Q: Which of the following is a correct application of the Morse equation for osmotic pressure ($$\Pi) in a $$solution containing 0.2 M NaCl at 25°C ($$R = 0.0821\ \mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$}$$, $$T = 298\ \mathrm{K}$$)? Assume complete dissociation.

$$\Pi = iMRT = 2 \times 0.2 \times 0.0821 \times 298 = 9.78\ \mathrm{atm}$$

Question 1

Which of the following statements best explains why water has a high heat of vaporization compared to other small molecules?

Accepted Answer

Water molecules form extensive hydrogen bonds, which require significant energy to disrupt during vaporization.

Question 2

A solution is prepared by dissolving 0.1 mol of acetic acid (pKa = 4.76) and 0.1 mol of sodium acetate in enough water to make 1 L of solution. What is the pH of this buffer? Use the Henderson-Hasselbalch equation.

Accepted Answer

$$\mathrm{pH} = 4.76 + \log_{10}\left(\frac{0.1}{0.1}\right) = 4.76$$

Question 3

Which amino acid does NOT have a chiral alpha carbon?

Accepted Answer

Glycine

Question 4

A patient with phenylketonuria (PKU) is unable to metabolize which amino acid, leading to the accumulation of phenylalanine and its derivatives?

Accepted Answer

Phenylalanine

Question 5

Which of the following best describes the main driving force for protein folding in aqueous environments?

Accepted Answer

Hydrophobic effect, where nonpolar side chains aggregate to minimize disruption of water's hydrogen bonding network

Question 6

Which of the following is a correct application of the Morse equation for osmotic pressure ($$\Pi) in a $$solution containing 0.2 M NaCl at 25°C ($$R = 0.0821\ \mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$}$$, $$T = 298\ \mathrm{K}$$)? Assume complete dissociation.

Accepted Answer

$$\Pi = iMRT = 2 	imes 0.2 	imes 0.0821 	imes 298 = 9.78\ \mathrm{atm}$$

Question 7

Which of the following best explains why ice is less dense than liquid water?

Accepted Answer

Hydrogen bonds in ice form a rigid, open lattice structure, increasing the volume and decreasing the density.

Question 8

Which of the following amino acids is most likely to be found at the turn of a beta turn in a protein structure?

Accepted Answer

Proline

Question 9

A peptide has the sequence Ala-Glu-Lys. Given the following pKa values: $$\alpha-$$COOH = 2.0, $$\alpha-NH$_2 = 9.0$$, Glu side chain = 4.1, Lys side chain = 10.5. What is the net charge of the peptide at pH 7?

Accepted Answer

+1

Question 10

Which of the following statements about the Ramachandran diagram is TRUE?

Accepted Answer

It shows the allowed values of phi ($$\phi) $$and psi ($$\psi) $$dihedral angles for amino acid residues in a polypeptide.

Question 11

Which of the following best describes the difference between prokaryotic and eukaryotic cells?

Accepted Answer

Prokaryotes lack a membrane-bound nucleus, while eukaryotes possess one.

Question 12

Which of the following functional groups is present in the side chain of cysteine?

Accepted Answer

Sulfhydryl ($$-\mathrm{SH})$$

Question 13

Which of the following best describes the Miller-Urey experiment and its significance?

Accepted Answer

It demonstrated that amino acids and other organic molecules could be synthesized abiotically under conditions thought to resemble those of early Earth.

Question 14

Which of the following is a property of amphiphilic molecules in water?

Accepted Answer

They spontaneously form micelles due to the hydrophobic effect.

Question 15

Which of the following best explains why the peptide bond is planar?

Accepted Answer

Resonance between the carbonyl oxygen and the amide nitrogen restricts rotation around the peptide bond.

Question 16

Which of the following diseases is associated with amyloid folding and aggregation?

Accepted Answer

Alzheimer's disease

Question 17

Which of the following best describes the effect of vitamin C deficiency on collagen?

Accepted Answer

It impairs the hydroxylation of proline and lysine residues, weakening collagen structure and leading to scurvy.

Question 18

Which of the following is TRUE regarding the self-ionization of water at 25°C?

Accepted Answer

$$K_w = [H^+][OH^-] = 1.0 	imes 10$$^{-14}$$

Question 19

Which of the following best describes the propagation of prion diseases?

Accepted Answer

Misfolded prion proteins induce normal proteins to adopt the misfolded, infectious conformation.

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