Proteins and Amino Acids Lecture

Vocabulary flashcards covering composition, classifications, reactions, and physicochemical properties of proteins and amino acids.

Protein

A macromolecule composed chiefly of C, H, O, N (sometimes S and P) made up of one or more polypeptide chains of amino acids.

Amino Acid

The monomer of proteins; consists of a central carbon bonded to an amino group, carboxyl group, hydrogen, and variable R group.

R Group

The variable side chain of an amino acid that determines its chemical properties and classification.

Polypeptide

A chain of many amino acids linked by peptide bonds.

Peptide Bond

The covalent bond formed between the carboxyl group of one amino acid and the amino group of another during condensation.

Condensation Reaction

Process that joins two amino acids by removing one molecule of water to form a peptide bond.

Hydrolysis

Breakdown of a peptide bond through the addition of water, splitting the bond into individual amino acids.

Non-polar Amino Acid

Amino acid with hydrophobic, uncharged R groups; e.g., Glycine, Alanine, Valine.

Polar Amino Acid

Amino acid whose R group contains polar atoms that increase solubility; e.g., Serine, Threonine, Cysteine.

Basic Amino Acid

Amino acid with an additional amino group in the R chain, carrying a positive charge; e.g., Lysine, Arginine, Histidine.

Acidic Amino Acid

Amino acid whose R group contains a carboxyl group, giving a negative charge; e.g., Aspartic acid, Glutamic acid.

Essential Amino Acid

An amino acid that cannot be synthesized by the body and must be obtained through diet.

Non-essential Amino Acid

An amino acid that the body can synthesize and is not required in the diet.

Hydrophobic

Property of molecules that are insoluble in water; characteristic of non-polar amino acids.

Hydrophilic

Property of molecules that interact readily with water; characteristic of polar, acidic, and basic amino acids.

Amphoteric Substance

A molecule capable of acting as both an acid and a base; amino acids exhibit this property.

Zwitterion

Dipolar form of an amino acid possessing both positive (NH3⁺) and negative (COO⁻) charges yet overall electrically neutral.

Isoelectric Point (pI)

Specific pH at which an amino acid exists predominantly as a zwitterion with zero net charge.

Buffer

A substance that resists changes in pH upon addition of small amounts of acid or base; amino acids and proteins act as buffers.

Protein Colloid

A dispersion of large protein molecules (1–100 nm) in water forming a colloidal system, as in blood plasma.

Disperse Phase

The finely divided suspended particles within a colloid (e.g., protein particles).

Dispersion Medium

The continuous liquid phase that surrounds disperse particles in a colloid (e.g., water in cytoplasm).

Plasma Proteins

Major colloids in blood plasma that cannot cross capillary walls and contribute to osmotic pressure.

Osmotic Pressure (Colloid)

Pressure exerted by plasma proteins that influences water movement across capillary membranes.

Colloidal Properties

Characteristic of proteins whereby they do not fully dissolve but form stable dispersions in water.

Buffering Capacity

Ability of proteins to maintain pH stability by accepting or donating H⁺ ions in solution.