Lecture 6 Flashcards

What determines the secondary structure of proteins?

Secondary structure is determined by regular ways to fold the polypeptide chain.

What are the two common types of secondary structure in proteins?

The two common types are alpha helices (α-helices) and beta sheets (β-sheets).

What stabilizes the α-helix structure in proteins?

The α-helix is stabilized by hydrogen bonds between the backbone atoms of the polypeptide chain.

How do side chains in α-helices and β-sheets differ in orientation?

In α-helices, side chains radiate away from the helical axis, while in β-sheets, neighboring side chains are on opposite faces.

What role do steric interactions play in protein structure?

Steric interactions restrict the allowable φ (phi) and ψ (psi) angles, influencing peptide conformation.

Which amino acids tend to be 'unhappy' in α-helices?

Proline, glycine, asparagine, tyrosine, serine, and cysteine are typically 'unhappy' in α-helices.

What structural motif is characteristic of collagen?

Collagen features a triple-stranded left-handed helix and contains a G-X-Y tripeptide motif.

What can lead to protein denaturation?

Protein denaturation can be caused by heating, pH changes, detergents, and chaotropic agents.

What is the significance of Anfinsen's experiment with ribonuclease A?

Anfinsen's experiment demonstrated that proteins can spontaneously renature to their functional form after denaturation.

What is the Ramachandran plot used for?

The Ramachandran plot graphs sterically allowed φ and ψ angles for amino acid residues, visualizing the conformational space of peptides.

What distinguishes fibrous proteins from globular proteins?

Fibrous proteins are elongated and structural, while globular proteins are compact with complex tertiary structures.

How does hydrophobicity influence protein folding?

Hydrophobic interactions drive the folding of proteins, positioning nonpolar residues in the interior away from water.

What is required for accurate prediction of tertiary structures from amino acid sequences?

Accurate prediction requires understanding interactions between residues that are far apart in the primary structure.

What defines the quaternary structure of proteins?

The quaternary structure refers to the spatial arrangement of multiple polypeptide chains that form multisubunit complexes.

What happens when proteins misfold?

Misfolded proteins can lead to loss of function and may be degraded by proteases.