The Living Cell

2. The Living Cell Biochemistry is the chemistry of living things and life processes.

3. The Living Cell The basic structural unit of all living organisms is the cell. All cells are enclosed in a cell membrane, which regulates the passage of nutrients and wastes. In addition to a cell membrane, plant cells are surrounded by a cell wall composed of cellulose.

4. The Living Cell Nucleus: The nucleus contains the genetic material that controls heredity. Ribosomes: The structure where protein synthesis occurs. Mitochrondria: The cell structure where energy production occurs. Chloroplasts: Found only in plant cells. In the chloroplasts, photosynthesis occurs.

5. The Living Cell Plant Cell

6. The Living Cell Animal Cell

7. Energy in Biological Systems Green plants contain chloroplasts, which are capable of taking the radiant energy of the sun and storing it as chemical energy in glucose molecules. 6 CO2 + 6 H2O → C6H12O6 + 6 O2 Plant cells can also convert carbohydrate molecules to fat molecules, and some are even capable of converting them to proteins. Animals cannot produce their own energy. They must obtain such energy by eating plants or other animals that eat plants.

8. Energy in Biological Systems Metabolism is defined as the series of chemical reactions that keep a cell alive. Metabolic reactions are divided into two categories: • Catabolism: The process of breaking down molecules to produce energy. • Anabolism: The process of synthesizing molecules.

9. Carbohydrates Carbohydrates are polyhydroxy aldehydes or ketones or compounds that can be hydrolyzed to form such compounds. Monosaccharides: Carbohydrates that cannot be hydrolyzed into simpler compounds.

10. Carbohydrates Monosaccharides: Carbohydrates that cannot be hydrolyzed into simpler compounds.

11. Carbohydrates Most monosaccharides actually exist in cyclic form.

12. Carbohydrates Disaccharides consist of molecules that can be hydrolyzed into two monosaccharide units.

13. Carbohydrates Polysaccharides are composed of large molecules that can be hydrolyzed into many monosaccharide units. Examples include starch, cellulose, and glycogen.

14. Carbohydrates Both starch and cellulose are polymers of glucose. The linkages between glucose molecules in starch are alpha (α) linkages, whereas in cellulose they are beta (β) linkages.

15. Carbohydrates Cellulose makes up the structural units of plants. Cellulose chains are composed of parallel bundles called fibrils.

16. Carbohydrates Starch is composed of two polymers, amyloseand amylopectin. In amylose, the glucose molecules are connected in long parallel chains. In amylopectin, the chains are branched.

17. Carbohydrates Glycogen is known as animal starch. It is similar to amylopectin in that the glucose polymers are branched.

18. Carbohydrates Amylose, Amylopectin, Glycogen

19. Fats and Other Lipids Lipids are biological molecules that are insoluble in water, but are soluble in nonpolar organic solvents. Fats are esters of long-chain fatty acids and glycerol. Fats are often called triglycerides or triacylglycerols.

20. Fats and Other Lipids Fatty Acids

21. Fats and Other Lipids Palmitic Acid

22. Fats and Other Lipids Triglyceridesare triesters of glycerol and fatty acids.

23. Fats and Other Lipids Saturated fatty acids have no carbon-to-carbon double bonds. Monounsaturated fatty acids have one carbon-to-carbon double bond. Polyunsaturatedfatty acids have two or more carbon-to-carbon double bonds.

24. Fats and Other Lipids Solid fats have a high proportion of saturated fatty acids. Liquid oils have only unsaturated fatty acids.

25. Fats and Other Lipids Iodine number is a measure of the degree of unsaturation of a fat or oil. Iodine number is the number of grams of I2 that are consumed by 100 g of a fat or oil.

26. Fats and Other Lipids Iodine Number

27. Proteins Proteins are a vital component of all living things.

28. Proteins Proteins are polymers of amino acids. Amino acids contain both an amine and carboxylate group attached to the same carbon called the alpha carbon.

29. Proteins Amino Acids

30. Proteins Amino acids tend to exist as a dipolar ion or inner ion at physiological pH. Such an ion is called a zwitterion.

31. Proteins Plants can synthesize proteins from carbon dioxide, water, and minerals contained in compounds like nitrates or sulfates. Animals must consume proteins as part of their diet. Humans can synthesize some amino acids, but must obtain essential amino acids in a normal diet.

32. The Peptide Bond Amino acids are linked to each other to form proteins by an amide linkage between the amine of one amino acid to the carboxylate of another amino acid. This amide linkage is known as the peptide bond.

33. The Peptide Bond A dipeptide is formed when two amino acids are joined. Tripeptides contain three amino acid units. Polypeptides contain ten or more amino acid units. Proteins may contain 10,000 or more amino acid units.

34. The Peptide Bond The sequence of the amino acids in a protein is critical. The sequence is always denoted from the free amino group (N-terminal) to the free carboxyl group (C-terminal).

35. Structure of Proteins Primary structure: The primary structure of a protein is simply the sequence of amino acids from N-terminal to C-terminal. Example: The primary structure of angiotensin II is Asp-Arg-Val-Tyr-Ile-His-Pro-Phe

36. Structure of Proteins Secondary structure: How the polypeptide chain folds and coils due to hydrogen bonding of the backbone amide groups. Examples include the alpha helix and beta-pleated sheet.

37. Structure of Proteins Alpha Helix

38. Structure of Proteins Beta-Pleated Sheet

39. Structure of Proteins Tertiary structure: The three-dimensional shape of a protein due to the spatial relationships of groups that are far apart on the protein chain. One example is the protein chain in globular proteins.

40. Structure of Proteins Quaternary structure: Involves the interaction of more than one peptide chain.

41. Structure of Proteins Four Ways to Link Protein Chains • Hydrogen bond: The secondary structures occur when hydrogen bonds are formed between amide hydrogen (N-H) and carboxyl oxygen (C=O). Tertiary structures also involve hydrogen bonding between side chains of the amino acids. • Ionic bonds: Sometimes called salt bridges, these occur between oppositely charged side chains. • Disulfide linkages: When two cysteine side chains are oxidized, a (-S-S-) disulfide linkage can form. • Dispersion forces: These are attractive forces between two nonpolar side chains.

42. Structure of Proteins

43. Enzymes Enzymes are biological catalysts. Most are proteins. Many are highly specific, only catalyzing a single reaction or related group of reactions. The substrate is the reactant molecule whose reaction the enzyme catalyzes.

44. Enzymes The activity of many enzymes can be explained by the induced-fit model. According to the induced-fit model, the substrate molecule bonds to the enzyme at the active site, forming an enzyme-substrate complex. This complex can then catalyze the reaction of the substrate and form products. Enzyme + Substrate → Enzyme-substrate complex ↔ Enzyme + Products

45. Enzymes Induced-Fit Model

46. Enzymes Inhibition The action of enzymes can be inhibited. In one mechanism for enzyme inhibition, a molecule bonds to the enzyme protein at a site other than the active site. This changes the shape of the protein and prevents the substrate from bonding at the active site.

47. Enzymes Inhibition

48. Enzymes Cofactors: Some enzymes require another molecule to be present for proper functioning of the enzyme. Cofactors can be inorganic ions (Zn2+, Mg2+, …) or organic molecules. Coenzyme: A cofactor that is a nonprotein organic molecule. Apoenzyme: The pure protein part of an enzyme without cofactors or coenzymes.

49. Enzymes Diabetic test strips use two enzymes to measure blood sugar. One enzyme catalyzes the oxidation of glucose, producing hydrogen peroxide as a by-product. The other enzyme catalyzes the breakdown of hydrogen peroxide and oxidizes a dye to produce a color change. Enzymes can be monitored to diagnose liver damage or heart damage. Enzymes can also be used to break up clots after a heart attack or to increase clotting to treat hemophelia.

50. Enzymes in Industry Enzymes have many industrial applications, including the production of baby foods, beer, sweeteners for soft drinks, animal feeds, and blue jeans.