Jacob | Knowledge Check #1

A buffer solution at pH 10 has a ratio of [HA]/[A−] of 10. What is the pKa of the acid? 11 12 9 8 10

11

"What is the isoelectric point (pI) for this amino acid titration curve?" (pKa 2.10) ---- zwitterion ---- (pKa 3.86)

2.98

Which will dissociate most in water, a weak acid or a strong acid? They should dissociate about the same. A strong acid A weak acid It's impossible to predict.

A strong acid

The water molecule is polar because: Electrons are not distributed symmetrically in the molecule. Hydrogen is less electronegative than oxygen. All of these are correct. The hydrogen atoms are found on one "side" of the molecule and hydrogen is less electronegative than oxygen. The hydrogen atoms are found on one "side" of the molecule.

All of these are correct.

Which of the following classes of compounds is hydrophilic? All of these Sugars Amino acids Sugars and amino acids Fatty acids

Sugars and amino acids

If atoms with greatly differing electronegativities form a bond, that bond will be: amphipathic polar nonpolar acidic

polar

Bases are: proton acceptors hydrogen bond acceptors proton donors hydrogen bond donors

proton acceptors

Which of the following is a correct listing of electronegativity values, from low to high? N, H, O, C H, C, N, O H, C, O, N C, H, O, N

H, C, N, O

How does the strength of hydrogen bonds compare with covalent bonds? Hydrogen bonds are much weaker than covalent bonds. Hydrogen bonds and covalent bonds have similar strengths. Hydrogen bonds are much stronger than covalent bonds. The question cannot be answered without knowing which covalent bonds are being referred to.

Hydrogen bonds are much weaker than covalent bonds.

The main difference between prokaryotic and eukaryotic cells is the existence of _____ in eukaryotes. RNA The nucleus Cell walls DNA Ribosomes

The nucleus

When does a weak acid buffer best? Weak acids do not make good buffers at all. Within one pH unit of its pKa, both above and below. From its pKa to one pH unit above its pKa. From one pH unit below its pKa to its pKa.

Within one pH unit of its pKa, both above and below.

The pKa values of the side chains of the common amino acids: are always at high pH pKa is not applicable here are always at low pH depend on the chemical nature of the side chain

depend on the chemical nature of the side chain

The tendency for an atom to attract electrons to itself in a chemical bond is called... hydrophilicity. polarity. electronegativity. electrophilicity.

electronegativity.