2. Quaternary structure. Mechanisms maintaining the conformation of proteins. Relation between the structure and the function of proteins – medical importance: defects in receptors (familial hypercholesterolemia, diabetes insipidus); diseases due to impaired conformation (prion disease, Alzheimer’s disease); molecular diseases (sickle cell anemia); defects in the post-translational modification of proteins (scurvy and glycated hemoglobin). Structure of hemoglobin. Isoelectric point, precipitation of protein. Denaturation. Electrophoresis. Methods for protein examination – electrophoresis, chromatography, etc. Electrophoresis of plasma proteins – fractions.

SECONDARY, TERTIARY, AND QUATERNARY STRUCTURE OF PROTEINS:

• Secondary structure refers to the local folding patterns of a polypeptide chain, such as alpha helices and beta sheets.
• Tertiary structure refers to the overall 3D shape of a single polypeptide chain, determined by interactions between amino acid side chains.
• Quaternary structure refers to the arrangement of multiple polypeptide chains into a larger protein complex.
• These different levels of structure are critical for determining a protein's function.

GLOBULAR AND FIBROUS PROTEINS:

• Globular proteins are typically spherical in shape and soluble in water, and often have enzymatic (metabolic reactions) or transport functions, hemoglobin in blood, complex tertiary and quaternary structures.
• Fibrous proteins are typically elongated and insoluble in water, and often have structural or supportive functions, such as in connective tissue, keratin and collagen examples, little to no tertiary structure and long polypeptide chains.

STRUCTURE AND FUNCTION OF HEMOGLOBIN:

Hemoglobin is a globular protein composed of four subunits, each of which contains a heme group that binds to oxygen.

Hemoglobin's function is to transport oxygen from the lungs to tissues throughout the body.

It is made up of 2 alpha chains and 2 beta chains which are held together by noncovalent interactions. It can carry 4 molecules of O2 from lungs to the cells.