Download to read offline
Proteins structures, need and formation .pptx
- 2. PRESENTED TO: PRESENTED BY: ROLLNO: INSTITUTE: * TOPIC: Important Clinicals of LowerLimb
- 3. OUTLINES: INTRODUCTION WHAT ARE PROTEINS ? WHATARE AMINO ACIDS ? GENERAL STRUCTURE OF AMINO ACIDS STANDARD AMINO ACIDS CLASSIFICATION OF AMINO ACIDS PROPERTIES OF AMINO ACIDS STRUCTURE OF PROTEINS CLASSIFICATION OF PROTEINS
- 6. WHAT ARE PROTEINS? Proteins are the polymers of amino acids. Proteins are the most abundant organic molecules of the living system. They occur in every part of the cell and constitute about 50% of the cellular dry weight. Proteins form the fundamental basis of structure and function of life.
- 7. of 809 Origin ofthe word ‘protein’ The term protein is derived from a Greek word proteios, meaning holding the first place. Berzelius (Swedish chemist) suggested the name proteins to the group of organic compounds that are utmost important to life. Mulder (Dutch chemist) in 1838 used the term proteins for the high molecular weight nitrogen-rich and most abundant substances present in animals and plants.
- 8. What are AminoAcids ? Amino Acids are monomers of proteins. Amino acids are a group of organic compounds containing two functional groups — amino and carboxyl. The amino group (—NH2) is basic while the carboxyl group (—COOH) is acidic in nature. Proteins on complete hydrolysis (with concentrated HCl for several hours) yield L-D-amino acids. This is a common property of all the proteins. Therefore, proteins are the polymers of L-D-amino acids
- 9. General structure ofamino acids The amino acids are termed as D-amino acids, if both the carboxyl and amino groups are attached to the same carbon atom. The D-carbon atom binds to a side chain represented by R which is different for each of the 20 amino acids found in proteins. The amino acids mostly exist in the ionized form in the biological system.
- 10. STANDARD AMINO ACIDS Asmany as 300 amino acids occur in nature— Of these, only 20—known as standard amino acids are repeatedly found in the structure of proteins, isolated from different forms of life— animal, plant and microbial. This is because of the universal nature of the genetic code available for the incorporation of only 20 amino acids when the proteins are synthesized in the cells.
- 11. Classification of AminoAcids There are different ways of classifying the amino acids based on the structure and chemical nature, nutritional requirement, metabolic fate etc. Hydrophilic & Hydrophobic Amino Acids Hydrophilic Hydrophobic Arginine Alanine Asparagine Isoleucine Aspartic acid Leucine Cysteine Methionine Glutamic acid Phenylalanine Glutamine Proline Glycine Tryptophan Histidine Tyrosine Lysine Valine Serine Threonine
- 12. Hydrophilic & HydrophobicAmino Acids Hydrophilic Hydrophobic Arginine Alanine Asparagine Isoleucine Aspartic acid Leucine Cysteine Methionine Glutamic acid Phenylalanine Glutamine Proline Glycine Tryptophan Histidine Tyrosine Lysine Valine Serine Threonine
- 13. Properties of aminoacids The amino acids differ in their physio– chemical properties which ultimately determine the characteristics of proteins. A. Physical properties 1. Solubility : Most of the amino acids are usually soluble in water and insoluble in organic solvents. 2. Melting points : Amino acids generally melt at higher temperatures, often above 200°C. 3. Taste : Amino acids may be sweet (Gly, Ala, Val), tasteless (Leu) or bitter (Arg, Ile). Monosodium glutamate (MSG; ajinomoto) is used as a flavoring agent in food industry, and Chinese foods to increase taste and flavor. In some individuals intolerant to MSG, Chinese restaurant syndrome (brief and reversible flulike symptoms) is observed. 4. Optical properties : All the amino acids except glycine possess optical isomers due to the presence of asymmetric carbon atom. Some amino acids also have a second asymmetric carbon e.g. isoleucine, threonine.
- 14. 5. Amino acidsas ampholytes : Amino acids contain both acidic ( COOH) and basic ( NH2) groups.They can donate or accept a proton, hence amino acids are regarded as ampholytes(Zwitterion or dipolar ion).The name zwitter is derived from the German word which means hybrid.Zwitter ion (or dipolar ion) is a hybrid molecule containing positive and negative ionic groups.The amino acids rarely exist in a neutral form with free carboxylic ( COOH) and free amino ( NH2) groups. In strongly acidic pH (low pH), the amino acid is positively charged (cation) while in strongly alkaline pH (high pH), it is negatively charged (anion).Each amino acid has a characteristic pH (e.g. leucine,pH 6.0)at which it carries both positive and negative charges and exists as zwitterion. Isoelectric pH (symbol pI) is defined as the pH at which a molecule exists as a zwitterion or dipolar ion and carries no net charge.The pI value can be calculated by taking the average pKa values corresponding to the ionizable groups. Leucine exists as cation at pH below 6 and anion at pH above 6. At the isoelectric pH (pI = 6.0), leucine is found as zwitterion.Thus the pH of the medium determines the ionic nature of amino acids. For the calculation of pI of amino acids with more than two ionizable groups, the pKas for all the groups have to be taken into account.The existence of different ionic forms of amino acids can be more easily understood by the titration curves.
- 15. STRUCTURE OF PROTEINS Proteinsare the polymers of L-D-amino acids. The structure of proteins is rather complex which can be divided into 4 levels of organization : 1. Primary structure : The linear sequence of amino acids forming the backbone of proteins (polypeptides). 2. Secondary structure : The spatial arrangement of protein by twisting of the polypeptide chain. 3. Tertiary structure : The three dimensional structure of a functional protein. 4. Quaternary structure : Some of the proteins are composed of two or more polypeptide chains referred to as subunits. The spatial arrangement of these subunits is known as quaternary structure.
- 17.
- 18. Functions of proteins Proteinsperform a great variety of specialized and essential functions in the living cells. These functions may be broadly grouped as static (structural) and dynamic. Structural functions : Certain proteins perform brick and mortar roles and are primarily responsible for structure and strength of body. These include collagen and elastin found in bone matrix, vascular system and other organs and D-keratin present in epidermal tissues. Dynamic functions : The dynamic functions of proteins are more diversified in nature. These include proteins acting as enzymes, hormones, blood clotting factors, immunoglobulins, membrane receptors, storage proteins, besides their function in genetic control, muscle contraction, respiration etc. Proteins performing dynamic functions are appropriately regarded as the working horses of cell.
- 19.
- 20.