After studying this chapter, you should be able to:
- List the major functions of blood.
- Explain the functions of the major plasma proteins, including albumin, haptoglobin, transferrin, ceruloplasmin, α1-antitrypsin, and α2-macroglobulin.
- Describe how iron homeostasis is maintained and how it is affected in certain disorders.
- Describe the general structures and functions of the five classes of immunoglobulins and the uses of monoclonal antibodies.
- Appreciate that the complement system is involved in a number of important biological processes.
- Indicate the causes of Wilson disease, Menkes disease, the lung and liver diseases associated with α1-antitrypsin deficiency, amyloidosis, multiple myeloma, and agammaglobulinemia.
The fundamental role of blood in the maintenance of homeostasis (see Chapter 51) and the ease with which blood can be obtained have meant that the study of its constituents has been of central importance in the development of biochemistry and clinical biochemistry. The basic properties of a number of plasma proteins, including the immunoglobulins (antibodies), are described in this chapter. Changes in the amounts of various plasma proteins and immunoglobulins occur in many diseases and can be monitored by electrophoresis or other suitable procedures. As indicated in an earlier chapter, alterations of the activities of certain enzymes found in plasma are of diagnostic use in a number of pathologic conditions. Plasma proteins involved in blood coagulation are discussed in Chapter 51.
The functions of blood—except for specific cellular ones such as oxygen transport and cell-mediated immunologic defense—are carried out by plasma and its constituents (Table 50–1).
Table 50–1 Major Functions of Blood |Favorite Table|Download (.pdf)
Table 50–1 Major Functions of Blood
Respiration—transport of oxygen from the lungs to the tissues and of CO2 from the tissues to the lungs
Nutrition—transport of absorbed food materials
Excretion—transport of metabolic waste to the kidneys, lungs, skin, and intestines for removal
Maintenance of the normal acid–base balance in the body
Regulation of water balance through the effects of blood on the exchange of water between the circulating fluid and the tissue fluid
Regulation of body temperature by the distribution of body heat
Defense against infection by the white blood cells and circulating antibodies
Transport of hormones and regulation of metabolism
Transport of metabolites
Plasma consists of water, electrolytes, metabolites, nutrients, proteins, and hormones. The water and electrolyte composition of plasma is practically the same as that of all extracellular fluids. Laboratory determinations of levels of Na+, K+, Ca2+, Mg2+, Cl−, HCO3−, PaCO2, and of blood pH are important in the management of many patients.
The concentration of total protein in human plasma is approximately 7.0–7.5 g/dL and comprises the major part of the solids of the plasma. The proteins of the plasma are actually ...