |
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Definition
1. a hormone binds to an RTK
2. the protein forms a dimer; in this conformation, the catalytic activity of the receptor is turned on, allowing it to phosphorylate itself using ATP inside the cell
3. proteins inside the cell bind to the phosphorylated RTK to form a bridge between the receptor & a peripheral membrane protein called Ras (G protein)
4. when Ras is activated, it triggers the phosphorylation & activation of another protein
5. the phosphorylated protein is a protein kinase, which then catalyzes the phosphorylation & activation of other kinases, which phosphorylate yet another population of proteins |
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| 5 steps in enzyme-linked receptors |
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Definition
1. signaling molecule arrives & binds to receptor monomers, causing them to dimerize
2. activated receptor complex turns on the receptor's kinase activity, which phosphorylates itself at tyrosine residues
3. binding proteins bind to the phosphorylated receptor & one of them activates Ras by causing it to exchange GDP for GTP
4. activated Ras triggers phosphorylation & activation of a protein kinase
5. a phosphorylation cascade results, where each kinase phosphorylates a different kinase until a response is triggered in the cell |
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| 2 results of the signal transduction event |
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Definition
1. it converts an easily transmitted extracellular message into an intracellular message
2. it amplifies the original message many times over |
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Definition
| enzymes that remove phosphate groups from cascade proteins |
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Definition
| the signals from different pathways interact to modify the cell response |
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| two sexes (mating types) of Saccharomyces cerevisiae (baker's yeast) |
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Definition
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| chemical signaling molecules involved in mating types in yeast cells |
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| the a mating type in yeast cells secretes the pheromone _____ factor |
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Definition
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| the alpha type in yeast cells secretes the pheromone _____ factor |
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| signaling pathways that respond to population density in microbes |
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