CHAPTER 3 The Molecules of Cells

1. CHAPTER 3The Molecules of Cells Modules 3.4 – 3.10

2. The monomers, the polymers and the macromolecules……. • For each of the four macromolecules we will fill in an organizer to study from. We will start with the simple sugars which, when linked together, form the carbohydrates.

3. 3.4 Monosaccharides are the simplest carbohydrates. They are the monomers. • Monosaccharides are single-unit sugars • These molecules typically have a formula that is a multiple of CH2O . Their formula is C6H12O6. • Each molecule contains hydroxyl groups and a carbonyl group as their functional group. The hydroxyl group renders most sugars hydrophillic or water loving. • Monosaccharides are the fuels for cellular work Figure 3.4A

4. They contain the same atoms but in different arrangements • The monosaccharides glucose, galactose and fructose are isomers Glucose Fructose Galactose Figure 3.4B

5. Many monosaccharides form rings, as shown here for glucose Abbreviatedstructure Figure 3.4C

6. 3.5 Cells link single sugars to form disaccharides through dehydration synthesis. • Monosaccharides can join to form disaccharides, such as sucrose (table sugar) and maltose (brewing sugar) and lactose (milk sugar) Sucrose=fruc-tose + glucose Glucose Glucose Maltose lactose

7. 3.6 Connection: How sweet is sweet? • Various types of molecules, including non-sugars, taste sweet because they bind to “sweet” receptors on the tongue. The tighter they bind the receptors, the sweeter the taste. Table 3.6

8. CARBOHYDRATES • Carbohydrates are a class of molecules • They range from small sugars to large polysaccharides • Polysaccharides are long polymers of monomers linked by dehydration synthesis.

9. Cellulose (plants) is a polysaccharide in plant cell walls. It passes as “fiber” through our digestive tract for most animals can not hydrolyze it. How do termites and cows get nutrients from plants???? Hum…. • Starch (plants) and glycogen (animals) are polysaccharides that store sugar for later use Starch granules in potato tuber cells Glucosemonomer STARCH Glycogen granules in muscle tissue GLYCOGEN Cellulose fibrils ina plant cell wall CELLULOSE Cellulosemolecules Figure 3.7

10. Carbohydrate morphology • Starch- coils of branched glucose, plants use it for energy. • Cellulose-rods of chains of glucose most abundant organic compound. B-glycosidic bonds prevent mammals from breaking it down to obtain glucose. • Glycogen-stored in liver more branched than starch. Hydrolyzed in liver and digestive tract.

11. 3.8 Lipids include fats, which are mostly energy-storage molecules • These compounds are composed largely of carbon and hydrogen • They are not true polymers • They are grouped together because they do not mix with water. They are hydrophobic. • Fats, oils, phospholipids and waxes are composed of glycerol and fatty acids. Figure 3.8A

12. Triglycerides= 3 fatty acid chains and a glycerol. A triglyceride molecule consists of one glycerol molecule linked to three fatty acids • Fats are triglycerides whose main function is energy storage in animals. Oils are analogous in plants. Fatty acid Figure 3.8B

13. These unsaturated fats form kinks which prevent them from solidifying at room temperature as they can not pack tightly together. They are better for you than saturated fats. • Saturated fatty acid chains (common in animal lard) lack double bonds. They are solid at room temperature. They should be limited in the diet as they can pack tightly together and clog arteries and veins. • Unsaturated fatty acid chains (common in plant oils) contain double bonds. Figure 3.8C

14. 3.9 Phospholipids, waxes, and steroids are lipids with a variety of functions • Phospholipids are a major component of cell membranes. They are composed of two fatty acid chains and a glycerol. • Waxes form waterproof coatings. They are composed of one fatty acid chain and a glycerol. Waxes are found on plants and in your ears. • Steroids are often hormones Figure 3.9

15. 3.10 Connection: Anabolic steroids and related substances pose health risks • Anabolic steroids are usually synthetic variants of testosterone • Use of these substances can cause serious health problems Figure 3.10