Amino Acids, Proteins, and Enzymes - Vocabulary

Flashcards containing vocabulary terms and definitions related to amino acids, proteins, and enzymes.

Proteins

Polymers made from 20 different amino acids that differ in characteristics and functions.

Amino Acids

The molecular building blocks of proteins, containing a central carbon atom (α-carbon) bonded to an ammonium group, a carboxylate group, a hydrogen atom, and an R group or side chain.

Nonpolar Amino Acids

Amino acids with hydrocarbon side chains; tend to be hydrophobic.

Polar Amino Acids

Amino acids with polar or ionic side chains; tend to be hydrophilic.

Acidic Amino Acids

Amino acids where the R group is a carboxylic acid.

Basic Amino Acids

Amino acids where the R group is an amine.

Isoelectric Point (pI)

The point at which an amino acid with positive and negative charges is overall neutral in charge.

Peptide Bond

An amide bond that forms when the — COO− group of one amino acid reacts with the — NH3 + group of the next amino acid.

Peptide

The linking of two or more amino acids by peptide bonds.

Protein

A polypeptide of 50 or more amino acids that has biological activity.

Primary Structure of a Protein

The particular sequence of amino acids held together by peptide bonds.

Alpha Helix

The shape of an alpha helix is similar to that of a spiral staircase.

Beta-Pleated Sheet

Hydrogen bonds form between the carbonyl oxygen atoms and hydrogen atoms in the amide groups bending the polypeptide chain into a sheet.

Triple Helix

Three polypeptide chains are woven together while hydrogen bonds hold the chains together, giving the polypeptide the added strength typical of collagen, connective tissue, skin, tendons, and cartilage

Tertiary Structure of a Protein

An overall three-dimensional shape caused by interactions of different parts of the chain, causing it to bend and twist.

Quaternary Structure

Combination of two or more protein units stabilized by the same interactions found in tertiary structures.

Globular Proteins

Proteins with compact, spherical shapes that carry out synthesis, transport, and metabolism in the cells; transport and store oxygen in muscle.

Fibrous Proteins

Proteins consist of long, fiber-like shapes for hair, wool, skin, and nails

Denaturation of Proteins

Involves the disruption of bonds in the secondary, tertiary, and quaternary protein structures by heat, organic compounds, acids and bases, heavy metal ions, and agitation.

Enzymes

Proteins that act as biological catalysts by binding a substrate at an active site and catalyzing a specific reaction for that substrate.

Active Site

A small region on the surface of an enzyme that binds a substrate and catalyzes a specific reaction for that substrate.

Inhibitors

Molecules that cause a loss of catalytic activity by preventing substrates from fitting into the active sites.

Competitive Inhibitor

Has a structure that is similar to that of the substrate, competes with the substrate for the active site, and has its effect reversed by increasing substrate concentration.

Noncompetitive Inhibitor

Has a structure that is much different than that of the substrate, binds to an enzyme at a site other than the active site, distorts the shape of the enzyme, prevents the binding of the substrate, and cannot have its effect reversed by adding more substrate.

Irreversible Inhibitor

A molecule that causes the enzyme to lose all activity, often a toxic substance that destroys enzymes, and usually forms a covalent bond with an amino acid side chain preventing catalytic activity.

Cofactor

A nonprotein part of an enzyme that is essential to the enzyme’s catalytic activity; a metal ion or a coenzyme.

Coenzyme

An organic molecule that acts as an enzyme cofactor.

Vitamin

An organic molecule, essential in trace amounts that must be obtained in the diet because it is not synthesized in the body.

Water-Soluble Vitamins

Soluble in aqueous solutions, cofactors for many enzymes, and not stored in the body.

Fat-Soluble Vitamins

Vitamins A, D, E, and K; soluble in lipids, but not in aqueous solutions; important in vision, bone formation, antioxidants, and blood clotting; are stored in the body.