Communication Signaling in Cells and Molecules Intelligent Design BIO Lesson 9 by Owen Borville August 20, 2024
Two types of communication among cells are: Intercellular signaling is communication between cells; Intracellular signaling is communication within cells
Signaling cells are cells that release signal molecules that allow communication with another cell, usually with ligands.
Ligands are signaling molecules produced by signaling cells that bind with a specific receptor, delivering a signal in the process.
Target cells are cells that have a receptor for a signal or ligand from a signaling cell. Ligands interact with proteins in target cells.
Receptors are proteins in or on a target cell that bind to ligands.
Types of Chemical Signaling: Signals that act locally between cells that are close together are called paracrine signals, which are delivered by ligands travelling in the liquid medium moving by diffusion.
Synaptic signaling involves chemical signals or neurotransmitters that travel between nerve cells. The junction between nerve cells where a signal transmission occurs is called a synapse. Paracrine signals occur with the transfer of signals across synapses between nerve cells. A nerve cell contains a cell body, several short, branched extensions called dendrites that receive stimuli, and a long extension called an axon, which transmits signals to other nerve cells or muscle cells. Signals within the nerve cells are propagated by fast-moving electrical impulses.
Neurotransmitters are chemical ligands that carry signals from one cell to the next from the end of the axion to the dendrite of the next cell.
Chemical synapses are small spaces between axion terminals and dendrites of nerve cells where neurotransmitters function.
Endocrine signals are from distant cells (endocrine cells) delivered by ligands or hormones travelling through an organism's circulatory system from the signaling cell to the target cell. Endocrine signals are produced in one part of the body but influence another part of the body. Hormones travel between endocrine and target cells through the bloodstream.
Autocrine signals are produced by signaling cells that can also bind to the ligand that is released. The signaling cell and the target cell can be the same or similar cell
Intracellular mediators, or second messengers, are small molecules that transmit signals within a cell through fluid-filled channels.
Receptors are protein molecules in or on a target cell that bind to ligands.
Internal receptors (intracellular receptors or cytoplasmic receptors), are receptor proteins that are located in the cytosol of a cell and bind to ligands that pass through the plasma membrane; they respond to hydrophobic ligand molecules that are able to travel across the plasma membrane.
Cell surface receptors (or transmembrane receptors) are cell surface proteins that transmit a signal from the exterior of the cell to the interior, even though the ligand does not enter the cell, and bind to external ligand molecules. Cell Surface Receptor components: external ligand binding domain called the extracellular domain, the transmembrane domain, and an intercellular domain inside the cell.
Cell Surface Receptor Types
Ion-channel linked receptors are cell surface receptors that form a plasma membrane channel, which open when a ligand binds to the extracellular domain (ligand-gated channels)
G-protein linked receptors are cell surface receptors that activate membrane-bound G-proteins to transmit a signal from the receptor to nearby membrane components
Enzyme-linked receptors are cell surface receptors with intracellular domains that are associated with membrane bound enzymes
Signaling Molecules Small hydrophobic ligands can directly diffuse through the plasma membrane and interact with internal receptors. Water-soluble ligands are polar, and therefore, cannot pass through the plasma membrane unaided, but rather bind to the extracellular domain of cell-surface receptors. NO (nitric oxide) is a gas that also acts as a ligand and is able to directly diffuse across the plasma membrane.
Signal transduction is the propagation of the signal through the cytoplasm (and sometimes the nucleus of the cell) and only occurs with cell-surface receptors.
Dimerization of receptor proteins is the interaction of two receptor proteins to form a functional complex called a dimer.
Dimer is a chemical compound formed when two molecules join together (often identical).
Signaling pathway or Signaling cascade is a chain of events that occurs in the cytoplasm of the cell to propagate the signal from the plasma membrane to produce a response. Second-messengers, or enzymes, and activated proteins interact with specific proteins, which are in turn activated in a chain reaction that eventually leads to a change in the cell's environment, such as an increase in metabolism or specific gene expression.
Signal integration is the interaction of signals from two or more different cell-surface receptors that merge to activate the same response in the cell.
Kinase is an enzyme that catalyzes the transfer of a phosphate group from ATP to another molecule.
Second messengers are small, non-protein molecules that propagate a signal within the cell after activation of a receptor causes its release. Calcium ion is widely used as a second messenger.
Cyclic Amp (cAMP) is a second messenger that is derived from ATP and the enzyme adenylyl cyclase
cAMP-dependent kinase (A-kinase) also, protein kinase A, or PKA, kinase that is activated by binding to cAMP
Inositol phospholipids are lipids present in small concentrations in the plasma membrane that is converted to a second messenger; it has inositol (a carbohydrate) as its hydrophilic head group
Diacylglycerol (DAG) is a cleavage product of PIP2 that is used for signaling within the plasma membrane
inositol triphosphate (IP3) is a cleavage product of PIP2 that is used for signaling within the cell
Gene Expression
Some signal transduction pathways regulate the transcription of RNA, while others regulate the translation of proteins from mRNA.
Proteins that regulate translation in the nucleus. Ex. MAP kinase ERK
Inhibitor is a molecule that binds to a protein (usually and enzyme) and keeps it from functioning or reduces its function
Increase in Cellular Metabolism
Another signaling pathway affects muscle cells by an increase in cellular metabolism. Beta-adrenergic receptors in muscle cells by adrenaline increases cyclic AMP in the cell.
Cell Growth: Cell signaling pathways play a major role in cell division.
Growth factors are ligands that bind to cell-surface receptors and stimulate cell growth.
Cell Death or apoptosis is when the cell initiates a mechanism to trigger or program cell death when a cell is damaged, superfluous, or potentially dangerous to an organism.
Phosphatases are enzymes that remove the phosphate group from a molecule that has previously been phosphorylated
Termination of the Signaling Cascade
Phosphodiesterase is the enzyme that degrades cAMP, producing AMP, to terminate the signaling cascade
Signaling in Yeast
Mating factor is the signaling molecule secreted by yeast cells to communicate to nearby yeast cells that they are available to mate
Signaling in Bacteria enables bacteria to monitor extracellular conditions, ensure that there are sufficient amounts of nutrients, and ensure that hazardous situations are avoided.
Quorum sensing is a method of cellular communication used by bacteria that informs them of the abundance of similar (or different) bacteria in the environment.
Autoinducers are signaling molecules secreted by bacteria to communicate with other bacteria of its kind
Two types of communication among cells are: Intercellular signaling is communication between cells; Intracellular signaling is communication within cells
Signaling cells are cells that release signal molecules that allow communication with another cell, usually with ligands.
Ligands are signaling molecules produced by signaling cells that bind with a specific receptor, delivering a signal in the process.
Target cells are cells that have a receptor for a signal or ligand from a signaling cell. Ligands interact with proteins in target cells.
Receptors are proteins in or on a target cell that bind to ligands.
Types of Chemical Signaling: Signals that act locally between cells that are close together are called paracrine signals, which are delivered by ligands travelling in the liquid medium moving by diffusion.
Synaptic signaling involves chemical signals or neurotransmitters that travel between nerve cells. The junction between nerve cells where a signal transmission occurs is called a synapse. Paracrine signals occur with the transfer of signals across synapses between nerve cells. A nerve cell contains a cell body, several short, branched extensions called dendrites that receive stimuli, and a long extension called an axon, which transmits signals to other nerve cells or muscle cells. Signals within the nerve cells are propagated by fast-moving electrical impulses.
Neurotransmitters are chemical ligands that carry signals from one cell to the next from the end of the axion to the dendrite of the next cell.
Chemical synapses are small spaces between axion terminals and dendrites of nerve cells where neurotransmitters function.
Endocrine signals are from distant cells (endocrine cells) delivered by ligands or hormones travelling through an organism's circulatory system from the signaling cell to the target cell. Endocrine signals are produced in one part of the body but influence another part of the body. Hormones travel between endocrine and target cells through the bloodstream.
Autocrine signals are produced by signaling cells that can also bind to the ligand that is released. The signaling cell and the target cell can be the same or similar cell
Intracellular mediators, or second messengers, are small molecules that transmit signals within a cell through fluid-filled channels.
Receptors are protein molecules in or on a target cell that bind to ligands.
Internal receptors (intracellular receptors or cytoplasmic receptors), are receptor proteins that are located in the cytosol of a cell and bind to ligands that pass through the plasma membrane; they respond to hydrophobic ligand molecules that are able to travel across the plasma membrane.
Cell surface receptors (or transmembrane receptors) are cell surface proteins that transmit a signal from the exterior of the cell to the interior, even though the ligand does not enter the cell, and bind to external ligand molecules. Cell Surface Receptor components: external ligand binding domain called the extracellular domain, the transmembrane domain, and an intercellular domain inside the cell.
Cell Surface Receptor Types
Ion-channel linked receptors are cell surface receptors that form a plasma membrane channel, which open when a ligand binds to the extracellular domain (ligand-gated channels)
G-protein linked receptors are cell surface receptors that activate membrane-bound G-proteins to transmit a signal from the receptor to nearby membrane components
Enzyme-linked receptors are cell surface receptors with intracellular domains that are associated with membrane bound enzymes
Signaling Molecules Small hydrophobic ligands can directly diffuse through the plasma membrane and interact with internal receptors. Water-soluble ligands are polar, and therefore, cannot pass through the plasma membrane unaided, but rather bind to the extracellular domain of cell-surface receptors. NO (nitric oxide) is a gas that also acts as a ligand and is able to directly diffuse across the plasma membrane.
Signal transduction is the propagation of the signal through the cytoplasm (and sometimes the nucleus of the cell) and only occurs with cell-surface receptors.
Dimerization of receptor proteins is the interaction of two receptor proteins to form a functional complex called a dimer.
Dimer is a chemical compound formed when two molecules join together (often identical).
Signaling pathway or Signaling cascade is a chain of events that occurs in the cytoplasm of the cell to propagate the signal from the plasma membrane to produce a response. Second-messengers, or enzymes, and activated proteins interact with specific proteins, which are in turn activated in a chain reaction that eventually leads to a change in the cell's environment, such as an increase in metabolism or specific gene expression.
Signal integration is the interaction of signals from two or more different cell-surface receptors that merge to activate the same response in the cell.
Kinase is an enzyme that catalyzes the transfer of a phosphate group from ATP to another molecule.
Second messengers are small, non-protein molecules that propagate a signal within the cell after activation of a receptor causes its release. Calcium ion is widely used as a second messenger.
Cyclic Amp (cAMP) is a second messenger that is derived from ATP and the enzyme adenylyl cyclase
cAMP-dependent kinase (A-kinase) also, protein kinase A, or PKA, kinase that is activated by binding to cAMP
Inositol phospholipids are lipids present in small concentrations in the plasma membrane that is converted to a second messenger; it has inositol (a carbohydrate) as its hydrophilic head group
Diacylglycerol (DAG) is a cleavage product of PIP2 that is used for signaling within the plasma membrane
inositol triphosphate (IP3) is a cleavage product of PIP2 that is used for signaling within the cell
Gene Expression
Some signal transduction pathways regulate the transcription of RNA, while others regulate the translation of proteins from mRNA.
Proteins that regulate translation in the nucleus. Ex. MAP kinase ERK
Inhibitor is a molecule that binds to a protein (usually and enzyme) and keeps it from functioning or reduces its function
Increase in Cellular Metabolism
Another signaling pathway affects muscle cells by an increase in cellular metabolism. Beta-adrenergic receptors in muscle cells by adrenaline increases cyclic AMP in the cell.
Cell Growth: Cell signaling pathways play a major role in cell division.
Growth factors are ligands that bind to cell-surface receptors and stimulate cell growth.
Cell Death or apoptosis is when the cell initiates a mechanism to trigger or program cell death when a cell is damaged, superfluous, or potentially dangerous to an organism.
Phosphatases are enzymes that remove the phosphate group from a molecule that has previously been phosphorylated
Termination of the Signaling Cascade
Phosphodiesterase is the enzyme that degrades cAMP, producing AMP, to terminate the signaling cascade
Signaling in Yeast
Mating factor is the signaling molecule secreted by yeast cells to communicate to nearby yeast cells that they are available to mate
Signaling in Bacteria enables bacteria to monitor extracellular conditions, ensure that there are sufficient amounts of nutrients, and ensure that hazardous situations are avoided.
Quorum sensing is a method of cellular communication used by bacteria that informs them of the abundance of similar (or different) bacteria in the environment.
Autoinducers are signaling molecules secreted by bacteria to communicate with other bacteria of its kind