Chapter 1: Molecules of Life - Proteins

Flashcards covering the properties, classification, and structural levels of proteins and amino acids based on lecture notes.

Proteins

Large complex biological molecules consisting of carbon, hydrogen, oxygen, and nitrogen atoms (sometimes sulphur and phosphorus) that play diverse roles in organisms.

Amino acid

The monomer, subunit, or basic unit of a protein; there are 20 common types that share a basic structure but differ in their side chain (R group).

Polypeptide

A polymer of amino acids joined together by peptide bonds.

$\alpha$-amino acids

Amino acids (except proline) where the amino group is attached to the same carbon atom to which the carboxyl group is attached.

Carboxyl group

A functional group ($-COOH$) in an amino acid that is characterized as acidic.

Amino group

A functional group ($-NH_2$) in an amino acid that is characterized as basic.

Side chain (R group)

The component of an amino acid that determines its specific chemical properties and used to group the 20 different amino acids.

Non-polar amino acids

A group of amino acids characterized by hydrophobic side chains, such as Glycine, Alanine, and Valine.

Polar amino acids

A group of amino acids characterized by hydrophilic side chains, such as Serine, Threonine, and Cysteine.

Acidic amino acids

Amino acids with side chains that are negatively charged and hydrophilic, including Aspartic acid and Glutamic acid.

Basic amino acids

Amino acids with side chains that are positively charged and hydrophilic, including Lysine, Arginine, and Histidine.

Condensation

The chemical reaction involved in the synthesis of a dipeptide, where one water molecule is removed to form a peptide bond.

Hydrolysis

The chemical reaction involved in the breakdown of a dipeptide where one water molecule is added to reform the carboxyl and amino groups.

Peptide bond

The specific chemical bond formed between the carboxyl group of one amino acid and the amino group of another.

Polypeptide backbone

The repeated sequence of ($\sim N-C-C \sim N-C-C \sim$) in a polypeptide chain.

Primary structure

The first level of protein structure consisting of a specific sequence of amino acids in a linear polypeptide chain joined by peptide bonds.

Secondary structure

The coiling or folding of a polypeptide chain maintained by hydrogen bonds, resulting in structures like $\alpha$-helix or $\beta$-pleated sheet.

Tertiary structure

The three-dimensional folding pattern of a polypeptide chain caused by interactions between side chains, such as disulphide bridges, ionic bonds, or hydrophobic interactions.

Quaternary structure

The fourth level of protein structure resulting from the aggregation of two or more polypeptide chains joined by various molecular interactions.

$\alpha$-helix

A type of secondary structure found in proteins like Keratin, which is present in hair, nails, and horns.

$\beta$-pleated sheet

A type of secondary structure found in proteins like Fibrion, produced by spiders and many insects.

Myoglobin

A protein with tertiary structure consisting of one polypeptide chain and one haem group, acting as an oxygen binding site in muscle.

Haemoglobin

A protein with quaternary structure consisting of four polypeptide chains and four haem groups, located in erythrocytes.

Collagen

A fibrous protein with quaternary structure consisting of three identical polypeptide chains intertwined into a triple helix for strength.

Conjugated Protein

A protein that contains a non-protein component called a prosthetic group, such as Glycoprotein (mucin) or Lipoprotein.

Prosthetic group

The non-protein part of a conjugated protein that plays an important role in its functioning.

Fibrous protein

Proteins with polypeptide chains forming long fibers that are water-insoluble, static, and perform structural functions, such as Keratin.

Globular protein

Proteins with polypeptide chains folded into spherical shapes that are water-soluble, dynamic, and perform metabolic functions, such as enzymes.

Denaturation

The process where a protein loses its specific 3D shape and function due to the disruption of secondary, tertiary, or quaternary bonds, often caused by extreme pH or high temperature.