Structural and Oral Biochemistry: Proteins and Oral Environment

Vocabulary practice flashcards covering structural and functional proteins, post-translational modifications, stabilizing forces, collagen synthesis, and salivary defense mechanisms in the oral cavity.

Fibrous Proteins

A class of proteins characterized by an extended structure and low solubility, serving primary mechanical support and structural roles in tissues (e.g., collagen and keratin).

Globular Proteins

A class of proteins characterized by a compact structure and high solubility, serving functional roles such as catalysis, transport, and immune defense (e.g., salivary amylase, histatins, and IgA).

Keratins

Fibrous proteins rich in $\alpha$-helical secondary structure that form dimers and intermediate filaments, serving as an intracellular scaffold that strengthens epithelial cells and forms a protective surface layer in oral tissues.

Gly-X-Y Repeat

The characteristic repeating amino acid motif of collagen, where glycine (Gly) occupies every third position to allow tight packing in the center of the triple helix due to its small size.

Lysyl Oxidase (LOX)

An enzyme in the extracellular matrix that catalyzes covalent cross-linking between collagen molecules, increasing the mechanical strength and stability of collagen fibrils and fibers.

Ehlers-Danlos Syndromes

A group of connective tissue disorders caused by defects in collagen structure, processing, or organization, clinically characterized by tissue fragility, hypermobile joints, delayed wound healing, and susceptibility to injury.

Prolyl Hydroxylase

An enzyme that requires vitamin C as an essential cofactor to hydroxylate selected proline residues in collagen polypeptides, forming hydroxyproline required for triple-helix stability.

Scurvy

A nutritional deficiency of vitamin C leading to reduced prolyl hydroxylase activity, impaired hydroxyproline formation, unstable collagen triple helices, gingival bleeding, delayed wound healing, and connective tissue fragility.

Acquired Pellicle

An acellular, transparent film composed of salivary proteins, glycoproteins, lipids, and carbohydrates that forms on tooth surfaces to maintain mineral balance and protect enamel from minor acid erosion.

Mucins

Salivary proteins responsible for lubrication and protection that lubricate oral tissues and form protective coatings over mucosal surfaces.

Histatins

Histidine-rich salivary proteins involved in innate oral defense whose positively charged residues promote interactions with negatively charged microbial surfaces to exert antimicrobial activity.

Secretory IgA

An adaptive immune protein in saliva stabilized by covalent disulfide bonds that functions in mucosal defense by preventing microbial adherence to oral tissues and tooth surfaces.

Statherin

A salivary protein involved in mineral homeostasis that maintains calcium and phosphate balance in saliva and helps protect tooth enamel.

Salivary Amylase

A digestive enzyme in saliva that initiates starch breakdown in the oral cavity and requires proper hydrophobic interaction-driven folding to form its catalytic active site.

Hydrogen Bonds

Non-covalent molecular interactions whose primary role in proteins is to stabilize secondary structures (such as $\alpha$-helices and $\beta$-pleated sheets) and tertiary structures.

Ionic Interactions

Electrostatic interactions between charged amino acid side chains that stabilize charged regions within proteins and mediate molecular recognition.

Hydrophobic Interactions

The major driving force for protein folding, occurring when nonpolar side chains cluster together away from the surrounding aqueous environment to achieve structural stability.

Disulfide Bonds

Covalent linkages formed between the sulfhydryl groups of cysteine residues that provide structural stabilization to extracellular proteins.

Protein Denaturation

The loss of a protein's three-dimensional structure and biological function caused by disruptions in stabilizing interactions from extreme pH, heat, organic solvents, or chemical agents.

Primary Structure

The unique linear sequence of amino acids linked together by covalent peptide bonds along a polypeptide chain.

Secondary Structure

Local folding patterns within a polypeptide chain, predominantly $\alpha$-helices and $\beta$-pleated sheets, stabilized by backbone hydrogen bonding.

Tertiary Structure

The overall three-dimensional architecture of a single folded polypeptide chain, stabilized by hydrogen bonds, ionic interactions, hydrophobic forces, and disulfide linkages.

Quaternary Structure

The structural assembly formed by the spatial arrangement and interaction of multiple polypeptide subunits into a multi-subunit protein complex.

Dentin Collagen Hierarchy

The structural arrangement of collagen in dentin organized from tropocollagen ($\sim 300\,\text{nm}$) to mineralized collagen fibrils ($\sim 1\,\mu\text{m}$), collagen fibril arrays ($\sim 10\,\mu\text{m}$), and intertubular dentin matrix ($\sim 50\,\mu\text{m}$).