Chapter 10: Nitrogen- and Phosphorus-Containing Compounds
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1. (10.1) The nitrogen in a primary amine is:
B. The lone pair makes the amine a Brønsted base and nucleophile. Amine inversion interconverts the two pyramidal forms rapidly.
2. (10.1) A tertiary amine has:
C. N-H count separates amines by degree (3 for 1°, 2 for 2°, 1 for 3°). Quaternary amines (R₄N⁺) carry a permanent positive charge.
3. (10.2) Compared with alcohols of similar mass, amines:
D. Still H-bond donors and acceptors, just weaker ones than -OH.
4. (10.2) Small amines are water-soluble because:
A. Methyl-, ethyl-, and propylamines are fully water-miscible.
5. (10.3) Amine basicity comes from:
B. Typical alkyl amine pKa is about 10-11. This means ammonium is slightly weaker than water as an acid.
6. (10.3) Aromatic amines (like aniline) are less basic than aliphatic amines because:
C. Aniline pKa of the conjugate acid is ~4.6, compared with ethylamine's ~10.7.
7. (10.4) Amines + acyl halides yield:
D. A fast acylation. A base is added to neutralize the HCl produced.
8. (10.4) Amines with nitrous acid (HNO₂):
A. Aromatic diazonium salts are key intermediates in azo-dye chemistry.
9. (10.5) Amino acids have:
B. Glycine's R = H, so glycine is not chiral. All other 19 standard amino acids are chiral; all have L configuration in natural proteins.
10. (10.5) At physiological pH (~7.4), typical amino acids exist as:
C. The α-amine pKa ~9.5 and α-COOH pKa ~2.3 bracket physiological pH, so the zwitterion dominates.
11. (10.6) Amino acid side chains can be:
D. This is what gives proteins a vast range of structural and chemical properties.
12. (10.6) Essential amino acids must be:
A. Nine essential amino acids in adults: His, Ile, Leu, Lys, Met, Phe, Thr, Trp, Val.
13. (10.7) A peptide bond forms when:
B. Ribosomes use the amino acid activated as aminoacyl-tRNA to catalyze peptide bond formation via nucleophilic acyl substitution.
14. (10.7) The peptide bond is:
C. The planarity of the peptide bond underlies Ramachandran plots of protein backbone geometry.
15. (10.8) Biologically important nitrogen heterocycles include:
D. Nitrogen heterocycles appear throughout pharmacology and biochemistry.
16. (10.8) Pyridine is:
A. The lone pair stays available for protonation or bonding to metals (like in heme).
17. (10.9) A phosphate ester (R-O-PO₃²⁻) forms when:
B. Biologically, kinases handle this (glucose-6-P from glucose + ATP).
18. (10.9) Phosphate groups are biologically important because they:
C. Phosphate chemistry is the currency of energy and information storage in cells.
19. (10.10) ATP (adenosine triphosphate):
C. Cellular conditions (magnesium binding, high ADP/Pi, crowded matrix) can raise the effective free-energy release.
20. (10.10) ATP hydrolysis to ADP + Pi is:
A. The charged phosphate groups repel each other in ATP; hydrolysis relieves that strain.
21. (10.11) Phospholipids have:
B. Amphipathic structure is the key to bilayer self-assembly.
22. (10.11) Phospholipids form bilayers in water because:
C. This is the basis of all cell membranes and many drug-delivery liposomes.
23. (10.12) Nitrogen-containing biomolecules critical to life include:
D. Nitrogen is in essentially every major biomolecule class except pure carbohydrates and lipids.
24. (10.12) Phosphorus-containing biomolecules critical to life include:
A. Phosphate chemistry links genetic information, energy currency, and cellular membranes.
Nitrogen and phosphorus together span the organic-biochemistry boundary. Amines form the backbone of proteins, neurotransmitters, and alkaloid natural products. Phosphate esters drive metabolism (ATP) and store genetic information (DNA). This chapter connects the organic mechanisms you learned in Chs 5-9 to the biological molecules you will encounter in the Biochemistry book.
The Central Analogy
In This Chapter
- 10.1 Amine Structure, Classification, and Nomenclature
- 10.2 Physical Properties of Amines
- 10.3 Basicity of Amines
- 10.4 Amine Reactions - Alkylation and Acylation
- 10.5 Amino Acids - Structure, Zwitterions, and Synthesis
- 10.6 Amino Acid Side Chains
- 10.7 Peptide Bond Formation and Hydrolysis
- 10.8 Nitrogen Heterocycles
- 10.9 Phosphoric Acid and Phosphate Esters
- 10.10 ATP - Structure and Bonds
- 10.11 Phospholipids and Membranes
- 10.12 Biological Roles of N and P Compounds
- Section Test