glyceraldehyde 3-phosphate
(GALP) A triose phosphate,
CHOCH(OH)CH 2 OPO 3 H 2 , that is an intermediate in the *Calvin cycle (see
also photosynthesis) and glycolysis.
glycerate 3-phosphate A phosphorylated three-carbon monosaccharide that is an intermediate in the
*Calvin cycle of photosynthesis and
also in *glycolysis. It was formerly
known as 3-phosphoglycerate or phosphoglyceric acid (PGA).
glycerides (acylglycerols) Fatty-acid
esters of glycerol. EsteriÜcation can
occur at one, two, or all three hydroxyl groups of the glycerol molecule producing mono-, di-, and
triglycerides respectively. *Triglycerides are the major constituent of
fats and oils found in living organisms. Alternatively, one of the hydroxyl groups may be esteriÜed with
a phosphate group forming a phosphoglyceride (see phospholipid) or to
a sugar forming a *glycolipid.
glycerine See glycerol.
glycerol (glycerine; propane1,2,3,-triol) A trihydric alcohol,
HOCH 2 CH(OH)CH 2 OH. Glycerol is a
colourless sweet-tasting viscous liquid, miscible with water but insoluble in ether. It is widely distributed
in all living organisms as a constituent of the *glycerides, which
yield glycerol when hydrolysed.
glycerophospholipids See phospholipids.
glycine See amino acid.
glycobiology The study of carbohydrates and carbohydrate complexes, especially *glycoproteins.
glycogen (animal starch) A *polysaccharide consisting of a highly
branched polymer of glucose occurring in animal tissues, especially in
liver and muscle cells. It is the major
store of carbohydrate energy in animal cells and is present as granular
clusters of minute particles.
glycogenesis The conversion of
glucose to glycogen, which is stimulated by insulin from the pancreas.
Glycogenesis occurs in skeletal muscles and to a lesser extent in the
liver. Glucose that is taken up by
cells is phosphorylated to glucose 6phosphate; this is converted successively to glucose 1-phosphate, uridine
diphosphate glucose, and Ünally to
glycogen. Compare glycogenolysis.
glycogenolysis The conversion of
glycogen to glucose, which occurs in
the liver and is stimulated by
glucagon from the pancreas and
adrenaline from the adrenal medulla.
These hormones activate an enzyme
that phosphorylates glucose molecules in the glycogen chain to form
glucose 1-phosphate, which is converted to glucose 6-phosphate. This is
then converted to glucose by a phosphatase enzyme. In skeletal muscle
glycogen is degraded to glucose 6phosphate, which is then converted
into pyruvate and used in ATP production during glycolysis and the
Krebs cycle. However, pyruvate can
also be converted, in the liver, to glucose; thus muscle glycogen is indirectly a source of blood glucose.
Compare glycogenesis.
glycol See ethane-1,2-diol.
glycolic acid (hydroxyethanoic
acid) A colourless crystalline compound, CH 2 (OH)COOH; m.p. 80°C. It
occurs in sugar cane and sugar beet,
and is made by the electrolytic reduction of oxalic acid or by boiling a
solution of sodium monochloroethanoate. Glycolic acid is used in
making textiles and leather and for
cleaning metals.
glycolipid Any of a group of sugarcontaining lipids, in which the lipid
glyceraldehyde 3-phosphate
248
g
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(GALP) A triose phosphate,
CHOCH(OH)CH 2 OPO 3 H 2 , that is an intermediate in the *Calvin cycle (see
also photosynthesis) and glycolysis.
glycerate 3-phosphate A phosphorylated three-carbon monosaccharide that is an intermediate in the
*Calvin cycle of photosynthesis and
also in *glycolysis. It was formerly
known as 3-phosphoglycerate or phosphoglyceric acid (PGA).
glycerides (acylglycerols) Fatty-acid
esters of glycerol. EsteriÜcation can
occur at one, two, or all three hydroxyl groups of the glycerol molecule producing mono-, di-, and
triglycerides respectively. *Triglycerides are the major constituent of
fats and oils found in living organisms. Alternatively, one of the hydroxyl groups may be esteriÜed with
a phosphate group forming a phosphoglyceride (see phospholipid) or to
a sugar forming a *glycolipid.
glycerine See glycerol.
glycerol (glycerine; propane1,2,3,-triol) A trihydric alcohol,
HOCH 2 CH(OH)CH 2 OH. Glycerol is a
colourless sweet-tasting viscous liquid, miscible with water but insoluble in ether. It is widely distributed
in all living organisms as a constituent of the *glycerides, which
yield glycerol when hydrolysed.
glycerophospholipids See phospholipids.
glycine See amino acid.
glycobiology The study of carbohydrates and carbohydrate complexes, especially *glycoproteins.
glycogen (animal starch) A *polysaccharide consisting of a highly
branched polymer of glucose occurring in animal tissues, especially in
liver and muscle cells. It is the major
store of carbohydrate energy in animal cells and is present as granular
clusters of minute particles.
glycogenesis The conversion of
glucose to glycogen, which is stimulated by insulin from the pancreas.
Glycogenesis occurs in skeletal muscles and to a lesser extent in the
liver. Glucose that is taken up by
cells is phosphorylated to glucose 6phosphate; this is converted successively to glucose 1-phosphate, uridine
diphosphate glucose, and Ünally to
glycogen. Compare glycogenolysis.
glycogenolysis The conversion of
glycogen to glucose, which occurs in
the liver and is stimulated by
glucagon from the pancreas and
adrenaline from the adrenal medulla.
These hormones activate an enzyme
that phosphorylates glucose molecules in the glycogen chain to form
glucose 1-phosphate, which is converted to glucose 6-phosphate. This is
then converted to glucose by a phosphatase enzyme. In skeletal muscle
glycogen is degraded to glucose 6phosphate, which is then converted
into pyruvate and used in ATP production during glycolysis and the
Krebs cycle. However, pyruvate can
also be converted, in the liver, to glucose; thus muscle glycogen is indirectly a source of blood glucose.
Compare glycogenesis.
glycol See ethane-1,2-diol.
glycolic acid (hydroxyethanoic
acid) A colourless crystalline compound, CH 2 (OH)COOH; m.p. 80°C. It
occurs in sugar cane and sugar beet,
and is made by the electrolytic reduction of oxalic acid or by boiling a
solution of sodium monochloroethanoate. Glycolic acid is used in
making textiles and leather and for
cleaning metals.
glycolipid Any of a group of sugarcontaining lipids, in which the lipid
glyceraldehyde 3-phosphate
248
g
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