Glucose respiration

Kemp et al. (1995) made an enthalpy balance for activated 2C11-12 mouse macrophage hybridoma cells, showing that glucose respiration and glycolysis plus... 

Respiration is a process that is, in many ways, a reversal of photosynthesis. Photosynthesis collects energy in the form of light to synthesize food in the form of glucose respiration involves the decomposition of glucose to acquire the necessary energy for life processes. Respiration may take place either aerobically (in the presence of oxygen) or anaerobically (in the absence of oxygen). The overall balanced chemical equation for aerobic respiration is written below. 

Riedel et al. (1985a) proposed utilization of the acceleration of glucose respiration by Bacillus subtilis resulting from active NH4 permeation in a sensor for the determination of ammonium ion. The normally repressed NH4 permease system of the cells was activated by nutrient limitation. The cells were fixed to the tip of an oxygen electrode. The sensor exhibited constant sensitivity for more than 12 days. 

From 1938 to 1945, Fulton and his associates, using the available analytical tools of Barcroft-Haldane manometry and colorimetry, found the parasites did not store glycogen, and P. knowlesi-m fee ted red cells rapidly depleted the medium of glucose respiration stimulated by the presence of glucose was inhibited by 0.001-M cyanide. Erythrocyte- free parasites prepared by saponin lysis behaved similarly. Surprisingly, uptake of oxygen also occurred with glycerol, fructose and mannose (Fulton, 1939). 

In order to realize the electrochanical equation set, it is only necessary to oxidize glucose without the presence of molecular oxygen (Oj). Various steps in the oxidation process thus proceed through a series of intermediate steps, with the electrons handed off from one intermediary to the next. This is how glucose respiration naturally occurs by enzymatic reactions. 

Actuators are the means for a control system to have an effect. Actuators may be local and mechanical, as are muscles, or they may be diffused and chemical, as are glucose respiration processes in cells. 

Glycolysis, catalysed by cytoplasmic enzymes, can operate under aerobic and anaerobic conditions to produce pyruvate, but in the absence of oxygen this is reduced further to ethanol, plus CO2 (or to lactic acid if no decarboxylation occurs). Anaerobic respiration (or fermentation) produces only two ATP molecules per molecule of glucose respired contrast this with six ATPs (though some authors claim eight ATPs) produced during pyruvate formation under aerobic conditions. In the presence of oxygen, further utilization of pyruvate occurs within the mitochondria. Here, oxidative decarboxylation of pyruvate to acetyl co-enzyme A (acetyl CoA), followed by complete oxidation of the... 

From the above discussion it will be seen that some 40 P (36 by oxidative and 4 by substrate phosphorylation), each with an energy content of 8-5 kcal/g-mol, are synthesised per g-mol of glucose respired and some 340 kcal therefore conserved as utilisable energy. Since the overall decrease in free energy involved in the complete oxidation of a g-mol of glucose is 686 kcal (eqn. 14, p. 85) this means that approximately 50% of this energy is trapped during respiration in a form which can be used in cellular metabolism for the synthesis of cell constituents or to perform work. 

I onsucrose Components from Storage or Damag e of Beets. Some nonsucrose components are associated with the conditions under which the beets have been stored prior to processing, as respiration products or products of microbial attack In either case they direcdy and indirectly reduce sucrose yield and may cause other processing problems. Glucose and fmctose have already been discussed and can derive from either source. 

Respiratory, or oxidative, metaboHsm produces more energy than fermentation. Complete oxidation of one mol of glucose to carbon dioxide and water may produce up to 36 mol ATP in the tricarboxyHc acid (TCA) cycle or related oxidative pathways. More substrates can be respired than fermented, including pentoses (eg, by Candida species), ethanol (eg, by Saccharomjces), methanol (eg, by Hansenu/a species), and alkanes (eg, by Saccharomjces lipoljticd). 

The modes of action for niclosamide are interference with respiration and blockade of glucose uptake. It uncouples oxidative phosphorylation in both mammalian and taenioid mitochondria (22,23), inhibiting the anaerobic incorporation of inorganic phosphate into adenosine triphosphate (ATP). Tapeworms are very sensitive to niclosamide because they depend on the anaerobic metaboHsm of carbohydrates as their major source of energy. Niclosamide has selective toxicity for the parasites as compared with the host because Httle niclosamide is absorbed from the gastrointestinal tract. Adverse effects are uncommon, except for occasional gastrointestinal upset. 

FIGURE 5.13 Two basic types of biological transport are (a) transport within or between different cells or tissues and (b) transport into or out of cells. Proteins function in both of these phenomena. For example, the protein hemoglobin transports oxygen from the lungs to actively respiring tissues. Transport proteins of the other type are localized in cellular membranes, where they function in the uptake of specific nutrients, such as glucose (shown here) and amino acids, or the export of metabolites and waste products. 

To release energy, the electrons can be removed from glucose and used to create ATP, a molecule that supplies a cell s short-term energy needs. This latter occurs in a series of reactions known as respiration. (Body heat is a by-product of these reactions.) The most efficient respiration reactions are those that use oxygen to accept the electrons removed from glucose. Thus respiration is the reverse of photosynthe-... 

Recall that during respiration, animals gain energy from glucose by oxidizing it—that is, by transferring... 

A bacterium was grown as a glucose-limited chemostat culture and steady state respiration rate (qo,) was measured at different dilution rates ... 

TO, a 77-year-old male nursing home resident is admitted to the hospital with a 3-day history of altered mental status. The patient was unable to give a history or review of systems. On physical examination the vital signs revealed a blood pressure of 100/60 mm Hg, pulse 110 beats per minute, respirations 14/minutes, and a temperature of 101°F (38.3°C). Rales and dullness to percussion were noted at the posterior right base. The cardiac exam was significant for tachycardia. No edema was present. Laboratory studies included sodium 160 mEq/L (160 mmol/L), potassium 4.6 mEq/L (4.6 mmol/L), chloride 120 mEq/L (120 mmol/L), bicarbonate 30 mEq/L (30 mmol/L), glucose 104 mg/dL (5.77 mmol/L), BUN 34 mg/dL (12.14 mmol/L), and creatinine 2.2 mg/dL (194.5 pmol/L). The CBC was within normal limits. Chest x-ray indicated a right lower lobe pneumonia. 

When in later years Krebs reviewed the major points which had to be established if the cycle was to be shown to be operative in cells, the obvious needs were to find the presence of the required enzymes and to detect their substrates. As the substrates are present in the cycle in catalytic amounts their accumulation required the use of inhibitors. Krebs also stressed that rates of oxidation of the individual substrates must be at least as fast as the established rates of oxygen uptake in vivo, an argument first used by Slator (1907) with reference to fermentation A postulated intermediate must be fermented at least as rapidly as glucose is. (See Holmes, 1991). This requirement did not always appear to be met. In the early 1950s there were reports that acetate was oxidized by fresh yeast appreciably more slowly than the overall rate of yeast respiration. It was soon observed that if acetone-dried or freeze-dried yeasts were used in place of fresh yeast, rates of acetate oxidation were increased more than enough to meet the criterion. Acetate could not penetrate fresh yeast cell walls sufficiently rapidly to maintain maximum rates of respiration. If the cell walls were disrupted by drying this limitation was overcome, i.e. if rates of reaction are to be... 

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