Protein Structure, Function, and Amino Acid Vocabulary

Vocabulary flashcards defining amino acid types, peptide bonding, primary, secondary, and tertiary structures, R-group properties, and protein denaturation based on the lecture transcript.

Peptide Bond

A strong covalent bond formed when amino acids join together, releasing $\text{H}_2\text{O}$ as a byproduct.

Essential Amino Acid

An amino acid that cannot be synthesized by the body and must be obtained directly from food or diet.

Non-essential Amino Acid

An amino acid that can be synthesized within the body from other amino acids.

Genetic Code Amino Acids

The $20$ distinct amino acids coded in the genetic code that can be arranged in any order and length to form peptide chains.

Polypeptide Examples

Specific examples of polypeptides noted in the material, including Insulin, $\text{a-amylase}$, $\text{b-endorphin}$, and Titin.

Denaturation

The process where heat and energy break the hydrogen, ionic, disulfide, and hydrophobic bonds of a protein, causing it to lose its 3D shape and higher-level folding indefinitely.

Non-Polar (Hydrophobic) R-groups

Water-repelling R-groups that do not form hydrogen bonds with water and can anchor a protein within the lipid interior of a membrane.

Polar Uncharged R-groups

Neutral overall R-groups containing oxygen or nitrogen that carry positive and negative charges, allowing them to form hydrogen bonds with water and other polar molecules.

Primary Structure

The linear sequence of amino acids in a polypeptide chain, held together by covalent peptide bonds.

Secondary Structure

Regular repeating patterns, such as the $\text{a-helix}$ and $\text{b-pleated}$ sheets, formed when a polypeptide chain folds due to hydrogen bonds between backbone atoms.

a-helix

A secondary structure where the polypeptide backbone coils into a right-handed spiral stabilized by parallel hydrogen bonds, with R-groups projecting outward (e.g., Keratin and haemoglobin).

b-pleated Sheet

A secondary structure formed when zig-zag sections of the polypeptide chain lie side-by-side and are connected by parallel or antiparallel hydrogen bonds.

Antiparallel b-pleated Sheets

A sheet arrangement that is more stable because its hydrogen bonds are more linear and stronger compared to parallel sheets.

Tertiary Structure

The complete 3D shape of a single folded polypeptide chain, determined by interactions among R-groups.

Ionic Bonds (in Proteins)

Electrostatic attractions formed between oppositely charged R-groups (such as $\text{NH}_3^+$ and $\text{COO}^-$) that are stronger than hydrogen bonds but susceptible to breaking from pH shifts.

Disulfide Bonds

Covalent bonds formed specifically between two cysteine amino acids in a protein.

Hydrophobic Effect

The phenomenon where non-polar R-groups cluster together in the interior of a protein to avoid water, minimizing free energy and producing a stable compact structure.