Baynes's Medical Biochemistry 2e 2005
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THE VALUE OF BIOCHEMISTRY
The study of human biochemistry will open your eyes to how the body works as a chemical system. From a physician's point of view, biochemistry not only describes how the system works, but also provides a foundation for understanding how to improve its operation (e.g. by appropriate nutrition and exercise), how to diagnose problems and, where possible, how to remedy them. Knowing biochemistry helps to understand current therapies, which include recombinant proteins, such as human insulin or erythropoietin synthesized by bacteria. It helps to understand the action of new drugs, such as thiazolidinediones used in type 2 diabetes, which act through cell signaling systems. In the future, therapies will possibly involve gene rather than organ transplants. Pharmacogenomics and nutritional genomics will create a basis for designer treatments, customized to an individual's genetic makeup.
To understand all this it is essential to know something not only about the 'nuts and bolts', but to appreciate functional interactions between metabolic pathways, organs, and tissues. This, in a broad sense, is the realm of physiologic biochemistry, and the scope of this text.
The living organism communicates with its environment .
It is useful to consider the human organism from two points of view: as a tightly controlled, internally integrated metabolic system, and as a flexible, open system that communicates with its environment. Interactions between these two are essential for the maintenance of our internal, homeostatic environment. We regularly consume fuel (food) and water, and we constantly take up oxygen from inspired air and transport it to tissues for oxidative metabolism. We use the energy from metabolism of foods to perform work and to maintain body temperature - respiration is in fact a controlled, low-temperature combustion reaction. We exhale or excrete the primary metabolic products, carbon dioxide, and water. Water represents approximately 50% of our total body mass; we control its loss, its electrolyte and metabolite concentrations, and use it as the common medium for biochemical reactions. Carbon dioxide, before elimination, is used for buffering the pH of body fluids.
The amount and composition of food we consume is immensely important for our health, and forms a background for a wide range of treatments and preventive actions. To understand links between nutrients, metabolism, and health and disease, is one of the most important reasons to study biochemistry.
Metabolic processes occur in a variety of spaces within cells.
Most metabolism occurs within the complex ecosystem of the cell, in subcellular organelles such as the nucleus, cell membrane, rough and smooth endoplasmic reticulum, Golgi apparatus, mitochondrion, lysosomes, or peroxisomes. Such compartmentalization of metabolic processes is important for several reasons: to protect the organism from autodigestion, to concentrate pathways and metabolites in space, and to enable different pathways, such as synthesis and degradation of proteins, to operate at the same time.
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