Biochemistry is the study of the chemicals and reactions that occur in living things.

1. 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

2. 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.

3. 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

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

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

10. 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.

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.

20. 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.

21. 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.

22. 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.

23. 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.

24. 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.

25. Section 2 Amino Acids and Proteins Chapter 23 Proteins, continued Amino Acid Substitution • A single substitution of one amino acid for another can change the shape and function of a protein. • The genetic disease sickle cell anemia can happen when glutamic acid—is replaced by valine.

26. Section 2 Amino Acids and Proteins Chapter 23 Proteins as Enzymes • An enzyme is a protein that catalyzes a biochemical reaction. • Enzymes make up the largest and most highly specialized class of proteins. • Most enzymes are water-soluble, globular proteins. • The amino acid side chains and the three-dimensional shape of enzymes play a very important role in the enzymatic activity.

27. Section 2 Amino Acids and Proteins Chapter 23 Proteins as Enzymes, continued • An enzyme also does not change the amount of product that is formed in a reaction; it only decreases the time it takes to form the product. • Enzymes catalyze both decomposition and synthesis reactions. • Enzymes are very efficient. • A single molecule of carbonic anhydrase can break down 36 million carbonic acid molecules in 1 minute.

28. Section 2 Amino Acids and Proteins Chapter 23 Proteins as Enzymes, continued Enzyme Specificity • Enzymes are very specific and often catalyze just a single reaction. • Enzymes act by binding to a specific substrate molecule. • The shape of the enzyme is such that the substrate can fit into the enzyme at a specific part of the enzyme molecule, called the active site.

29. Section 2 Amino Acids and Proteins Chapter 23 Proteins as Enzymes, continued Enzyme Specificity • The resulting compound is called the enzyme-substrate complex. • This model of enzyme action is called the lock and key model.

30. Section 2 Amino Acids and Proteins Chapter 23 Proteins as Enzymes, continued Enzymes and Reaction Rates • The presence of an enzyme in a chemical reaction can increase the rate of a reaction by a factor of up to 1020. • Only collisions that have enough energy to overcome the activation energy and have the proper orientation change reactants into products. • Enzymes lower the activation energy by forming the enzyme-substrate complex, which makes breaking bonds in the reactants and forming new bonds in the products easier.

31. Section 2 Amino Acids and Proteins Chapter 23 Proteins as Enzymes, continued Temperature and Enzyme Activity • Enzymes typically have maximum activity within a relatively narrow range of temperatures. • Enzymes in the human body work optimally at the normal body temperature of 37°C (98.6°F).

32. Section 2 Amino Acids and Proteins Chapter 23 Proteins as Enzymes, continued Temperature and Enzyme Activity • High heat can denature, or alter, the shape of a protein, which in turn alters the protein’s function. • Denaturationis a change in a protein’s characteristic three-dimensional shape due to changes of its secondary, tertiary, and quaternary structure. • example: cooking an egg

33. Section 2 Amino Acids and Proteins Chapter 23 Proteins as Enzymes, continued pH and Enzyme Activity • The optimal pH for normal cell enzyme functions is almost neutral, about 7.3 to 7.4. • Changes in pH can cause changes in protein structure and shape. • Most enzymes become inactivated, or no longer work, because of denaturation when the pH changes.

34. Section 2 Amino Acids and Proteins Chapter 23 Proteins as Enzymes, continued pH and Enzyme Activity, continued • Pre-enzymes,inactive forms of protein-digesting enzymes, become activated by the stomach’s low pH of 1.5 to 2.0. This prevents the active form of the enzymes from digesting the stomach lining. • Pepsin is a stomach enzyme found in adults.