this is catalyzed by phosphohexose isomerase 6-phosphate glucose sugar (aldehydesaldose) to 6-phosphate fructose ( the process of fructose-6-phosphate, F-6-P), this reaction is reversible.
(3) 6 - Phosphorylation of fructose (phosphorylation of fructose-6-phosphate
this reaction is 6 phosphate fructose on the first C Further phosphatization produces 1,6-phosphate fructose, the root of which is supplied by ATP, and the enzyme that catalyses this reaction is phosphoructic fructose kinase 1 (phosphofructokinase l, PFK1).
PFK1 catalytic reaction is irreversible, it is the most important speed limit enzyme in the process of aerobic oxidation of sugar, it is also a variant enzyme, citric acid, ATP, etc. is a variant inhibitor, ADP, AMP, Pi, 1,6-phosphate fructose, etc. is a variant activator, insulin can induce its generation.
(4) 1.6 diphosphate fructose lysis reaction (cleavage of fructose 1,6 di/bisphosphate)
aldolase catalyzed 1.6-diphosphate fructose to produce phosphate dihydroxypropane and 3-phosphate glycerides, this reaction is reversible.
(5) isomer reaction of dihydroxyacetone (isomerization of dihydroxyacetonephosphate)
the catalytic reaction of propylene phosphate isomerase to 3-phosphate glycerol, which is also reversible.
1 molecule glucose to produce 2 molecules 3-phosphate glycerides, through two phosphate effects to consume 2 molecules ATP.
2. Phase II:
(6) 3- Oxidation reaction of glycerol glycerides (oxidation of glyceraldehyde-3-phosphate
This reaction consists of 3-phosphate glyceridesdehydrogenase (glyceral) dehyde 3-phosphedatedehydrogenase) catalytic 3-phosphate glyceride oxidation dehydrogenation and phosphate production contains a high-energy phosphoric acid bond of 1,3-diphosphate glyphosate, the reaction of the hydrogen and electron transfer to dehydrogenase coenzyme NAD plus the generation of NADH plus H, phosphoric acid root from inorganic phosphoric acid.
(7) 1.3-high-energy phosphoric acid bond transfer reaction
catalyzed by phosphaglycerate kinase (PGK), 1.3-phosphate glycerate Lyoic acid produces 3-phosphate glyceric acid, and the high-energy phosphoric acid root on C1 is transferred to ADP to generate ATP, the energy generated during the oxide process of this substrate directly affects the process by which ADP phosphorylation produces ATP, known as substrate level phosphorylation. The catalytic reaction of this kinase is reversible.
(8) 3- Phosphate glyceric acid change reaction
under the catalysis of phosphoglycerrate mutase 3-phosphoric acid Glycerate C3-bit phosphoric acid transformation to C2 bit to produce 2-phosphate glyceric acid. This reaction is reversible.
(9) 2 - Dehydration reaction of glyphosate
catalyzed by enolase, 2-phosphate glyceric acid dehydrated at the same time, energy redistribution, the production of high-energy phosphoric acid bonds of phosphorusol-type acrylic acid (phosphorenolpyruvate PEP). The reaction is also reversible.
(10) Phosphate transfer of phosphate-type acetone acid
But this reaction is irreversible.
Acetone kinase is a speed limit enzyme in the process of aerobic oxidation of sugar, with variable enzyme properties, ATP is a variant inhibitor, ADP is a variant activator, Mg2 plus or K plus can activate the activity of acetone kinase, insulin can induce PK production, oleol-type acetone acid can be automatically converted into acetone acid.
Summarize the oxygen-free enzyme of sugar In the course of the cell fluid phase, a molecular glucose or glycogen in a glucose unit, oxidized and decomposed to produce 2 molecules of acetone acid, acetone acid will enter the mitochondrial continued oxidation and decomposition, the process of producing two pairs of NADH plus H, by the delivery of hydrogen Body α-phosphate glycelin (muscle and nerve tissue cells) or apple acid (heart muscle or liver cells) is transmitted into the mitochondrials, and then through the mitochondrial body oxidized respiratory chain transmission, and finally hydrogen and oxygen combined to produce water, in the hydrogen transfer process to release energy, some of which is stored in atTP form.
In the 10 or 11-step enzymatic reaction in the whole cell fluid stage, there are three irreversible one-way reactions under physiological conditions, the enzyme activity of catalyzing these three-step reactions is low, is the key enzyme of the oxygen oxidation process of the whole sugar, its active size, the oxidation and decomposition rate of sugar plays a decisive role in this stage by the substrate level phosphate to produce four molecules ATP.
, a molecule of glucose oxidizes and breaks down to produce two molecules of acetone acid through a glycolysis pathway. In this process, the substrate level phosphate can produce 4 molecules ATP, such as phosphate consumption of phosphate consumption with the first stage of glucose phosphate consumption of two molecules ATP offset each other, each molecule glucose degradation to acetone acid net production of 2 molecules ATP, such as from the beginning of the glycogen, because the beginning stage consumes only 1 molecule ATP, so each glucose unit can net generation of 3 molecules ATP. Glucose, 2Pi, 2NAD, 2ADP→2 acetone acid, 2ATP, 2NADH, 2H2O
(iii) acetone acid is produced under anaerobic conditions
and when oxygen supply is insufficient, it is converted from acetone acid produced by the glycolysis route to lactic acid. When oxygen is lacking, glucose breaks down into lactic acid called glycolysis, because it is very similar toyeast" fermentation. Acetone acid is converted into lactic acid by lactate dehydrogenase (lactate dehydrogenase) catalytic lactic acid dehydrogenase lactate acetone in this reaction acetone acid played a hydrogen recipient role. NADH plus H , produced by the reaction of 3-phosphate glyceal dehydrogenase, cannot be oxidized by electron transfer chain when oxygen is lacking. It is by reducing acetone acid to lactic acid that NADH is transformed into NAD plus that glycolysis can continue.
lactic acid dehydrogenase is a tumour of M and H subunits, consisting of five isoenzymes. These isoenzymes are distributed differently in tissues and have large differences in KM for acetone acid. H4 is mainly distributed in the heart muscle. Its enzyme dynamics parameters indicate that H4 is beneficial for catalyzing lactic acid oxidation into acetone acid. So the heart muscle oxidizes and uses lactic acid as fuel. The skeletal muscle is type M4. It has no tendency to react, but the concentration of the substrate in myoblasts is conducive to the production of lactic acid.
(iv) sugar enzymes and their physiological significance
Sugar enzymes are a common energy supply in the biological world, but they release little energy and are physiological in general In some cases, most tissues have enough oxygen for aerobic oxidation and rarely sugar dissevenation, so this metabolic pathway provides little energy, but a small number of tissues, such as tissue cells such as the retina, testicles, renal myelin, and red blood cells, still need to obtain energy from sugar enzymes, even under aerobic conditions.
in some cases, sugar enzymes have special physiological significance. For example, during vigorous exercise, the energy demand increases and the sugar decomposition accelerates, at which point even if breathing and circulation speed up to increase the supply of oxygen, the energy required for the complete oxidation of sugar in the body is still not enough, when the muscles are in a relatively oxygen-deprived state, the sugar enzyme process must be passed to supplement the required energy. After intense exercise,
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