PROTEINS

RODNEY L. PEÑAFIEL

Fish known as the

cheapest source of

protein as became major

part of the family

consumption in the

Philippines.

Proteins Any a large numbers of

organinc compounds thatmake up living organismsand are essential to theirfunctioning.

Are made up of aminoacids.

Amino Acids

An important class of

organic compounds thatcontain both the amino (-NH2) and carboxyl (-COOH)groups.

Of these acids,20 serve as thebuilding blocksof proteins.

20 Amino Acids Alanine Glycine Serine

Arginine Histidine Threonine

Asparagine Isoleucine Tryptophan

Aspartic acid Leucine Tyrosine

Cysteine Lysine Valine

Glutamic acid Methionine Proline

Glutamine Phenylalanine

When a living cellmakes protein, thecarboxyl group of oneamino acid is linkedto the amino group ofanother to form apiptide bond.

The carboxyl groupof the second aminoacid is similarly linkedto the amino group of athird, and so on, until along cahin is produced.

This chainlike molecule, which may contain from 50 to several hundred amino acid subunits, is called a polypeptide.

A protein may be formedof a single polypetidechain, or it may consistof several such chainheld together by weakmolecular bonds.

Bonds of Proteins

The primary (1° ) structure of a protein is simply the sequence of the amino acids.

Lys-glu-pro-leu- and so on.

The secondary (2° ) structure of a protein is the

interactions between portions of the peptide chain. Hydrogen bonding is one such

interaction that leads to a helix, b sheet and triple

helix structures.

The tertiary (3°) structure of a protein can be thought of as

its three dimensional structure. The

tertiary structure involves the

overlapping or folding of a peptide upon

itself.

A protein has quaternary (4°)

structure if two or more polypeptides interact

with one another to from a biologically active

protein.

Each protein is formed according to a

precise set of instructions

contained within the nucleic acid, which is the genetic material

of the cell.

These instructions determine which of the

20 standards amino acids are to be incorporated into the protein, and in

what sequence.

Classification of Proteins

1. Accrdg. to composition

2. Accrdg. to fucntion

Accrdg. to Composition

1. Simple Proteins

2. Conjugated Proteins

*Simple Proteins

Chemically madeup of amino acid

Simple Proteins

1. Albumin

-most impotant andcommon group ofprotein. Present in eggwhite and blood.

2. Globulin

-widely distributed group of proteins e.g. as antibodies and fibrinogen.

3. Histones

-are found to beassociated with nucleicacids of the cell.

4. Scleroprotein(albuminoids)

-Have structural and protective functions.

E.g. Keratin (hair,skin, and nails)

Collagen (bone, tendon and cartilage)

Elastin (elastic fibers of connective tissue)

*Conjugated Proteins

Contains other chemical groups other than amino

acids.

May be carbohydrates,lipids, bound metalsions and organicgroups.

Conjugated proteins

Prosthetic group1. Phosphoproteins - e.g.

casein

2. Glycoproteins - e.g. mucin

3. Nucleoprotein

4. Lipoproteis - compound lipids

5. Chromoprotein –pigmented prothetic group e.g hemoglobin (with iron – containing pigment, heme) coordinated to a simple protein portion, globin.

Accrdg. to function

1.Structural proteins– more than half ofthe total protein ofthe mammalian bodyis collagen, found inskin, cartillage andbone.

2. Contactile protein-examples are actinand myosin isolatedfrom skeletal muscle.

3. Enzymes- these biological catalysts are vitally important to all living systems.

4. Hormones- e.g. insulins

5. Antibodies

the body producesantibodies to destroyany foreign materials(antigens) releasedinto the body by aninfectious agent.

6. Blood proteins

the albumins, globulins and fibrinogen are the three major protein constituents of the blood.

PROTEIN AUTOLYSIS

Autolysis

au-tol-sis

noun Self-digestion of cell: the digestion of cells by their own enzymes.

Leads to structural changes = softening of fish flesh

(basis of TOUCH TEST)

Proteins are brokendown by steps intoamino acids andother nitrogenousend products.

1. Amines

2. Ammonia

Indole

Skatole

H2O

3. CO2

Biogenic amines-are volatile amines

that are produced as a result of the breakdown of amino acids, typically on death of the animal.

Other end products used in estimating of seafood spoilage:

Indole

pH

Tyrosin

Protein Denaturation

Any change the secondaryand tertiary structure ofprotein without causing aconcomitant cleavage ofthe peptide bonds.

Accompanied by changes in the physical and

biochemical nature of the protein.

Thank you!

Rodney