Chapter 8 - Biochemistry

chichi's version from 2017-05-02 19:16

Section 1

Question Answer
The compound that consists of ribose linked by a N-glycosidic bond to N-9 adenine is:adenosine
A major component of RNA but not DNA is:uracil
The difference between a ribonucleotide and a deoxyribonucleotide is:a deoxyribonucleotide has a ---H instead of an ---OH at C-2.
Which one of the following is true of the pentoses found in nucleic acids?The pentoses are always in the beta-furanose forms
The phosphodiester bonds that link adjacent nucleotides in both RNA and DNA:join the 3'hydroxyl of one nucleotide to the 5'hydroxyl of the next
The phosphodiester bond that joins adjacent nucleotides in DNA:associates ionically with metal ions, polyamines, and proteins

Section 2

Question Answer
The DNA oligonucleotide abbreviated pATCGAC:has a hydroxyl at its 3'end
For the oligoribonucleotide pACGUAC:the nucleotide at the 5'end has a phosphate on its 5'hydroxyl
The nucleic acids bases:are roughly planar
In a double-stranded nucleic acid, cytosine typically base-pairs with:guanine
In the Watson-Crick model for the DNA double helix (B form) the A-T and G-C base pairs share which of the following properties?The distance between the two glycosidic (base-sugar) bonds is the same in both base pairs, within a few tenths of an angstrom.
The experiment of Avery, MacLeod, and McCarty in which nonvirulent bacteria were made virulent by transformation was significant because it showed that:genes are composed of DNA only

Section 3

Question Answer
Chargaff's rules state that in typical DNA:A + G = T + C
In the Watson-Crick model of DNA, structure: the distance between two adjacent bases in one strand is about 3.4 A.
Which of the following is not true of all naturally occurring DNA?The ratio A+T/G+C is constant for all natural DNAs.
In the Watson-Crick model of DNA structure (now called B-form DNA):the bases occupy the interior of the helix
In the Watson-Crick structure of DNA, the:absence of 2'-hydroxyl groups allows bases to lie perpendicular to the helical axis
The double helix of DNA in the B-form is stabilized by:nonspecific base-stacking interaction between two adjacent bases in the same strand

Section 4

Question Answer
In double-stranded DNA:the two strands have complementary sequences
Which of the following is a palindromic sequence?GGATCC CCTAGG
Triple-helical DNA structures can result from Hoogsteen (non Watson-Crick) interactions. These interactions are primarily:hydrogen bonds involving the bases
Double-stranded regions of RNA:can form between two self-complementary regions of the same single strand of RNA do not occur
When double-stranded DNA is heated at neutral pH, which change does NOT occur?The covalent N-glycosidic bond between the base and the pentose breaks
Which of the following deoxyoligonucleotides will hybridize with a DNA containing the sequence (5')AGACTGGTC(3')? (5')GACCAGTCT(3')

Section 5

Question Answer
The ribonucleotide polymer (5')GTGATCAAGC(3') could only form a double-stranded structure with:(5')GCTTGATCAC(3')
In the laboratory, several factors are known to cause alteration of the chemical structure of DNA. The factor(s) likely to be important in a LIVING cell is (are):oxygen and UV light
Compounds that generate nitrous acid (suc as nitrites, nitrates, and nitrosamines) change DNA molecules by:deamination of bases
In DNA sequencing by the Sanger (dideoxy) method:the role of the dideoxy CTP is to occasionally terminate enzymatic synthesis of DNA where Gs occur in the template strands
In the chemical synthesis of DNA:the nucleotide initially attached to the silica gel support will become the 3' end of the finished product
In living cells, nucleotides and their derivatives can serve as:all the above: carriers or metabolic energy, enzyme cofactors, intracellular signals, precursors for nucleic acid synthesis

Section 6

Question Answer
How are a nucleotide and a nucleotide similar and how are they different?Both have a nitrogenous base and a pentose; nucleotides also have a phosphate group, which nucleosides lack
N-glycosidiclinks base to pentose in nucleotide
phosphodiesterjoins adjacent nucleotides in one strand
hydrogenjoins complementary nucleotides in two strands
phosphate esterdifference between a nucleoside and a nucleotide
What is the approximate length of a DNA molecule (in the B form) containing 10,000 base pairs?3.4A x 10,000 = 34,000 A = 3.4um

Section 7

Question Answer
Describe briefly what is meant by saying two DNA strands are complementaryTh nucleotide sequences of complementary strands are such that wherever an A occurs in one strand, there is a T in the other strand with which it can form a hydrogen-bonded base pair. Whereever a C occurs in the one strand, a G occurs in the other. A is the base complementary to T, C is the base complementary to G.
In one sentence, identify the most obvious structural difference between A-form (Watson-Crick) DNA and Z-form DNA.A-form DNA is a right-handed helix; Z-form DNA is a left-handed helix
Mouse DNA hybridizes more extensively with human DNA than with yeast DNA. Explain by describing the factor or factors that determine extent of hybridization:In general, the more similar the sequences in two DNA molecules are, the more readily they will hybridize. Because the evolutionary distance between mouse and yeast is great than that between mouse and human, mouse and human DNA sequences arae more similar than those of mouse and yeast
What is the prinicpal effect of ultraviolet radiation of DNA?UV radiation, causes the formation of a dimer between adjacent thymine bases on the same DNA strand. This results in a kink in the double helix at that site
Explain how nucleoside triphosphates (such as ATP) act as carriers of chemical energy. In these molecules, there is a phosphoric anhydride linkage between the phosphates. Hydrolysis of linkage (i.e., of ATP to ADP and phosphate) is a highly exergonic reaction that results in the release of a large amount of free energy. Conversely, the input of a large amount of free energy is required for the synthesis of the linkage; i.e., for the phosphorylation of ADP to form ATP. Thus, synthesis of ATP results in the storage of energy that can be released upon hydrolysis