10 Nitrogen- and Phosphorous-Containing Compounds

Question 1

properties

Answer 1

alpha carbon is a chiral (stereogenic) center
except glycine (R group is H)

optically active; all L-isomers

amphoteric molecules

zwitterions in neutral solution (protonated amino group, deprotonated carboxyl group)

Question 2

nonpolar, nonaromatic R group characteristics

Answer 2

saturated hydrocarbons

alanine
valine
leucine
isoleucine
glycine
proline
methionine

Question 3

aromatic R group characteristics

Answer 3

tryptophan
phenylalanine
tyrosine

Question 4

polar R group characteristics

Answer 4

terminal groups are usually O, N, or S

serine
threonine
asparagine
glutamine
cysteine

Question 5

negatively charged (acidic) R group characteristics

Answer 5

terminal carboxylate anions

aspartic acid
glutamic acid

Question 6

positively charged (basic) R group characteristics

Answer 6

protonated amino group (in R group)

arginine
lysine
histidine

Question 7

peptide bond

Answer 7

condensation reaction between amino acids

Question 8

polypeptides

Answer 8

result of peptide bond

base units of proteins

Question 9

Strecker synthesis

Answer 9

aldehyde, NH4Cl, KCN
can generate both L- and D-amino acids (racemic mixtures)
starts with planar carbonyl-containing compound

Step 1: aminonitrile generated from aldehyde/ketone
Step 2: amino acid generated from aminonitrile

Question 10

Gabriel (malonic-ester) synthesis

Answer 10

amino acid generated from phtalamide and diethylbromomalonate

2 SN2 reactions
1 hydrolysis
1 decarboxylation

starts with planar molecule –> racemic mixture (L- and D- amino acids generated)

Question 11

phosphoric acid

Answer 11

forms the high-energy bonds that carry energy in ATP

• phosphate group
• inorganic phosphate (Pi)

at physiological pH: HPO4(2-) and H2PO4(-)

energy-carrying nucleotide phosphates
backbone of DNA in phosphodiester bonds linking sugar moieties of the nucleotides

excellent buffer (3 hydrogens with pKa values than span nearly the entire pH scale = 2.15, 7.20, 12.52)