Test 1 Ours Real
B) formation of free e-.
Biological oxidation-reduction reactions never involve: A) transfer of e- from one molecule to another. B) formation of free e-. C) transfer of H+ (or H3O+) from one molecule to another. D) formation of free H+ (or H3O+). E) none of the above.
D) they buffer best for polyprotic acids half-way between the two pKa values.
Buffers have all of the following characteristics EXCEPT: A) they have relatively flat titration curves at the pH(s) where they buffer. B) they resist changes in their pH as acid or base is added. C) they are typically composed of a weak acid and its conjugate base. D) they buffer best for polyprotic acids half-way between the two pKa values. E) buffer where the amounts of conjugate base are nearly equivalent to the amounts of weak acid.
A) 0.13 M acetate and 0.07 M acetic acid
Calculate the concentrations of acetic acid (pKa = 4.76) and sodium acetate necessary to prepare a 0.2M buffer solution at pH 5.0. A) 0.13 M acetate and 0.07 M acetic acid B) 0.07 M acetate and 0.13 M acetic acid C) 1.7 M acetate and 2.7 M acetic acid D) 0.34 M acetate and 2.36 M acetic acid E) 2.36 M acetate and 2.36 M acetic acid
A) 262
Calculate the equilibrium constant, Keq, for the following reactions at pH 7.0 and 25 °C. (Find out the standard gibbs free energy from the table given) Glucose 6-phosphate + H2O Glucose + Pi A) 262 B) 324 C) 576 D) 626 E) 126
E) Both A) and C)
For the helix in double-stranded B-form DNA, the majority of the stability can be attributed to: A) base-pairing interactions via H-bonding. B) interactions along the phosphate backbone. C) base-stacking interactions via van-der-Waals interactions. D) covalent bonds between adjacent bases in one strand. E) Both A) and C)
D) the nucleotide at the 5' end has a phosphate on its 5' hydroxyl.
For the oligoribonucleotide pACGUAC: A) the nucleotide at the 3' end has a phosphate at its 3' hydroxyl. B) the nucleotide at the 3' end is a purine. C) the nucleotide at the 5' end has a 5' hydroxyl. D) the nucleotide at the 5' end has a phosphate on its 5' hydroxyl. E) the nucleotide at the 5' end is a pyrimidine.
A) At equilibrium, there will be far more B than A.
For the reaction A à B, the Keq is 104. If a reaction mixture originally contains 1 mmol of A and no B, which one of the following must be true? A) At equilibrium, there will be far more B than A. B) The rate of the reaction is very slow. C) The reaction requires coupling to an exergonic reaction in order to proceed. D) The reaction will proceed toward A at a very high rate. E) DG'° for the reaction will be large and positive.
A) 3.16 x 10-4
Formic acid is the active agent in an ant bite. What is the ratio of acid / conjugate base for formic acid (pKa = 3.9) in the blood stream at pH 7.4? A) 3.16 x 10-4 B) 3.16 x 103 C) 0.54 D) 1.90 E) cannot be determined based upon the provided information.
D) 7.16
If 0.2 moles of Na2HPO4 and 0.1 moles of NaH2PO4 are mixed in water, what is the resulting pH? The pKa values for phosphoric acid are provided in the pKa table. A) 2.1 B) 4.65 C) 6.86 D) 7.16 E) 12.4
E) hydrocarbon tails are excluded from the water into hydrophobic domains.
In micelles: A) polar ends form hydrophobic interactions with water. B) nonpolar ends form hydrophilic interactions with water. C) hydrocarbon tails form hydrophobic interactions with water. D) polar ends are hydrophobic and nonpolar ends are hydrophilic. E) hydrocarbon tails are excluded from the water into hydrophobic domains.
C) rotation around the sugar-base bond.
In nucleotides and nucleic acids, syn and anti conformations relate to: A) base stereoisomers. B) rotation around the phosphodiester bond. C) rotation around the sugar-base bond. D) sugar pucker. E) sugar stereoisomers
D) Mg+2
Nucleotide triphosphates and nucleotide diphosphates often form stable complexes with: A) Na+ B) Fe+3 C) K+ D) Mg+2 E) None of the above
A) ATP < 1 M, ADP > 1 M, Pi > 1 M
The standard free energy change (ΔG'°) for ATP hydrolysis is -30.5 kJ/mol. ATP, ADP, and Pi are mixed together at initial concentrations of 1 M of each, then left alone until the reaction ADP + Pi à ATP has come to equilibrium. For each species (i.e., ATP, ADP, and Pi), indicate whether the concentration will be equal to 1 M, less than 1 M, or greater than 1 M. A) ATP < 1 M, ADP > 1 M, Pi > 1 M B) ATP < 1M, ADP < 1M, Pi < 1M C) ATP > 1M, ADP > 1M, Pi > 1M D) ATP = 1M, ADP > 1M, Pi > 1M E) ATP = 1M, ADP = 1M, Pi = 1M
B) Open systems can exchange matter with other open systems.
Which statement pertaining to the three basic systems (open, closed, isolated systems) is true? A) The internal energy of an isolated system is mostly conserved. B) Open systems can exchange matter with other open systems. C) Open systems can exchange matter with a closed system. D) The internal energy of an open system is always constant. E) A closed system can accept heat from an isolated system.
A) 5 45 45 0 5 B) 25 25 25 0 25
Which of the following are possible base compositions for single-stranded RNA? %A %G %C %T %U A) 5 45 45 0 5 B) 25 25 25 0 25 C) 35 10 30 0 25 D) All of the above E) None of the above
B) (5')GACCAGTCT(3')
Which of the following deoxyoligonucleotides will hybridize with a DNA containing the sequence (5')AGACTGGTC(3')? A) (5')CTCATTGAG(3') B) (5')GACCAGTCT(3') C) (5')GAGTCAACT(3') D) (5')TCTGACCAG(3') E) (5')TCTGGATCT(3')
E) The base pairs are stacked on one other with their planes at 180o to the helix axis.
Which of the following does NOT describe the secondary structure of DNA as proposed by Watson and Crick? A) The two strands of the double helix are stabilized by hydrogen-bonding between A and T and between G and C. B) The two strands of the double helix run in opposite directions. C) The distance between the 1' carbons of the deoxyribose units is the same between the A-T and the G-C base pair. D) The phosphate deoxyribose backbones of the helix are on the outside. E) The base pairs are stacked on one other with their planes at 180o to the helix axis.
C) The ratio A+T/G+C is constant for all natural DNAs.
Which of the following is not true of all naturally occurring DNA? A) Deoxyribose units are connected by 3',5'-phosphodiester bonds. B) The amount of A always equals the amount of T. C) The ratio A+T/G+C is constant for all natural DNAs. D) The two complementary strands are antiparallel. E) Two hydrogen bonds form between A and T.
E) both A and C are correct
Which of the following properties describe both purines and pyrimidines? A) they are aromatic B) they are composed of 6-membered rings C) they exhibit strong absorption of UV light D) they always contain a carbonyl group E) both A and C are correct
A) The donor is a hydrogen atom bonded to an atom that is less electronegative than hydrogen.
Which of the following statements is INCORRECT about the nature of the hydrogen bond. A) The donor is a hydrogen atom bonded to an atom that is less electronegative than hydrogen. B) The more linear the bond, the stronger the interaction. C) The acceptor is a fairly electronegative atom containing a nonbonding pair of electrons. D) It is a type of noncovalent bond. E) All of the above statements are true about the nature of the hydrogen bond