认k (c) The protein keratin is the chief structural components of hair. scales, horn wool. nails and feathers
The protein keratin is the chief structural components of hair, scales, horn, wool, nails and feathers
2. All natural proteins were found to be built from a repertoire of 20 standard a-amino acids 2.1 The earliest studies of proteins focused on the free amino acids derived from these proteins. 2.1.1 The 1st amino acid(asparagine)was discovered in 1806 from asparagus(a green vegetable) 2.1.2 The last(threonine) was not identified until 1938! 2.1.3 All the amino acids were given a trivial (common) name. Glutamate from wheat gluten(sticky). yrosine from cheese(“ tyros” in greek)
2. All natural proteins were found to be built from a repertoire of 20 standard -amino acids 2.1 The earliest studies of proteins focused on the free amino acids derived from these proteins. 2.1.1 The 1st amino acid (asparagine) was discovered in 1806 from asparagus (a green vegetable). 2.1.2 The last (threonine) was not identified until 1938! 2.1.3 All the amino acids were given a trivial (common) name. Glutamate from wheat gluten (sticky). Tyrosine from cheese (“tyros” in Greek)
2. 2 The 20 a-amino acids share common structural features 2.2.1 Each has a carboxyl group and an amino group(but one has an imino group in proline) bonded to the same carbon atom, designated as the a-carbon 2.2.2 Each has a different side chain(or r group,R=“ Remainder of the molecule”) 2. 2.3 The a-carbons for 19 of them are asymmetric (or chiraL), thus being able to have two enantiomers. Glycine has no chiralit ity
2.2 The 20 -amino acids share common structural features. 2.2.1 Each has a carboxyl group and an amino group (but one has an imino group in proline) bonded to the same carbon atom, designated as the -carbon. 2.2.2 Each has a different side chain (or R group, R=“Remainder of the molecule”). 2.2.3 The -carbons for 19 of them are asymmetric (or chiral), thus being able to have two enantiomers. Glycine has no chirality
COO gN—C—H R
6 2 CH2—CH2—CH2—CH2—CH—COO +NH3 +NH3 ysine In protein chemistry, we use Greek letter nomenclature
In protein chemistry, we use Greek letter nomenclature