Starch and sucrose metabolism - Homo sapiens (human)

Curator(s): Generative Medicine Class

Carbohydrates are a major component of the human diet, and include starch (amylose and amylopectin) and disaccharides such as sucrose, lactose, maltose and, in small amounts, trehalose. The digestion of starch begins with the action of amylase enzymes secreted in the saliva and small intestine, which convert it to maltotriose, maltose, limit dextrins, and some glucose. Digestion of the limit dextrins and disaccharides, both dietary and starch-derived, to monosaccharides – glucose, galactose, and fructose – is accomplished by enzymes located on the luminal surfaces of enterocytes lining the microvilli of the small intestine. Once released from starch or once ingested, sucrose can be degraded into beta-D-fructose and alpha-D-glucose via lysosomal alpha-glucosidase or sucrose-isomaltase. Glycogen functions as the secondary short term energy storage in animal cells. It is made primarily by the liver and the muscles, but can also be made by glycogenesis within the brain and stomach. Glycogen is the analogue of starch, a less branched glucose polymer in plants, and is commonly referred to as animal starch, having a similar structure to amylopectin. Glycogen is cleaved from the nonreducing ends of the chain by the enzyme glycogen phosphorylase to produce monomers of glucose-1-phosphate that is then converted to glucose 6-phosphate (G6P).    
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Starch and sucrose metabolism - Homo sapiens (human) node1 B-D -Fructose-6P node2 node2->node1 node3 a-D -Glucose-6P node2->node3 Amino sugar and nucleotide sugar and metabolism node7 UDP -D -galacturonate Amino sugar and nucleotide sugar and metabolism->node7 node36 GDP-Glucose Amino sugar and nucleotide sugar and metabolism->node36 node4 a-D -Glucose node6 node4->node6 node9 node4->node9 node5 3 node6->node1 node6->node3 node6->node5 node57 B-D -Fructose node6->node57 node17 node7->node17 node99 node7->node99 node8 2 node9->node3 node9->node8 node10 node10->node3 node10->node4 node11 node35 UDP-glucose node11->node35 node12 a-D -Glucose-1P node12->node11 node25 node12->node25 node76 Glycolysis / Gluconeogenesis node12->node76 node13 node13->node3 node13->node12 node14 node14->node12 node18 a-D -Glucose-1,6P 2 node14->node18 node15 D-Fructose node16 node16->node12 node16->node18 Pectin node17->Pectin node20 node18->node20 node19 node19->node12 node19->node15 Sucrose node19->Sucrose node20->node4 node20->node18 node21 Pectin->node21 Pectate node21->Pectate node22 node22->node12 node23 CDP-glucose node22->node23 node51 Pectate->node51 node56 Pectate->node56 node100 Pectate->node100 node53 Sucrose->node53 node54 Sucrose->node54 node55 Sucrose->node55 node60 Sucrose->node60 node62 Sucrose->node62 node63 Sucrose->node63 node23->Amino sugar and nucleotide sugar and metabolism node24 ADP-glucose node26 node24->node26 node27 node24->node27 node32 Glycogen; Amylose node26->node32 node27->node4 node27->node12 node27->node36 node28 D-Galacturonate Ascorbate metabolism node28->Ascorbate metabolism node66 node28->node66 node29 1 node30 node30->node29 node30->node32 node31 node31->node32 node46 node32->node46 node48 node32->node48 node33 node33->node12 node33->node36 node34 Cellulose node34->Cellulose node35->node31 node49 node35->node49 node64 node35->node64 node81 node35->node81 node36->node34 node37 Cellulose->node37 node38 Cellulose->node38 Cellobiose node37->Cellobiose node39 1,4 -B -D-Glucan node37->node39 node38->Cellobiose node38->node39 node40 Cellobiose->node40 node77 Cellobiose->node77 node39->node40 node40->node4 node41 B-D -Glucose node40->node41 node42 node42->node35 node42->Cellulose node43 node43->node12 node44 node44->node35 Glucoside node44->Glucoside Glucoside->node40 Starch Glycogen Starch Glycogen->node30 node65 Starch Glycogen->node65 node67 Starch Glycogen->node67 Maltodextrin Maltodextrin->node65 node45 node45->node4 node46->Starch Glycogen node47 1,3 -B -Glucan node47->node45 node48->Starch Glycogen node49->node47 node50 node52 D-Glucose node50->node52 node51->node28 node53->node52 node54->node15 node55->node15 node56->node28 node58 node58->node1 node58->node57 Isomaltose node59 Isomaltose->node59 node59->node4 node59->node4 node60->node4 node60->node57 node61 node61->node12 node61->Cellobiose node61->node52 node62->node57 node63->node57 Ascorbate metabolism->node28 node96 D-Glucuronate Ascorbate metabolism->node96 node64->Sucrose Maltose Maltose->node60 node78 Maltose->node78 node79 Maltose->node79 node83 Maltose->node83 node65->Maltodextrin node65->Maltose node66->node28 node68 UDP -D -glucuronate node66->node68 Dextrin node67->Dextrin node70 node68->node70 Dextrin->node59 node69 Dextrin->node69 node69->node4 node71 UDP -D -xylose node70->node71 node72 node71->node72 node73 1,4 -B -D-Xylan node72->node73 node74 node73->node74 node75 D-Xylose node74->node75 Pentose and glucuronate interconversions node75->Pentose and glucuronate interconversions node76->node12 node77->Cellobiose node77->node52 Cellotriose node77->Cellotriose Cellotetraose node77->Cellotetraose Cellopentaose node77->Cellopentaose Cellohexaose node77->Cellohexaose Cellotriose->node77 Cellotetraose->node77 Cellopentaose->node77 Cellohexaose->node77 Celloheptaose Celloheptaose->node77 node78->node52 node92 B-D -Glucose-1P node78->node92 node79->node4 node80 node80->Maltodextrin Cyclomaltodextrin Cyclomaltodextrin->node80 node82 a,a' -Trehalose -6P node81->node82 node87 node82->node87 node89 node82->node89 node90 node82->node90 node83->node82 node86 Maltose-6'P node83->node86 node84 a,a-Trehalose node84->node83 node91 node84->node91 node95 node84->node95 node85 node85->Maltose node85->node84 node87->node86 node88 D-Glucose -6P node87->node88 node89->node88 node90->node84 node91->node92 node93 node93->node92 node94 B-D -Glucose-6P node93->node94 node95->node52 node97 node97->node96 node98 B-D -Glucuronoside node98->node97 node99->node98 node100->node28 print "