Muscle cells, carbohydrate metabolism

PPI is a major dass of eukaryotic Ser/Thr-specific protein phosphatases that regulate diverse cellular processes such as cell cycle progression, muscle contraction, carbohydrate metabolism, protein synthesis, transcription, and neuronal signaling. Its action is modulated and regulated by assodation with subunits induding various inhibitor proteins and multiple targeting subunits of which nearly 30 proteins have now been identified (review Aggen et al., 2000). The activity of the inhibitory proteins can be controlled via phosphorylation by protein kinase A as outlined in Fig. 7.16. 

The calorific capacity of amino acids is comparable to that of carbohydrates so despite their prime importance in maintaining structural integrity of cells as proteins, amino acids may be used as fuels especially during times when carbohydrate metabolism is compromised, for example, starvation or prolonged vigorous exercise. Muscle and liver are particularly important in the metabolism of amino acids as both have transaminase enzymes (see Figures 6.2 and 6.3 and Section 6.4.2) which convert the carbon skeletons of several different amino acids into intermediates of glycolysis (e.g. pyruvate) or the TCA cycle (e.g. oxaloacetate). Not all amino acids are catabolized to the same extent... 

Mechanism of Action A polypeptide hormone that stimulates cartilaginous growth areas of long bones, increases the number and size of skeletal muscle cells, influences the size of organs, and increases RBC mass by stimulating erythropoietin. Influences the metabolism of carbohydrates (decreases insulin sensitivity), fats (mobilizes fatty acids), minerals (retains phosphorus, sodium, potassium by promotion of cell growth), and proteins (increases protein synthesis). Therapeutic Effect Stimulates growth. 

Lactic acid, present in blood entirely as lactate ion (pK = 3.86), is an intermediate of carbohydrate metabolism and is derived mainly from muscle cells and erythrocytes (see Chapter 25). It represents the end product of anaerobic metabolism and is normally metabolized by the liver. The blood lactate concentration is, therefore, affected by the rate of production and the rate of metabolism, both of which are dependent on adequate tissue perfusion. An increase in the concentration of lactate to >2 mmol/L and the associated increased is considered lactic acidosis. 

Potassium appears to perform many of the same functions inside the cell that sodium performs in the plasma and interstitial fluid. Potassium, in various ways 1) regulates the maintenance of the osmotic equilibrium of body fluids 2) acts as an available base to neutralize acids 3) maintains an ionic balance between potassium, sodium, calcium, and magnesium, which in turn affects capillary and cell functions and the excitability of nerves and muscles 4) maintains correct water balance in the body and 5) acts as a cofactor in several enzyme systems, including those used for energy transfer and utilization, protein synthesis, and carbohydrate metabolism (Oberleas et al. 

Polnalum Involved in acid-base balance and Iransler ol nutrients in and out of individual cells relates heart muscle required for secretion of insulin, pbosphoiylabon oi crealin, carbohydrate metabolism, and protein synthesis. Fruits, molassasi rice bran, sunflower seeds, wheat bran, beel, most raw vegetables, nuls, pork, poulby, and sardines... 

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