Amino Acids and Protein Structure

This set of flashcards encompasses key vocabulary related to amino acids and protein structure, aiding in exam preparation.

Amino Acids

Molecules with four groups attached to a central (α) carbon: an amino group, a carboxylic acid group, a hydrogen atom, and an R Group.

R Group

The variable group in amino acids that determines the function of the amino acid.

Stereochemistry of α-Carbon

The configuration is L for all chiral amino acids in eukaryotes; all chiral amino acids except cysteine have (S) configuration.

Chirality of Amino Acids

All amino acids are chiral except Glycine.

Hydrophilic Amino Acids

Amino acids with charges; they interact well with water.

Hydrophobic Amino Acids

Amino acids with long alkyl chains; they do not interact well with water.

Amphoteric

Describes amino acids' ability to act as either a base or an acid.

pKa

The pH at which half of the species is deprotonated; [HA] = [A-].

Isoelectric Point (pI)

The pH at which an amino acid is in zwitterion form, resulting in a neutral molecule.

Dipeptide

A molecule consisting of two amino acid residues.

Peptide Bond Formation

A dehydration reaction where the nucleophilic amino group of one amino acid attacks the electrophilic carbonyl group of another.

Amide Bonds

The C-N bonds within peptide bonds; rigid due to resonance.

Hydrolysis Reaction

The process of breaking a peptide bond.

Primary Protein Structure

The linear sequence of amino acids in a peptide, stabilized by peptide bonds.

N-Terminus

The end of a polypeptide chain that is positively charged due to a –NH3+ group.

Secondary Protein Structure

Local folding of the polypeptide chain into structures such as α-helices or β-pleated sheets.

α-Helices

A common secondary structure that coils clockwise around a central axis.

β-Pleated Sheets

A common secondary structure consisting of rippled strands that can be parallel or antiparallel.

Proline

An amino acid that can interrupt secondary structure due to its rigid cyclic structure.

Tertiary Protein Structure

The three-dimensional folding pattern of a protein due to side chain interactions.

Quaternary Protein Structure

A protein that consists of more than one amino acid chain.

Denaturation

The loss of a protein's 3°, 2°, and 4° structures due to breaking non-covalent interactions.

Disulfide Bonds

Covalent bonds formed between two oxidized cysteine molecules, resulting in cystine.

Conjugated Proteins

Proteins that have covalently attached molecules, such as metal ions or vitamins.

Prosthetic Group

The attached molecule in a conjugated protein.