Question 1

Which of the following functional groups is most likely to be found in its ionized (deprotonated) form at physiological pH (pH ~7.4)?

A) Hydroxyl ($$-OH)
B) $$Carboxyl ($$-COOH)
C) $$Amino ($$-NH_2$)
D) Sulfhydryl (-SH$)

Accepted Answer

Carboxyl ($$-COOH)$$

Question 2

Which type of non-covalent interaction is primarily responsible for the stabilization of the hydrophobic core in globular proteins?

A) Hydrogen bonds
B) Charge-charge interactions
C) Hydrophobic interactions
D) van der Waals interactions

Accepted Answer

Hydrophobic interactions

Question 3

Given the following reaction at 25°C:

$$A + B \rightleftharpoons C + D

If$$ $$k_1 = 2.0$$\ \mathrm{$$M^{-1}s$$^{-1}$$}$$ and $$k_{-1} = 0.5\ \mathrm{M$$^{-1}$$s^{-1}$$}$$, what is the equilibrium constant K$$_{eq}$$ for this reaction?

A) 0.25$
B) 1.0$
C) 2.5$
D) 4.0$

Accepted Answer

$$2.5$$

Question 4

Which of the following best describes the relationship between $$\Delta G$$ and $$K_{eq} at $$equilibrium?

A) $$\Delta G = 0$$ and $$K_{eq} = 1
B$$) $$\Delta G = 0$$ and $$K_{eq}$$ can be any value
C) $$\Delta G  1
D$$) $$\Delta G \u003e 0$$ and $$K_{eq} \u003c 1$$

Accepted Answer

$$\Delta G = 0$$ and $$K_{eq}$$ can be any value

Question 5

A solution contains 0.10 M acetic acid ($$CH_3COOH) $$and 0.20 M sodium acetate ($$CH_3COONa). $$Given $$pK_a = 4.76$$, what is the pH of the solution? Use the Henderson-Hasselbalch equation.

A) $$4.46
B$$) $$4.76
C$$) $$5.06
D$$) $$5.36$$

Accepted Answer

$$5.06$$

Question 6

Which of the following statements about peptide bonds is FALSE?

A) Peptide bonds are planar due to resonance.
B) Peptide bonds can freely rotate around the C-N bond.
C) Peptide bonds are usually found in the trans configuration.
D) Peptide bond formation results in the loss of a water molecule.

Accepted Answer

Peptide bonds can freely rotate around the C-N bond.

Question 7

Which amino acid is most likely to form a disulfide bond?

A) Methionine
B) Cysteine
C) Serine
D) Lysine

Accepted Answer

Cysteine

Question 8

A protein has two ionizable groups with $$pK_a$$ values of 2.0 and 9.0. What is the isoelectric point ($$pI) of $$this protein?

A) $$2.0
B$$) $$4.5
C$$) $$5.5
D$$) $$5.0$$

Accepted Answer

$$5.5$$

Question 9

Which of the following best explains why water is an excellent solvent for polar molecules?

A) Water has a linear structure and high boiling point.
B) Water can form up to four hydrogen bonds per molecule.
C) Water is nonpolar and forms clathrate cages.
D) Water has a low dielectric constant.

Accepted Answer

Water can form up to four hydrogen bonds per molecule.

Question 10

Which of the following is a correct statement about the Bohr effect in hemoglobin?

A) Lower pH increases hemoglobin's affinity for O$$_2
B) $$Higher pH decreases hemoglobin's affinity for O$$_2
C) $$Lower pH decreases hemoglobin's affinity for O$$_2
D) $$The Bohr effect is unrelated to pH

Accepted Answer

Lower pH decreases hemoglobin's affinity for O$$_2$$

Question 11

Which of the following best describes the effect of 2,3-bisphosphoglycerate (2,3-BPG) on hemoglobin?

A) It increases hemoglobin's affinity for oxygen
B) It stabilizes the R-state of hemoglobin
C) It stabilizes the T-state of hemoglobin
D) It has no effect on oxygen binding

Accepted Answer

It stabilizes the T-state of hemoglobin

Question 12

Which of the following equations correctly relates the standard free energy change ($$\Delta G^\circ) to $$the equilibrium constant ($$K_{eq}$$)?

A) $$\Delta G^\circ = RT \ln K_{eq}
B$$) $$\Delta G^\circ = -RT \ln K_{eq}
C$$) $$\Delta G^\circ = RT \ln Q
D$$) $$\Delta G^\circ = -RT \ln Q$$

Accepted Answer

$$\Delta G^\circ = -RT \ln K_{eq}$$

Question 13

Which of the following amino acids absorbs the most UV light at 280 nm?

A) Phenylalanine
B) Tyrosine
C) Tryptophan
D) Histidine

Accepted Answer

Tryptophan

Question 14

Which of the following best describes the main driving force for the formation of a lipid bilayer in water?

A) Hydrogen bonding between fatty acid tails
B) van der Waals interactions between polar head groups
C) Hydrophobic effect
D) Covalent bonding between phospholipids

Accepted Answer

Hydrophobic effect

Question 15

A redox reaction has $$n = 2$$ electrons transferred and $$\Delta E^\circ' = 0.50\ \mathrm{V}. $$What is the standard free energy change ($$\Delta G^\circ') $$for this reaction? ($$F = 96.48\ \mathrm{kJ\ V$$^{-1}$$\ $$mol^{-1}$$})

A$$) $$-48.2\ \mathrm{kJ/mol}
B$$) $$-96.5\ \mathrm{kJ/mol}
C$$) $$+48.2\ \mathrm{kJ/mol}
D$$) $$+96.5\ \mathrm{kJ/mol}$$

Accepted Answer

$$-48.2\ \mathrm{kJ/mol}$$

Question 16

Which of the following best describes the difference between the T and R states of hemoglobin?

A) The T state binds oxygen more tightly than the R state
B) The R state is stabilized by 2,3-BPG
C) The T state has lower affinity for oxygen than the R state
D) The T state is only found in fetal hemoglobin

Accepted Answer

The T state has lower affinity for oxygen than the R state

Question 17

Which of the following is a correct statement about the Ramachandran plot?

A) It shows the possible values of $$\phi$$ and $$\psi$$ angles for a polypeptide
B) It shows the possible values of $$\omega$$ and $$\psi$$ angles for a polypeptide
C) It is used to determine the primary structure of proteins
D) It is only relevant for proline residues

Accepted Answer

It shows the possible values of $$\phi$$ and $$\psi$$ angles for a polypeptide

Biochemistry Foundations: Functional Groups, Macromolecules, and Chemical Interactions

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