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2	Carbohydrates Carbohydrates have the general molecular formula CH₂O, "hydrated carbon". However, the arrangement of atoms in carbohydrates has little to do with water molecules.
3	Macromolecules Starch and cellulose are two common carbohydrates. Both are macromolecules with molecular weights in the hundreds of thousands. Both are polymers (hence "polysaccharides"); that is, each is built from repeating units, monomers, much as a chain is built from its links.
4	Glucose The monomers of both starch and cellulose are the same: units of the sugar glucose.
5	Sugars Monosaccharides Three common sugars share the same molecular formula: C₆H₁₂O₆. Because of their six carbon atoms, each is a hexose. glucose, "blood sugar", the immediate source of energy for cellular respiration
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10	"Glucose" Glucose, galactose, and fructose are "single" sugars or monosaccharides. Two monosaccharides can be linked together to form a "double" sugar or disaccharide.
11	DISACCHARIDES Three common disaccharides: sucrose — common table sugar = glucose + fructose lactose — major sugar in milk = glucose + galactose maltose — product of starch digestion = glucose + glucose
12	"Although the process of linking..." Although the process of linking the two monomers is rather complex, the end result in each case is the loss of a hydrogen atom (H) from one of the monosaccharides and a hydroxyl group (OH) from the other. The resulting linkage between the sugars is called a glycosidic bond. The molecular formula of each of these disaccharides is C₁₂H₂₂O₁₁ = 2 C₆H₁₂O₆ − H₂O
13	SOLUBILITY All sugars are very soluble in water because of their many hydroxyl groups. Although not as concentrated a fuel as fats, sugars are the most important source of energy for many cells.
14	ENERGY Carbohydrates provide the bulk of the calories (4 kcal/gram) in most diets, and starches provide the bulk of that. Starches are polysaccharides.
15	POLYSACCHARIDES Starches Starches are polymers of glucose. Two types are found: 1. amylose consists of linear, unbranched chains of several hundred glucose units. The glucose units are linked by a glycosidic bond
16	POLYSACCHARIDES Starches 2. Amylopectin differs from amylose in being highly branched. The total number of glucose units in a molecule of amylopectin is several thousand.
17	STARCHES Starches are insoluble in water and thus can serve as storage depots of glucose. Plants convert excess glucose into starch for storage.
18	STARCH DIGESTION Before starches can enter (or leave) cells, they must be digested. The hydrolysis of starch is done by amylases. With the aid of an amylase (such as pancreatic amylase), water molecules enter at the linkages, breaking the chain and eventually producing a mixture of glucose and maltose. A different amylase is needed to break the 1 -> 6 bonds of amylopectin.
19	GLYCOGEN Animals store excess glucose by polymerizing it to form glycogen. The structure of glycogen is similar to that of amylopectin, although the branches in glycogen tend to be shorter and more frequent. Glycogen is broken back down into glucose when energy is needed (a process called glycogenolysis).
20	GLYCOGENOLYSIS In glycogenolysis, phosphate groups — not water — break the 1 -> 4 linkages the phosphate group must then be removed so that glucose can leave the cell. The liver and skeletal muscle are major depots of glycogen.
21	CARBO’ LOADING There is some evidence that intense exercise and a high-carbohydrate diet ("carbo-loading") can increase the reserves of glycogen in the muscles and thus may help marathoners work their muscles somewhat longer and harder than otherwise. But for most of us, carbo loading leads to increased deposits of fat.
22	CELLULOSE Cellulose is probably the single most abundant organic molecule in the biosphere. It is the major structural material of which plants are made. Wood is largely cellulose while cotton and paper are almost pure cellulose.
23	CELLULOSE Like starch, cellulose is a polysaccharide with glucose as its monomer. Cellulose differs profoundly from starch in its properties. Orientation of the glycosidic bonds linking the glucose residues, the rings of glucose are arranged in a flip-flop manner. This produces a long, straight, rigid molecule. There are no side chains in cellulose as there are in starch. The absence of side chains allows these linear molecules to lie close together.
24	CELLULOSE Because of the many -OH groups, as well as the oxygen atom in the ring, there are many opportunities for hydrogen bonds to form between adjacent chains. The result is a series of stiff, elongated fibrils — the perfect material for building the cell walls of plants.
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27	Sugar Utilization by Our Bodies Some interesting statistics on sugar consumption: About 100 years ago, the average sugar consumption in our country was about 40 lb./person/year. As of 1986, when Laurel Robertson, et al. revised their book, Laurel’s Kitchen, Americans were averaging 1/3 lb. of sugar per person per day, which came to about 127 lb./person/year, mostly from soft drinks. According to the July 1998 issue of Better Nutrition, the average American sugar consumption has risen to 148 lb./person/yr, roughly 2¾ to 3 lb. per week!