Muscular energy source

Adenosine triphosphate creatine A-phosphotransferase (EC 2.7.3.2), also creatine phosphokinase. Creatine kinase is found in muscle and is responsible for the formation of creatine phosphate from creatine and adenosine triphosphate creatine phosphate is a higher energy source for muscle contraction. Creatine kinase is elevated in all forms of muscular dystrophy. Creatine kinase is dimer and is present as isozymes (CK-1, BB CK-2, MB CK-3, MM) and Ck-mt (mitochondrial). Creatine kinase is also used to measure cardiac muscle damage in myocardial infarction. See Bais, R. and Edwards, J.B., Creatine kinase, CRC Crit. Rev. Clin. Lab. ScL 16, 291-355, 1982 McLeish, M.J. and Kenyon, G.L., Relating structure to mechanism in creatine kinase, Crit. Rev. Biochem. Mol. Biol 40, 1-20, 2005. 

Glycogen— A starchy substance that is synthesized and stored in the muscles and a ready source of energy for muscular contraction. 

The energy source reserved for strenuous muscular activity... 

The answer is c. (Murray, pp 199-207. Scriver, pp 1521-1552. Sack, pp 121-138. Wilson, pp 287-317.) Muscle phosphorylase deficiency leads to a glycogen storage disease [McArdles disease (232600)] and, in young adults, an inability to do strenuous physical work because of muscular cramps resulting from ischemia. The compromised phosphorylation of muscle glycogen characteristic of McArdle s disease compels the muscles to rely on auxiliary energy sources such as free fatty acids and ambient glu-... 

Skeletal muscle is specialized to perform intermittent mechanical work. As described previously, the energy sources that provide ATP for muscle contraction depend on the degree of muscular activity and the physical status of the individual. During fasting and prolonged starvation, some skeletal muscle protein is degraded to provide amino acids (e.g., alanine) to the liver for gluconeogenesis. 

The high-energy compound steadily depleted during muscular activity is creatine phosphate (see here). Because the equilibrium for this reaction lies well to the right, virtually all of the muscle adenylate is maintained in the ATP form, rather than as ADP or AMP, as long as creatine phosphate is available. Thus, the energy source in red muscle is creatine phosphate, which regenerates ATP continually as it is depleted by muscle contraction. 

He worked on the sources of energy for muscular contraction, a continuation of his first interest in muscle creatine. Phosphagen had been recently discovered. Einar Lundsgaard had just shown that muscle poisoned with iodoacetic acid was able to perform a certain amount of work without liberation of lactic acid. Using muscles with low carbohydrate content, Ochoa was able to demonstrate the muscle s ability to perform work using sources of energy different from those then known. It was an important piece of work on a topic of great interest at the time. 

It is of interest to go back to the sources of these modem developments. Table 1 shows in chronological order some of the early work on lactic acid in three parts first, the chemistry second, the search for the source of energy for muscular work which is intimately connected with the lactic acid problem and third, what is called here the classical period for want of a better name. Only the first two parts will be covered in this presentation. 

The main topic I would like to discuss is the long debate about the source of energy for muscular work. This was only one of the great controversies that were going on at that time. In fact, most of the prominent scientists of this period were engaged in heated discussions with each other. 

For the sake of argument the authors assumed that all of the protein calories were available for climbing. This implied 100% efficiency of the muscle machine, whereas between 20-30% efficiency is the present-day assumption. They concluded that protein could not be the sole source of energy for muscular work and that most of the work was done at the expense of carbohydrate and fat. The nitrogen excretion in the urine merely indicated the wear and tear of the machine. 

CAS 56-65-5. C10H16N5OBP3. A nucleotide that serves as a source of energy for biochemical transformations in plants (photosynthesis) and also for many chemical reactions in the body, especially those associated with muscular activity and replication of cell components. 

As explained earlier (see p. 261), energy expended in the maintenance of an animal leaves the body in the form of heat. The quantity of heat arising in this way is known as the animal s basal metabolism, and its measurement provides a direct estimate of the NE that the animal requires from its food in order to meet the demands of maintenance. The measurement of basal metabolism is complicated by the fact that heat produced by the animal comes not only from this source but also from the digestion and metabolism of food components (the heat increment of feeding) and from the voluntary muscular activity of the animal. Heat production may also be increased further if the animal is kept in a cold environment (see p. 350). 

A nitrogenous compound formed in the liver, which is converted to phosphocreatine in muscle, where it serves as a source of high energy phosphate for muscle contraction. Greater than normal amounts of creatine are excreted in the urine when muscle disorders and other abnormal conditions are present. In muscular dystrophy, the muscle is unable to accept creatine, and it is excret in the urine. 

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