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Which Of The Following Animals Must Receive The Essential Amino Acids Within Their Diets?

IX. Proteins

This chapter provides an introduction and discussion of proteins and amino acids that are important in the nutrition of food-producing animals.

New Terms
Amino acid
Dipeptide
Essential amino acid
Nonessential amino acid
Peptide bail
Polypeptide
Protein

Chapter Objectives

  • To describe the chemic structure of proteins and amino acids
  • To discuss the different classification of protein and amino acids
  • To discuss essential and nonessential amino acids

Proteins

What Are Proteins?

The word proteins was coined by a Dutch chemist Chiliad. J. Mulder and originated from the Greek word "proteios", meaning showtime or nigh important. Proteins are organic compounds made upwardly of unlike building blocks (basic units) chosen amino acids joined together past peptide bonds (Figure nine.1). A dipeptide contains one peptide bond and ii amino acids, whereas a tripeptide contains 3 amino acids and two peptide bonds. A peptide with more than ten amino acids is called a polypeptide. Proteins are substantially large polypeptides. The structure of a protein is determined first by the sequence of individual amino acids it has in the polypeptide chain. This is also chosen the chief structure of the protein.

Protein: Functions

  • Body proteins (east.one thousand., musculus, pilus, hooves, skin)
  • Blood proteins (east.g., albumin, globulin)
  • Tissue proteins (e.thou., collagen, keratin)
  • Enzymes and hormones
  • Immune system antibodies and other peptide growth factors
Figure ix.1. Peptide bond between amino and carboxyl group  (Source: Google)

Protein Functions: Proteins are vital for life and are the major structural components of animal tissues (east.g., skin, muscles, wool, feather, tendons, eggs). In addition, proteins are as well involved in biochemical (e.g., enzymes), immunological (e.k., immunoglobulins), transportational (east.thou., lipoproteins), and other regulatory (e.yard., hormones) activities. Proteins can as well provide energy when needed.
Many of the structures in fauna tissue (e.g., muscle) and metabolic reactions (due east.g., enzymes, hormones) are catalyzed by proteins. Therefore, poly peptide synthesis is essential for maintaining life process. Provision of adequate dietary protein and amino acids are essential for maintaining growth, health, and productivity in nutrient-producing animals. Intestinal microflora can synthesize proteins from nonprotein sources in ruminant animals.

Poly peptide requirements vary with life stages and are high during phases of fast growth in young animals and during pregnancy and lactation. Similar other macronutrients, proteins contain carbon, oxygen, and hydrogen. In addition, proteins also contain nitrogen and sulfur (in some amino acids). It is the nitrogen that makes proteins very unique in animal nutrition with respect to its digestibility, metabolism, and disposal within the brute body.

Nomenclature of Proteins

Proteins can exist classified based on their shape; solubility in water, salt, acid, base, or booze; or according to the nature of the prosthetic group.

Classification Based on Solubility and Prosthetic Group

    1. Globular proteins: soluble in h2o or dilute acids, bases, or alcohol
      1. Albumin (water soluble; present as albumen in egg white; in blood circulation, it performs various functions [e.g., as a carrier of lipids])
      2. Globulin (soluble in dilute neutral solutions; functions equally office of the allowed organisation in torso defense [e.one thousand., immunoglobulins]
    2. Fibrous proteins: insoluble in water and are resistant to digestive enzymes
      1. Keratins (due east.g. wool, hair, feather, hooves, horn)
      2. Collagen (can exist converted to gelatin when heated; present in bone, teeth, tendons, and soft connective tissue)
    3. Conjugated proteins: contain other nonprotein compounds in structure. Some examples follow:
      1. Lipoproteins (lipid-carrying poly peptide)
      2. Hemoprotein (proteins with heme units)
      3. Glycoproteins (proteins with sugar)
      4. Nucleoprotein (proteins bound to nucleic acid

These proteins have express nutritional value simply are important in biochemical, structural, and other metabolic functions. For instance, plumage meal is high in poly peptide (keratin) but very low in digestibility and is of limited employ in animal nutrition equally a feed ingredient. Amino acids in the polypeptide chain in plumage meal form disulfide bonds (-S-South-), which twist the polypeptide chain into a specific coiled structure such as helix or sheet. This is chosen a secondary structure. These bonds business relationship for the tough physical properties of hooves and horns and their low digestibility.

The disruption of secondary structure by estrus treatment causes denaturation of the proteins (e.g., egg white coagulation during cooking). Sure antinutritional factors in feed (due east.g., trypsin inhibitor in soybean meal) are proteins. Heat processing denatures trypsin inhibitor in soybean repast and tin can enhance digestibility.

Amino Acids: Amino acids are the edifice blocks of proteins. There are more than 300 different amino acids known to exist in nature. Out of these, about 20 amino acids are of import constituents of animal proteins and are associated with muscles, connective tissues, skin, feathers, horns, claret, enzymes, and hormones. In that location about 10 amino acids that should be present in the diet of animals considering animal tissues cannot synthesize them or cannot make the adequate corporeality needed for metabolic functions; these are called essential amino acids. A few other amino acids such as citrulline and ornithine practise not occur in animal tissues but are involved in cellular metabolic functions.

Amino acids are the building blocks of proteins.

Essential amino acids must be supplied through the diet.
Animals cannot synthesize them or cannot make the acceptable amount needed.

All amino acids by definition contain at least one amino group (-NH2) and one carboxyl group (–COOH) on the C atom side by side to the carboxyl group (Figure 9.2). An exception to this is proline (imino acid), which is defective a free amino group. The general construction of an amino acid is shown below by the amino acid glycine, the simplest of the amino acids (Figure 9.2). The R grouping (shown in the red circle) in amino acids varies for dissimilar amino acids. The R grouping is the rest of the molecule or any other group attached to the C cantlet. In the example of glycine, it is an H group. The amino grouping (NH2) provides basic backdrop to the amino acid, and the carboxyl (COOH) group provides acidic properties. Amino acids important in animal nutrition are blastoff (α) amino acids, which are carboxylic acids with an amino grouping on the α-carbon (or the first carbon attached to a functional grouping). A list of amino acids important in animal nutrition, their essentiality and classification are shown in Table nine.1.

Figure 9.2. General structure of amino acid

Amino acids can exist in two isomeric forms, the D- and L-isomers. The D- and L-amino acids differ in their configuration of groups around the disproportionate α-carbon. But L-amino acids are used in protein synthesis, except methionine, where both D- and  Fifty-amino acids tin be used by the animal. DL methionine is unremarkably used as an amino acid supplement in brute feeds.

 All amino acids except glycine comprise an disproportionate α-carbon (with four dissimilar chemical groups fastened to it). Compounds with disproportionate carbons can exist as isomers.

Essential Amino Acids: Animal body can synthesize some amino acids in sufficient amounts. However, animals cannot synthesize some amino acids, or not in the amount that is needed for body requirements. Such amino acids demand to be provided through nutrition in monogastric animals; these are called essential (indispensable) amino acids. Pigs, dogs, and humans need a total of ten, and chickens and cats need a full of eleven essential amino acids. A list of essential amino acids needed past monogastric animals is shown beneath.
It should exist borne in heed that other nonessential amino acids are besides physiologically important for metabolic functions in the body and are made from other precursors available through nutrition (e.m., carbohydrates, nonprotein nitrogenous substances).
The need for essential amino acids varies in animals. For example, horses need essential amino acids, whereas ruminant animals (e.1000., cattle, sheep, goats) by and large do not have a requirement of essential amino acids as they are synthesized past rumen microbes.

Listing of Essential Amino Acids and Their Common Abbreviations

  1. Arginine (Arg)
  2. Histidine (His)
  3. Lysine (Lys)
  4. Isoleucine (Ile)
  5. Leucine (Leu)
  6. Methionine (Met)
  7. Phenylalanine (Phe)
  8. Threonine (Thr)
  9. Tryptophan (Attempt)
  10. Valine (Val)

In add-on to these 10 essential amino acids, cats and chickens demand the following actress amino acids.
Cats need taurine (Tau), and chickens need glycine (Gly).

Table nine.1. Classification of amino acids according to construction, nature of side chain, and essentiality. E=essential; NE=nonessential.
Amino acid Essentiality Classification
Ariginine (Arg) E Bones
Histidine (His) E Basic
Lysine (Lys) Due east Basic
Aspartic acid (Asp) NE Acidic
Glutamic acid (Glu) NE Acidic
Alanine (Ala) NE Aliphatic-Straight chain
Glycine (Gly) E (chickens) Neutral- Aliphatic-Directly chain
Isoleucine (Ilu) E Branched concatenation
Leucine (Leu) Eastward Branched chain
Valine (Val) E Branched chain
Serine (Ser) NE Hydroxy
Threonine (Thr) East Branched chain
Cysteine (Cys) NE Sulfur-containing
Methionine (Met) E Sulfur-containing
Phenylalanine (Phe) E Aromatic
Tryptophan (Try) Eastward Aromatic
Tyrosine (Tyr) Ne Aromatic
Hydroxyproline (Hydro) Ne Imino acid
Proline (Pro) Ne Imino acid

Fundamental Points

  1. Proteins can be found in structural components of the body and are needed for many metabolic functions.
  2. The presence of Nitrogen makes protein unique.
  3. More than 300 amino acids are identified. Only only 20 amino acids are used to synthesize all proteins.
  4. Three features of a typical amino acid include a carbon skeleton, a carboxyl group, and an amino group.
  5. Acidic amino acids comprise more carboxyl groups, and basic amino acids incorporate more amino groups. Neutral amino acids comprise an equal number of carboxyl and amino groups.
  6. Sulfur-containing amino acids are methionine and cysteine. Among these amino acids, methionine is essential because animals cannot synthesize it. Cysteine is non considered essential because if S is available, the body tin make it.
  7. Effluvious amino acids incorporate a band structure.
  8. Imino acids contain an imino instead of an amino group (e.g., proline).
  9. Essential amino acids are those that cannot exist synthesized past the animal body. At that place are 10 essential amino acids; cats need taurine, and chickens need glycine.
  10. Amino acids are joined together by peptide bonds. A long concatenation of amino acids formed this fashion is called a polypeptide.
  11. The main structure of an amino acid is determined by the sequence of individual amino acids in the polypeptide chain. The amino acids in the polypeptide chain class disulfide bonds and hydrogen bonds, which twist the polypeptide chain into a specific coiled structure, such every bit a helix or a canvas. This is called a secondary structure. Proteins tin can exist classified based on their shape; solubility in h2o, salt, acid, base, or alcohol; or according to the nature of prosthetic groups.

Review Questions

  1. Name the linkage betwixt two amino acids in a protein.
  2. What are the essential amino acids? Why are they essential?
  3. Compared to carbohydrates, why are proteins unique?
  4. Which amino acid is essential to chickens merely not humans? How about to cats?
  5. Name ane amino acid from the following groups: acidic, basic, aromatic, and sulfur-containing.
  6. Differentiate between essential and nonessential amino acids.
  7. Is proline an amino acid?
  8. List the 10 essential amino acids for monogastric animals.
  9. How many peptide bonds are there in a tripeptide?
  10. Requite an instance of a globular, gristly, and conjugated protein.

Source: https://open.oregonstate.education/animalnutrition/chapter/chapter-9/

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