Fig. 3-6, p. 38

Fig. 3-5, p. 37

one of the estrogens

Fig. 3-4, p. 37

testosterone

glucose fructose

sucrose

Fig. 3-6, p. 38

c Formation of a sucrose molecule

Fig. 3-8, p. 39

Fig. 3-8, p. 39

c Glycogen. In animals, thispolysaccharide is a storage form for excess glucose. It is especially abundant in the liver and muscles of highly active animals, including fishes and people.

Structure of cellulose

glycerol

three fatty acid tails Triglyceride, a neutral fat

Fig. 3-11, p. 40

Fig. 3-12, p. 41

hydrophilic head

two hydrophilic tails

Fig. 3-13, p. 41

Fig. 3-13, p. 41

c Cell membrane section

Fig. 3-15, p. 42

carboxylgroup

aminogroup

Fig. 3-17, p. 43

a Protein primarystructure: Aminoacids bonded in apolypeptide chain.

Fig. 3-17, p. 43

b Protein secondarystructure: A coiled(helical) or sheetlikearray, held in placeby hydrogen bonds( dotted lines) betweendifferent parts of thepolypeptide chain.

helical coil sheet

Fig. 3-17, p. 43

c Protein tertiary structure: A chain’s coiled parts, sheetlikearrays, or both have folded and twisted into stable, functionaldomains, including clusters, pockets, and barrels.

barrel

Fig. 3-17, p. 43

d Protein quaternarystructure: Many weakinteractions hold twoor more polypeptidechains together asa single molecule.

alpha globin

beta globin beta globin

Fig. 3-18, p. 44

alpha globin

b Hemoglobin is one of the proteins with quaternary structure. Itconsists of four globin molecules held together by hydrogen bonds.To help you distinguish among them, the two alpha globin chainsare shown here in green, and the two beta globins are in brown.

Fig. 3-19, p. 45

VALINE HISTIDINE LEUCINE GLUTAMATEVALINETHREONINE PROLINE

sickle cell

normal cell

b One amino acid substitution results in theabnormal beta chain in HbS molecules. Insteadof glutamate, valine was added at the sixthposition of the polypeptide chain.

c Glutamate has an overall negative charge; valine has no net charge. At low oxygen levels, this difference gives rise to a water-repellent, sticky patch on HbS molecules. They stick togetherbecause of that patch, forming rodshaped clumps that distort normally rounded red blood cells into sickle shapes. (A sickle is a farm tool that has a crescent-shaped blade.)

Fig. 3-20, p. 46

three phosphate groups

base (blue)

sugar (orange)

Fig. 3-21, p. 46

Fig. 3-22, p. 47

covalentbonding incarbonbackbone

hydrogen bondingbetween bases