Proteins and Amino Acids PDF

BASC102A: Proteins and Amino Acids **Proteins** - Building blocks are called amino acids - 16% N - Aside from CHON, some also contains S, P, and Fe - AA are linked by peptide bond - Amphoteric compounds (zwitter ions) *Crude Protein= True protein + NPN* A **zwitterion** is a molecu...

BASC102A: Proteins and Amino Acids **Proteins** - Building blocks are called amino acids - 16% N - Aside from CHON, some also contains S, P, and Fe - AA are linked by peptide bond - Amphoteric compounds (zwitter ions) *Crude Protein= True protein + NPN* A **zwitterion** is a molecule with functional groups, of which at least one has a positive and one has a negative electrical charge. The net charge of the entire molecule is zero. **Functions:**  **Structure of Proteins** 1\. Primary structure- sequence of amino acids 2\. Secondary structure- conformation of the amino acid chain by hydrogen bonds 3\. Tertiary structure- bending and folding of polypeptide chains giving a characteristic biological activity. 4\. Quaternary structure- multi-sub-unit structure stabilized by non-covalent interactions **Classification of Proteins** **1. Simple-** composed solely of amino acids and yield only amino acids or their derivatives upon hydrolysis. They are typically classified based on their solubility and biological function. **A. Fibrous proteins** (Sceloproteins) i\. Collagens ii\. Elastin iii\. Keratins iv\. Myosin and tropomyosin **B. Globular** **2. Conjugated proteins** **Other nitrogenous compounds** 1\. Amines 2\. Amides (e.g. Urea) 3\. Nitrates- converted to toxic nitrite in rumen 4\. Alkaloids- poisonous nitrogen-containing compounds formed by some plants and fungi Amino Acids - Organic acid containing one or more amino groups(NH2) and carboxyl group (COOH) and is the basic structural units of protein. - Proteins are polymers of amino acids that vary in relative amounts and in kind from protein to protein. - Although there are 200 naturally occurring amino acids, only 20 to 25 are present in feed proteins and enter in the make up of animal tissues. Classification of Amino Acids Based on Structure and Properties The body needs amino acids as nutrients rather than proteins. All proteins taken in by the body are broken down into amino acids by the digestive system, and the body is provided with amino acids, which in turn utilized to build its own proteins. Amino acids can be classified based on the needs of animals Essential Amino Acids(EAA) Nonessential Amino Acids (NEAA) - Neutral AA is absorbed fastest - Acidic AA is absorbed slowest - Only Leucine and Lysine are strictly Ketogenic - Only Isoleucine, Phenylalanine, Tyrosine, and Tryptophan are both glucogenic and ketogenic - Methionine is the most toxic AA (lethal at 2% in low protein diet), followed by tryptophan, tyrosine and threonine - AA antagonism -Lysine-Arginine antagonism -Leucine-Isoleucine-Valine antagonism Limiting Amino Acid (LAA) - Present in a protein in the least amount in relation to the animal's need for that particular amino acid (also known as limiting amino acid) - Other essential amino acids can be utilized by the animal toward meeting requirements depending on the presence or availability of that particular limiting amino acid. - **Lysine** is the first limiting amino acid of corn-soy diets in **growing pigs**. - **Methionine and cystine** are common limiting amino acids in **poultry diets** especially corn-soy diets. **Biological value-** % of the digestible protein of a feed which is usable by the animal **Good quality protein-** has a desirable balance of EAA; high BV (e.g. Milk, meat meal, fish meal, soybean meal) **Low quality protein-** extremely deficient in\>1 EAA (e.g. Blood meal, feather meal, corn) **By-pass protein** Proteins not acted upon by **microbial fermentation** in the rumen which may result to better protein utilization and performance of animals - Contains C, H, and O - More C and H in proportion to O than do carbohydrates - Insoluble in water but soluble in ether, chloroform, and benzene - Fats and oils principally important Thank you!