Carbohydrates energy equivalent

The energy equivalent of red light is about 190 kJ (45 kcal) mol-1, but >e actual energy requirement for the reduction of 1 mole ofC02 to carbohydrate is 470 kJ (c==t 112 kcal) mol-1. This shows that the mechanism of... 

The substrates of catabolism—proteins, carbohydrates, and lipids—are good sources of chemical energy because the carbon atoms in these molecules are in a relatively reduced state (Figure 18.9). In the oxidative reactions of catabolism, reducing equivalents are released from these substrates, often in the form of hydride ions (a proton coupled with two electrons, H ). These hydride ions are transferred in enzymatic dehydrogenase reactions from the substrates... 

Most of the energy liberated during the oxidation of carbohydrate, fatty acids, and amino acids is made available within mitochondria as reducing equivalents (—H or electrons) (Figure 12-2). Mitochondria contain the respiratory chain, which collects and transports reducing equivalents directing them to their final reaction with oxygen to form water, the machinery for... 

Fat is only an energy storage form (Fig. 17-4). Fat cannot be converted to carbohydrate equivalents. This is a very important point. Remember it The reason for this is a bit subtle. The carbon skeleton of fatty acids is metabolized to acetyl-CoA only. Glucose precursors such as oxaloacetate can be synthesized from acetyl-CoA by going around the TCA cycle. However, acetyl-CoA has 2 carbon atoms. Going around the TCA cycle burns off 2 carbon atoms (as C02). The net number of carbon atoms that ends up in oxaloacetate is then zero. No carbohydrate can be made from fat.5... 

This value of 20 kJ/L O2 can be very useful for example, it can be used to calculate that a top-class marathon runner requires oxidation of 5 g of carbohydrate every minute during the race, provided that no other fuel is used. The athlete takes up 4 litres of oxygen each minute, which is equivalent to 4 x 20, or 80 kJ each minute as 1 g of glucose releases 16 kJ of energy, the glucose or glycogen used is 80/16 or 5 g each minute. 

Niacin, a water-soluble vitamin vital for oxidation by living cells, functions in the body as a component of two important coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). NAD and NADP are involved in the release of energy from carbohydrate, fat, and protein, and in the synthesis of protein, fat, and pentoses for nucleic acid formation. Milk is a poor source of preformed niacin, containing about 0.08 mg per 100 g. However, milk s niacin value is considerably greater than indicated by its niacin content (Horwitt et al. 1981). Not only is the niacin in milk fully available, but the amino acid tryptophan in milk can be used by the body for the synthesis of niacin. For every 60 mg of tryptophan consumed, the body synthesizes 1 mg of niacin. Therefore, the niacin equivalents in 100 g milk equal 0.856 mg including that from pre-... 

In defining the nutritional equivalence of dairy foods, FDA considered only 11 to 15 nutrients for milk substitutes, 1 nutrient for cream substitutes, and 4 to 9 nutrients for cheese substitutes (FDA 1978). Yet, data from the Consumer and Food Economics Institute, USDA (1976), reveal that traditional milk, cream, and cheese contain an array of nutrients including protein, fat, carbohydrate, and at least 15 minerals and vitamins and 18 amino acids. Thus, under FDA s proposal (FDA 1978), which has been withdrawn (FDA 1983) but, as mentioned above, may in effect be applied, a substitute dairy product could be declared nutritionally equivalent to its traditional counterpart and yet (1) not contain all of the nutrients in the traditional food, or (2) contain some or all of these other nutrients but in lesser quantities, or (3) contain some of the nutrients such as sodium in excessive amounts, or (4) contain more or less energy (NDC 1983C). 

Substitute milk products may not be equivalent to cow s milk in terms of the quantity and in some cases the quality of fat, carbohydrate, vitamins, and minerals. Fat, carbohydrate, sodium, fiber, and energy, as well as the nutrients for which no U.S. RDA has been established, were not considered by FDA in its proposed definition of nutritional equivalency. In terms of quality, coconut oil, the primary and in most instances the sole fat used in substitute as well as imitation milk products, is a more saturated fat than milk fat and lacks linoleic acid, an essential fatty acid. Thus, a substitute dairy product formulated with hydrogenated coconut oil and sucrose and containing more so-... 

Turning to photobiological schemes for producing H2 (Chapter 8), a complex reaction scheme uses solar energy to convert H2O into O2 and reducing equivalents which appear as NADPH. In photosystem 1, the reducing equivalents in NADPH are used to reduce CO2 to carbohydrates ... 

The fatty acids produced on hydrolysis are then oxidized in a stepwise fashion, ultimately yielding CO2 and H2O, as well as a great deal of energy. Oxidation of fatty acids yields twice as much energy per gram as oxidation of an equivalent weight of carbohydrate. 

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