318
BIOLOGICAL MATERtALS
bond
i
J
/
Flgure 12.7. The four levels of structure of a protein: (a) primary structure of a stretched-out
polypeptide, (b) secondary struclures ol an x helix (Iefl) and a /i’ sheet (right), (c) lertiary structure
01 a polypeptide held tcgelher by disullide b n d s (-S-S-).
and quaternary struclure Iormed by
two polypeplides. [From S . S. Mader, Bology, McGraw-Hill, Boston, 2001 p. 47.1
attachment points where the bases bond to the desoxyribose sugar are indicated by
vertical arrows in Fig. 12.9, and the bases pair off with each other in the doublestranded DNA in accordance with the horizontal arrows in the figure; that is,
cytosine (C) pairs with guanine (G), and thyminc (T) pairs with adenine (A), in the
manner shown in Fig. 12.10, We see from this figure that the acid-phosphate group
BIOLOGICAL MATERtALS
bond
i
J
/
Flgure 12.7. The four levels of structure of a protein: (a) primary structure of a stretched-out
polypeptide, (b) secondary struclures ol an x helix (Iefl) and a /i’ sheet (right), (c) lertiary structure
01 a polypeptide held tcgelher by disullide b n d s (-S-S-).
and quaternary struclure Iormed by
two polypeplides. [From S . S. Mader, Bology, McGraw-Hill, Boston, 2001 p. 47.1
attachment points where the bases bond to the desoxyribose sugar are indicated by
vertical arrows in Fig. 12.9, and the bases pair off with each other in the doublestranded DNA in accordance with the horizontal arrows in the figure; that is,
cytosine (C) pairs with guanine (G), and thyminc (T) pairs with adenine (A), in the
manner shown in Fig. 12.10, We see from this figure that the acid-phosphate group