Nutritional studies: proteins

Proteins, nucleic acids, and other nitrogenous compounds

peptide linkage: two amino acids come together, release water

Peptide functions: building blocks for polypeptides and protein. biological activity (sleep inducing effects, immune response, control of food intake, flavors of food, analgesia)

structure of proteins

-tertiary structure, further interaction through the R groups, interaction causes folding and bending of polypeptide chain.

-Quaternary structure: in more than one polypeptide chain. hydrogen bonds and electrostatic bonds and stabilizes structure.

Properties of proteins

-colloidal: insoluble in water (keratin) to highly soluble (albumins)

-Amphoteric like amino acids contained in the polypeptide chains.

Ampoteric: can have negative, positive, or neutral charges, have certain ph in neutral form

-they exibit isoelectric points and have buffering qualities

-can be denatured by heat, acids and alkali, alcohol and heavy metals

Denatured: structure changes by process of heating

Classification of proteins

simple proteins: produce only amino acids on hydrolysis, two groups (fibrous and globular) according to shape, solubility, and chemical composition

Conjugated protein: contain a non-protein moiety termed a prosthetic group in addition to amino acids

Fibrous protein: mostly structural roles, insoluble in water and resistant to digestive enzymes

-includes: collagens, elastin, keratins

elastin: the elastic tissue protein of tendons and arteries

Collagens: main connective tissue protein

Keratin: main proteins of wool, hair, feathers, skin, beaks, and scales

Globular protein: contain polypeptide chains folded into compact structures.

includes: enzymes, antigens, and protein hormones

Globular protein subgroups

Albumins: water soluble and heat coaguable

-in milk eggs and blood

Histines: basic proteins of the cell nuclei

-associated with DNA

Protamines: basic proteins found in male germ cells

Globulins: occur in milk, eggs, blood, and reserve protein in seeds

Conjugated proteins

Phosphoproteins: contain phosphoric acid as prosthetic group

-include: caesins (in milk) and phosvitin (in egg yolk)

Chromoprotein: contain a pigment as the prosthetic group

-include: haemoglobin, cytochromes, and flavoproteins.

Nucleic acids

Nucleic acid: high modular weight compounds that store genetic information and can be utilized in protein synthesis in living organisms

-hydrolysis of nucleic acid yields basic nitrogenous compounds (purines and pyrimidines), a pentose (ribose or deoxyribose) and phosphoric acid.

nucleoside: forms by linking purine or pyrimidines to pentose

Nucleotide: formed when nucleoside and phosphoric acid is esterfied

Nucleic acid types

Deoxyribonucleic acid (DNA): contains deoxyribose.

Ribonucleic acid (RNA): contains ribose, pyrimidine uracil (in place of thymine (found in DNA))

Nucleotide functions: cellular metabolism. energy transformations (AMP, ADP, ATP)

Other nitrogenous compounds

-amines

-amides

-free amino acids (glutamic acid, aspartic acid, alanine, serine, glycine, and proline)

-nitrogenous lipids

-nitrates

-alkaloids

-b vitamins