Amino Acids and Protein Structure

Amino Acid Structures

• The main structural difference between an alpha amino acid and a beta amino acid is the position of the amino group with respect to the carboxyl group
• Valine is classified as a neutral nonpolar amino acid.
• Neutral polar amino acids possess functional groups capable of forming hydrogen bonds.

Amino Acid Functions

• Amino acids are important for forming nitrogenous bases and nucleic acids
• Methionine is an essential amino acid in humans
• A peptide bond is characteristic of peptides.

Protein Denaturation

• Strong acids, detergents, temperature changes, and reducing agents can cause protein denaturation.
• The quaternary structure in proteins is defined as the union of two or more polypeptide chains or subunits.
• Reducing agents denature proteins by breaking disulfide bonds, affecting the tertiary and quaternary structure.

Heteroproteins and Protein Structure

• Phosphoproteins, chromoproteins, and glycoproteins belong to the group of conjugated heteroproteins.
• A protein may lose partial or total function when its structure changes.
• Simple holoproteins are not composed of amino acids, peptides or nucleotides.

Nucleic Acid Bases

• The main function of nitrogenous bases in nucleic acids is to form the nucleotides that constitute DNA and RNA.
• Nitrogenous bases are divided into purines and pyrimidines.
• Adenine and guanine are purines.
• Nitrogenous bases have heterocyclic structures with nitrogen.
• Uracil is a nitrogenous base found in RNA but not in DNA.
• Hydrogen bonds stabilize the double helix of DNA through the union of complementary nitrogenous bases.

Protein Structures

• The primary structure of a protein is defined by the sequence of amino acids specified by genetic information.
• The secondary structure of a protein is formed by the localized folding of the polypeptide chain into alpha helices or beta sheets.
• The quaternary structure of a protein is characterized by the arrangement of multiple polypeptide chains or subunits.
• Simple proteins are formed only by amino acids.
• A protein without its prosthetic group is called an apoprotein.
• Glucoproteins are not a classification of conjugated proteins and albuminoproteins are
• Hemoglobin is the protein that serves as an example of a transport protein.
• Casein is a protein found in milk that acts as a nutrient reserve.
• Fibrous proteins are insoluble in water and physically resistant.
• Globular proteins are spherical molecules and are water-soluble.
• Based on their composition, proteins are classified into simple and conjugated proteins.

Conjugated Proteins

• Conjugated proteins contain a non-protein component called a prosthetic group.
• Nitrogenous bases are classified as purines and pyrimidines.
• Adenine and guanine are nitrogenous bases that form part of the purines.
• Hydrogen bonds hold together the nitrogenous bases in the double helix of DNA.
• Gout is a disease associated with alterations in the metabolism of purines.
• Analogs of nitrogenous bases have antiviral and chemotherapeutic medical applications.
• The main function of nitrogenous bases in DNA and RNA is to encode genetic information

Protein Basics

• The basic unit that forms proteins are amino acids.
• Enzymes direct and accelerate biochemical reactions in cellular metabolism.
• Collagen provides structural support in the body.
• Actina and tubulin are involved in cellular movement
• Immunoglobulin is related to the defense of the organism.
• Insulin regulates glucose levels in the blood

Isomers and Amino Acid Reactions

• L isomers are exclusively found in proteins.
• 4-hydroxyproline is an important component of collagen.
• Enantiomers are non-superimposable mirror images of each other.
• The formation of peptide bonds occurs in amino acids due to their functional groups.
• The formation of a peptide bond between amino acids eliminates a molecule of water.
• Disulfide bridges in proteins stabilize the three-dimensional structure of proteins.

Amino Acid Characteristics

• The carboxyl group is a functional group that is present in all amino acids.
• The structure of the R group determines the chemical properties of an amino acid.
• Non-standard amino acids are not found in proteins and can result from chemical modifications.
• Proline presents a secondary amino group due to a ring closure between the R group and the amide nitrogen.
• The classification of amino acids is based on their ability to interact with water.
• Neutral nonpolar amino acids are defined by having hydrocarbon R groups and being poorly soluble in water.