Chapter 24 The Chemistry of Life 24.2 Carbohydrates 24.1 A Basis for Life 24.2 Carbohydrates 24.3 Amino Acids and Their Polymers 24.4 Lipids 24.5 Nucleic Acids 24.6 Metabolism Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Why does a cow chew all day? CHEMISTRY & YOU Why does a cow chew all day? A cow’s diet is rich in cellulose, which belongs to a class of organic molecules known as carbohydrates. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates What is the general formula of carbohydrates? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Long-distance runners often prepare for a race by eating a great deal of bread and pasta, a process called carbohydrate loading. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Long-distance runners often prepare for a race by eating a great deal of bread and pasta, a process called carbohydrate loading. Breads and pastas are excellent sources of the family of important molecules called carbohydrates. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Long-distance runners often prepare for a race by eating a great deal of bread and pasta, a process called carbohydrate loading. Breads and pastas are excellent sources of the family of important molecules called carbohydrates. Carbohydrates are monomers and polymers of aldehydes and ketones that have numerous hydroxyl groups attached; they are made up of carbon, hydrogen, and oxygen. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Most carbohydrates have the general formula Cn(H2O)n. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Most carbohydrates have the general formula Cn(H2O)n. The name carbohydrate comes from the early observation that because of the formula, Cn(H2O)n, the compounds appear to be hydrates of carbon. But carbohydrates are not true hydrates. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Carbohydrates are the main source of energy for the body. They are found in most foods, including fruits, breads, pastas, and legumes. Carbohydrates are also in many sweets, such as cookies and pies. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Monosaccharides The simplest carbohydrate molecules are called simple sugars, or monosaccharides. Glucose and fructose are examples of simple sugars. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Monosaccharides Glucose is abundant in plants and animals. Glucose is the primary source of energy for our bodies. Depending on the source, glucose has also been called corn sugar, grape sugar, or blood sugar. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Monosaccharides Fructose occurs in a large number of fruits and in honey. Glucose and fructose both have the molecular formula C6H12O6. However, glucose has an aldehyde functional group, whereas fructose has a ketone functional group. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Monosaccharides Glucose and fructose are constitutional isomers. Both undergo many of the same reactions as ordinary aldehydes and ketones. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Monosaccharides In aqueous solution, simple sugars such as glucose and fructose exist in a dynamic equilibrium between straight-chain and cyclic forms. The cyclic form predominates. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Monosaccharides The structures for each sugar in both forms are below. Straight-chain and cyclic forms of glucose Straight-chain and cyclic forms of fructose Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Monosaccharides O Note the aldehyde functional group (—CHO) on the straight-chain form of glucose and the ketone functional group (—C—) on the straight-chain form of fructose. Straight-chain and cyclic forms of glucose Straight-chain and cyclic forms of fructose Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Disaccharides Simple sugars form the building blocks of more complex carbohydrates. The cyclic forms of two simple sugars can be linked by means of a condensation reaction. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Disaccharides The linking of glucose and fructose with the loss of a water molecule produces sucrose—common table sugar. Glucose + Fructose Sucrose –H2O Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Disaccharides Sugarcane plants are a major source of sucrose. A sugar such as sucrose that forms from the condensation of two monosaccharides is known as a disaccharide. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Polysaccharides The formation of a disaccharide is sometimes the first step in a condensation polymerization reaction that produces extremely large molecules. The polymers produced by the linkage of many monosaccharide monomers are called polysaccharides. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Polysaccharides Starches, the major storage form of glucose in plants, are polysaccharide polymers that consist of glucose monomers. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Polysaccharides A typical linear starch molecule contains hundreds of glucose monomers. Other starches are branched molecules, each branch containing about a dozen glucose units. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Polysaccharides Glycogen, the energy source stored in the liver and muscles of cells of animals, is more highly branched than plant starches. Glycogen, too, consists of glucose monomers. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Polysaccharides Cellulose is probably the most abundant biological molecule on Earth. Cellulose is also a polymer of glucose. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Polysaccharides The orientation of the bond that links the glucose monomers in cellulose is different from the bond orientation in glycogen. Starch can be digested by most animals and is partially soluble in water. Cellulose, however, can be digested by only a few kinds of microorganisms, such as those that live in the digestive tracts of cattle and termites. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Classifying Carbohydrates Polysaccharides Cellulose is insoluble in water and is an important structural polysaccharide that provides form, hardness, and rigidity in plants. Plant cell walls are made of cellulose. Cotton is 80 percent cellulose. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

CHEMISTRY & YOU A cow’s diet consists mostly of cellulose. A cow’s stomach contains several parts. Food enters the first part of the stomach and is then regurgitated so the cow can chew it again. The regurgitated food then goes to a later part of the stomach where special bacteria live. Why is chewing and regurgitating necessary for a cow to digest cellulose? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

CHEMISTRY & YOU Why is chewing and regurgitating necessary for a cow to digest cellulose? Cellulose is hard to break down. It is digested by the bacteria that live in part of a cow’s stomach. Chewing, regurgitating, and chewing again breaks down the plants cows eat into small particles with lots of exposed surface area that can be digested by the bacteria. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

What are some common examples of the three classes of carbohydrates discussed in this lesson? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

What are some common examples of the three classes of carbohydrates discussed in this lesson? Glucose and fructose are common monosaccharides. Sucrose is a common disaccharide. Starch and cellulose are common polysaccharides. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Most carbohydrates have the general formula Cn(H2O)n. Key Concepts Most carbohydrates have the general formula Cn(H2O)n. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Glossary Terms carbohydrate: the name given to monomers and polymers of aldehydes and ketones that have numerous hydroxyl groups; sugars and starches are carbohydrates monosaccharide: a carbohydrate consisting of one sugar unit; also called a simple sugar Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Glossary Terms disaccharide: a carbohydrate formed from two monosaccharide units; common table sugar (sucrose) is a disaccharide polysaccharide: a complex carbohydrate polymer formed by the linkage of many monosaccharide monomers; starch, glycogen, and cellulose are polysaccharides Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

Chemistry as the Central Science BIG IDEA Chemistry as the Central Science Most carbohydrates are polymers that release energy when broken down. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .

END OF 24.2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. .