Protein Structure and Lipids - Vocabulary Flashcards

Vocabulary-style flashcards covering key protein structure concepts (amino acids, bonds, levels of structure, chaperones) and lipid/membrane properties (amphipathic phospholipids, saturated vs. unsaturated fats).

Amino acid

The monomer that makes up proteins; each has an amino group, a carboxyl group, a hydrogen, and a variable side chain (R group) that determines which amino acid it is.

R group (side chain)

The variable side chain of an amino acid that determines its identity and properties (e.g., polarity, ability to hydrogen bond).

Dipeptide

Two amino acids linked by a peptide bond; a brief building block toward a polypeptide.

Polypeptide

A long chain of amino acids linked by peptide bonds; folds to form a protein.

Peptide bond

Covalent bond between the amino group of one amino acid and the carboxyl group of the next; relatively rigid, limiting rotation.

Primary structure

The linear sequence of amino acids in a polypeptide; the basic code that determines higher levels of structure and function.

Secondary structure

Local folding patterns of the polypeptide backbone, stabilized by hydrogen bonds; includes alpha helices and beta pleated sheets.

Alpha helix

A common right-handed helical secondary structure stabilized by backbone hydrogen bonds.

Beta pleated sheet

A secondary structure with strands aligned side-by-side, held together by backbone hydrogen bonds, creating a pleated sheet.

Tertiary structure

The overall three-dimensional shape of a single polypeptide, stabilized by interactions among side chains (hydrogen bonds, ionic bonds, hydrophobic interactions, disulfide bonds).

Quaternary structure

The arrangement and interaction of multiple polypeptide subunits in a protein; not all proteins have this level.

Chaperone proteins

Proteins that assist other proteins in folding toward their proper three-dimensional structure.

Heat shock proteins

A class of chaperone proteins induced by heat or stress to protect and assist in proper protein folding.

Denaturation

Unfolding or loss of a protein’s native structure due to disruption of bonds, leading to loss of function.

Insulin

A protein hormone that regulates blood sugar; used as an example of structure-function relationship in proteins.

N-terminus (amino end)

The end of a polypeptide chain with the free amino group.

C-terminus (carboxyl end)

The end of a polypeptide chain with the free carboxyl group.

Amphipathic

A molecule that has both a hydrophilic (polar) and a hydrophobic (nonpolar) region, as seen in phospholipids.

Phospholipid

A lipid with two fatty acid tails (nonpolar) and a polar phosphate-containing head; forms cell membranes.

Fatty acid tail

Nonpolar hydrocarbon chain of a lipid that interacts poorly with water; part of phospholipids and triglycerides.

Saturated fat

Fatty acid chains with no double bonds; fully hydrogenated; tends to be solid at room temperature.

Unsaturated fat

Fatty acid chains with one or more double bonds; creates kinks and increases membrane fluidity.

Membrane

A phospholipid bilayer that forms the boundary of cells; its amphipathic nature drives spontaneous formation in water.

Hydrophobic exclusion

Nonpolar regions are repelled by water and segregate from polar regions, aiding folding and membrane formation.

Hydrogen bond

A weak attraction between a hydrogen atom and an electronegative atom (like O or N); crucial for stabilizing secondary structures.

Polar

Molecules or regions with partial charges that interact with water (hydrophilic).

Nonpolar

Molecules or regions lacking partial charges; tend to avoid water (hydrophobic).