In order to get into or out of cell membranes of cells and membranes of cell compartments, glucose requires special transport proteins from the major facilitator superfamily. In the small intestine (more precisely, in the jejunum),Harold A. Harper: Medizinische Biochemie. Springer-Verlag, 2013, , p. 641. (german) glucose is taken up into the intestinal epithelial cells with the help of glucose transporters via a secondary active transport mechanism called sodium ion-glucose symport via the sodium/glucose cotransporter 1. Further transfer occurs on the basolateral side of the intestinal epithelial cells via the glucose transporter GLUT2, as well uptake into liver cells, kidney cells, cells of the islets of Langerhans, nerve cells , astrocytes, and tanycytes. Glucose enters the liver via the vena portae and is stored there as a cellular glycogen. In the liver cell, it is phosphorylated by glucokinase at position 6 to glucose-6-phosphate , which cannot leave the cell. With the help of glucose-6-phosphatase, glucose-6-phosphate is converted back into glucose exclusively in the liver, if necessary, so that it is available for maintaining a sufficient blood glucose concentration. In other cells, uptake happens by passive transport through one of the 14 GLUT proteins. In the other cell types, phosphorylation occurs through a hexokinase, whereupon glucose can no longer diffuse out of the cell. The glucose transporter GLUT1 is produced by most cell types and is of particular importance for nerve cells and pancreatic β-cells. GLUT3 is highly expressed in nerve cells. Glucose from the bloodstream is taken up by GLUT4 from muscle cells (of the skeletal muscle and heart muscle) and fat cells. GLUT14 is formed exclusively in testicles. Excess glucose is broken down and converted into fatty acids, which are stored as triacylglycerides . In the kidneys, glucose in the urine is absorbed via SGLT1 and SGLT2 in the apical cell membranes and transmitted via GLUT2 in the basolateral cell membranes. About 90\% of kidney glucose reabsorption is via SGLT2 and about 3\% via SGLT1.
In order to get into or out of cell membranes of cells and membranes of cell compartments, glucose requires special transport proteins from the major facilitator superfamily. In the small intestine (more precisely, in the jejunum),Harold A. Harper: Medizinische Biochemie. Springer-Verlag, 2013, , p. 641. (german) glucose is taken up into the intestinal epithelium with the help of glucose transporters via a secondary active transport mechanism called sodium ion-glucose symport via sodium/glucose cotransporter 1 (SGLT1). Further transfer occurs on the basolateral side of the intestinal epithelial cells via the glucose transporter GLUT2, as well uptake into liver cells, kidney cells, cells of the islets of Langerhans, neurons , astrocytes, and tanycytes. Glucose enters the liver via the portal vein and is stored there as a cellular glycogen. In the liver cell, it is phosphorylated by glucokinase at position 6 to form glucose 6-phosphate , which cannot leave the cell. Glucose 6-phosphatase can convert glucose 6-phosphate back into glucose exclusively in the liver, so the body can maintain a sufficient blood glucose concentration. In other cells, uptake happens by passive transport through one of the 14 GLUT proteins. In the other cell types, phosphorylation occurs through a hexokinase, whereupon glucose can no longer diffuse out of the cell. The glucose transporter GLUT1 is produced by most cell types and is of particular importance for nerve cells and pancreatic β-cells. GLUT3 is highly expressed in nerve cells. Glucose from the bloodstream is taken up by GLUT4 from muscle cells (of the skeletal muscle and heart muscle) and fat cells. GLUT14 is expressed exclusively in testicles. Excess glucose is broken down and converted into fatty acids, which are stored as triglycerides . In the kidneys, glucose in the urine is absorbed via SGLT1 and SGLT2 in the apical cell membranes and transmitted via GLUT2 in the basolateral cell membranes. About 90\% of kidney glucose reabsorption is via SGLT2 and about 3\% via SGLT1.
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epithelial cells
epithelium
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the
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1.
1 (SGLT1).
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nerve cells
neurons
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vena portae
portal vein
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glucose-6-phosphate
form glucose 6-phosphate
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With the help of glucose-6-phosphatase, glucose-6-phosphate is converted
Glucose 6-phosphatase can convert glucose 6-phosphate
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if necessary, so that it is available for maintaining
so the body can maintain
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formed
expressed
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triacylglycerides
triglycerides