Amino Acids Lecture Practice Flashcards

Comprehensive vocabulary flashcards covering the structure, biological roles, nomenclature, classification, physical properties, and optical activity of amino acids.

Amino Acid

An organic compound containing at least one amino group ($-NH_2$) and one carboxyl group ($-COOH$), serving as the building blocks of proteins.

Proteins

Polymers of amino acids that form via peptide bonds and serve roles in metabolism, signaling, and as biosynthetic precursors.

$\alpha$-amino acid

An amino acid where the amino group ($-NH_2$) is attached to the $\alpha$-carbon, which is the carbon atom directly attached to the carboxyl group.

Neutral Amino Acid

A type of amino acid containing exactly one $-COOH$ group and one $-NH_2$ group, such as Alanine or Glycine.

Acidic Amino Acid

A type of amino acid containing two $-COOH$ groups and one $-NH_2$ group, such as Aspartic acid or Glutamic acid.

Basic Amino Acid

A type of amino acid containing one $-COOH$ group and two $-NH_2$ groups, such as Lysine, Arginine, or Histidine.

Essential Amino Acids

Amino acids that cannot be synthesized by the human body and must be supplied through diet (e.g., Valine, Leucine, Tryptophan).

Non-essential Amino Acids

Amino acids that can be synthesized by the human body from other compounds, such as Alanine and Glycine.

Kwashiorkor

A malnutrition disease caused by a deficiency of dietary proteins and essential amino acids, often resulting in edema (swollen belly) and stunted growth.

Zwitter ion

A neutral molecule with both positive ($-NH_3^+$) and negative ($-COO^-$) electrical charges, resulting in a net charge of zero; also called an 'Internal Salt Structure'.

Amphoteric

The property of a substance that allows it to act as both an acid and a base; amino acids exhibit this due to their zwitterionic form.

Electrophoresis

The movement of charged ions toward respective electrodes under the influence of an electric field; cations move to the cathode and anions move to the anode.

Isoelectric point ($pI$)

The specific $pH$ value at which an amino acid exists as a neutral zwitterion and does not migrate during electrophoresis.

Optical Activity

The ability of a substance to rotate plane-polarized light; it requires the molecule to be asymmetric or chiral.

Chiral Carbon (Asymmetric Carbon)

A carbon atom attached to four different atoms or groups, which imparts optical property to the amino acid.

Enantiomers

A pair of stereoisomers that are non-superimposable mirror images of each other, categorized as D-configuration or L-configuration.

Dextrorotatory ($d$ or $+$)

An enantiomer that rotates plane-polarized light in a clockwise direction.

Levorotatory ($l$ or $-$)

An enantiomer that rotates plane-polarized light in an anti-clockwise direction.

Glycine

The only naturally occurring amino acid that is optically inactive because it lacks a chiral center (its R-group is hydrogen).

L-configuration

The structural configuration where the amino group is on the left-hand side; most naturally occurring amino acids belong to this group.