Cellulose is another complex carbohydrate that is a polymer of glucose. However, glucose molecules are bonded together differently in cellulose than they are in starches. Cellulose molecules bundle together to form long, tough fibers, as you can see in the Figure 1.3. Have you ever eaten raw celery? If you have, then you probably noticed that Foods that are good sources of starches. the stalks contain long, stringy fibers. The fibers are mostly cellulose. Cellulose is the most abundant biochemical compound. It makes up the cell walls of plants and gives support to stems and tree trunks. Cellulose also provides needed fiber in the human diet. We cant digest cellulose, but it helps keep food wastes moving through the digestive tract.
Starches are complex carbohydrates. They are polymers of glucose. A polymer is a large molecule that consists of many smaller, repeating molecules, called monomers. The monomers are joined together by covalent bonds. Starches contain hundreds of glucose monomers. Plants make starches to store extra glucose. Consumers get starches by eating plants. Common sources of starches in the human diet are pictured in the Figure 1.2. Our digestive system breaks down starches to sugar, which our cells use for energy.
Sugars are simple carbohydrates. Molecules of sugars have relatively few carbon atoms. Glucose (C6 H12 O6 ) is one of the smallest sugar molecules. Plants and some other organisms make glucose in the process of photosynthesis. Living things that cannot make glucose obtain it by consuming plants or these other organisms. In the Figure 1.1, you can see structural formulas for glucose and two other sugars, named fructose and sucrose. Fructose is a sugar that is found in fruits. It is an isomer of glucose. Isomers are compounds that have the same atoms but different arrangements of atoms. Do you see how the atoms are arranged differently in fructose than in glucose? Youre probably most familiar with the sugar sucrose, because sucrose is table sugar. Its the sugar that you spoon onto your cereal or into your iced tea. Q: Compare the structure of sucrose with the structures of glucose and fructose. How is sucrose related to the other two sugars? A: Sucrose consists of one molecule of glucose and one molecule of fructose bonded together.
what are carbohydrates
Carbohydrates are one of four classes of biochemical compounds. The other three classes are proteins, lipids, and nucleic acids. In addition to cellulose, carbohydrates include sugars and starches. Carbohydrate molecules contain atoms of carbon, hydrogen, and oxygen. Living things use carbohydrates mainly for energy. Q: Which carbohydrates do you use for energy? A: You may eat a wide variety of carbohydratesfrom sugars in fruits to starches in potatoes. However, body cells use only sugars for energy.
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carbohydrates consist of atoms of
a) carbon. b) hydrogen. c) oxygen. --> d) all of the above
plants stores extra glucose as starches.
--> a. true b. false
cellulose is a polymer of starch.
a. true --> b. false
No diagram questions associated with this lesson