Polar

Some amino acids are polar, meaning that there is an asymmetrical distribution of electronic charge throughout the molecule. The polarity of amino acids is an important factor in biological systems because it has a significant effect on how a protein folds into its active conformation. The amino acid glycine lacks a side chain and is the least polar in this group. Asparagine derives its polarity from bonds that contain nitrogen and oxygen atoms, around which electrons tend to cluster. Serine and threonine both contain polar hydroxyl groups, while glutamine, like asparagine, possesses polar bonds containing nitrogen and oxygen atoms. The final two polar amino acids shown here are distinguished by unique structural features. Tyrosine contains a planar benzene ring as part of its side group as well as a polar hydroxyl group, and cysteine possesses a bond containing sulfur, shown in yellow, another atom with a tendency to collect electrons.

Question 1: What makes amino acids polar?
  1. A polar distribution of electronic charge throughout the molecule.
  2. An unsymmetrical distribution of electronic charge throughout the molecule.
  3. A symmetrical distribution of electronic charge throughout the molecule.
  4. An apolar distribution of electronic charge throughout the molecule.


Answer 1 Answer - (b) An unsymmetrical distribution of electronic charge throughout the molecule.

Question 2: The ____________ of amino acids is an important factor in biological systems because it has a significant effect on how a protein folds into its active conformation.
  1. linearity
  2. binding
  3. polarity
  4. charges


Answer 2 Answer - (c) Polarity

Question 3: Both Serine and Threonine contain polar ------------ groups.
  1. hydroxyl
  2. sulfadryl
  3. amino
  4. carboxy


Answer 3 Answer - (a) Hydroxyl

Question 4: Which amino acid is the least polar out of polar amino acids because it lacks a side chain?
  1. Serine
  2. Glycine
  3. Threonine
  4. Asparagine


Answer 4 Answer - (b) Glycine

Question 5: What makes the polar amino acid tyrosine unique?
  1. Its size.
  2. Presence of a polar benzene ring as part of its side group as well as a planar hydroxyl group.
  3. Presence of a planar amino acid ring as part of its side group as well as a polar hydroxyl group.
  4. Presence of a planar benzene ring as part of its side group as well as a polar hydroxyl group.


Answer 5 Answer - (d) Presence of a planar benzene ring as part of its side group and a polar hydroxyl group.

Question 6: What kind of bond can improperly form between two cysteines?
  1. A sulfur bond.
  2. A hydrogen bond.
  3. A disulfide bond.
  4. A hydroxyl bond.


Answer 6 Answer - (c) A disulfide bond