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17. The transport of glucose from the blood to the cell is accomplished by which process? a. Active-mediated transport (active transport) b. Active diffusion c. Passive osmosis d. Passive-mediated transport (facilitated diffusion)
May 19, 2019 · Ans: Transport of glucose from the blood to the cell is accomplished by facilitated diffusion (passive process) and secondary active transport or primary active transport (active process requires ATP to transport against concentration gradient). Facilitated diffusion is the major mode of glucose in to the cells is achieved by the special transmembrane protein …
Apr 22, 2018 · Glucose Transport. The oxidation of glucose represents a major source of metabolic energy for mammalian cells. Because the plasma membrane is impermeable to polar molecules such as glucose, the cellular uptake of this important nutrient is accomplished by special carrier proteins called glucose transporters[1][2][3][4][5][6][7].
The movement of K+ ions against its concentration gradient is accomplished by Definition: active transport; membrane potential Term: The Na, K-ATPase is an _____ that movs Na+ ions from _____ and L ions from Definition: antiporter; inside to out; outside to in Term: transport of glucose from the intestine into the intestinal cells is ...
Glucose is transported from the blood to the cell using facilitated diffusion. Facilitated diffusion is a type of passive transport, which moves...
Glucose transporters are a wide group of membrane proteins that facilitate the transport of glucose across the plasma membrane, a process known as facilitated diffusion.
facilitated diffusionActive transport and diffusion. Glucose is transported by active transport, against the concentration gradient, from the gut into intestinal epithelial cells. Whereas glucose is transported by facilitated diffusion into red blood cells.
Glucose is transported across the cell membranes and tissue barriers by a sodium-independent glucose transporter (facilitated transport, GLUT proteins, and SLC2 genes), sodium-dependent glucose symporters (secondary active transport, SGLT proteins, and SLC5 genes), and glucose uniporter—SWEET protein ( SLC50 genes).
The glucose we eat is broken down through glycolysis and used to power the many processes of our cells. Thus, it is essential to supply each of our cells with a steady stream of glucose. Glucose is delivered throughout the body by the blood, and each cell gathers what it needs using glucose transporters.
Glucose enters cells where it undergoes phosphorylation to form glucose-6-phosphate. Changing the form that the glucose is in means that glucose cannot be transported back outside the cell, and the cells sense that the concentration of glucose is higher outside the cell than inside.
The two ways in which glucose uptake can take place are facilitated diffusion (a passive process) and secondary active transport (an active process which depends on the ion-gradient which is established through the hydrolysis of ATP, known as primary active transport). Facilitated diffusion There are over 10 different types of glucose transporters; however, the most significant for study are GLUT1-4. GLUT1 and GLUT3 are located in the plasma membrane of cells throughout the body, as they are responsible for maintaining a basal rate of glucose uptake. Basal blood glucose level is approximately 5mM (5 millimolar). The Km value (an indicator of the affinity of the transporter protein for glucose molecules; a low Km value suggests a high affinity) of the GLUT1 and GLUT3 proteins is 1mM; therefore GLUT1 and GLUT3 have a high affinity for glucose and uptake from the bloodstream is constant. GLUT2 in contrast has a high Km value (15-20mM) and therefore a low affinity for glucose. They are located in the plasma membranes of hepatocytes and pancreatic beta cells (in mice, but GLUT1 in human beta cells; see Reference 1). The high Km of GLUT2 allows for glucose sensing; rate of glucose entry is proportional to blood glucose levels. GLUT4 transporters are insulin sensitive, and are found in muscle and adipose tissue. As muscle is a principal storage site for glucose and adipose tissue for triglyceride (into which glucose can be converted for storage), GLUT4 is important in post-prandial uptake of excess glucose from the bloodstream. Moreover, several recent papers show that GLUT 4 is present in the brain also. The drug Metformin phosphor Continue reading >>
The oxidation of glucose represents a major source of metabolic energy for mammalian cells. Because the plasma membrane is impermeable to polar molecules such as glucose, the cellular uptake of this important nutrient is accomplished by special carrier proteins called glucose transporters [1] [2] [3] [4] [5] [6] [7].
Go to: The Intestinal Epithelium Is Highly Polarized An epithelial cell is said to be polarized because one side differs in structure and function from the other. In particular, its plasma membrane is organized into at least two discrete regions, each with different sets of transport proteins. In the epithelial cells that line the intestine, for example, that portion of the plasma membrane facing the intestine, the apical surface, is specialized for absorption; the rest of the plasma membrane, the lateral and basal surfaces, often referred to as the basolateral surface, mediates transport of nutrients from the cell to the surrounding fluids which lead to the blood and forms junctions with adjacent cells and the underlying extracellular matrix called the basal lamina (Figure 15-23). Extending from the lumenal (apical) surface of intestinal epithelial cells are numerous fingerlike projections (100 nm in diameter) called microvilli (singular, microvillus). Often referred to collectively as the brush border because of their appearance, microvilli greatly increase the area of the apical surface and thus the number of transport proteins it can contain, enhancing the absorptive capacity of the intestinal epithelium. A bundle of actin filaments that runs down the center of each microvillus gives rigidity to the projection. Overlying the brush border is the glycocalyx, a loose network composed of the oligosaccharide side chains of integral membrane glycoproteins, glycolipids, and enzymes that catalyze the final stages in the digestion of ingested carbohydrates and proteins (Figure 15-24). The action of these enzymes produces monosaccharides and amino acids, which are transported across the intestinal epithelium and eventually into the bloodstream. Go to: Transepithelial Movement Continue reading >>
Recall that membranes have two major components: phospholipids arranged in a bilayer, and membrane proteins . One of the functions of membranes is to control what passes into and out of the cell. In this module you will review mechanisms of membrane transport. There are several different types of membrane transport, depending on the characteristics of the substance being transported and the direction of transport. SIMPLE DIFFUSION In simple diffusion, small noncharged molecules or lipid soluble molecules pass between the phospholipids to enter or leave the cell, moving from areas of high concentration to areas of low concentration (they move down their concentration gradient). Oxygen and carbon dioxide and most lipids enter and leave cells by simple diffusion. Illustrations of simple diffusion. Note that the arrows indicate that the substance is moving from where there is more of that substance to where there is less of it, and that the substances are passing between the phospholipids of the membrane. OSMOSIS Osmosis is a type of simple diffusion in which water molecules diffuse through a selectively permeable membrane from areas of high water concentration to areas of lower water concentration. (Note that the more particles dissolved in a solution, the less water there is in it, so osmosis is sometimes described as the diffusion of water from areas of low solute concentration to areas of high solute concentration). Illustration of Osmosis. Assume that the membrane is permeable to water, but not to sucrose (represented by the small black squares). The sucrose molecules will not leave the cell because they cannot pass through the membrane. However, since there is less water on the side with the sucrose, water will enter the cell by osmosis. Another way to describe the two Continue reading >>
The epithelium forms a barrier because cells are linked by tight junctions, which prevent many substances from diffusing between adjacent cells. For a substance to cross the epithelium, it must be transported across the cell's plasma membranes by membrane transporters. Not only do tight junctions limit the flow of substances between cells, they also define compartments in the plasma membrane. The apical plasma membrane faces the lumen. In the drawing, the apical plasma membrane is drawn as a wavy line, because intestinal epithelial cells have a high degree of apical plasma membrane folding to increase the surface area available for membrane transport (these apical plasma membrane folds are known as microvilli). The basolateral plasma membrane faces the ECF. Epithelial cells are able to transport substances in one direction across the epithelium because different sets of transporters are localized in either the apical or basolateral membranes. Absorption Absorption is the means whereby nutrients such as glucose are taken into the body to nourish cells. Glucose is transported across the apical plasma membrane of the intestine by the sodium-glucose cotransporter (purple). Because transport of Na+ and glucose is coupled, we need to add the free energy inherent in Na+ transport to the free energy inherent in glucose transport to get the overall free energy for the process. Just after a meal, there will be abundant glucose in the lumen of the intestine, favoring absorption. Towards the e Continue reading >>
Passive Transport - Taking The Easy Road. While active transport requires energy and work, passive transport does not. There are several different types of this easy movement of molecules. It could be as simple as molecules moving freely such as osmosis or diffusion.
GLUT4 transporters are insulin sensitive, and are found in muscle and adipose tissue. As muscle is a principal storage site for glucose and adipose tissue for triglyceride (into which glucose can be converted for storage), GLUT4 is important in post-prandial uptake of excess glucose from the bloodstream.
Glucose travels from the intestinal lumen into the intestinal epithelial cells through active transport, and then glucose enters red blood cells through facilitated diffusion. GLUT-1 is one of the major glucose transporters for red blood cells. Red blood cell glucose transporters GLUT-1 are regulated by intracellular ATP and AMP levels.
Brown, G.K. Glucose transporters: Structure, function, and consequences of deficiency. Journal of Inherited Metabolic Disease. May 2000, Volume 23, Issue 3, 237-246.
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