signal

Examples of signal in the following topics:

• Forms of Signaling

  • There are four categories of chemical signaling found in multicellular organisms: paracrine signaling, endocrine signaling, autocrine signaling, and direct signaling across gap junctions .
  • Signals that act locally between cells that are close together are called paracrine signals.
  • A synaptic signal is a chemical signal that travels between nerve cells.
  • In chemical signaling, a cell may target itself (autocrine signaling), a cell connected by gap junctions, a nearby cell (paracrine signaling), or a distant cell (endocrine signaling).
  • Paracrine signaling acts on nearby cells, endocrine signaling uses the circulatory system to transport ligands, and autocrine signaling acts on the signaling cell.

• Termination of the Signal Cascade

  • Signal cascades convey signals to the cell through the phosphorylation of molecules by kinases.
  • Ligand binding to the receptor allows for signal transduction through the cell.
  • The chain of events that conveys the signal through the cell is called a signaling pathway or cascade.
  • The aberrant signaling often seen in tumor cells is proof that the termination of a signal at the appropriate time can be just as important as the initiation of a signal.
  • Describe the process by which the signal cascade in cell communication is terminated

• Signaling in Yeast

  • Yeasts utilize cell-surface receptors, mating factors, and signaling cascades in order to communicate.
  • The components and processes found in yeast signals are similar to those of cell-surface receptor signals in multicellular organisms.
  • Because yeasts contain many of the same classes of signaling proteins as humans, these organisms are ideal for studying signaling cascades.
  • Therefore, the signaling cascades are also simpler and easier to study, although they contain similar counterparts to human signaling
  • Describe how cell signaling occurs in single-celled organisms such as yeast

• Signaling Consideration

  • Signaling is the conveyance of nonpublic information through public action, and is often used as a technique in capital structure decisions.
  • That party would then interpret the signal and adjust its purchasing behavior accordingly -- usually by offering a higher or lower price than if the signal had not been received.
  • A basic example of signaling is that of a student to a potential employer.
  • Therefore, investors generally view all capital structure decisions as some sort of signal.
  • Explain how a company's attempts at signaling can affect its capital structure

• Binding Initiates a Signaling Pathway

  • This type of receptor spans the plasma membrane and performs signal transduction in which an extracellular signal is converted into an intracellular signal.
  • Another complicating element is signal integration of the pathways in which signals from two or more different cell-surface receptors merge to activate the same response in the cell.
  • The effects of extracellular signals can also be amplified by enzymatic cascades.
  • At the initiation of the signal, a single ligand binds to a single receptor.
  • However, activation of a receptor-linked enzyme can activate many copies of a component of the signaling cascade, which amplifies the signal.

• Signaling in Bacteria

  • Bacterial signaling allows bacteria to monitor cellular conditions and communicate with each other.
  • Because the number of cells present in the environment (the cell density) is the determining factor for signaling, bacterial signaling was named quorum sensing.
  • Quorum sensing uses autoinducers as signaling molecules.
  • The peptide autoinducers stimulate more complicated signaling pathways that include bacterial kinases.
  • Describe how cell signaling occurs in single-celled organisms such as bacteria

• Carbon NMR Spectroscopy

  • The results of repeated pulse sequences are accumulated to provide improved signal strength.
  • The dispersion of 13C chemical shifts is nearly twenty times greater than that for protons, and this together with the lack of signal splitting makes it more likely that every structurally distinct carbon atom will produce a separate signal.
  • The only clearly identifiable signals in the proton spectrum are those from the methyl groups.
  • The methyl carbon signal will appear at high field (near 20 ppm), and the aromatic ring carbons will all give signals having δ > 100 ppm.
  • Isomer A displays only four carbon nmr signals (δ 15.4, 133.4, 145.8 & 187.9 ppm); whereas, isomer B displays five signals (δ 15.9, 133.3, 145.8, 187.5 & 188.1 ppm), the additional signal coming from the non-identity of the two carbonyl carbon atoms (one colored orange and the other magenta).

• Cell Signaling and Cell Growth

  • Cell signaling pathways play a major role in cell division.
  • Cells do not normally divide unless they are stimulated by signals from other cells.
  • Signaling pathways control cell growth.
  • Mutations in these genes can result in malfunctioning signaling proteins.
  • Herceptin therapy helps to control signaling through HER2.

• Phasors

  • There are two key ideas behind the phasor representation of a signal:
  • a real, time-varying signal may be represented by a complex, time-varying signal; and
  • a complex, time-varying signal may be represented as the product of a complex number that is independent of time and a complex signal that is dependent on time.
  • With so defined, the signal x(t) may also be written as
  • In this form the signal is easy to plot.

• Methods of Intracellular Signaling

  • The induction of a signaling pathway depends on the modification of a cellular component by an enzyme.
  • They are small molecules that propagate a signal after it has been initiated by the binding of the signaling molecule to the receptor.
  • Phosphatidylinositol (PI) is the main phospholipid that plays a role in cellular signaling.
  • Termination of the signal occurs when an enzyme called phosphodiesterase converts cAMP into AMP.
  • Explain how the binding of a ligand initiates signal transduction throughout a cell