Energy-yielding substrates

PN should provide a balanced nutritional intake, including macronutrients, micronutrients, and fluid. Macronutrients, including amino acids, dextrose, and intravenous lipid emulsions, are important sources of structural and energy-yielding substrates. A balanced PN formulation includes 10% to 20% of total daily calories from amino acids, 50% to 60% of total daily calories from dextrose, and 20% to 30% of total daily calories from intravenous lipid emulsion. Micronutrients, including electrolytes, vitamins, and trace elements, are required to support essential biochemical reactions. Parenteral... 

Energy-yielding substrates enter the brain from the blood through the blood-brain barrier 533... 

Reference intakes (see Table 6.2) are based on 0.5 mgper 1,000 kcal (0.12 mg per MJ) for adults consuming more than 2,000 kcal per day, with the proviso that even in fasting there is a requirement for 0.8 mg of thiamin per day to permit the metabolism of endogenous energy-yielding substrates. 

Interference with respiration, the overall process by which electrons are transferred to molecular oxygen in the biological oxidation of energy-yielding substrates ... 

Microorganisms use these reduction reactions to consume the electrons generated by the oxidation of their energy-yielding substrate. Although this substrate can be any of a variety of substances, let us take for an example the oxidation of formaldehyde CH2O) to CO2 and HjO by the reaction ... 

The formation and disappearance of transport intermediates resulting from the interaction of the energy-yielding substrates with the transport protein can be followed during ion translocation at every moment. 

Fig. I. Minimum levels of ionized calcium approached in the presence of different calcium-precipitating agents and energy-yielding substrates. Note that ADP induces a calcium release only in the presence of phosphate.

The sarcoplasmic reticulum vesicles start to release calcium passively when the activity of the calcium pump is blocked, either by inhibition of the transport enzyme or by depletion of energy-yielding substrates [45]. The rate of passive calcium efflux from vesicles loaded in the absence of calcium-precipitating agents, is approx. 20... 

More recently, it has been shown by Marr (7 ), Pirt (8 ) and others (5,9,ll)that the yield is not a constant. Rather endogene-ous respiration utilizes the energy yielding substrates for maintenance functions hence,the substrate utilization by cells can be better expressed by... 

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