Protein and Amino Acid 06 PDF

 Fundamental biochemistry of proteins Lec.6  TABLE CONTENTS 01 02 Definition of proteins Importance of proteins 03 04 Properties of Amino acids classification of amino acids Definition of protien  Very large compared with...

 Fundamental biochemistry of proteins Lec.6  TABLE CONTENTS 01 02 Definition of proteins Importance of proteins 03 04 Properties of Amino acids classification of amino acids Definition of protien  Very large compared with molecules of sugar or salt  are polymers made up of smaller units called amino acids  Contain C, H, O and N To build a protein: must remove water; dehydration synthesis link together amino acids using peptide bonds proteins=polypeptides  Importance of proteins  It is commonly found in animal products, and plant products as well such as nuts and legumes.  Proteins are large, complex molecules that play many critical roles in the body  It is essential to building muscle mass.  They do most of the work in cells and are required for the structure, function, and regulation of the body’s tissues and organs. Proteins can be used as enzymes o Enzymes are catalysts; they speed up chemical reactions o Enzymes lower activation energy o Enzymes are specific to temperature and pH Proteins can act as chemical messengers: Hormones o Hormones are chemical-signaling molecules, usually small proteins or steroids, secreted by endocrine cells. o act to control or regulate specific physiological processes, including growth, development, metabolism, and reproduction. o ex, insulin is a protein hormone that helps to regulate the blood glucose level.  Amino Acids Building Blocks of Protein Monomer: amino acids The major key elements for amino acids are carbon, hydrogen, nitrogen, oxygen. About 500 amino acids are known (though only 20 appear in the genetic code) and can be classified in many ways  General properties of Amino acids They have a very high melting and boiling point. Amino acids are white crystalline solid substances. In taste, few Amino acids are sweet, tasteless, and bitter. Most of the amino acids are soluble in water and are insoluble in organic solvents.  Amino Acid Structure The basic structure of an amino acid consists of: 1. an amino group (-NH2), 2. a carboxylic acid group (-COOH), 3. a hydrogen atom, 4. and a unique side chain termed "R-group". Each. molecule contains a central carbon atom, known as α-carbon, to which both the amino and carboxylic acid groups are attached. The remaining two bonds of the α-carbon atom are usually satisfied by a hydrogen atom and an R group. Thus, the α-carbon atom is attached to four substituents.  Amino acid classification Amino acids differ from each other in the specific chemical properties and structure of the R groups.The nature of R- group determines the properties of proteins.  Based on the properties of the R group Electrochemical Physiological polarity classification Classification of amino acids structural Metabolic classification classification  Structural classification Aliphatic R group No ring Aromatic R group R=Benzne Heterocycleic Neutral Acidic Basic R not Benzne NH2=COOH COOH > NH2 NH2> COOH Not branched , pranched OH S  I. Aliphatic 1. Neutral 1. Branched and not branched  1. Aliphatic (Neutral) 2. Non aromatic Amino acids with hydroxyl Neutral. OH group  1. Aliphatic (Neutral) 3. Amino acids with Sulfur-contaning R S group.  2. Aliphatic (Acidic) Amino acids and their Amides. Acidic Amides ?????? COOH > NH2 Neutral  3. Aliphatic (Basic) Basic Amino acids The basic amino acids all have exposed N, NH or NH2 groups Basic NH2> COOH  II. Aromatic Amino acids with Aromatic ring The aromatic side chains contain what are called conjugated rings. In the right circumstances, these are called "aromatic" rings. Aromatic compounds have familiar smells, like the smells of bananas and oranges. TPT ????  III.Heterocycleic R group not Benzne  Electrochemical classification Each of the 20 a-amino acids found in proteins can be distinguished by the R-group substitution on the a-carbon atom. There are two broad classes of amino acids based upon whether the R-group is hydrophobic or hydrophilic. 1.Hydrophobic or non-polar amino acid The hydrophobic amino acids tend to repel the aqueous environment and, therefore, reside predominantly in the interior of proteins. Thus class of amino acids does not ionize nor participate in the formation of H-bonds Hydrophobic amino acids can be further divided into 1. Non polaror hydrophobic  2. Hydrophilic or polar amino acids These amino acids are soluble in water The R group contains polar functional group that can interact with the aqueous environment and participate in hydrogen bond formation) a) Positively charged amino acıd Polar amino acids with positive charge have more amino groups as compared to carboxyl groups making it basic. and are very hydrophilic eg Arginine, Histidine, and Lysine (b) Negatively Charged Amino Acid Polar amino acids with negative charge have more carboxyl groups than amino groups making them acidic.E.g. Aspartic acid, Glutamic Acid  c) Uncharged amino acid They are polar, uncharged non onizable, they include Amide containing amino acids as Asparagine, Glutamine Hydroxyl containing amino acids as Serine, Threonine Sulfur containing amino acid e.g. cysteine 2. Polaror hydrophilic  Biological or Physiological classification Essential Semi-essential Non-Essential These amino acids These amino These amino acids can be synthesized acids can be which not in the body in biosynthesized in synthesized in the amounts sufficient body and must be adequate amounts for adult but not for provided in the in the body. children diet to meet an include Arginine and animal's metabolic Histidine. needs.  Biological or Physiological classification Semi-Essential Arginine Histidine