Protein Structure and Properties

Flashcards covering levels of protein organization, general properties, structural classifications, and denaturation factors based on the lecture material.

Protein Molecular Weights

Range from $5 \times 10^3$ to $1 \times 10^6$.

Amphoteric

The property of proteins to act as both acids and alkalies (can form salts) and possess a specific electronic net charge.

Isoelectric point

The specific pH at which protein solubility is at its lowest.

Primary structure

The linear sequence of AAs (amino acids) in the polypeptide chain.

Peptide bond

A biological linkage formed by a dehydration reaction between the $\alpha$-carboxyl group of one AA and the $\alpha$-amino group of another; it is an amide more stable than an ester.

Trans configuration

The spatial arrangement which the peptide bond usually assumes, where successive $\alpha$-carbons and their R groups are located on opposite sides of the bond.

N-terminus and C-terminus

The dissociable amine group at one end and the carboxyl group at the other end of a polymer, respectively, which remain after peptide bonds are formed.

Secondary structure

Local regions of polypeptide chains stabilized by a repeating pattern of H bonds, forming regular structures like $\alpha$-helices and $\beta$-sheets.

Tertiary structure

The overall 3D conformation formed by the folding of secondary structural elements, often resulting in a densely packed hydrophobic core in globular proteins.

Forces in protein folding

Primarily non-covalent interactions, including ionic interactions (attraction between $+$ and $-$ charged molecules), hydrophobic effect, hydrogen bonding, and van der Waals interactions.

Quaternary structure

The combination of two or more subunits, each composed of a polypeptide chain, into a multi-subunit complex.

Globular proteins

Proteins that are typically soluble in aqueous medium and resemble irregular balls, such as myoglobin or hemoglobin.

Fibrous proteins

Proteins like collagen that are geometrically linear, arranged around a single axis, and have a repeating unit structure linked by hydrogen and covalent bonds.

Transmembrane proteins

Proteins that have one or more regions aligned to cross the lipid membrane.

Denaturation

The destruction of a protein's quaternary, tertiary, and secondary structures by chemical means, temperature, pH, solvent, or misfolding.

Prion

Standing for PRoteinaceous InfectiOus ageNt, it is a misfolded protein that acts as a template to misfold other cellular prion proteins into a form that cannot be degraded.