Energy in muscles

Coenzyme QIO, or CoQlO, is a substance that occurs naturally in virtually all of our bodies tissues, especially in muscle tissue. It s so widespread throughout the body that another name for it is ubiquinone, referring to its ubiquitous nature. CoQlO regulates energy in muscle cells. As we age, the amount in our bodies declines. For that reason, it has been speculated that supplementation would improve energy levels. That claim hasn t been well substantiated, but there are other and better reasons to consider supplementation. 

Proteins are unique among the biological macromolecules and have attracted active interest from various disciplines. For the physicist it is the structure that has the characteristics of order as well as of disorder. The chemist is attracted by the unique properties that show up in the catalytic activity of enzymes and in the conversion of chemical into mechanical energy in muscle. Biologists tend to put the emphasis on the functional role of proteins. 

The fatty acids form complexes with albumin in the blood and are taken up by muscle, kidney, and other tissues, where ATP is generated by their oxidation to CO2 and water. Liver also converts some of the carbon to ketone bodies, which are released into the blood. Ketone bodies are oxidized for energy in muscle, kidney, and other tissues during fasting, and in the brain during prolonged starvation (see Chapter 23). 

The fatty acids released from triacylglycerols by LPL are not very soluble in water. They become soluble in blood by forming complexes with the protein albumin. The major fate of the fatty acids is storage as triacylglycerol in adipose tissue. However, these fatty acids also may be oxidized for energy in muscle and other tissues (see Fig. 32.13). The LPL in the capillaries of muscle cells has a lower than adipose LPL. Thus, muscle cells can obtain fatty acids from blood lipoproteins whenever they are needed for energy, even if the concentration of the lipoproteins is low. 

Fat mobilization is the process of hydrolyzing triglycerides to produce fatty acids and glycerol, both of which can be used for energy in muscle cells. 

Bessman SP, Geiger PJ (1981) Transport of energy in muscle the phoshorylcreatine shuttle. Science 211 448-452... 

Description of Method. Creatine is an organic acid found in muscle tissue that supplies energy for muscle contractions. One of its metabolic products is creatinine, which is excreted in urine. Because the concentration of creatinine in urine and serum is an important indication of renal function, rapid methods for its analysis are clinically important. In this method the rate of reaction between creatinine and picrate in an alkaline medium is used to determine the concentration of creatinine in urine. Under the conditions of the analysis, the reaction is first-order in picrate, creatinine, and hydroxide. 

FIGURE 14.21 The structures of creatine and creatine phosphate, guanidiniutn compounds that are important in muscle energy metabolism. 

In the kidney and in muscle tissues, fructose is readily phosphorylated by hexokinase, which, as pointed out above, can utilize several different hexose substrates. The free energy of hydrolysis of ATP drives the reaction forward ... 

The crossbridge cycle in muscle. Myosin crossbridges interact cyclically with binding sites on actin filaments. Note that the energy release step—when ATP is broken down to ADP—recocks the crossbridge head. 

Lipoprotein metabolism is the process by which hydrophobic lipids, namely triglycerides and cholesterol, are transported within the interstitial fluid and plasma. It includes the transport of energy in the form of triglycerides from intestine and liver to muscles and adipose, as well as the transport of cholesterol both from intestine and liver to peripheral tissues, as well as from peripheral tissues back to the liver. 

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