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| A response by a living cell to a change in it’s environment. |
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| In autocrine signaling, a cell secretes signaling molecules that binds to receptors on it’s own surface. This may affect neighboring cells of the same type. |
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| a signaling molecule transmitted from cell and inhibited by light. (Darwin and plants) |
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-Genetically predetermined cell death. (occurs in eukaryotes)
-Cell shrinks due to destruction of nucleus and cytoskeleton.
-Plasma membrane forms blebs.
-Different pathways have been discovered that lead to Apoptosis. |
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| inhibits phosphodiesterase (causes heart to beat faster) |
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| Contact-dependent signaling |
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Definition
| Some molecules are bound to the surface of cells and provide a signal to other cells that make contact with the surface of that cell. The cell has a membrane-bound signaling molecule that receptors on the surface of other cells can recognize. |
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| may be synthesized by adenylyl cyclase via ATP. (example of 2nd messenger) (p.186) |
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| Direct intercellular signaling |
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| In multicellular organisms, cells adjacent to each other may have contacts (cell junctions) that enable them to pass ions, signaling molecules from cytosol to cytosol. |
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| Signaling that covers long distances using hormones. Hormones secreted into the bloodstream can affect virtually all cells. |
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Fight-or-flight hormone. Acts differently on different cells:
-Promotes breakdown of glycogen in skeletal muscle cells
-Relaxes airways in lungs |
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| First (primary) messengers |
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Definition
| The small molecules or ions that bind surface receptors on the plasma membrane of a cell. (p. 186) |
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| They activate adenylyl cyclase and they activate phospholipase C |
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| cause a rapid increase in the expression of many genes in mammals. (involved in cancer) |
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| An enzyme that transfers a phosphate group to another molecule |
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| signaling molecule that binds noncovelently with high specificity to receptor causing a conformational change. (creates a ligand-receptor complex). Receptors do not change the ligand like enzymes and substrates. (p.177) |
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| A specific cell secretes a signaling molecule that does not affect the cell secreting the signal but instead influences the behavior of target cells in close proximity. Typically short duration. Example - Synaptic signaling - Neurotransmitters. |
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| An enzyme that removes a phosphate group from another molecule |
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| Receptor tyrosine kinases |
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Definition
| category of enzyme-linked receptor. Recognize various type of signaling molecules (animals only) |
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Definition
| small molecules or ions that relay signals inside the cell. (speed and size & amplification) |
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| agents that influence the properties of cells. Affects the conformation of a receptor, leading to a response in the cell. (ex. Glucose acts as a signal to yeast to increase transporters and enzymes.) |
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| Enzyme-inked receptors... |
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Definition
| function by phosphorylation of a protein from ATP in their intracellular domain. (p.182) |
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| Occurs during the signal transduction phase in G protein activation... |
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| Promotion of cellular responses due to dissociation of activated (Alpha) subunit and (Beta/Gamma) subunit. (p. 182-183) |
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| The receptor for the steroid hormone estrogen is found... |
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Cell-to-cell communication:
Direct intercellular communication |
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Definition
| cell junctions between cell are able to pass signaling molecules from cell to cell |
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Cell-to-cell communication:
Contact-dependent signaling |
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Definition
| Signaling molecules on the surface of cells make contact with adjacent receptors on other cells |
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| Cell-to-cell communication: Autocrine signaling |
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Definition
| A cell secretes signaling molecules that bind to receptors on it’s own surface but make also affect adjacent cells |
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Cell-to-cell communication:
Paracrine signaling |
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Definition
| A cell secretes signaling molecules that are aimed at adjacent target cells. (ex. Neurotransmitters / synaptic signaling.) |
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| Cell-to-cell communication: Hormones |
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Definition
| Hormones travel long distances and affect many cells. Can last a longer period of time than other forms of signaling. (steroid hormone receptors are intracellular) |
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| Signal Response - Receptor activation (1) |
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Definition
| A signaling molecule attaches to a receptor and causes a conformational change. (usually an activation of enzymes). |
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| Signal Response - Signal transduction (2) |
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Definition
| The initial signal is changed to another signal inside the cell. Signal Transduction Pathway - the series of changes proteins go through as a result of the signal. |
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| Signal response - Cellular response (3) |
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Definition
-can cause different responses in the cell by affecting different components:
i. Enzymes - Altered metabolism or other cell functions.
ii. Structural proteins - Altered cell shape and/or movement.
iii. Transcription factor - Altered gene expression, which changes the types and the amounts of proteins in the cell. |
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| Cell surface receptors - Enzyme-linked receptors |
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Definition
| Has extracellular domain (allows for signal binding) and intercellular domain (has a catalytic function). Many function as protein-kinases: enzymes that transfer a phosphate group from an ATP to a specific amino acid in a protein. |
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| Cell surface receptors - G-Protein-Coupled Receptors (GPCRs) |
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Definition
| Typically contain 7 trans-membrane segments and interact with G Proteins. Called G Protein because can bind with GTP or GDT. Creates GTP from GDT and P. |
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| Cell surface receptors - Ligand-Gated Ion Channels |
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Definition
| Ligand allows receptor to open and allows the flow of ions through the membrane. |
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| -Functions as a protease (an enzyme that digests other proteins) |
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| enzymes that transfer a phosphate group from an ATP to a specific amino acid in a protein. |
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| an enzyme that digests other proteins. |
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