Biology C.1 Protein Structure Flashcards

Study Notes

Levels of Protein Structure

Proteins are structured in four levels: primary, secondary, tertiary, and quaternary.

Primary Structure

Unique linear sequence of amino acids in a protein, determining its folding and shape.
The sequence is determined during translation with 20 different amino acids resulting in nearly infinite combinations.
Small alterations in primary structure can significantly impact protein function.

Secondary Structure

Involves localized folding patterns within the polypeptide chain.
Two main types: alpha helix and beta pleated sheet.
Alpha helix forms via hydrogen bonding within the same chain, while beta sheets arise from hydrogen bonds between different chains or sections.

Tertiary Structure

Represents the overall three-dimensional shape of the protein, affecting functionality.
Most proteins (e.g., lysozyme, hemoglobin) have a compact globular shape; fibrous proteins (e.g., collagen, keratin) retain extended structures.
Influenced by various interactions: ionic bonds between charged R-groups, hydrogen bonds, and hydrophobic interactions.
Disulfide bridges, formed by cysteine residues, are critical for stabilizing tertiary structure.

Quaternary Structure

Occurs in proteins composed of multiple polypeptide chains.
Enhances biological diversity and activity; for example, collagen consists of three intertwined subunits, while hemoglobin has four distinct polypeptides.
Prosthetic groups, non-peptide molecules bound to proteins, are vital for functions like oxygen transport in hemoglobin.

Fibrous vs. Globular Proteins

Globular proteins (e.g., enzymes like lysozyme) exhibit compact structures, enhancing functionality.
Fibrous proteins (e.g., collagen and keratin) have extensive formations, providing structural support.

Significance of Polar and Non-Polar Amino Acids

Amino acids differ based on R groups; some are polar (charged), while others are non-polar (hydrophobic).
Polar amino acids are hydrophilic, promoting water solubility, while non-polar amino acids favor aggregation in aqueous environments.
The hydrophilic/hydrophobic nature influences protein folding and cellular membrane interactions.
Membrane proteins are dual-faced, engaging with both extracellular fluid and cytoplasm, with a hydrophobic core that anchors them within lipid bilayers.
Polar-lined protein channels facilitate the transport of polar molecules across membranes, highlighting the functional importance of amino acid polarity.

Description

Test your knowledge of protein structure with this set of flashcards focused on chapter C.1. Explore the four levels of protein structure: primary, secondary, tertiary, and quaternary, and understand their significance in biology.