Preview

1. Chapter 23 Preview Lesson Starter Objectives Carbohydrates Lipids

2. Section 1 Carbohydrates and Lipids Chapter 23 Lesson Starter Why does the can of diet soft drink float and the can of regular soft drink sink? The aspartame used to sweeten the diet soft drink is about 200 times as sweet as sucrose. The regular soft drink is denser than the diet soft drink, because there is such a large amount of sugar in the regular soft drink, and only a small amount of sweetener in the diet soft drink.

3. Section 1 Carbohydrates and Lipids Chapter 23 Objectives Describe the structural characteristics of simple carbohydrates and complex carbohydrates. Explain the role of carbohydrates in living systems. Describe the structural characteristics of lipid molecules. Identify the functions of lipids in living cells.

4. Section 1 Carbohydrates and Lipids Chapter 23 Biochemistry is the study of the chemicals and reactions that occur in living things. Biochemical compounds are often large and complex organic molecules, but their chemistry is similar to that of the smaller organic molecules

5. Section 1 Carbohydrates and Lipids Chapter 23 Carbohydrates • Carbohydratesare 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.

6. Section 1 Carbohydrates and Lipids Chapter 23 Carbohydrates Click below to watch the Visual Concept. Visual Concept

7. Section 1 Carbohydrates and Lipids Chapter 23 Typesof Carbohydrates

8. Section 1 Carbohydrates and Lipids Chapter 23 Carbohydrates, continued Monosaccharides • A monosaccharideis 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

9. Section 1 Carbohydrates and Lipids Chapter 23 Carbohydrates, continued Monosaccharides, continued • The most common monosaccharides are glucose (also called dextrose) and fructose. • Both have the formula C6(H2O)6. • Their structural formulas differ.

10. Section 1 Carbohydrates and Lipids Chapter 23 Structures of Carbohydrates

11. Section 1 Carbohydrates and Lipids Chapter 23 Monosaccharides Click below to watch the Visual Concept. Visual Concept

12. Section 1 Carbohydrates and Lipids Chapter 23 Carbohydrates, continued Disaccharides • A disaccharideis 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.

13. Section 1 Carbohydrates and Lipids Chapter 23 Disaccharides Click below to watch the Visual Concept. Visual Concept

14. Section 1 Carbohydrates and Lipids Chapter 23 Carbohydrates, continued Carbohydrate Reactions Carbohydrates undergo two important kinds of reactions: condensation reactions and hydrolysis reactions. A condensation reactionis a reaction in which two molecules or parts of the same molecule combine.

15. Section 1 Carbohydrates and Lipids Chapter 23 Carbohydrates, continued Carbohydrate Reactions, continued • Hydrolysisis 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.

16. Section 1 Carbohydrates and Lipids Chapter 23 Cation Hydrolysis Click below to watch the Visual Concept. Visual Concept

17. Section 1 Carbohydrates and Lipids Chapter 23 Anion Hydrolysis Click below to watch the Visual Concept. Visual Concept

18. Section 1 Carbohydrates and Lipids Chapter 23 Carbohydrates, continued Polysaccharides • When many monosaccharides or disaccharides combine in a series of condensation reactions, they form a polysaccharide. • A polysaccharideis a carbohydrate made up of long chains of simple sugars. • Cellulose, starch, and glycogen are polymersof glucose. • Sheets of cellulose make up plant cell walls. • Starch is the storage form of glucose in plants.

19. Section 1 Carbohydrates and Lipids Chapter 23 Carbohydrates, continued Polysaccharides, continued Glycogen, cellulose, and starch differ in their arrangement of glucose monomers.

20. Section 1 Carbohydrates and Lipids Chapter 23 Lipids A lipidis a type of biochemical that does not dissolve in water, has a high percentage of C and H atoms, and is soluble in nonpolar solvents. As a class, lipids are not nearly as similar to each other as carbohydrates are. Long-chain fatty acids, phospholipids, steroids, and cholesterol are lipids.

21. Section 1 Carbohydrates and Lipids Chapter 23 Types of Lipids Click below to watch the Visual Concept. Visual Concept

22. hydrophilic region hydrophobic region Section 1 Carbohydrates and Lipids Chapter 23 Lipids, continued Fatty Acids and Triglycerides • Fatty acidsconsist of a long, nonpolar hydrocarbon “tail” and a polar carboxylic acid functional group at the “head.” • They have hydrophilic polar heads, but their hydrocarbon chains make them insoluble in water.

23. Section 1 Carbohydrates and Lipids Chapter 23 Lipids, continued Fatty Acids and Triglycerides, continued • Triglycerides are formed by condensation reactions in which three fatty acid molecules bond to one glycerol (a type of alcohol) molecule. • Fats and oils that are the most common group of lipids in your diet. • Because they have a large amount of saturated fatty acids, fats are solids at room temperature. • Oils have more unsaturated fatty acids than fats, and are liquids • Fat is stored in adipose tissue until it is needed as an energy source.

24. Section 1 Carbohydrates and Lipids Chapter 23 Lipids, continued Fatty Acids and Triglycerides, continued When a fat combines with NaOH, an acid-base reaction called saponificationoccurs, and a salt and water form. This salt is made up of molecules that have long carboxylic acid chains and is called soap. Lipids that react with a base to form soap are called saponifiable lipids, which include fats, oils, and fatty acids.

25. Section 1 Carbohydrates and Lipids Chapter 23 Lipids, continued Other Important Lipids • Compound saponifiable lipidsplay an important role in biochemical processes. • These lipids are structurally similar to triglycerides in that at least one fatty acid is bonded to the central glycerol or glycerol-like unit. • These molecules may also have phosphate groups, sugar units, or nitrogen containing groups. • Phospholipids, are compound saponifiable lipids and are the main structural component of cell membranes.

26. Section 1 Carbohydrates and Lipids Chapter 23 Lipids, continued Other Important Lipids, continued Phospholipids are arranged in a bilayer,or double layer, at the surface of the cell.

27. Section 1 Carbohydrates and Lipids Chapter 23 Lipids, continued Other Important Lipids, continued Nonsaponifiablelipids are nonpolar compounds that do not form soap. • steroids, many vitamins, and bile acids • Cholesterolis a steroid present in animal cell membranes and is a precursor of many hormones.

28. Section 2 Amino Acids and Proteins Chapter 23 Preview Lesson Starter Objectives Amino Acids Proteins Proteins as Enzymes

29. O R–C–OH R–N–R˝ R´ + + H2O Section 2 Amino Acids and Proteins Chapter 23 Lesson Starter carboxylic acid amine condensation reaction to form dipeptide bond

30. Section 2 Amino Acids and Proteins Chapter 23 Objectives Describe the basic structure of amino acids and the formation of polypeptides. Determine the significance of amino acid side chains to the three-dimensional structure of a protein and the function of a protein. Describe the functions of proteins in cells. Identify the effects of enzymes on biological molecules.

31. Section 2 Amino Acids and Proteins Chapter 23 • Amino acid molecules are the basic building blocks of proteins. • More than 700 types of amino acids occur in nature. • Only 20 types of amino acids are found in human proteins. • The human body can synthesize only 11 of the 20 amino acids as needed. • The other nine, called the essential amino acids,have to be supplied by the food that we eat.

32. Section 2 Amino Acids and Proteins Chapter 23 Amino Acids Amino acidsare organic molecules that contain two functional groups: a basic —NH2 amino group and an acidic —COOH carboxylic acid group. or The R-groups of the amino acids present in a protein determine the protein’s biological activity.

33. Structures of Amino Acids Section 2 Amino Acids and Proteins Chapter 23

34. Section 2 Amino Acids and Proteins Chapter 23 Amino Acid Click below to watch the Visual Concept. Visual Concept

35. Section 2 Amino Acids and Proteins Chapter 23 Amino Acids, continued Amino Acid Reactions • Two amino acids can react with each other in an acid-base reaction. • The basic amino group of one amino acid reacts with the acidic carboxylic acid group of another amino acid to form a peptide,and a molecule of water is lost. • This reaction is classified as a condensation reaction • The bond formed is called a peptide bond. • The product is a dipeptide.

36. Section 2 Amino Acids and Proteins Chapter 23 Formation of Dipeptides and Polypeptides Click below to watch the Visual Concept. Visual Concept

37. + + H2O Section 2 Amino Acids and Proteins Chapter 23 Amino Acids, continued Amino Acid Reactions, continued

38. Section 2 Amino Acids and Proteins Chapter 23 Amino Acids, continued Amino Acid Reactions Longer chains of amino acids are called polypeptides. Chains of 50 or more amino acids are called proteins. Peptide bonds can be broken, or hydrolyzed,by enzymes called proteases.

39. Section 2 Amino Acids and Proteins Chapter 23 Proteins • Proteins are the most complex and varied class of biochemical molecules. • A proteinis an organic biological polymer that is made up of polypeptide chains of 50 or more amino acids and is an important building block of all cells. • Proteins are made up of specific sequences of amino acids. • They have molecular masses that range from 6000 to more than 9 million atomic mass units. • About 9000 different protein molecules are found in cells in the human body.

40. Section 2 Amino Acids and Proteins Chapter 23 Proteins Click below to watch the Visual Concept. Visual Concept

41. Section 2 Amino Acids and Proteins Chapter 23 Proteins, continued • Nitrogen accounts for about 15% of the mass of a protein molecule. Most proteins also contain sulfur. Some contain phosphorus or other elements, such as iron, zinc, and copper. • Proteins have many important catalytic, structural, regulatory, and antibody defense functions. • Keratinis the main component of hair and fingernails. • Enzymes catalyze biochemical reactions. • Hemoglobin carries oxygen in the blood. • Insulinregulates glucose levels. • Antibodies protect the body from foreign substances.

42. Section 2 Amino Acids and Proteins Chapter 23 Proteins, continued Arrangement of Amino Acids in Peptides and Proteins • Each peptide, polypeptide, or protein is made up of a special sequence of amino acids. • A simple set of three-letter abbreviations is used to represent each amino acid in these kinds of molecules. • The tripeptide made up of valine, asparagine, and histidine would be written as Val–Asp–His. • Polypeptide and protein function depend not only on the kinds and number of amino acids but also on their order.

43. Section 2 Amino Acids and Proteins Chapter 23 Proteins, continued Amino Acid Side-Chain Reactions • The properties of amino acids—and ultimately polypeptides and proteins—depend on the properties of the side chains present. • The side chain of glutamic acid is acidic. • The side chain of histidine is basic. • The side chains of asparagine and several other amino acids are polar. • Some amino acid side chains can form ionic or covalent bonds with other side chains.

44. Section 2 Amino Acids and Proteins Chapter 23 Proteins, continued Amino Acid Side-Chain Reactions, continued Cysteine is a unique amino acid, because the —SH group in cysteine can form a covalent bond with another cysteine side chain to form a disulfide bridge.

45. Section 2 Amino Acids and Proteins Chapter 23 Proteins, continued Shape and Structure of Protein Molecules • The interaction of amino acid side chains determines the shape and structure of proteins. • These are important to the proteins’ biological functions. • In a polypeptide chain or protein, the sequence of the amino acids is called the primary (1°) structure. • The secondary (2°) structuredescribes how the chain is coiled or otherwise arranged in space.

46. Section 2 Amino Acids and Proteins Chapter 23 Proteins, continued Shape and Structure of Protein Molecules, continued • Secondary structures form because hydrogen bonding occurs between a hydrogen atom attached to the nitrogen atom in one peptide bond and the oxygen atom of another peptide bond farther down the backbone of the protein. • The alpha (α) helix is a secondary structure that resembles a coiled spring. • The beta (β) pleated sheet is a secondary structure that has accordion-like folds.

47. Section 2 Amino Acids and Proteins Chapter 23 Proteins, continued Shape and Structure of Protein Molecules, continued • A protein’s characteristic three-dimensional shape is called its tertiary (3°) structure. • Side-chain interactions at various positions along the protein backbone cause the tertiary structure. • The side-chain interactions can include • hydrogen bonding • salt bridges • cysteine-cysteine disulfide bonds • hydrophobic interactions between nonpolar side chains

48. Section 2 Amino Acids and Proteins Chapter 23 Proteins, continued Shape and Structure of Protein Molecules, continued • Nonpolar side groups tend to be found in the interior of the protein where contact with water is minimal. • Polar and ionic side chains tend to be on the protein surface, where they are in contact with water. • In some proteins, different polypeptides, each of which has its own 3° structure, come together. • In the case of hemoglobin, four different polypeptides make up the quaternary (4°) structure.

49. Levels of Protein Structure Section 2 Amino Acids and Proteins Chapter 23

50. Section 2 Amino Acids and Proteins Chapter 23 Proteins, continued Biological Functions of Proteins