Exam 1 Flashcards
2019
Four vitalist statements are listed below. Each time one was disproved, vitalists took refuge in a less general, more restricted statement. Order the four statements from most restrictive to least restrictive.
- a) The reactions constituting life occur only in living cells.
- b) The substances composing living matter are qualitatively different from those of the non-living world.
- c) Structure of “ferments” is too complex to be described in chemical terms, and the nature of catalysis is not comprehensible.
- d) Organisms arise from non-living matter by spontaneous generation through the intervention of the “vital force.”
c, a, d, b
2019
The structure of 11-cis-retinal is shown below. The side chain carbon directly attached to the ring is #7, and the aldehyde carbon is #15. When the molecule isomerizes from cis to trans, for which of the following pairs of atoms would the interatomic distance change?
- A. a methyl on the ring and carbon 12
- B. carbon 13 and carbon 15
- C. a methyl on the ring and the methyl at carbon 9
- D. a ring carbon and the aldehyde carbon
- E. more than one of the above

D. a ring carbon and the aldehyde carbon
2019
For a cell to convert glucose to acetate or ethanol, it is necessary that
- A. the cell be able to live in an atmosphere containing molecular oxygen.
- B. the cell has a nucleus.
- C. the cell contains chloroplasts.
- D. the cell contains mitochondria.
- E. none of the above
E. none of the above
2019
A short peptide (an oligopeptide) consists of eleven amino acid residues. Asn and gln are not present. How many water molecules would be required to hydrolyze the oligopeptide to free amino acids? (Adapted from last year’s exam)
- A. Ten
- B. Nine
- C. Eight
- D. Twenty
- E. none of these
A. Ten
2019
Given the data in the table below, estimate the number of residues in the muscle protein myosin.
- A. 1100
- B. 9900
- C. 4500
- D. 564,500
- E. None of these is even close to correct.

C. 4500
2019
Which of the following reactions involves dehydration?
- A. the formation of a polypeptide from amino acids
- B. oxidation of two sulfhydryl groups to make a disulfide bond C. conversion of sugar molecules into starch
- D. breakdown of a DNA to single nucleotides
- E. more than one of the above
E. more than one of the above
2019
The enthalpy of dissolving hydrophobic material in water is less than zero, i.e. heat is released to the surroundings when a hydrophobe is shaken with water and some dissolves. Why, then, are hydrophobic materials like olive oil not appreciably soluble in water?
- A. Hydrophobic substances actively repel water.
- B. Hydrophobic molecules have a strong attraction for one another, stronger than any attraction they have for water.
- C. Water molecules have a strong attraction for one another, stronger than any attraction they have for hydrophobes.
- D. Hydrophobes reduce the number of possible arrangements of water molecules that are near them, an effect that opposes dissolving them in the water.
- E. none of the above
D. Hydrophobes reduce the number of possible arrangements of water molecules that are near them, an effect that opposes dissolving them in the water.
2019
Water molecules have a diameter of approximately 2.8 Å. They are not exactly spherical, though, and the diameter is an average obtained from rotating the molecule through all possible orientations. The Van der Waals radii of hydrogen and oxygen are given in the table below, which was discussed in class. The Van der Waals radius is the closest atoms can come to one another without steric hindrance. The total of the radii does not add up to the approximate diameter, and the difference exceeds experimental error. Why? Van der Waals radii
- A. Formation of the molecule shrinks the noncovalent radii.
- B. The approximate diameter describes the closest approach of the oxygens of two water molecules
- C. Hydrogens do not count in determining the molecular diameter.
- D. The covalent O-H bond length has not been taken into account in the total value to the left.
- E. none of the above.
The diagram to the left, also from class, may be helpful. Bear in mind that 1 nm = 10 Å.

D. The covalent O-H bond length has not been taken into account in the total value to the left.
2019
If a crystal of sodium chloride were to be placed in water, which of the following factors would NOT favor the dissolving of the crystal?
- A. the entropy of departure of sodium ions from the crystal
- B. the change in electrostatic interactions between sodium and chloride ions
- C. the change in state of water
- D. electrostatic interactions between the ions and water molecules
- E. more than one of the above
E. more than one of the above
2019
Fully protonated glycine can be purchased as a white crystalline solid. Because it has a net charge of +1, the crystals must contain a compensating negatively charged ion, which is usually chloride. The bottle will be labeled ‘glycine hydrochloride.’ If a 0.1 M solution of glycine hydrochloride were to be prepared, the approximate concentration of gly+1 would be
A. slightly less than 0.1 M
B. 10-2.34 M
C. 10-9.6 M
D. 0.01 M
E. none of these
A. slightly less than 0.1 M
2019
Why does citric acid not have a pH at which it would migrate toward a cathode? (This is derived from a question posed on p. 1 of the Polyprotic Molecules hand-out.)
A. Its molecules always carry a negative charge.
B. Its molecules are always uncharged regardless of the pH.
C. Its molecules can never carry a positive charge.
D. It is always combined with an immobile protein molecule
E. more than one of the above
C. Its molecules can never carry a positive charge
2019
Why are proteins least soluble at their isoionic pH?
- A. They do not bind counterions at the isoionic pH.
- B. At any other pH they repel one another.
- C. They bind counterions at the isoionic pH.
- D. They do not bind proteins at the isoionic pH.
- E. cannot tell from data given.
B. At any other pH they repel one another.
2019
DNA in cells is always found in association with other molecules, most of which are proteins. What characteristic of these proteins is primarily responsible for enabling this association?
A. Their shapes are complementary to the shape of the DNA.
B. Their size allows them to wrap around the DNA, fitting it into the cell.
C. Their charge cancels much of the charge on the DNA.
D. They prevent hydrolysis of the DNA to nucleotides.
E. None of the above contributes.
C. Their charge cancels much of the charge on the DNA
2019
Most salts, including those found in the cytoplasm of cells, are more soluble in hot water than in cold. If enough potassium chloride were to be dissolved in water at 60 C to make a saturated solution, and the solution were then cooled to 37 C, which of the following reactions would be spontaneous?
A. KClsolution → KClsolid
B. an overall decrease in entropy
C. the dissolving of more KCl
D. a reaction involving a decrease in enthalpy
E. more than one of the above
A. KClsolution → KClsolid
2019
It is often the case that molecules must cross membranes from a zone in which their concentration is less than the zone to which they go. Which of the following must be true?
A. The transfer must be coupled to a reaction whose free energy is positive.
B. The transfer must be coupled to a reaction whose free energy is zero.
C. The transfer must be coupled to a reaction whose free energy is negative.
D. Such transfers are not spontaneous and cannot occur.
E. Such transfers are spontaneous and need no “assistance.”
C. The transfer must be coupled to a reaction whose free energy is negative.
2019
Which term in the Gibbs equation for free energy is analogous to the pKa in the Henderson-Hasselbalch equation?
A. log([salt]/[acid])
B. ∆G
C. ∆Gº’
D. RT ln [C]c [D]d / [A]a [B]b
E. none of the above
C. ∆Gº’
2019
Of the twenty amino acids found in proteins, how many have only atoms of carbon and hydrogen in their side chains?
A. all twenty
B. seven
C. six
D. three
E. none of these is correct
B. seven
2019
Which of the reactions in the figure below is driven solely by the entropy?
A. Reaction (a)
B. Reaction (b)
C. Reaction (c)
D. Reactions (a) and (c)
E. Cannot tell from data given.

C. Reaction (c)
2019
Which of the following characteristics of an atom other than hydrogen would allow it to participate in a hydrogen bond?
- A. being bonded only to hydrogens or carbons
- B. being part of a carbon to carbon double bond
- C. having unshared pairs of electrons
- D. being bonded to an oxygen atom
- E. none of these (From last year’s exam)
C. having unshared pairs of electrons
2019
Sulfhydryl groups react with iodoacetic acid according to the following reaction, which we discussed in class: RSH + ICH2COO- → RSCH2COO- + H+ + I- . The group added to the sulfur atom is called a carboxymethyl group. A native protein is reacted with excess iodoacetic acid, whereupon three moles of carboxymethyl groups are found to be bound per mole of protein. In a second experiment a sample of the protein is completely unfolded and reacted with excess mercaptoethanol and then with excess iodoacetic acid. Thirteen moles of carboxymethyl groups are now found to be bound per mole of protein. How many disulfides does the native protein contain?
A. three
B. ten
C. eight
D. four
E. none of these is correct
E. none of these is correct
2019
Consider a solution of aspartic acid and lysine. At which pH would they migrate in opposite directions, one moving toward the cathode and one toward the anode? (Hint: remember that asp is acidic, while lys is basic.)
A. pH 2
B. pH 6
C. pH 11
D. all of these
E. none of these B. pH 6
B. pH 6
2019
At pH 6.5 ribonuclease has a net charge of +4. At pH 2 it has a net charge of +19. The most likely reason for this change in charge is
- A. the protonation of 15 lysine side chains.
- B. the deprotonation of 15 lysine side chains.
- C. the protonation of 15 glutamic and/or aspartic acid side chains.
- D. the deprotonation of 15 glutamic and/or aspartic acid side chains.
- E. None of these could account for the change. (You may want to look at the table of pKa values at the end of this section of the exam.)
C. the protonation of 15 glutamic and/or aspartic acid side chains.
2019
Consider a carbon atom which is involved in a double bond to another atom and in single bonds to two other atoms. These four atoms
- A. form a tetrahedron.
- B. are co-linear.
- C. lie in a plane.
- D. form one half of an enantiomeric pair.
- E. more than one of these answers is correct
C. lie in a plane
2019
Consider a carbon atom which is involved in single bonds to four other atoms, each of which is different from the others. These atoms
- A. form a tetrahedron.
- B. are co-linear.
- C. lie in a plane.
- D. form one half of an enantiomeric pair.
- E. more than one of these answers is correct
E. more than one of these answers is correct







