2.20–2.21: Nucleic acids store information on how to build and run a body.

The nucleic acids DNA and RNA are macromolecules that store information by having unique sequences of nucleotides. Both play central roles in directing protein production in organisms. RNA acts as a translator of the genetic code into proteins. It reads DNA sequences and directs the production of a sequence of amino acids.

Question 2.31

Dietary proteins:

  • a) are considered “complete” only if they contain the 8 essential amino acids required by humans.
  • b) consist of all 20 amino acids required in the human body.
  • c) are considered “complete” only if they contain the 12 non-essential amino acids required by humans.
  • d) are nutritionally identical, since all are broken down into their constituent amino acids in the digestive system.
  • e) can be obtained from animal sources but not plant sources.

Question 2.32

The primary structure of proteins is often described as amino acids connected like beads on a string. In this same vein, which of the following images best describes a protein’s quaternary structure?

  • a) threads in a cloth
  • b) needles in a haystack
  • c) rungs on a ladder
  • d) links on a chain
  • e) coils in a spring

Question 2.33

Which of the following statements about enzymes is incorrect?

  • a) Enzymes can initiate chemical reactions.
  • b) Enzymes speed up chemical reactions.
  • c) Enzymes are proteins.
  • d) Enzymes contain an active site for binding of particular substrates.
  • e) Enzymes undergo a permanent change during the reactions they promote.

Question 2.34

Which of the following nucleotide bases are present in equal amounts in DNA?

  • a) adenine and cytosine
  • b) thymine and guanine
  • c) adenine and guanine
  • d) thymine and cytosine
  • e) adenine and thymine

Question 2.35

Which type of macromolecule contains an organism’s genetic information?

  • a) polysaccharide
  • b) monosaccharide
  • c) fatty acid
  • d) DNA
  • e) phospholipid