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Home >> Dictionary of Bioinformatics, Biochemistry, Biotechnology >> Glycaemic Load (GL) - Glycolysis
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Glycaemic load (GL)
An index that describes the blood glucose-increasing potential of the carbohydrate in a food and the quantity of carbohydrate in a food. The GL of a food is calculated by multiplying the GI by the amount of carbohydrate in grams provided by a food and dividing the total by 100.
GlyCAM
A cell adhesion molecule used by lymphocytes to enter the lymphoid tissues.
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Glycerides
A class of lipids in which one or more fatty acids are covalently linked to a glycerol molecule. based on the number of fatty acid molecules, glycerides are classified into monoglycerides (one fatty acid), diglycerides (two fatty acids) and triglycerides (three fatty acids). Glycerides functions as storage depots of fat.
Glycerol
A small organic molecule that is the parent compound of many biomolecules including phospholipids.
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Glycerophospholipids
An amphipathic lipid containing a glycerol backbone with fatty acids linked to C1 and C2 of glycerol and a polar alcohol attached to C3 by a phosphodiester linkage. See phosphatidic acid, phospholipids, cephalin, lecithin.
Glycine
The simplest amino acid whose side chain contains a hydrogen atom.
Glycobiology/Glycochemistry
The study of glycosylation (addition of sugar residues) of proteins that occurs after translation.
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Glycocalyx
A carbohydrate-rich layer that forms the outer coat of a eukaryotic cell. It is made up of oligosaccharides linked to intrinsic plasma membrane glycoproteins and glycolipids as well as glycoproteins and proteoglycans that are secreted and reabsorbed onto the cell surface.
Glycogen
A branched polymer of glucose in which the glucose residues are linked by α1→ 4and α1→6 (branch points) linkages. storages from of glucose in animals.
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Glycogen storage disease, type I (von Gierke’s disease)
A glycogen storage disease characterised by glucose 6-phospahates deficiency. The resulting hypoglycaemia causes breakdown of muscle glycogen to lactate. In these patients, there is an inability to convert glucose 6-phosphate to glucose. The glucose 6-phosphate that accumulates is channelised into two pathways: i. Pentose phosphate pathway, which increases PRPP synthesis, accounting for urate overproduction, ii. Glycolysis, with increase in lactate production. Hyperlactacidaemia inhibits renal urate excretion by blocking tubular secretion of urate.
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Glycogen Phosphorylase
Key enzyme in glycogenolysis. It exists in two forms and active phosphorylated form (Phosphorylase) and an inactive dephosphorylated form (Phosphorylase b). Phosphorylase b is converted to Phosphorylase a by Phosphorylase b kinase which also exists in an active phosphorylated form and inactive dephosphorylated form.
Glycan
A polymer of monosaccharide units linked by glycosidic bonds. Another term for polysaccharide.
Glycation
The nonenzymatic addition of a sugar residue to amino groups of proteins.
Glycogen storage disease type VIII
A fairly common, X-linked/autosomal relatively benign disease due to a defect in liver Phosphorylase kinase. The disease is characterised by hepatomegaly, occasional hypoglycaemia, and increase hepatic glycogen with normal structure.
Glycogen storage diseases
A group of genetic disorders involving glycogen formation and degradation. These are divided into three categories based on th pathophysiology- hepatic- hypoplycaemic, muscle-energy and individual pathophysiology.
Glycogen synthase
Key enzyme in glycogenesis. It adds glucose units 1→4 linkage to the end of a glycogen chain. It exists in two forms- an inactive phosphorylated form (a) and an active dephosphorylated form (b).
Glycogenesis
The pathway of glycogen formation that occurs in the muscle and liver. The rate-limiting step in glycogenesis is the addition of glucosyl residues from UDPGIc to a pre-existing glycogen synthase. This is followed by branching of the glycogen molecule, in which a part of the chain consisting of six glucose residues is transferred to a neighbouring chain establishing a branch point with a 1→6 linkage.
Glycogenin
The protein primer that undergoes glycosylation on specific tyrosine residues during glycogenesis.
Glycogenolysis
The pathway of glycogen breakdown. The glycogen molecule is completely broken by the combines action of glycogen Phosphorylase, glycosyl transferase and embryo – [1→ 6] Glucosidase. The terminal glycosyl residues in glycogen are removed sequentially by glycogen Phosphorylase until a glycogen chain containing approximately four glucose residues n wither side of a branch point remain. The debranching enzyme system removes the branches in the glycogen molecule. Glucose-1 phosphate formed is converted to glucose-6-phospahte by th action of phosphoglucomutase. In the liver, the enzyme glucose-6- phosphates dephosphorylates glucose-6-phosphates to form glucose which diffuses into the blood.
Glycogenoses
See Glycogen storage disease.
Glycolipid
A lipid containing a carbohydrate group.
Glycolysis
The pathway that converts glucose into pyruvate, with the concomitant production of ATP. Glycolysis occurs in the cytoplasm of all living cells. It functions to produce energy as well as intermediates for biosynthetic pathways. The glycolytic pathway may be divided into two main stages: stage 1 involves glucose phosphorylation and cleavage whereas stage 2 involves the conversion of glyceraldehyde 3-phosphates to pyruvate.
Under anaerobic conditions, lactate dehydrogenase converts pyruvate to lactate and the oxidised Nicotinamide adenine dinucleotide (NAD+) regenerated in th reaction allows glycolysis to continue. In yeast, pyruvate is converted to ethanol by the reaction of alcohol dehydrogenase. Anaerobic glycolysis yields only 2 molecules of ATP. Under aerobic conditions, pyruvate enters the TCA cycle to carbon dioxide and water. The complete oxidation of glucose to carbon dioxide and water yields 38 ATPs.
GlycoMed
A predication tool for oligosaccharide modifications from mass differences.
Glycopeptide
A polypeptide covalently attached to a sugar or polysaccharide.
Glycopeptides may be O-linked if the sugar(s) (are) attached to the polypeptide by an oxygen atom, or N-linked if attached to a nitrogen atom.
Glycophorin
A transmembrane glycoprotein present in erythrocyte membrane. Charged residues on the extracellular domain of Glycophorin are believed to prevent blood cells from sticking to one another. The protein is an attachment site for the influenza virus and the malaria parasite. Plasmodium falciparum.
Glycoprotein
proteins linked to sugars and/or polysaccharides present on th outside surfaces of cell membranes.
Glycosaminoglycan
An heteropolysaccharide containing two alternating units of uronic acid N-acetylglucosamine (N- acetylglucosamine). Also known as mucopolysaccharide.
Glycosidases
Enzymes that break up complex sugars such as starch into simple sugars such as glucose.
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