synthesis of anabolic precursors for
amino-acid synthesis.
amphiphilic Describing a molecule
that has both hydrophilic and hydrophobic parts, as in *detergents.
amphiprotic See amphoteric; solvent.
ampholyte A substance that can
act as either an acid, in the presence
of a strong base, or a base, when in
the presence of a strong acid.
ampholyte ion See zwitterion.
amphoteric Describing a compound that can act as both an acid
and a base (in the traditional sense of
the term). For instance, aluminium
hydroxide is amphoteric: as a base
Al(OH) 3 it reacts with acids to form
aluminium salts; as an acid H 3 AlO 3 it
reacts with alkalis to give *aluminates. Oxides of metals are typically
basic and oxides of nonmetals tend
to be acidic. The existence of amphoteric oxides is sometimes regarded as
evidence that an element is a *metalloid. Compounds such as the amino
acids, which contain both acidic and
basic groups in their molecules, can
also be described as amphoteric. Solvents, such as water, that can both
donate and accept protons are usually described as amphiprotic (see solvent).
AMT See alphamethyltryptamine.
a.m.u. See atomic mass unit.
amylase Any of a group of closely
related enzymes that degrade starch,
glycogen, and other polysaccharides.
Plants contain both α- and βamylases; the name diastase is given
to the component of malt containing
β-amylase, important in the brewing
industry. Animals possess only αamylases, found in pancreatic juice
(as pancreatic amylase) and also (in
humans and some other species) in
saliva (as salivary amylase or ptyalin).
Amylases cleave the long polysaccharide chains, producing a mixture of
glucose and maltose.
amyl group Formerly, any of several isomeric groups with the formula C 5 H 11 –.
amylopectin A *polysaccharide
comprising highly branched chains
of glucose molecules. It is one of the
constituents (the other being amylose) of *starch.
amylose A *polysaccharide consisting of linear chains of between 100
and 1000 linked glucose molecules.
Amylose is a constituent of *starch.
In water, amylose reacts with iodine
to give a characteristic blue colour.
anabolic steroids Steroid hormones related to the male sex hormone testosterone. They promote
the development of masculine characteristics and increase muscle
growth. Anabolic steroids have been
used medically for various conditions
but are also used illegally by sportsmen and women and by bodybuilders. They have a number of
deleterious side effects and are a controlled drug in the UK and many
other countries. Their use is banned
by nearly all major sports regulating
bodies. They can be detected in blood
and urine by gas chromatography–
mass spectroscopy.
anabolism The metabolic synthesis
of proteins, fats, and other constituents of living organisms from
molecules or simple precursors. This
process requires energy in the form
of ATP. Drugs that promote such
metabolic activity are described as
anabolic. See metabolism. Compare catabolism.
Analar reagent A chemical
reagent of high purity with known
35
Analar reagent
a
www.AzShimi.ir www.AzShimi.com
amino-acid synthesis.
amphiphilic Describing a molecule
that has both hydrophilic and hydrophobic parts, as in *detergents.
amphiprotic See amphoteric; solvent.
ampholyte A substance that can
act as either an acid, in the presence
of a strong base, or a base, when in
the presence of a strong acid.
ampholyte ion See zwitterion.
amphoteric Describing a compound that can act as both an acid
and a base (in the traditional sense of
the term). For instance, aluminium
hydroxide is amphoteric: as a base
Al(OH) 3 it reacts with acids to form
aluminium salts; as an acid H 3 AlO 3 it
reacts with alkalis to give *aluminates. Oxides of metals are typically
basic and oxides of nonmetals tend
to be acidic. The existence of amphoteric oxides is sometimes regarded as
evidence that an element is a *metalloid. Compounds such as the amino
acids, which contain both acidic and
basic groups in their molecules, can
also be described as amphoteric. Solvents, such as water, that can both
donate and accept protons are usually described as amphiprotic (see solvent).
AMT See alphamethyltryptamine.
a.m.u. See atomic mass unit.
amylase Any of a group of closely
related enzymes that degrade starch,
glycogen, and other polysaccharides.
Plants contain both α- and βamylases; the name diastase is given
to the component of malt containing
β-amylase, important in the brewing
industry. Animals possess only αamylases, found in pancreatic juice
(as pancreatic amylase) and also (in
humans and some other species) in
saliva (as salivary amylase or ptyalin).
Amylases cleave the long polysaccharide chains, producing a mixture of
glucose and maltose.
amyl group Formerly, any of several isomeric groups with the formula C 5 H 11 –.
amylopectin A *polysaccharide
comprising highly branched chains
of glucose molecules. It is one of the
constituents (the other being amylose) of *starch.
amylose A *polysaccharide consisting of linear chains of between 100
and 1000 linked glucose molecules.
Amylose is a constituent of *starch.
In water, amylose reacts with iodine
to give a characteristic blue colour.
anabolic steroids Steroid hormones related to the male sex hormone testosterone. They promote
the development of masculine characteristics and increase muscle
growth. Anabolic steroids have been
used medically for various conditions
but are also used illegally by sportsmen and women and by bodybuilders. They have a number of
deleterious side effects and are a controlled drug in the UK and many
other countries. Their use is banned
by nearly all major sports regulating
bodies. They can be detected in blood
and urine by gas chromatography–
mass spectroscopy.
anabolism The metabolic synthesis
of proteins, fats, and other constituents of living organisms from
molecules or simple precursors. This
process requires energy in the form
of ATP. Drugs that promote such
metabolic activity are described as
anabolic. See metabolism. Compare catabolism.
Analar reagent A chemical
reagent of high purity with known
35
Analar reagent
a
www.AzShimi.ir www.AzShimi.com