Glucose metabolism anaerobic

Antidiabetic Drugs other than Insulin. Figure 3 The antihyperglycaemic effect of metformin involves enhanced insulin-mediated suppression of hepatic glucose production and muscle glucose uptake. Metformin also exerts non-insulin-dependent effects on these tissues, including reduced fatty acid oxidation and increased anaerobic glucose metabolism by the intestine. FA, fatty acid f, increase i decrease. 

The CNS is not the only vulnerable tissue as red cells also rely upon a constant supply of glucose to maintain structure and function. Because they lack mitochondria, and therefore the mechanism to produce ATP via oxidative phosphorylation, RBCs are entirely dependent upon anaerobic glucose metabolism to synthesize ATP through substrate level phosphorylation. 

Under anaerobic conditions, glycolysis results in a net synthesis of only two ATP molecules for each molecule of glucose metabolized (Table 6-1). 

O Fallon JV, Wright RW, Calza RE (1991) Glucose metabolic pathways in the anaerobic rumen fungus Neocallimastix frontalis EB188. Biochem J 274 595-599 Orpin CG (1975) Studies on rumen flagellate Neocallimastix frontalis. J Gen Microbiol 91 249-262... 

Platt, T. B., and Foster, E. M. 1958. Products of glucose metabolism by homo-fermentative streptococci under anaerobic conditions. J. Bacteriol 75, 453-459. 

In fast white fibers, glycolysis catabolizes glucose. The relative lack of mitochondria in these fibers causes the white appearance. The rapid breakdown of glucose by anaerobic metabolism means that ATP is made rapidly. These muscles are used in rapid, short-duration movement and exhibit a fast twitch when electrically stimulated. The flight muscles of birds are of this type—remember that you find the white meat of a chicken on the breast. 

But even if a combination of pathways usually is used, the ATP yield can nevertheless be elevated two- to fourfold any animal anaerobes utilizing such fermentations therefore automatically reduce by a factor of two to four their anaerobic needs for glucose. Although impressive, this factor is still a long way from the order-of-magni-tude difference between anaerobic glycolysis and oxidative glucose metabolism. 

Figure 18.4 The Cori cycle. Glucose is metabolized anaerobically to lactate, as in white muscle fibers or red blood cells. Lactate is exported into the bloodstream, extracted from there by the liver, and reconverted to glucose via gluconeogenesis. Glucose is then returned to the muscle.

Addition of oxygen to cells metabolizing glucose under anaerobic conditions leads to (a) a decrease in the rate of glucose consumption and (b) cessation of lactate accumulation. The latter phenomenon is known as the Pasteur effect. Explain why these changes occur in glucose and lactate metabolism. 

Figure 14.1. Glucose Metabolism. Glucose is metabolized to pyruvate in 10 linked reactions. Under anaerobic conditions, pyruvate is metabolized to lactate and, under aerobic conditions, to acetyl CoA. The glucose-derived carbons are subsequently oxidized to CO2.

As seen in the above, NAD works as the coenzyme in glucose metabolism, therefore, NADH has to be re-oxidized to NAD to support continued glucose oxidation. Anaerobic bacteria such as Clostridia re-oxidizes NADH by producing organic acids like lactate, acetate and butyrate as well as alcohols like ethanol, butanol and butanediol, from pyruvate. Many bacteria have multiple metabolic pathways, and change the pathway in accordance with metabolite availability and/or pH in the culture liquid. Therefore, in general, it is very... 

Lactate, the end product of anaerobic glucose metabolism, is produced by most tissues of the body, particularly skin, muscle, erythrocytes, brain, and intestinal mucosa. In a normal adult, under basal conditions, these tissues produce 1,300 mM of lactate per day, and the normal serum lactate concentration is less than 1.2 mM/L. During vigorous exercise, the production of lactate can be increased several fold. Lactate is normally removed from the circulation by liver and kidney. Because of its great capacity to use lactate, liver plays an important role in the pathogenesis of lactic acidosis, which may be thought of as an imbalance between the relative rates of production and utilization of lactate (Chapter 39). 

Fumarate-reductase, which converts fumarate into succinate in mitochondria, plays an important role in the anaerobic glucose metabolism and eventual energy production in many helminths. Thus, inhibition of this enzyme was considered to... 

The glucose metabolism in aerotolerant anaerobes like trichomonad flagellates, Amoeba and Giardia spp. is somewhat different than in trypanosomes. These parasites carry out anaerobic production of energy from glucose, which may be stored in the form of glycogen upto 30% of their dry weight. 

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