Chapter 1 1. a. carboxylic acid; b. amine; c. ester; d. alcohol. 2. a. ether; b. phosphoric acid ester; c. thiol; d. ketone. 3. a. aldehyde; b. imine; c. thioester; d. diphosphoric acid. 4. a. alcohol; b. aldehyde; c. carboxylic acid. 5. Hydroxyl group Imino group Ether linkage CH3 O N OH [From Li, S.-Y. et al., Eur. J. Med. Chem. 71, 36–45 (2014).] 6. 7. CH2 CH2 H3C CH3 C O HN CH2 SH O− O O OH O H H H H Amino group Hydroxyl group Hydroxyl group Phosphoryl group Amido group Sulfhydryl group CH2 CH2 NH C O C H O HO P C −O O P O −O O− O O P CH2 NH2 N N N N Phosphoanhydride linkage 8. A thioester linkage is formed. 9. Amino acids, monosaccharides, nucleotides, and lipids are the four types of biological small molecules. Amino acids, monosaccharides, and nucleotides can form polymers of proteins, polysaccharides, and nucleic acids, respectively. 10. a. N-Acetylglucosamine is a monosaccharide. b. CMP is a nucleotide. c. Homocysteine is an amino acid. d. Cholesteryl ester is a lipid. 11. a. 11-Cyclohexylundecanoate is a lipid. b. Selenocysteine is an amino acid. c. Galactose is a monosaccharide. d. O6 -Methylguanosine monophosphate is a nucleotide. 12. The compound contains both a lipid and a monosaccharide. [From Malyarenko, T.V. et al., Molecules 23, 1077 (2018).] 13. a. C and H plus some O. b. C, H, and O. c. C, H, O, and N plus small amounts of S. 14. It is a lipid (it is actually lecithin). It is mostly C and H, with relatively little O and only one N and one P. It has too little O to be a carbohydrate, too little N to be a protein, and too little P to be a nucleic acid. 15. You should measure the nitrogen content, since this would indicate the presence of protein (neither lipids nor carbohydrates contain appreciable amounts of nitrogen). 16. You could add the compound that contains the most nitrogen, compound B, which is melamine. (Melamine is a substance that in the past was added to some pet foods and milk products from China so that they would appear to contain more protein. Melamine is toxic to pets and children.) Compound C is an amino acid, so it would already be present in protein-containing food. 17. A diet high in protein results in a high urea concentration, since urea is the body’s method of ridding itself of extra nitrogen. Nitrogen is found in proteins but is not found in significant amounts in lipids or carbohydrates. A low-protein diet provides the patient with just enough protein for tissue repair and growth. In the absence of excess protein consumption, urea production decreases, and this puts less strain on the patient’s weakened kidneys. 18. Asn has an amido group and Cys has a sulfhydryl group. 19. Serine has a hydroxyl group and lysine does not. 20. a. O− O− −O O O P CH CH2 O C +H3N b. OH O− HC CH CH2 CH2 CH2 O C +H3N NH3 + c. O O− C (CH2)4 CH2 NH CH3