Carbohydrate metabolism anabolic

Carbohydrate metabolism in the organism tissues encompasses enzymic processes leading either to the breakdown of carbohydrates (catabolic pathways), or to the synthesis thereof (anabolic pathways). Carbohydrate breakdown leads to energy release or intermediary products that are necessary for other biochemical processes. The carbohydrate synthesis serves for replenishment of polysaccharide reserve or for renewal of structural carbohydrates. The effectiveness of various routes of carbohydrate metabolism in tissues and organs is defined by the availability of appropriate enzymes in them. 

Somatotropin (STH) (Growth hormone, GH somatotrophic hormone hypophyseal growth hormone) Structure Known and synthesized coiled, unbranched Promotes general growth of organism Promotes skeletal growth, protein anabolism, fat metabolism, carbohydrate metabolism, water, and salt meiabolism Relates with all vitamins in connection with growth actions... 

Regulates growth, differentiation, oxidative metabolism, electrolytic balance Increases carbohydrate metabolism, calorigenesis, protein anabolism, ba.sal metabolic rate, oxygen consumption, fat catabolism, fertility Sensitizes nervous system... 

The biological roles of phosphorus include (1) anabolic and catabolic reactions, as exemplified by its essentiality in high-energy bond formation, e.g., ATP (adenosine triphosphate), ADP (adenosine diphosphate), etc., and the formation of phosphorylated intermediates in carbohydrate metabolism ... 

Figure 4 summarizes the result of these experiments. All reactions associated with carbohydrate metabolism are decreased by exposure to radiation, while all associated with the citric acid cycle and acetate catabolism are increased. Also, in every case studied, anabolic reactions were reduced by radiation. 

Various inborn errors of metabolism (Table 25-1) result from deficiencies or absence of some of the enzymes listed in Figure 25-9. Some of these are discussed later in the chapter. The relationship of carbohydrate metabolism to the production of lactate, ketone bodies, and triglycerides is also depicted in Figure 25-9. The pentose phosphate pathway, also known as the hexose monophosphate shunt, is an alternative pathway for glucose metaboUsm that generates the reduced form of nicotinamide-adenine dinucleotide phosphate (NADPH), which is used in maintaining the integrity of red blood cell membranes, in lipid and steroid biosynthesis, in hydroxylation reactions, and in other anabolic reactions. The complete picture of intermediary metabolism of carbohydrates is rather complex and interwoven with the metabolism of lipids and amino acids. For details, readers should consult a biochemistry textbook. 

Biotin is the coenzyme required by enzymes that catalyze carboxylation of a carbon adjacent to a carbonyl group. For example, pymvate carboxylase converts pyruvate—the end product of carbohydrate metabolism—to oxaloacetate, a citric acid cycle intermediate (Figure 25.2). Acetyl-CoA carboxylase converts acetyl-CoA into malonyl-CoA, one of the reactions in the anabolic pathway that converts acetyl-CoA into fatty acids (Section 19.21). Biotin-requiring enzymes use bicarbonate (HCOs ) for the source of the carboxyl group that becomes attached to the substrate. 

This reaction, which produces oxaloacetate from pyruvate, provides a connection between the amphibolic citric acid cycle and the anabolism of sugars by gluconeogenesis. On this same topic of carbohydrate anabolism, we should note again that pyruvate cannot be produced from acetyl-GoA in mammals. Because acetyl-GoA is the end product of catabolism of latty acids, we can see that mammals could not exist with fats or acetate as the sole carbon source. The intermediates of carbohydrate metabolism would soon be depleted. Garbohydrates are the principal energy and carbon source in animals (Figure 19.11), and glucose is especially critical in humans because it is the preferred fuel for our brain cells. Plants can carry out the conversion of acetyl-GoA to pyruvate and oxaloacetate, so they can exist without carbohydrates as a carbon source. The conversion of pyruvate to acetyl-GoA does take place in both plants and animals (see Section 19.3). 

The starting point of lipid anabolism is acetyl-GoA. The anabolic reactions of lipid metabolism, like those of carbohydrate metabolism, take place in the cytosol these reactions are catalyzed by soluble enzymes that are not bound to membranes. Acetyl-GoA is mainly produced in mitochondria, whether from pyruvate or from the breakdown of fatty acids. An indirect transfer mechanism exists for transfer of acetyl-CoA in which citrate is transferred to the cytosol (Figure 19.13). Citrate reacts with GoA-SH to produce citryl-CoA, which is then cleaved to yield oxaloacetate and acetyl-GoA. The enzyme that catalyzes this reaction requires ATP and is called ATP-citrate lyase. The overall reaction is... 

The two ways of producing NADPH clearly indicate that all metabolic pathways are related. The exchange reactions involving malate and citryl-GoA constitute a control mechanism in hpid anabolism, while the pentose phosphate pathway is part of carbohydrate metabolism. Both carbohydrates and lipids are important energy sources in many organisms, particularly animals. 

Goenzymes are introduced in this chapter and are discussed in later chapters in the context of the reactions in which they play a role. Chapter 16 discusses carbohydrates. Chapter 17 begins the overview of the metabohc pathways by discussing glycolysis. Glycogen metabolism, gluconeogenesis, and the pentose phosphate pathway (Chapter 18) provide bases for treating control mechanisms in carbohydrate metabolism. Discussion of the citric acid cycle is followed by the electron transport chain and oxidative phosphorylation in Chapters 19 and 20. The catabolic and anabolic aspects of lipid metabohsm are dealt with in Chapter 21. In Chapter 22, photosynthesis rounds out the discussion of carbohydrate metabolism. Chapter... 

Carbohydrate metabolism the involvement of Mn(II) with key enzymes of glucose storage, mobilization, and catabolic and anabolic metabolism is now well established. Effects at the cell, organ, and whole organism levels are less well understood, especially those related to interaction of Mn(II) with hormonal systems and receptors. 

Cells—Functional Units Nutrients For Metabolism Carbohydrates Catabolism Anabolism Fats... 

ANABOLISM. Two processes involved in carbohydrate metabolism may be considered anabolic in that they require energy (1) storage of glucose as glycogen and (2) the formation of glucose from noncarbohydrate sources, or gluconea... 

Theory Cortisol (or hydrocortisone) was introduced in the year 1951, for the treatment of rheumatoid arthritis. It has a significant effect on protein metabolism. It also exerts widespread effects on carbohydrates, lipid and protein synthesis (or anabolism). The cardinal side effects such as excessive potassium excretion and sodium retention, enhanced gastric acidity, oedema, psychosis and negative nitogen balance are some of the exaggerated manifestations of the normal metabolite functions of cortisol. 

The citric acid cycle is at the heart of aerobic cellular metabolism, or respiration. This is true of both prokaryotic and eukaryotic organisms, of plants and animals, of organisms large and small. Here is the main point. On the one hand, the small molecule products of catabolism of carbohydrates, lipids, and amino acids feed into the citric acid cycle. There they are converted to the ultimate end products of catabolism, carbon dioxide and water. On the other hand, the molecules of the citric acid cycle are intermediates for carbohydrate, lipid, and amino acid synthesis. Thus, the citric acid cycle is said to be amphibolic, involved in both catabolism and anabolism. It is a sink for the products of degradation of carbohydrates, lipids, and proteins and a source of building blocks for them as well. 

Il.f.l.1. Insulins. Insulin is the most effective of diabetes medications. Insulin has profound effects on carbohydrate, protein, fat metabolism and electrolytes. It has anabolic and anticatabolic actions. In a state of insulin deficiency, glycogenesis, glucose transport, protein synthesis, triglyceride synthesis, LPL activity in adipose tissue, cellular potassium uptake all decrease on the other hand, gluconeogene-sis, glycogenolysis, protein degradation, ketogene-sis, lipolysis increase. 

Catabolism is the degradative phase of metabolism in which organic nutrient molecules (carbohydrates, fats, and proteins) are converted into smaller, simpler end products (such as lactic acid, C02, NH3). Catabolic pathways release energy, some of which is conserved in the formation of ATP and reduced electron carriers (NADH, NADPH, and FADH2) the rest is lost as heat. In anabolism, also called biosynthesis, small, simple precursors are built up into larger and more complex... 

Chapters 20 through 22 describe the major anabolic pathways by which cells use the energy in ATP to produce carbohydrates, lipids, amino acids, and nucleotides from simpler precursors. In Chapter 23 we step back from our detailed look at the metabolic pathways—as they occur in all organisms, from Escherichia coli to humans—and consider how they are regulated and integrated in mammals by hormonal mechanisms. 

J to their molecular components. Then one of two things happens either your body burns these molecular components for their energy content through a process known as cellular respiration, or these components are used as the building blocks for your body s own versions of carbohydrates, lipids, proteins, and nucleic acids. The sum total of all these biochemical activities is what we call metabolism. Two forms of metabolism are catabolism and anabolism, and Figure 13.41 shows the major catabolic and anabolic pathways of living organisms. 

Somatotropin, the adrenergic agonists, and the anabolic steroids are considered metabolism modifiers because these compounds alter protein, lipid, carbohydrate, mineral metabolism, or combinations of these and they partition nutrient use toward greater rates of protein deposition, ie, muscle growth, and lesser rates of lipid accretion. Historical data leading to understanding of the mechanism (s) of action are found in reviews on anabolic steroids (1), somatotropin (2—4), and the phenethanolamines (5—7). 

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