1. The Molecules of Life Figures 3.8 – 3.15
CHAPTER 3
The Molecules of Life
Figures 3.8 – 3.15

2. There are four categories of large molecules in cells
BIOLOGICAL MOLECULES
There are four categories of large molecules in cells
Carbohydrates
Lipids
Proteins
Nucleic acids

3. Carbohydrates include
Small sugar molecules in soft drinks
Long starch molecules in pasta and potatoes

4. Monosaccharides are simple sugars
Glucose, found in sports drinks
Fructose, found in fruit
Honey contains both glucose and fructose
Figure 3.8

5. The monosaccharides glucose and fructose are isomers
Their atoms are arranged differently
Glucose
Fructose
Figure 3.9

6. In aqueous solutions, monosaccharides form rings
Monosaccharides are the main fuel that cells use for cellular work
(b) Abbreviated ring
structure
(a) Linear and ring
structures
Figure 3.10

7. A disaccharide is a double sugar
Disaccharides
A disaccharide is a double sugar
It is constructed from two monosaccharides

8. Disaccharides are joined by the process of dehydration synthesis
Glucose
Glucose
Maltose
Figure 3.11

9. The most common disaccharide is sucrose, common table sugar
It consists of a glucose linked to a fructose
Sucrose is extracted from sugar cane and the roots of sugar beets

10. The United States is one of the world’s leading markets for sweeteners
The average American consumes about 64 kg of sugar per year
Figure 3.12

11. Complex carbohydrates are called polysaccharides
They are long chains of sugar units
They are polymers of monosaccharides

12. Polysaccharides Glucose monomer (a) Starch (b) Glycogen (c) Cellulose
Starch granules in
potato tuber cells
(a) Starch
Glycogen
Granules
In muscle
tissue
(b) Glycogen
Cellulose fibril in
a plant cell wall
Cellulose molecules
(c) Cellulose
Figure 3.13

13. One familiar example of a polysaccharide is starch
Plant cells store starch for energy
Potatoes and grains are major sources of starch in the human diet

14. Animals store excess sugar in the form of a polysaccharide called glycogen
Glycogen is similar in structure to starch

15. Cellulose is the most abundant organic compound on Earth
It forms cable-like fibrils in the tough walls that enclose plants
It is a major component of wood
It is also known as dietary fiber

16. Most animals cannot derive nutrition from fiber
How do grazing animals survive on a diet of cellulose?
They have bacteria in their digestive tracts that can break down cellulose
Figure 3.14

17. Simple sugars and double sugars dissolve readily in water
They are hydrophilic, or “water-loving”

18. Lipids are hydrophobic
They do not mix with water
Examples: fats and steroids

19. Dietary fat consists largely of the molecule triglyceride
Fats
Dietary fat consists largely of the molecule triglyceride
A combination of glycerol and three fatty acids
Fatty acid
Glycerol
(a) Dehydration synthesis linking a fatty acid to glycerol
Figure 3.15a

20. Fats perform essential functions in the human body
Energy storage
Cushioning
Insulation

21. Unsaturated fatty acids
Have less than the maximum number of hydrogens bonded to the carbons
Saturated fatty acids
Have the maximum number of hydrogens bonded to the carbons

22. (b) A fat molecule
Figure 3.15B

23. Most animal fats have a high proportion of saturated fatty acids
Example: butter
Most plant oils tend to be low in saturated fatty acids
Example: corn oil