To Estimate the Amount of Total Protein
and Albumin in Serum and to Find A/G
Ratio
10
10.1 Theory
Proteins are present in all bodyfluids but show very high concentration (> 3 g/dl) in
plasma, lymphaticfluids, and some exudates. The amount of total proteins in serum
decreases in the third trimester of pregnancy. The measurement of total proteins in
serum is useful to assess the conditions related to changes in plasma orfluid
volumes, such as shock and dehydration. Atotal serum proteintest measures the
total amount ofproteinsin theblood. Serum proteins mainly consist of albumin but
few globulins (such asα 1 -globulin) also may be measured. Fibrinogen is the protein
present in plasma but not in serum. Albumin is a major constituent of human plasma
and represents about 40–60% of total proteins. After its synthesis in the liver
(hepatocytes), it is secreted in plasma, a process dependent on protein intake. The
half-life of albumin is 15–19 days. Albumin has molecular weight of approximately
66,000 dalton which makes it a marker of both glomerular and blood-brain barrier
functions. The pI of albumin lies between 4 and 5.8; hence it is present as an anion at
pH 7.4. Albumin is involved in transport and storage of wide variety of ligands and
maintaining the osmotic pressure of plasma. It also serves as a source of endogenous
amino acids. Albumin is mainly measured to checkliverand kidneyfunctions but is
also important in determining the cause of swelling of theankles(edema)or
abdomen(ascites). The globulins constitute various proteins likeα,β, andγtypes
that can be separated into distinct bands on electrophoresis. Few globulins are
synthesized by theliverwhile others by theimmune system. Globulins perform
wide variety of functions including transport and immunity.
10.2 Principle........................................
When a protein solution is treated with Cu2+in an alkaline solution, a colored chelate
complex of unknown composition is formed between Cu2+and carbon ion and imine
group of peptide bond. An analogous reaction takes place between Cu2+and organic
#Springer Nature Singapore Pte Ltd. 2018
V. Kumar, K. D. Gill,Basic Concepts in Clinical Biochemistry: A Practical Guide,
https://doi.org/10.1007/978-981-10-8186-6_10
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