Protein Chemistry Flashcards

Study Notes

Protein Structure

Primary Structure: Sequence of amino acids in polypeptide chains; determining factor for protein folding, shape, and function.
Secondary Structure: Regular arrangements of polypeptide chains, stabilized by hydrogen bonds.
Alpha Helix Structure: Coiled configuration with 3.6 amino acids per turn; stabilized by intra-chain hydrogen bonds, where R groups point outwards, providing flexibility and elasticity.
Beta Pleated Sheet Structure: Consists of aligned polypeptides linked side-by-side by hydrogen bonds, resulting in a stable structure with R groups alternating above and below the sheet.

Advanced Protein Architecture

Tertiary Structure: 3-dimensional shape formed by extensive folding of a single polypeptide chain.
Quaternary Structure: Combination of multiple polypeptide chains (subunits) that maintain their own tertiary structures; stabilized by non-covalent interactions such as van der Waals forces and hydrogen bonds.

Protein Properties

Globular Protein: Contains hydrophilic amino acids on the surface and hydrophobic amino acids hidden within, making them soluble in water.
Denaturation: Disruption of secondary, tertiary, and quaternary structures through breaking weak bonds, while primary structures remain intact.

Factors Affecting Protein Structure

Heating: Causes disruption of weaker interactions like van der Waals forces and some hydrogen bonds.
pH Changes:
- Low pH: Excess H+ ions react with basic R groups.
- High pH: Excess OH- ions react with acidic R groups.
- These changes disrupt critical ionic and hydrogen bonds, altering enzyme shape and activity.
Metal Ions: Disrupt ionic interactions among charged R groups, potentially forming insoluble salts and affecting tertiary/quaternary structures. Heavy metals can also interfere with disulfide bonds in cysteine.
Urea Addition: Competes for intra-molecular hydrogen bonds, destabilizing protein structure.

Fundamental Concepts

Isoelectric Point (pI): The pH at which an amino acid exists as a zwitterion, having both positive and negative charges.
Zwitterion: A neutral molecule with both positive and negative charges present simultaneously; different from simple dipolar ions, representing a stable internal state of charge.

Description

Explore key concepts in protein chemistry with these flashcards. Each card provides essential definitions related to protein structure, including primary and secondary structures, to enhance your understanding of how proteins function. Perfect for students learning biochemistry.