Protein Structure Flashcards

Flashcards about protein structure

Differentiate between primary, secondary, tertiary, and quaternary structure.

Primary: Covalent bonds (Peptide bonds). Secondary: Hydrogen bonds along backbone. Tertiary: Covalent & electrostatic between R groups. Quaternary: Covalent & electrostatic between subunits.

What defines the primary structure of a protein?

The linear order of amino acids (N → C direction) linked by covalent peptide bonds.

What dictates all higher-order structure in proteins?

Primary structure.

What reaction type creates a peptide bond?

Condensation reaction (dehydration).

What two bonds along the backbone allow for rotation in a peptide?

Phi (Φ) bond: Amino N to Cα. Psi (ψ) bond: Cα to carbonyl C.

What stabilizes secondary structure?

Hydrogen bonds between backbone N-H and C=O groups.

What are the two main types of secondary structure?

α-helix and β-sheet.

How is α-Helices stabilized?

The C=O group of each amino acid forms a hydrogen bond with the N-H group situated 4 residues ahead

How is β-Sheets stabilized?

β-Sheets are formed by hydrogen bonds between adjacent β-strands.

What does a Ramachandran Diagram plot?

The allowed φ (phi) and ψ (psi) backbone angles of amino acid residues

What stabilizes tertiary structure?

Interactions between R-groups

Name the key stabilizing forces of the tertiary structure.

Van der Waal forces, ionic interactions, hydrogen bonds, and disulfide bonds.

What type of interactions dominate quaternary structure?

Noncovalent interactions, though disulfide bonds may occur.

In Anfinsen's experiment with ribonuclease A, what reagents were used to denature the protein?

Urea and β-mercaptoethanol.

What did Anfinsen's experiment prove?

Folding is sequence driven

What is the Levinthal Paradox?

Random sampling of conformations = 1034 years; Proteins fold <1 minute; folding cannot be random, but cumulative.

What drives protein folding?

Energy is derived from the hydrophobic effect.

Free water molecules can assume more conformations, leading to an increase in?

Entropy

What level of protein structure is most directly altered in prion diseases?

Secondary structure (switch from α-helix-rich to β-sheet-rich).