Chapter 1 The Chemistry of Life • MHR 29+
C OHH
H
C OHH
C OHH C
H H
H
H CO
H
H CO
H CO
H
C
H
C
H
C
H
H
C
O
C
H
H
H C
HO
H
C
H
C
H
C
H
H
C
C
C
H
H
H
O
C
H
H H H
C
H
C
H
C
H
H
C
O
HO
C
H
H
C
H
H
HC
H
H H H
C
H
C
H
C
H
H
C
O
C
H
H
C
H
H
H
C
H
H H H
C
H
C
H
C
H
H
C
O
H C
H
H H H
C
H
C
H
C
H
H
H
glycerol 3 fatty acids fat 3 watersHO
HO
- 3 HO 2
condensation
synthesishydrolysisFigure 1.22Condensation and hydrolysis of a fat molecule. When a fat molecule
forms, three fatty acids combine with glycerol and three water molecules are produced.
Unsaturated fats have double bonds (shown in yellow) between carbon atoms.
CH 2
CH 2CH 2 CH 2CH 2 CH 2
CH 2 CH 2
CH 2 CH 2
CH 2 CH 2
CH 2 CH 2
CH 2 CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 3CH 2CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 3CH 3
CH 3
CH 3headtailhydrophilic
(polar) head
groupnitrogen
groupglycerolphosphate
grouphydrophobic
(nonpolar)
tail groupdouble
bond
fatty acidsP
CH
O
O
OCOC
O O
CH
CH
O
+NO−waterinterior of cellhydrophilic
headshydrophobic
tailshydrophilic
headsBA
Each of the units in the bilayer is a phospholipid molecule.
Each individual circle represents the negatively charged
phosphate group, while the tails are two non-polar
hydrocarbon chains. The negatively charged phosphate
groups are hydrophilic, and the hydrocarbon chains are
hydrophobic.A
The tails of the phosphate groups in the phospholipid
bilayer of the cell membrane point toward each other,
creating a hydrophobic environment within the cell
membrane. The charged phosphate groups face out
into the hydrophilic environment surrounding the cell.B
Figure 1.23Phospholipid structure and shapeatoms as it can hold. Saturated fatty acids are
generally solid at room temperature. In contrast,
unsaturated fatty acids have one or more double
bonds between carbon atoms. Therefore, the fatty
acid is not saturated with hydrogen atoms. Fat
molecules are split by hydrolysis for use in cells.
Figure 1.23(a) shows another lipid
macromolecule with a different function in cells.