(C_{6}H_{10}O_{5})_{_n_} C_{6}H_{12}O_{6} C_{6}H_{12}O_{6}
glycogen glucose fructose
^| ^| ^|
|| H_{3}PO_{4} || <-- ATP || <--ATP
|v |v |v
---------------+ ------+
H--C--OPO_{3}H_{2}| H--C--OH | H _{2}C--OH
| | | | |
H--C--OH | H--C--OH | C--(OH)--+
| | | | | |
HO--C--H O <==> HO--C--H O <=======> HO--C--H |
| | | | | O
H--C--OH | H--C--OH | H--C--OH |
| | | | | |
H--C--------------+ H--C-----+ H--C--------+
| | |
CH_{2}OH H_{2}C--OPO_{3}H_{2}+ADP H_{2}C--OPO_{3}H_{2}+ADP
glucose-1-phosphate glucose-6-phosphate fructose-6-phosphate
(Cori-ester) (Robison-ester) (Neuberg-ester)
^ |
| | <-- ATP
+----| |
| +------|
| |
| v
H_{2}C--OPO_{3}H_{2}
|
C(OH)--+
| |
HO--C--H |
fructose-1,6-diphosphate | O
(Harden-Young-ester) H--C--OH |
| |
H--C------+
|
H_{2}C--OPO_{3}H_{2} + ADP
^|
|| O
|| //
CH_{2}OPO_{3}H_{2} || CH
| |v | 3-phosphoglycer-aldehyde
dihydroxyacetone-phosphate C=O <=============> CHOH (Fischer-ester)
| |
CH_{2}OH CH_{2}OPO_{3}H_{2}
|| + coenzyme + H_{3}PO_{4}
O=C--OPO_{3}H_{2}
|
1,3-diphosphoglyceric acid CHOH + dihydro-coenzyme
(Negelein-ester) |
CH_{2}OPO_{3}H
^|
ADP --> ||
|| O
|v//
C--OH
| +---+
3-phosphoglyceric acid CHOH + |ATP|
(Nilsson-ester) | +---+
CH_{2}OPO_{3}H_{2}
^|
|v
COOH
2-phosphoglyceric acid |
CHOPO_{3}H_{2}
|
CH_{2}OH
^|
|v
COOH
|
phosphopyruvic acid COPO_{3}H_{2}
(enol-) ||
CH_2
ADP --> ||
COOH
+------+ | +---+
|CO_{2}| + CH_3CHO <-------- C=O + |ATP|
+------+ acetaldehyde | +---+
carbon | CH_{3}
dioxide | + dihydro-coenzyme pyruvic acid
|
v
+----------------+
| CH_{3}CH_{2}OH | + coenzyme
+----------------+
ethyl alcohol
[Illustration: Figure 13.--SURVEY OF ALCOHOLIC FERMENTATION, 1951. The
"well-known scheme of alcoholic fermentation" according to Albert Jan
Kluyver (1888-1956), presented before the Society of Chemical Industry
in the Royal Institution, March 7, 1951. In _Chemistry & Industry_,
1952, page 136 ff., Kluyver restates that "... the fermentation of one
molecule of glucose is indissolubly connected with the formation of two
molecules of adenosine triphosphate (ATP) out of two molecules of
adenosine diphosphate (ADP)."]
Shortly after this experience had been gained, it became valuable for
understanding the chemical nature of a new substance extracted from a
natural organ. This substance was named lecithin by its discoverer,
Nicolas Théodore Gobley[27] (1811-1876), because he obtained it from egg
yolk (in Greek, _lékidos_). He used ether and alcohol for this
extraction. Had he used water and mineral acid instead, he would not
have found lecithin, but only its components. As Gobley and, slightly
later, Oscar Liebreich (1839-1908), subjected lecithin to treatment with
boiling water and acid, they separated it into three parts. One of them
was the glycerophosphoric acid of Pelouze, the second was the well-known
stearic acid of Chevreul, but the third was somewhat mysterious. This
third substance was the same as one previously noticed when nerves had
been subjected to an extraction by boiling water and acid and,
therefore, called nerve-substance or neurine. Adolf Friedrich Strecker
(1822-1871) established the identity of this neurine with a product he
had extracted from bile and which went under the name of choline.
Adolphe Wurtz (1817-1884) succeeded in synthesizing this substance from
ethylene oxide, CH_2.O.CH_2 and trimethylamine N(CH_3)_3.[28] Thus, all
three parts were identified, and Strecker put them together to construct
a chemical formula for lecithin, glycerophosphoric acid combined with a
fatty acid and with choline (a hydrate of neurine).
{ OH }
N { (CH_3)_3 } Choline
{ C_2H_4O }
C_18H_33O_2 } HO }
} } PO
C_16H_31O_2 } C_3H_5O }
Fatty Acids Glycerophosphate
\--------v-------/
Lecithin
according to Strecker
This formula was not quite correct. Richard Willstätter showed that an
internal neutralization takes place between the amino group and the free
acidic residue. This is expressed in his lecithin formula of 1918.
CH_{2}·O·R
|
CH_{2}·O·R_2
|
| O·CH_{2}·CH_{2}
| / \
CH_{2}·O--P=O N(CH_{3})_{3}
\ /
\---O----/
[Illustration: Lecithin (1918)]
When the aim was to distill elementary phosphorus out of an organic
material, it did not matter whether this was fresh or putrified. For
obtaining lecithin out of egg yolk and similar materials, it was
essential to use it in fresh condition. Otherwise, enzymes would have
decomposed it. Through more recent work, four enzymes have been
separated, which act specifically in decomposing lecithin. Enzyme A
removes one fatty acid and leaves a complex residue, called
lysolecithin, intact. Enzyme B attacks this residue and splits off the
remaining fatty acid group from it, enzyme C liberates only the choline
from lecithin, and enzyme D opens lecithin at the ester bond between
glycerol and phosphoric acid. This is shown in the following diagram.