Biomolecules (Nucleic Acids)

What do you call the monomers (building blocks) of nucleic acids?

• phosphate group

• pentose sugar

• nitrogenous base

• nucleotide

Which structure correctly shows how the 3 components of a nucleotide are joined together?

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Answer explanation

The base is linked to carbon 1 of pentose, and the phosphate is linked to carbon 5 of pentose.

Which nitrogenous bases are purines?

• cytosine & thymine

• adenine & thymine

• adenine & guanine

• cytosine & guanine

Answer explanation

What do you call the bond that is formed between two nucleotides?

• peptide bond

• phosphate bond

• ester bond

• phosphodiester bond

Answer explanation

In a double-stranded DNA molecule, what bond holds the two strands together?

• glycosidic bond

• hydrogen bond

• phosphodiester bond

• ionic bond

Answer explanation

In a double-stranded DNA molecule,

(i) between which two bases are hydrogen bonds formed?

(ii) how many hydrogen bonds are formed between these two bases?

• 2 H-bonds between A & T

  3 H-bonds between C & G

• 3 H-bonds between A & T

  2 H-bonds between C & G

• 2 H-bonds between A & G

  3 H-bonds between C & T

• 3 H-bonds between A & G

  2 H-bonds between C & T

Answer explanation

In a DNA molecule, the two strands orientate in the opposite direction.

What term is used to describe the orientation of the two strands?

(a)  

Answer explanation

The twisting of DNA into a helix is not regular.

This gives rise to alternating grooves on the DNA called _____ groove and _____ groove.

• primary, secondary

• central, peripheral

• major, minor

• wide, narrow

Answer explanation

In a DNA molecule, one complete turn comprises _____ base pairs and is _____ nm long.

• 10 base pairs,

  3.4 nm

• 3.4 base pairs,

  10 nm

• 10 base pairs,

  2 nm

• 20 base pairs,

  3.4 nm

Answer explanation

[CHALLENGING] What structures are found only in RNA but not in DNA?

(multiple selection)

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