AMINO ACID AND PROTEINS : AMINO ACID AND PROTEINS
Slide 2 : Any structures of the body are formed from proteins Proteins are large, complex molecules that play many critical roles in the body.
They do most of the work in cells and are required for the structure,
function, and regulation of the body’s tissues and organs
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Slide 4 : PROTEINS
Slide 5 : Proteins are made up of hundreds or thousands of smaller units called amino acids, which are attached to one another in long chains. There are 20 different types of amino acids that can be combined to make a protein
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Slide 8 : AMINO ACID
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Slide 10 : Proteins consist of amino acids which are characterized by the -CH(NH2)COOH substructure. Nitrogen and two hydrogens comprise the amino group, -NH2, and the acid entity is the carboxyl group, -COOH. Amino acids link to each when the carboxyl group of one molecule reacts with the amino group of another molecule, creating a peptide bond -C(=O)NH- and releasing a molecule of water (H2O). Amino acids are the basic building blocks of enzymes, hormones, proteins, and body tissues. A peptide is a compound consisting of 2 or more amino acids. Oligopeptides have 10 or fewer amino acids. Polypeptides and proteins are chains of 10 or more amino acids, but peptides consisting of more than 50 amino acids are classified as proteins.
Slide 11 : PEPTIDE BOND FORMATION
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Slide 22 : Amino acids are colorless, crystalline solids.
They are water-soluble high melting solids and behave like salts.
The a-carbon atom has 'R' which is a side chain.
This side chain is different for different amino acids.
The carboxyl and amino groups interact resulting in the transfer of proton from carboxyl group to amino group. Thus the amino acid exists in ionized form known as zwitter ion.
This explains the physical properties of these a-amino acids. PROPERTIES
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Slide 25 : ISOELECTRIC POINT In acidic solution, an amino acid exists as a positive ion and migrates towards the cathode in an electric field, while in alkaline solution it exists as a negative ion and migrates towards anode. At a certain hydrogen ion concentration (pH), the dipolar ion exists as a neutral ion and does not migrate to either electrode. This pH is known as the isoelectric point of the amino acid.
Slide 26 : BUFFER ACTION Amino acids are zwitter-ions, meaning they can have charges on both the amino & carboxylic groups, and yet have no net charge. Confused? wait! The amino group, -NH2 can become -NH3+, while the carboxylic group -COOH becomes -COO-. This is the zwitter ion. This is the form that predominates at ambient conditions. When in acidic media, the -COO- group grabs a proton, becoms -COOH and gets rid of the H+. The amino acid now has a net positive charge, (fully protonated, two protons at both acid & amino ends), so we call it the protonated form.In basic media, the -NH3+ group donates a proton to the medium (with extra OH-), to form H2O, thus getting rid of extra OH-. The amino acid now bears a net negative charge, so we call it anionic form. This is known as pseudo-buffer action.
Slide 27 : mino acid profiles of food proteins
The following table shows representative amino acid profiles of some common foods and dietary protein supplements. The percentages are averages of several commercial products. Casein and whey are milk proteins. Casein is the protein that precipitates from milk when curdled with rennet; it is the basis for making cheese. Whey is the watery part of milk that remains after the casein is separated.
Percentage (%) by weight of amino acid