1. The Structure and Function of Macromolecules
Chapter 5
The Structure and Function of Macromolecules
Part A

2. Macromolecules Are large molecules composed of smaller molecules
Are complex in their structures

3. Biological Macromolecules
There are four classes of large molecules in cells:
Carbohydrates
Lipids
Proteins
Nucleic acids

4. Most macromolecules are polymers, built from monomers
Three of the classes of life’s organic molecules are polymers
Carbohydrates
Proteins
Nucleic acids

5. A polymer Is a long molecule
consists of many similar or identical building blocks called monomers
Monomers are linked by covalent bonds

6. The Synthesis and Breakdown of Polymers
Monomers form larger molecules by:
condensation reactions called:
dehydration reactions
(a) Dehydration reaction in the synthesis of a polymer HO H 1 2 3 4
H2O
Short polymer
Unlinked monomer
Longer polymer
Dehydration removes a water molecule, forming a new bond
Figure 5.2A

7. (b) Hydrolysis of a polymer
Polymers can disassemble by
Hydrolysis
(b) Hydrolysis of a polymer HO 1 2 3 H 4
H2O
Hydrolysis adds a water molecule, breaking a bond
Figure 5.2B

8. Carbohydrates serve as:
Immediate source of food energy (fuel)
Building material for other molecules (energy source)
They include both:
Sugars (monomers) and
Sugar polymers

9. Carbohydrates Carbohydrates include: Monosaccharides: Disaccharides:
Single or simple sugars
Disaccharides:
Double sugars
Polysaccharides:
Long chain of sugar units

10. Sugars Monosaccharides Are the simplest sugars
Can be used for fuel (cellular)
Can be converted into other organic molecules
Can be combined into polymers
Named according to:
No. of C atoms, or
Funtional group

11. Examples of monosaccharides
Triose sugars (C3H6O3)
Pentose sugars (C5H10O5)
Hexose sugars (C6H12O6)
H C OH
H C OH
HO C H
H C OH
C O
HO C H H C O
Aldoses
Glyceraldehyde
Ribose
Glucose
Galactose
Dihydroxyacetone
Ribulose
Ketoses
Fructose
Figure 5.3

12. Monosaccharides May be linear Can form rings (in aqueous solution) 4C
H C OH
HO C H
H C O C 1 2 3 4 5 6 OH 4C
6CH2OH 5C
H OH
2 C 1C
3 C 2C
1 C
CH2OH HO
(a) Linear and ring forms. Chemical equilibrium between the linear and ring
structures greatly favors the formation of rings. To form the glucose ring,
carbon 1 bonds to the oxygen attached to carbon 5.
Figure 5.4

13. Disaccharides Consist of two monosaccharides A dehydration reaction
Monosaccharisdes are joined by:
a covalent bond, also called glycosidic linkage

14. Example of Disaccharides
Maltose:
Malt sugar
Made of two glucose units
Sucrose:
Table sugar
Made of glucose & fructose
Lactose:
Milk sugar
Made of glucose & galactose

15. Examples of disaccharides
Dehydration reaction in the synthesis of maltose. The bonding of two glucose units forms maltose. The glycosidic link joins the number 1 carbon of one glucose to the number 4 carbon of the second glucose. Joining the glucose monomers in a different way would result in a different disaccharide.
Dehydration reaction in the synthesis of sucrose. Sucrose is a disaccharide formed from glucose and fructose. Notice that fructose, though a hexose like glucose, forms a five-sided ring.
(a)
(b) H HO
H OH OH O
CH2OH
H2O 1 2 4
1– 4 glycosidic linkage
1–2 glycosidic linkage
Glucose
Fructose
Maltose
Sucrose
Figure 5.5

16. Polysaccharides Polysaccharides Are polymers of sugars
Serve many roles in organisms

17. Storage Polysaccharides
Starch
Consists entirely of glucose monomers
The major storage form of glucose in plants
Glycogen
Consists of glucose monomers
Is the major storage form of glucose in animals
Stored in:
Liver
muscles

18. (a) Starch: a plant polysaccharide
Chloroplast
Starch
Amylose
Amylopectin
1 m
(a) Starch: a plant polysaccharide
Figure 5.6

19. (b) Glycogen: an animal polysaccharide
Mitochondria
Giycogen granules
0.5 m
(b) Glycogen: an animal polysaccharide
Glycogen
Figure 5.6

20. Cellulose Is a polymer of glucose
Has different glycosidic linkages than starch
Indigestible by humans & simple stomach animals due to lack of cellulase enzyme
Digestible by ruminant animals thru microbes
(c) Cellulose: 1– 4 linkage of  glucose monomers H O
CH2OH OH HO 4 C 1
(a)  and  glucose ring structures
(b) Starch: 1– 4 linkage of  glucose monomers
 glucose
 glucose
Figure 5.7 A–C

21. Is a major component of the tough walls that enclose plant cells
Cell walls
Cellulose microfibrils
in a plant cell wall 
Microfibril
CH2OH OH O
Glucose monomer
Parallel cellulose molecules are
held together by hydrogen
bonds between hydroxyl
groups attached to carbon
atoms 3 and 6.
About 80 cellulose
molecules associate
to form a microfibril, the
main architectural unit
of the plant cell wall.
A cellulose molecule
is an unbranched 
glucose polymer.
Cellulose
molecules
Figure 5.8

22. Cellulose is difficult to digest
Cows have microbes in their stomachs to facilitate this process
Figure 5.9

23. Lipids Lipids: Are the one class of large biological molecules
They do not consist of polymers
Share the common trait of being hydrophobic
Include fats, phospholipid, and steroids

24. Fats perform essential functions in the human body:
Stored form of energy
Cushioning (internal organs)
Insulation (skin)

25. (a) Dehydration reaction in the synthesis of a fat
Fats
Fats
Are constructed from two types of smaller molecules, a single glycerol and usually three fatty acids H O H H H H H H H H H H H H H H H H
O H C OH
Glycerol
Fatty acid
(palmitic acid) HO O
(a) Dehydration reaction in the synthesis of a fat
Ester linkage
Figure 5.11
(b) Fat molecule (triacylglycerol)

26. Fatty acids Vary in the: Length of their chains
Number and locations of double bonds they contain

27. (a) Saturated fat and fatty acid
Saturated fatty acids
Have the maximum number of hydrogen atoms possible
Have no double bonds
Form fats (solid at room temp.)
(a) Saturated fat and fatty acid
Stearic acid
Figure 5.12

28. (b) Unsaturated fat and fatty acid
Unsaturated fatty acids
Have one or more double bonds
Form fat that is liquid (oils) at room temp.
(b) Unsaturated fat and fatty acid
cis double bond
causes bending
Oleic acid
Figure 5.12

29. Phospholipids Phospholipids
Have only two fatty acids (tail of the molecule)
Have a phosphate group instead of a third fatty acid (head of the molecule)

30. (a) Structural formula (b) Space-filling model
Phospholipid structure:
A polar hydrophilic “head”
A non polar hydrophobic “tails”
CH2 O P CH C
Phosphate
Glycerol
(a) Structural formula
(b) Space-filling model
Fatty acids
(c) Phospholipid
symbol
Hydrophobic tails
Hydrophilic
head
Hydrophobic
tails –
Hydrophilic head
Choline +
Figure 5.13
N(CH3)3

31. The structure of phospholipids
Results in a bilayer arrangement found in cell membranes
Hydrophilic
head
WATER
Hydrophobic
tail
Figure 5.14

32. Break Slide Biol1406.--------- ----/-----/2015