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TCA cycle—See Tricarboxylic acid

Citric acid cycle. See tricarboxylic acid (TCA) cycle. [Pg.909]

Possibly the most serious nutrition problem in the United States is excessive food consumption, and many people have experimented with fad diets in the hope of losing excess weight. One of the most popular of the fad diets has been the high-protein, high-fat (low-carbohydrate) diet. The premise for such diets is tantalizing because the tricarboxylic acid (TCA) cycle (see Chapter 20) is the primary site of fat metabolism, and because glucose is usually needed to replenish intermediates in the TCA cycle, if carbohydrates are restricted in the diet, dietary fat should merely be converted to ketone bodies and excreted. This so-called diet appears to work at first because a low-carbohydrate diet results in an initial water (and weight) loss. This occurs because... [Pg.585]

Oxidation of acetyl CoA The tricarboxylic acid (TCA) cycle (see p. 107) is the final common pathway in the oxidation of fuel molecules such as acetyl CoA. Large amounts of ATP are gener ated as electrons flow from NADH and FADH2 to oxygen via oxidative phosphorylation (see p. 77). [Pg.91]

Acetyl CoA feeds into a remarkable biochemical sequence, variously known as the tricarboxylic acid (TCA) cycle, the citric acid cycle or, after its discoverer, the Krebs cycle (Fig. 14.1). It is called a cycle because it does indeed end up where it started, at a compound called oxaloacetate. Oxaloacetate combines with acetyl CoA, releasing the CoA and forming citric acid (so named because plentiful in citrus fruit juices). A sequence of seven further reactions takes citrate back to oxaloacetate. What has happened is that the two carbons in the acetyl group of acetyl CoA have been taken up (into citrate) and two carbons have been separately released as CO2 in the reactions of the cycle. If we tracked individual carbon atoms like ringed birds (as we can with radioactive isotopes - see Chemistry X), we would find that the cycle does not release precisely the same two carbon atoms that entered, but that need not concern us. In net chemical terms, it does not matter where the atoms came from. At the end of the cycle, the amounts of aU the TCA cycle intermediates are unchanged, and in effect an acetyl group has been oxidised to 2CO2 (see Appendix 8). [Pg.109]

The tricarboxylic acid cycle (TCA cycle, also known as the citric acid cycle or Krebs cycle) is a cyclic metabolic pathway in the mitochondrial matrix (see p. 210). in eight steps, it oxidizes acetyl residues (CH3-CO-) to carbon dioxide (CO2). The reducing equivalents obtained in this process are transferred to NAD"" or ubiquinone, and from there to the respiratory chain (see p. 140). Additional metabolic functions of the cycle are discussed on p. 138. [Pg.136]

In mammals, muscle breakdown or excess protein intake results in an imbalance between the fates of the carbon chains and the amino nitrogen. Unlike fat (lipid storage) or glycogen (carbohydrate storage), excess amino acids are not stored in polymeric form for later utilization. The carbon chains of amino acids are generally metabolized into tricarboxylic acid (TCA) cycle intermediates, although it is also possible to make ketone bodies such as acetoacetate from some. Conversion to TCA intermediates is easy to see in some instances. For example, alanine is directly transaminated to pyruvate. [Pg.72]


See other pages where TCA cycle—See Tricarboxylic acid is mentioned: [Pg.918]    [Pg.531]    [Pg.918]    [Pg.531]    [Pg.913]    [Pg.517]    [Pg.269]    [Pg.106]    [Pg.712]    [Pg.58]    [Pg.59]    [Pg.532]    [Pg.54]    [Pg.107]    [Pg.9]    [Pg.69]    [Pg.310]    [Pg.18]    [Pg.196]    [Pg.1265]   


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TCA

TCA = Tricarboxylic acids

TCA cycle

TCAs

Tricarboxylate cycle

Tricarboxylates

Tricarboxylic acid cycle

Tricarboxylic acid cycle (TCA

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