Fat, from carbohydrates

Fat, from carbohydrates, II, 120-125 feeding experiments with, II, 134 metabolism of, II, 119-160 metabolism, effect of lactose on, II, 159 nutritive values of, II, 160 from sugars, IV, 114 transformation to carbohydrate, II, 125-145... 

In this chapter, we ll look at some of the pathways by which organisms carry out their chemistry, focusing primarily on how they metabolize fats and carbohydrates. The treatment will be far from complete, but it should give you an idea of the kinds of processes that occur. 

The source of long-chain fatty acids is either dietary lipid or de novo synthesis from acetyi-CoA derived from carbohydrate. Fatty acids may be oxidized to acetyl-CoA (P-oxidation) or esterifred with glycerol, forming triacylglycerol (fat) as the body s main fuel reserve. 

Carbon dioxide is essential to photos Tithesis because plants use the carbon atoms of CO2 to make glucose. Furthermore, animals and plants use fats and carbohydrates for energy production and eliminate the carbon atoms from these molecules as CO2. 

Matrix Components The term matrix component refers to the constituents in the material aside from those being determined, which are denoted as analyte. Clearly, what is a matrix component to one analyst may be an analyte to another. Thus, in one hand for the case of analyses for elemental content, components such as dietary fibre, ash, protein, fat, and carbohydrate are classified as matrix components and are used to define the nature of the material. On the other hand, reference values are required to monitor the quality of determinations of these nutritionally significant matrix components. Hence, there is a challenging immediate need for certified values for dietary fibre, ash, protein, fat, and carbohydrate. Concomitantly, these values must be accompanied by scientifically sound definitions (e.g. total soluble dietary fibre, total sulpha-ted ash, total unsaturated fat, polyunsaturated fat, individual lipids, simple sugars, and complex carbohydrates). 

The water-soluble vitamins generally function as cofactors for metabolism enzymes such as those involved in the production of energy from carbohydrates and fats. Their members consist of vitamin C and vitamin B complex which include thiamine, riboflavin (vitamin B2), nicotinic acid, pyridoxine, pantothenic acid, folic acid, cobalamin (vitamin B12), inositol, and biotin. A number of recent publications have demonstrated that vitamin carriers can transport various types of water-soluble vitamins, but the carrier-mediated systems seem negligible for the membrane transport of fat-soluble vitamins such as vitamin A, D, E, and K. 

Although it ia becoming increasingly evident with each new discovery that the metabolism of no single foodstuff proceeds in a course entirely isolated from that of the other foodstuffs, the interrelationships are nowhere so apparent as they are between the utilization of carbohydrate and that of fat. The conversion of carbohydrate to fat is a phenomenon which has been repeatedly demonstrated experimentally the reverse change, namely, the conversion of natural fats to carbohydrate, is a disputed reaction and must certainly not occur except to a limited extent, if at all. 

Most of the perfusion studies have been carried out on the isolated liver since it is in this organ that the change of fat to carbohydrate presumably takes place. On the basis of some of these studies, carbohydrate formation from fat has been postulated.161-166 In such cases more carbohydrate has been present at the end of the perfusion experiment than could be accounted for on the basis of known carbohydrate precursors. In several cases, a decrease in the fat content of the liver was accompanied by a concomitant increase in carbohydrate. However, Gregg166 has been... 

Adults should consume 45% to 65% of total calories from carbohydrates, 20% to 35% from fat, and 10% to 35% from protein. Recommendations are similar for children, except that infants and younger children should consume 40% to 50% of total calories from fat. 

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