Protein Structures

Amino Acid

Building blocks of proteins, containing an amino group, a carboxyl group, and a unique R-group.

Primary Structure

The sequence of amino acids that forms a polypeptide chain, defining the protein's uniqueness.

Secondary Structure

The local folded structures that form within a protein due to hydrogen bonding between backbone atoms; examples include α-helices and β-sheets.

Tertiary Structure

The overall 3D structure of a protein formed by the interactions between R-groups of the amino acids.

Quaternary Structure

The complex structure formed by the assembly of multiple polypeptide chains, resulting in a functional protein.

Denaturation

The process in which proteins lose their structure and function due to external stress, such as changes in pH, temperature, or salt concentration.

Hydrophobic

A term describing nonpolar amino acids that do not interact favorably with water.

Hydrophilic

A term used to describe polar amino acids that can form favorable interactions with water.

Peptide Bond

The covalent bond that links amino acids together in a protein, formed between the carboxyl group of one amino acid and the amino group of another.

R-group

The variable group specific to each amino acid that determines its unique chemical properties.

Cystine

An amino acid formed by the oxidation of two cysteine residues, containing a disulfide bond that plays a role in protein folding.

Polypeptide

A chain of amino acids linked by peptide bonds, which can fold into functional proteins.

N-terminus

The start of a polypeptide chain, characterized by the presence of a free amino group.

C-terminus

The end of a polypeptide chain, characterized by the presence of a free carboxyl group.

Basic Amino Acids

Amino acids with a positive charge at physiological pH, contributing to the overall charge of proteins.

Acidic Amino Acids

Amino acids with a negative charge at physiological pH, contributing to the overall charge of proteins.

Polar Amino Acids

Amino acids that have side chains capable of forming hydrogen bonds, thus interacting well with water.

Non-polar Amino Acids

Amino acids with side chains that do not interact favorably with water, contributing to the hydrophobic core of proteins.

Alpha-helix

A common secondary structure in proteins characterized by a right-handed coil.

Beta-sheet

A common secondary structure in proteins formed by hydrogen bonds between adjacent strands, producing a sheet-like structure.