Human component, living systems

The major classes of organic compounds common to living systems are lipids pro terns nucleic acids and carbohydrates Carbohydrates are very familiar to us— we call many of them sugars They make up a substantial portion of the food we eat and provide most of the energy that keeps the human engine running Carbohy drates are structural components of the walls of plant cells and the wood of trees Genetic information is stored and transferred by way of nucleic acids specialized derivatives of carbohydrates which we 11 examine m more detail m Chapter 28... 

The breakdown of proteins during digestion and reuse of the components that result permit living systems to continue to function. However, excess nitrogen may be produced and many land animals (including humans) excrete it as urea (H2NCONH2). 

Polyalphaolefin Hydraulic Fluids. Because no chronic-duration human or animal inhalation, oral, or dermal exposure studies using polyalphaolefin hydraulic fluids were located, chronic-duration inhalation or oral MRLs could not be derived. Systemic toxicity studies in which animals were exposed via inhalation, oral, and dermal routes would be useful in identifying the end points of toxicity for humans living at or near hazardous waste sites and exposed for chronic durations. Further carcinogenicity studies on individual organophosphate ester components of hydraulic fluids maybe useful. 

---