2. Protein Structure & Function

Vocabulary flashcards covering key terms related to protein structure, levels of organization, bonding interactions, and functional roles.

Proteins

Biomolecules made of amino acids that perform structural, regulatory, and energetic roles in living organisms.

Amino Acid

Organic molecule containing an amino group, carboxyl group, hydrogen atom, and side chain; building block of proteins.

Peptide Bond

Covalent bond linking the carboxyl carbon of one amino acid to the amino nitrogen of the next in a polypeptide.

Primary Structure

Linear, one-dimensional sequence of amino acids in a protein, written from N-terminus to C-terminus; nonfunctional by itself.

N-terminus

The end of a polypeptide chain with a free amino group; starting point for primary sequence notation.

C-terminus

The end of a polypeptide chain with a free carboxyl group; terminal point of the primary sequence.

Secondary Structure

Local 3-D folding of the backbone into α-helices or β-sheets stabilized mainly by hydrogen bonds.

α-Helix

Right-handed spiral secondary structure stabilized by intra-chain hydrogen bonds every fourth residue.

β-Sheet

Secondary structure consisting of aligned β-strands connected by hydrogen bonds; can be parallel or anti-parallel.

Tertiary Structure

Overall 3-D arrangement of a single polypeptide, formed by interactions among secondary structures and solvent.

Quaternary Structure

Assembly of multiple tertiary-structured subunits into a functional multi-subunit complex.

Electrostatic Interaction

Attraction between oppositely charged side chains (ionic bonds) within or between polypeptides.

Hydrogen Bond

Weak interaction between a hydrogen atom covalently bonded to electronegative atom and another electronegative atom; stabilizes secondary and higher structures.

Hydrophobic Interaction

Association of non-polar side chains to avoid water, driving protein folding and stability.

Disulfide Bond

Covalent linkage between sulfur atoms of two cysteine residues, reinforcing tertiary and quaternary structures.

Van der Waals Interaction

Weak, distance-dependent forces between atoms that contribute to protein stability when closely packed.

Ribosome

Cellular organelle where amino acids are polymerized into polypeptides, establishing primary structure.

Actin & Myosin

Contractile proteins enabling muscle movement; examples of proteins with specialized functions.

Enzyme

Protein catalyst that accelerates biochemical reactions without being consumed.

Hormone (Protein-based)

Protein or peptide acting as a chemical messenger to regulate physiological processes.

Antibody

Immunoglobulin protein that recognizes and neutralizes pathogens.

Transport Protein

Protein that carries nutrients or molecules across membranes or within the bloodstream.

Fluid Balance (Protein Role)

Proteins act as buffers to maintain osmotic pressure and regulate body fluid volume.

Protein Energy Yield

Proteins provide approximately 4 calories of energy per gram when metabolized.

Hemoglobin

Quaternary protein (α₂β₂ tetramer) in red blood cells; each subunit binds a heme group for O₂ transport.

Catalase

Tetrameric enzyme containing heme and NADP that detoxifies hydrogen peroxide.

Myoglobin

Monomeric oxygen-binding protein in muscle; classic example of tertiary structure.

Fatty Acid Binding Protein

Example of a single-chain protein whose tertiary structure allows lipid transport within cells.

CD4

Cell-surface protein important in immune response; tertiary structure enables specific ligand binding.