Glycolysis and Fermentation - Đuờng Phân và Lên men
Glycolysis
Từ khó :
Anaerobic catabolism: Chuyển hóa kị khí
: Đường phân
: Lên men
: Xúc tác
Glycolysis is the anaerobic catabolism of glucose.
* It occurs in virtually all cells.
* In eukaryotes, it occurs in the cytosol.
*
* The free energy stored in 2 molecules of pyruvic acid is somewhat less than that in the original glucose molecule.
* Some of this difference is captured in 2 molecules of ATP.
Xem hình bên :
Sơ đồ tóm tắt đườg phân :
In aerobic organisms, pyruvate produced in Glycolysis is oxidized to
via Krebs Cycle, and the NADH produced in Glycolysis and Krebs Cycle is reoxidized via the respiratory chain, with production of much additional ATP.
Xem Krebs Cycle:
Fermentation
Anaerobic organisms lack a respiratory chain. They must reoxidize NADH produced in Glycolysis through some other reaction, because NAD+ is needed for the Glyceraldehyde-3-phosphate Dehydrogenase reaction (see above). Usually
is reoxidized as pyruvate is converted to a more reduced compound.
The complete pathway, including Glycolysis and the re-oxidation of NADH, is called fermentation.
For example, Lactate Dehydrogenase catalyzes reduction of the keto group in pyruvate to a hydroxyl, yielding lactate, as NADH is oxidized to
.
Lactate, in addition to being an end-product of fermentation, serves as a mobile form of nutrient energy, and possibly as a signal molecule in mammalian organisms. Cell membranes contain carrier proteins that facilitate transport of lactate.
* Skeletal muscles ferment glucose to lactate during exercise, when the exertion is brief and intense. Lactate released to the blood may be taken up by other tissues, or by skeletal muscle after exercise, and converted via Lactate Dehydrogenase back to pyruvate, which may be oxidized in Krebs Cycle or (in liver) converted to back to glucose via gluconeogenesis.
Xem Lactate Dehydrogenase
* Lactate serves as a fuel source for cardiac muscle as well as brain neurons.
Astrocytes, which surround and protect neurons in the brain, ferment glucose to lactate and release it. Lactate taken up by adjacent neurons is converted to pyruvate that is oxidized via Krebs Cycle.
Some anaerobic organisms metabolize pyruvate to ethanol, which is excreted as a waste product. is converted to in the reaction catalyzed by Alcohol Dehydrogenase. Thiamine pyrophosphate, the cofactor for Alcohol Dehydrogenase, is discussed elsewhere.
Xem pyruvate to ethanol
Xem Glucose metabolisme in liver
Anaerobic catabolism of glucose yields only 2 “high energy” bonds of
.
Từ khó :
Anaerobic catabolism: Chuyển hóa kị khí
: Đường phân : Lên men : Xúc tácGlycolysis is the anaerobic catabolism of glucose.
* It occurs in virtually all cells.
* In eukaryotes, it occurs in the cytosol.
*
* The free energy stored in 2 molecules of pyruvic acid is somewhat less than that in the original glucose molecule.
* Some of this difference is captured in 2 molecules of ATP.
Xem hình bên :
Sơ đồ tóm tắt đườg phân :
In aerobic organisms, pyruvate produced in Glycolysis is oxidized to
via Krebs Cycle, and the NADH produced in Glycolysis and Krebs Cycle is reoxidized via the respiratory chain, with production of much additional ATP.Xem Krebs Cycle:
Fermentation
Anaerobic organisms lack a respiratory chain. They must reoxidize NADH produced in Glycolysis through some other reaction, because NAD+ is needed for the Glyceraldehyde-3-phosphate Dehydrogenase reaction (see above). Usually
is reoxidized as pyruvate is converted to a more reduced compound.The complete pathway, including Glycolysis and the re-oxidation of NADH, is called fermentation.
For example, Lactate Dehydrogenase catalyzes reduction of the keto group in pyruvate to a hydroxyl, yielding lactate, as NADH is oxidized to
.Lactate, in addition to being an end-product of fermentation, serves as a mobile form of nutrient energy, and possibly as a signal molecule in mammalian organisms. Cell membranes contain carrier proteins that facilitate transport of lactate.
* Skeletal muscles ferment glucose to lactate during exercise, when the exertion is brief and intense. Lactate released to the blood may be taken up by other tissues, or by skeletal muscle after exercise, and converted via Lactate Dehydrogenase back to pyruvate, which may be oxidized in Krebs Cycle or (in liver) converted to back to glucose via gluconeogenesis.
Xem Lactate Dehydrogenase
* Lactate serves as a fuel source for cardiac muscle as well as brain neurons.
Astrocytes, which surround and protect neurons in the brain, ferment glucose to lactate and release it. Lactate taken up by adjacent neurons is converted to pyruvate that is oxidized via Krebs Cycle.
Some anaerobic organisms metabolize pyruvate to ethanol, which is excreted as a waste product.
is converted to in the reaction catalyzed by Alcohol Dehydrogenase. Thiamine pyrophosphate, the cofactor for Alcohol Dehydrogenase, is discussed elsewhere.Xem pyruvate to ethanol
Xem Glucose metabolisme in liver
Anaerobic catabolism of glucose yields only 2 “high energy” bonds of
.Click here: http://forum.hoahoc.org/forumdisplay.php?f=396
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