4. Biomolecules

Which of the following descriptions best fits the class of molecules known as nucleotides?

a) A nitrogenous base & a phosphate group.

b) A nitrogenous base & a sugar.

c) A nitrogenous base, phosphate group & a sugar.

d) A nitrogenous base, a carbohydrate, & a sugar.

The four nitrogenous bases commonly found if DNA are:  

a) Adenine, thymine, cytosine, uracil 

b) Uracil, adenine, cytosine, guanine.

c) Uracil, cytosine, guanine, thymine.

d) Adenine, thymine, cytosine, guanine.

e) None are correct.

Which of the following statements about DNA structure is true?

a) The nucleic acid strands in a DNA molecule are oriented antiparallel to each other.

b) Nucleic acids are formed through phosphodiester bonds that link complementary nucleobases together.

c) Hydrogen bonds formed between the sugar-phosphate backbones of the two DNA chains stabilize the structure.

d) The pentose sugar in DNA is ribose (containing two hydroxyl groups).

What are the four nitrogenous bases found in RNA? a. cytosine, guanine, thymine, uracil (C, G, T, U) b. adenine, cytosine, guanine, thymine (A, C, G, T) c. adenine, cytosine, guanine, uracil (A, C, G, U) d. alanine, cysteine, glycine, threonine (A, C, G, T)

What determines the primary structure of a DNA molecule? a. stem-and-loop configuration b. complementary base pairing c. deoxyribonucleotide sequence d. hydrophobic interactions and hydrogen bonding

Evaluate the following statements related to the synthesis of nucleic acids. Select True or False for each statement. T/F Ribonucleotides are added to the 3′ end of a DNA strand. T/F Polymerization of nucleic acids occurs by the formation of phosphodiester bonds. T/F Complementary pairing between sugars is required for copying nucleic acids. T/F Strands in a double helix are synthesized in an antiparallel orientation.

Single strands of nucleic acids are directional, meaning that there are two different ends. What functional groups define the two different ends of a strand?

What is responsible for the increased stability of DNA compared to RNA?

Enzymes that break down DNA catalyze the hydrolysis of the covalent bonds that join nucleotides together. What would happen to DNA molecules treated with these enzymes? a. The two strands of the double helix would separate. b. The phosphodiester linkages of the polynucleotide backbone would be broken. c. The pyrimidines would be separated from the deoxyribose sugars. d. All bases would be separated from the deoxyribose sugars.

If nucleotides from the DNA of a human were quantified and 30 percent of them contained the base adenine, what percentage of them would contain the base guanine? a. 20 percent b. 30 percent c. 40 percent d. 70 percent

Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA? a. 5′-AGCT-3′ with 5′-TCGA-3′ b. 5′-GCGC-3′ with 5′-TATA-3′ c. 5′-ATGC-3′ with 5′-GCAT-3′ d. All of these pairs are correct.

What would be the sequence of the strand of DNA that is made from the following template: 5′-GATATCGAT-3′? (Your answer must be written 5'→3'.) How would the sequence be different if RNA were made from this DNA template?

According to the RNA world model, a ribozyme would replicate by creating a double-stranded RNA intermediate. Would you expect the intermediate to have the same catalytic activity as the original ribozyme? Justify your answer with an explanation.

Make a concept map (see BioSkills 12) that relates DNA's primary structure to its secondary structure. Your diagram should include deoxyribonucleotides, base-stacking interactions, purines, pyrimidines, phosphodiester linkages, DNA's primary structure, DNA's secondary structure, complementary base pairing, and antiparallel double helix.

RNA and DNA are similar because                  . a. both are double-stranded helices; b. uracil is found in both of them; c. both contain the sugar deoxyribose; d. both are made up of nucleotides consisting of a sugar, a phosphate, and a base

DRAW IT Copy the polynucleotide strand in Figure 5.23a and label the bases G, T, C, and T, starting from the 5′ end. Assuming this is a DNA polynucleotide, now draw the complementary strand, using the same symbols for phosphates (circles), sugars (pentagons), and bases. Label the bases. Draw arrows showing the 5'→3' direction of each strand. Use the arrows to make sure the second strand is antiparallel to the first. Hint: After you draw the first strand vertically, turn the paper upside down; it is easier to draw the second strand from the 5′ toward the 3′ direction as you go from top to bottom.

In the field of nanotechnology, single-stranded DNA molecules are used like Velcro to assemble tiny particles (<0.0001 mm) into structures by complementary base pairing. If the single-stranded DNA molecules are all 20 bases in length, how many different connections could be made between the particles?