biochem exam 2

Hydrogen bonding helps to stabilize all of the structural levels of protein except for...

• Primary structure

• Secondary structure

• Tertiary structure

• Quaternary structure

• Quaternary structure

The hydrophobic effect helps to stabilize which of the structural levels of protein below?

• Primary structure

• Secondary structure

• Tertiary structure

• Quaternary structure

• Tertiary & Quaternary

Which of the following is true for both alpha helices and beta sheets?

• Formation of these motifs are enthalpically stabilized by hydrogen bonding

• Compared to unfolded polypeptides, their formations are entropically unfavored.

• Formation of these motifs are enthalpically stabilized by the hydrophobic effect.

• All of above

True or false: Tertiary and quaternary structure are never stabilized by covalent bonds

• True

• False

Which of the following is the least likely to denature a protein?

• Addition of sodium dodecyl sulfate to the protein solution

• Boiling the protein solution

• Addition of 10 M NaOH to the protein solution

• Addition of benzene to the protein solution.

• Addition of 1 M NaCl to the protein solution

Which of the following provide no enthalpic contribution to the stability of the 3D structure of a protein?

• Hydrophobic effect

• Disulfide bonds

• London’s forces

• Dipole-dipole interactions

• Ion-dipole interactions

What concentration of ligand ([L]) is needed for 80. % of the binding sites to bind ligand if the Kd for ligand binding is 500 μM? The protein is a homodimer that exhibits no cooperativity between binding sites.

• 250 μM

• 500 μM

• 2000 μM

• 200,000 μM

Which secondary structure motifs can be observed in
cytochrome P450? Its protein structure is shown on the right

• α-helices

• Parallel β-sheets

• Antiparallel β-sheets

• α-helices and β-sheets

The enzyme cytochrome P450cam contains a heme cofactor (see figure on right question above) and catalyzes oxidation of camphor:

Camphor + NADPH + H+ + O2 -> 5-exo-hydroxycamphor + NADP+ + H2O

Which of the following correctly classifies the NADPH and the heme cofactor?

• NADPH is a co-substrate and heme is a prosthetic group

• NADPH is a prosthetic group and heme is a metal ion cofactor

• NADPH is a co-substrate and heme is a co-substrate

• NADPH is a co-substrate and heme is a co-substrate

You are given a protein that is an α2 homodimer (i.e., the subunits that make up the protein are identical). Which SDS-PAGE lane in the figure to the right would be expected for this protein?

• A

• B

• C

• D