Membrane transport symport

Examples of such intra cellular membrane transport mechanisms include the transfer of pyruvate, the symport (exchange) mechanism of ADP and ATP and the malate-oxaloacetate shuttle, all of which operate across the mitochondrial membranes. Compartmentalization also allows the physical separation of metabolically opposed pathways. For example, in eukaryotes, the synthesis of fatty acids (anabolic) occurs in the cytosol whilst [3 oxidation (catabolic) occurs within the mitochondria. 

A membrane protein or protein complex that is responsible for the simultaneous transport of two molecular entities or ions across the membrane, each entity traveling in opposite directions. See Uniport Symport Membrane Transport... 

Figure 3.7 Membrane transporters involved in active transport. (A) a uniport, (B) a symport, and (C) an antiport.

A second membrane transport system essential to oxidative phosphorylation is the phosphate translocase, which promotes symport of one H2PO4 and one H+ into the matrix. This transport process, too, is favored by the transmembrane proton gradient (Fig. 19-26). Notice that the process requires movement of one proton from the P to the N side of the inner membrane, consuming some of the energy of electron transfer. A complex of the ATP synthase and both translocases, the ATP synthasome, can be isolated from... 

Figure 9.29 Some mammalian (left) and microbial (right) membrane transport systems. (A) Primary electrogenic mechanisms (pumps) creating either a Na+ or a H+ gradient. (B) Secondary active transport systems of the symport type, in which the entry of a nutrient S into the cell is coupled with the entry of either the sodium ions or protons. (D) Various passive ion movements, possibly via channels or uniports. (Reproduced by permission from Serrano R. Plasma Membrane ATPase of Plants and Fungi. Boca Raton CRC Press, 1985, p. 59.)...

A FIGURE 18-1 Overview of synthesis of major membrane lipids and their movement into and out of cells. Membrane lipids (e.g., phospholipids, cholesterol) are synthesized through complex multienzyme pathways that begin with sets of water-soluble enzymes and intermediates in the cytosol (D) that are then converted by membrane-associated enzymes into water-insoluble products embedded in the membrane (B), usually at the interface between the cytosolic leaflet of the endoplasmic reticulum (ER) and the cytosol. Membrane lipids can move from the ER to other organelles (H), such as the Golgi apparatus or the mitochondrion, by either vesicle-mediated or other poorly defined mechanisms. Lipids can move into or out of cells by plasma-membrane transport proteins or by lipoproteins. Transport proteins similar to those described in Chapter 7 that move lipids (0) include sodium-coupled symporters that mediate import CD36 and SR-BI superfamily proteins that can mediate... 

A second membrane transport system essential to oxidative phosphorylation is the phosphate translocase, which promotes symport of one H2POT and one into the matrix. This transport process, too, is favored by the transmembrane proton gradient (Fig. 

The interplay of H, K, Na", and the transmembrane potential and their effect on membrane transport is a complex phenomenon. Which factors are the independent variables in a transport process and which are the dependent variables is difficult to determine. However, it is well-established that transport of many amino acids, sugars, and other carbon and nitrogen sources requires the co-transport (symport) of an ion along with it and probably the reverse transport (antiport) of a similarly charged ion. 

Cox and Henick-Kling (1989, 1990) reported activity similar to that of a proton pump and ATPase in the formation of ATP during MLF. L-malate enters the cell through the action of a specific transport enzyme and is decarboxylated as described previously. To prevent proton accumulation and, eventually, cell death, it is necessary to export them continually. This is accomplished by transport (symport) of L-lactate along with a a single proton. Repeated proton translocation creates a protonmotive force, or delta-pH (A-pH), across the membrane. Reentry of protons through membrane-associated ATPase generates ATP. Theoretically, one ATP is... 

Antiport A membrane transport process that couples the transport of a substance in one direction across a membrane to the transport of a different substance in the other direction. Compare symport. 

Figure 2.24 Alkali-metal chloride transport (symport) through a membrane by the receptor 2.108.

Reporter genes can also encode for extracellular receptors such as dopamine D2 (200) and SST type-2 receptors (201), or membrane transporters such as the sodium/iodide symporter (202). These human genes have been suggested as candidate reporter genes because they exhibit limited expression in the body. At the same time, radiolabeled tracers with high affinity for these extracellular gene-products have been extensively studied and are approved for human use [e.g., [ F]fluoroethylspiperone for D2 receptors (203), " in-pentetreotide for SST receptors (121), and 123/124/I3ij... 

Previously the possibility of using Sc, Sm, and Nd mono- and diphosphorylated amines 1-3 as membrane carriers in conditions of active transport with use of 1,2-dichlorobenzene as a membrane solvent has been shown. At the same time, a high rate of transmembrane transfer of ions Sc and Nd N,N-bis(dihexyl phosphoryl methyl) octyl amine (1) was set. In this paper, the new results of research of membrane transport properties of 1-3 carriers, by symport mechanism are described, and in this case the environmentally acceptable solvent—kerosene as a membrane phase was used. Besides that the membrane-transport properties of diphosphorilamine 4, that have not been described previously containing simultaneously highly lipophilic methyl dioctyl phosphorylic and practically hydrophilic 0,0-diethyl ethyl phosphonate groups in a molecule was studied. It is well-known that creation of optimal hydrophilic-lipophilic balance is a precondition of transmembrane transport effectiveness with organophosphorous carriers. ... 

In bacteria, accumulation of substrates against a concentration gradient can occur through two main classes of transport systems (see [30] for a summary). The prototype of the first class of transporters is the /3-galactoside permease of Escherichia coli (see [31]). It is a relatively simple system involving only a single membrane-bound protein. It catalyzes a lactose-H symport. Other transporters... 

The recovery of neurotransmitters from synaptic clefts and their storage in cytoplasmic vesicles is accomplished by the tandem actions of the secondary transporters in plasma and vesicular membranes. Sodium-dependent symporters mediate neurotransmitter reuptake from synaptic clefts into neurons and glia, whereas proton-dependent antiporters concentrate neurotransmitters from neuronal cytoplasm into synaptic vesicles (Fig. 5-13). 

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