Biochemistry: Transmembrane Receptors

A voltage-gated sodium ion channel opens when there is a change in the voltage of the membrane and allows sodium ions to flow across its electrochemical gradient. These voltage-gated channels are made up of amino acids and they aid in generating and moving an action potential down a membrane or axon (Brooker, Robert, 106).

Introduction: Cell membranes contain many different types of molecules which have different roles in the overall structure of the membrane. Phospholipids form a bilayer, which is the basic structure of the membrane. Their non-polar tails form a barrier to most water soluble substances. Membrane proteins serves as channels for transport of metabolites, some act as enzymes or carriers, while some are receptors. Lastly carbohydrate molecules of the membrane are relatively short-chain polysaccharides, which has multiple functions, for example, cell-cell recognition and acting as receptor sites for chemical signals.

What is the basic function of a sensory receptor? What are the different types of receptors and what are their functions?

24.Which of the following are common means by which binding of an intercellular chemical messenger with a cell’s receptor brings about an intracellular response?

They approach receptors and, if they fit the particular receptors, they attach to them. When they become attached, they can have either an agonist or antagonist effect. As soon as they are fired from the neuron, the neurotransmitters do not stay in the synaptic cleft, nor do they permanently bind to receptors. Instead, they attach and discharge. They also do not bind forever to receptors but bind and release or are uprooted by other molecules that then proceed to attach to the receptor. “These neurotransmitters are either “recycled” by transporter molecules that carry them back into the cell for future use (reuptake) or they are deactivated by enzymes in the extracellular fluid and their constituent parts are either destroyed or recycled as precursors” (Ingersoll, year, p.

Ionotropic receptors is a binding site that opens when an ion attaches to the binding site. The ionotropic receptor is also a direct method to the ion channels. Ionotropic receptors has a channel where molecules move in and out of the ion channel. The ions that goes into the ion channel are made out of sodium which cause the membrane to become small.

The thrombopoietin receptor is turned on (activated) when a protein called thrombopoietin attaches (binds) to it. The activated thrombopoietin receptor stimulates

These are ion channels found in the membrane that can open in response to the binding of a ligand. This type of receptor has a hydrophilic channel through the middle of it, which allows ions to cross the membrane through the phospholipid bilayer (without this, it wouldn’t be able to because the bilayer is hydrophobic).

The physiological function of each receptor subtype has not been established and is currently the subject of intensive investigation (1).

Reception is the target cell's detection of the signal via binding of a signaling molecule, or ligand. Ligand is a complex biomolecule, usually a protein. Receptor proteins span the cell’s plasma membrane and provide specific sites for water-soluble signaling molecules to bind to Receptors are found in two places; Intracellular proteins are found inside the plasma membrane in the cytoplasm or nucleus.Cell-surface proteins are embedded in the plasma membrane These transmembrane receptors are able to transmit information from outside the cell to the inside because they can transform, when a specific ligand binds to it.

The Sensing Receptors is – Nala listening to Simba, Timon and Pumbaa listening to the conversation between Nala and Simba.

Kir channels contribute to functions such as the repolarization of cardiac action potentials, trans-epithelial transport, and the maintenance of the voltage gradient across the cell membrane. These functions are achieved by regulating the opening and closing (i.e., gating) of Kir channels (Hibino et al., 2010). For this reason, genetic alterations in Kir channels underlie many of the hereditary ion channel diseases known as channelopathies, and which affect the function of multiple organ systems (Abraham et al., 1999; Neusch et al., 2003).

Presenilins have 9 transmembrane domains are evolutionarily conserved integral membrane proteins. Presenilin, along with Aph-1, Pen-2 and nicastrin constitute integral components of a multi-protein protease complex, termed γ-secretase, which is responsible for the intramembranous cleavage of both the amyloid precursor protein (APP) and Notch. Many γ-secretase substrates have diverse cellular functions, including cell adhesion, ion conductance, and receptor kinase activity, to name a few. Presenilins are also known to exert γ-secretase-independent activities including regulation of the Wnt/β-catenin signalling pathway, calcium release from the ER, and lysosomal proteolysis. PS1 operates as a negative regulator of the Wnt/β-catenin signaling

Metabotropic receptors are a type of membrane receptors that act through the action of secondary messenger; these receptors are indirectly linked with ion channels on the plasma membrane through signal transduction mechanisms. They are able to open and close the ion channels. Metabotropic receptors are primarily G-protein coupled receptors and other types are tyrosine kinases and guanylyl cyclase receptors. Metabotropic receptors are commonly activated by neurotransmitters, and few other examples are glutamate receptors and serotonin receptors.

Receptor dimers are receptor complexes formed by two covalently or non-covalently bound receptor subunits. Receptor dimerisation regulates signal transduction in various receptors or alter pharmacology. The Enzyme linked transmembrane receptors (they dimerise only when bound by a ligand to cause activation via autophosphorylation), The G-protein coupled receptors (GPCRs) (they form constitutive dimers to mask the E.R retention motif on the C- terminal) and The intracellular receptors (They form dimers after binding with the ligand).