Chapter 2 Biochem Test

Considering the energetics of transferring nonpolar molecules from water to a non polar solvent, the factor TΔS is generally _____, causing ΔG to be _____.

positive; negative

In a water molecule, hydrogens are partially _____; oxygens are partially _____.

positive; negative

In a hydrogen bond between a water molecule and another biomolecule, _____.

the hydrogen bond will typically form between a hydrogen atom and either a nitrogen, sulfur, or oxygen atom

Which of the following is an example of the hydrophobic effect?

the lipid membrane of cells and organelles, protein folding that places hydrophobic amino acids in the interior of the protein, the separation of salad dressing, oil sheens seen on the ocean following an oil spill (all of the above)

When a non-polar substance is added to water, how do the molecules of water behave?

the regular hydrogen bond pattern is disrupted resulting in a decrease of entropy

Which of the following explains the attractive forces between hydrophobic molecules in an aqueous solution?

there is no increase in attractive forces between nonpolar molecules in an aqueous environment

Which of the following is true regarding hydrophobic interactions between non polar molecules or groups?

they require the presence of surrounding water molecules

At any given moment, a single water molecule participates in _____ strong hydrogen bond(s). The role played by the water molecule is best characterized as _____.

two ; one H-bond donor, one H-bond acceptor

Considering a 0.1 M formic acid buffer, what is the concentration of formic acid present in a solution of pH 4.25 if the pK of formic acid is 3.75?

0.024 M

Metabolic acidosis often causes increased respiratory rates. What portion of the bloodstream buffer is lost through increased respiration?

CO2

Which of the following shows the buffer that is found in the blood stream?

H2CO3 HCO3 - + H+

Which of the following shows the intracellular buffer?

H2PO4 - HPO4 2- + H+

During vigorous exercise, hydrogen ions are produced within cells as a result of increased metabolism. What component of the intracellular buffer would increase as a result of the increased H+ production?

H2PO4-

If the pK values for phosphoric acid are 2.15, 6.82 and 12.38, _____ would predominate at pH 5 while _____ would predominate at pH 10.

H2PO4-; HPO4^2-

What is the conjugate acid of H2PO4-?

H3PO4

If a phosphate buffer (pK=6.82) was formulated such that its pH was 7.3, it would be best suited to buffer against _____. If instead, it was formulated such that its pH was 6.3, it would be best suited to buffer against _____.

acid; base

Which of the following functional groups has two hydrogen bond donors and one hydrogen bond acceptor?

amine

A molecule that has both a polar and nonpolar region is called _____________.

amphiphilic

Hydrogen bonds within liquid water are _________.

dipole-dipole interactions

Which of the following would be the strongest acid?

formic acid, pK=3.75

Which of the following molecules would be prevented from readily crossing a lipid bilayer?

glucose, sodium ions, potassium ions, water (all of the above)

Which of the following is a physical property of water that results from hydrogen bonding?

high boiling point relative to molecular weight, a solid state that is less dense than the liquid state, high surface tension, ability to solubilize polar molecules (all of the above)

Which of the following explains the interactions that occur between the atoms of water molecules and the ions that form when sodium chloride dissolves in water?

hydrogens interact with the chloride ion, oxygens interact with the sodium ion

What term is used to describe the exclusion of nonpolar substances from an aqueous solution?

hydrophobic effect

The strongest non-covalent interactions are _____.

ionic interactions

Due to the formation of hydrogen bonds, _____ is highly soluble in water.

methanol

Fatty acid anions most commonly assemble into _____ in aqueous solution.

micelles

In aqueous solution, globules of up to several thousand amphiphilic molecules arranged with the hydrophilic groups on the surface and the hydrophobic groups buried in the center are called _____.

micelles

Which of the following is an example of an amphipathic molecule?

palmitic acid, a fatty acid

What would be the resulting pH if one ml of 1.0 M NaOH was added to one liter of pure water (assume pH 7.0)?

11

Which of the following could be used to formulate 100 mls of a 0.10 M phosphate buffer (pK=6.82) at pH 7.2?

2.9 mmoles of Na2HPO4 and 7.1 mmoles of NaHPO4; 10 mmoles of Na2HPO4 and 7.1 mmoles of NaOH; 10 mmoles of NaHPO4 and 7.1 mmoles of HCl; 10 mmoles of H3PO4 and 17.1 mmoles of NaOH (all of the above)

In an aqueous solution, if the [OH-] is 3.0×10-5 M, what is the [H+]?

3.3×10-10

If 1.0 mL of 1.0 M acetic acid (pK = 4.76, K = 1.74 x 10-5) was added to one liter of pure water, what is the resulting pH?

3.9

Which of the following could be used to formulate 100 mls of a 0.10 M acetate buffer (pK=4.76) at pH 5 if you start with 64 mls of 0.10 M sodium acetate?

34 mls of 0.10 M acetic acid

What is the pH of a solution that contains three parts of acetic acid and one part sodium acetate? The pK for acetic acid is 4.76.

4.28

What would be the resulting pH if one drop (0.05 ml) of 1.0 M HCl was added to one liter of pure water (assume pH 7.0)?

4.3

Hydrogen bonds are approximately _____% of the bond strength of covalent C-C or C-H bonds.

5

What is the [H+] of an aqueous solution with a pH of 6.2?

6.3×10-7

If the pK values for phosphoric acid are 2.15, 6.82 and 12.38, at what pH would one observe equal amounts of H2PO4- and HPO4^2-?

6.82

What is the resulting pH if 10 millimoles of HCl is added to 1 liter of a 0.1 M phosphate buffer at pH 7.00 (pK=6.82)?

6.82