carbohydrates the simplest carbohydrates are the simple sugars, or monosaccharides, which commonly...

carbohydrates

• The simplest carbohydrates are the simple sugars, or monosaccharides, which commonly have five or six carbon atoms.

Monosaccharides

Biochemistry: Basic ConceptsBiochemistry: Basic ConceptsBiochemistry: Basic ConceptsBiochemistry: Basic Concepts

• Glucose, the main ingredient in corn syrup, is a familiar monosaccharide.

Topic 25Topic 25

Carbohydrates

• Carbohydrates are molecules that are composed of carbon, hydrogen, and oxygen atoms in a 1:2:1 ratio, and provide nutrients to the cells of living things.

• sugars, starches, and cellulose

• Carbohydrates are produced by plants through a process called photosynthesis.

• Carbohydrates provide nearly all of the energy that is available in most plant-derived food.

Section 1 Carbohydrates and LipidsChapter 23

Types of Carbohydrates

Section 1 Carbohydrates and LipidsChapter 23

Carbohydrates, continuedMonosaccharides

• A monosaccharide is a simple sugar that is the basic subunit of a carbohydrate.

• A single monosaccharide molecule contains three to seven carbon atoms.

• Monosaccharide compounds are

• typically sweet-tasting

• white solids at room temperature

• water soluble

Section 1 Carbohydrates and LipidsChapter 23

• Glucose has the molecular formula C6H12O6 and can be represented by the following structures.

Monosaccharides

Biochemistry: Basic ConceptsBiochemistry: Basic ConceptsBiochemistry: Basic ConceptsBiochemistry: Basic ConceptsTopic 25Topic 25

• The most common simple sugars are glucose, fructose, and ribose.

Monosaccharides

Biochemistry: Basic ConceptsBiochemistry: Basic ConceptsBiochemistry: Basic ConceptsBiochemistry: Basic ConceptsTopic 25Topic 25

• Food source for most organisms and structural material for plants.

• Empirical formula = CH2O

• Monosaccharides (simple sugars)– pentoses - ribose, arabinose– hexoses - fructose, glucose

• SUGARS IN STRUCTURES

• An important structural polysaccharide is cellulose. Cellulose is found in plants. It is one of those carbohydrates used to support or protect an organism. Cellulose is in wood and the cell walls of plants.

Carbohydrates, continuedMonosaccharides, continued

• The most common monosaccharides are glucose (also called dextrose) and fructose.

• Both have the formula C6(H2O)6.

• Their structural formulas differ.

Section 1 Carbohydrates and LipidsChapter 23

• Disaccharides (formed from 2 monosaccharides joined by a glycoside linkage)

sucrose (glucose + fructose)

• Polysaccharides (many monosaccharide units)

starch, cellulose

Carbohydrates, continuedDisaccharides

• A disaccharide is a sugar that consists of two monosaccharide units that are joined together.

• sucrose, C12H22O11

• A molecule of sucrose forms when a glucose molecule bonds to a fructose molecule.

• lactose • Lactose is made up of a sugar called galactose and

glucose.

Section 1 Carbohydrates and LipidsChapter 23

Carbohydrates, continuedPolysaccharides

• When many monosaccharides or disaccharides combine in a series of condensation reactions, they form a polysaccharide.

• A polysaccharide is a carbohydrate made up of long chains of simple sugars.

• Cellulose, starch, and glycogen are polymers of glucose.

• Sheets of cellulose make up plant cell walls.• Starch is the storage form of glucose in plants.

Section 1 Carbohydrates and LipidsChapter 23

• A polymer of many monosaccharides bonded into a chain is called a polysaccharide.

Polysaccharides

Biochemistry: Basic ConceptsBiochemistry: Basic ConceptsBiochemistry: Basic ConceptsBiochemistry: Basic Concepts

• Starch is a polysaccharide that consists only of glucose units.

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Polysaccharides

Biochemistry: Basic ConceptsBiochemistry: Basic ConceptsBiochemistry: Basic ConceptsBiochemistry: Basic ConceptsTopic 25Topic 25

• Plants also link glucose units together in a different way to form the polysaccharidecellulose, which forms plant cell walls.

• Animals store glucose as a polysaccharide called glycogen, which is similar to starch.

Polysaccharides

Biochemistry: Basic ConceptsBiochemistry: Basic ConceptsBiochemistry: Basic ConceptsBiochemistry: Basic ConceptsTopic 25Topic 25

Carbohydrates, continuedPolysaccharides, continued

• Glycogen, cellulose, and starch differ in their arrangement of glucose monomers.

Section 1 Carbohydrates and LipidsChapter 23

Carbohydrates, continuedCarbohydrate Reactions

• Carbohydrates undergo two important kinds of reactions: condensation reactions and hydrolysis reactions.

Section 1 Carbohydrates and LipidsChapter 23

• A condensation reaction is a reaction in which two molecules or parts of the same molecule combine.

Carbohydrates, continuedCarbohydrate Reactions, continued

• Hydrolysis is a chemical reaction between water and another substance to form two or more new substances.

• Disaccharides and longer-chain polysaccharides can be broken down into smaller sugar units by hydrolysis.

Section 1 Carbohydrates and LipidsChapter 23

• Polysaccharides are also used in the shells of such crustaceans as crabs and lobsters (chitin). It is similar in some ways to the structure of cellulose but has a far different use. The shells are solid, protective structures that need to be molted (left behind) when the crustacean needs to grow. It is very inflexible. On the other hand, it is very resistant to damage. While a plant may burn, it takes very high temperatures to hurt the shell of a crab.