The Three Dimensional Structure of Proteins

These flashcards cover key concepts and definitions related to the structure and function of proteins as discussed in the lecture notes.

What are the four levels of protein structure?

Primary, Secondary, Tertiary, and Quaternary.

What is the function of hydrogen bonds in secondary structure?

They stabilize the secondary structure, such as α-helices and β-sheets.

What characterizes the secondary structure of proteins?

It consists of structures such as α-helices and β-sheets formed by backbone hydrogen bonds.

What is the rise per residue in an α-helix?

1.5 Å.

What is the twist per residue in an α-helix?

100 degrees.

What is the significance of the Ramachandran plot?

It shows sterically allowed φ and ψ angles in polypeptides.

What is a key feature of β sheets in proteins?

They are stabilized by interchain hydrogen bonds and have alternating side chains.

Describe the polypeptide II helix found in collagen.

It is a left-handed helix not stabilized by hydrogen bonds, consisting largely of prolines.

How does the presence of disulfide bonds affect protein stability?

Disulfide bonds increase stability by reducing conformational diversity.

What structural motif is typical in collagen?

The G-X-Y tripeptide motif, where X is often Proline.

What type of protein structure is associated with keratin?

Elongated fibrous structure with α-helical coiled-coil configurations.

What is the primary difference between globular and fibrous proteins?

Globular proteins fold into compact structures, while fibrous proteins are elongated and have defined secondary structures.

What is the importance of chaperones in protein folding?

Chaperones assist in proper protein folding and prevent aggregation.

Why are terrestrial proteins predominantly globular?

They have compact structures with a nonpolar interior and hydrophilic exterior.

What role does vitamin C play in collagen synthesis?

Vitamin C is a cofactor for the hydroxylation of proline and lysine residues in collagen.