2. THE MOLECULES OF LIFE Organic Molecules

3. ORGANIC MOLECULES  FOUR MAIN CATEGORIES : carbohydrates: fuel & building material lipids: fats & oils proteins: perform most cell functions nucleic acids: information storage

4. ORGANIC vs. INORGANIC  Carbon based molecules are called organic molecules.  Non-carbon based molecules— water, oxygen, and ammonia are inorganic molecules.

5. Carbon

6. Atomic Structure of Carbon  Carbon atoms can form four bonds  Connecting point for other atoms in four directions  Can produce endless variety of carbon skeletons that can bond with carbon or with other elements

7. CARBON BACKBONES  Types of carbon backbones : - straight chain - branched chain - can form double bonds - can form ring structures

8. CARBON SKELETONS

9. FUNCTIONAL GROUPS  Group of atoms within molecules— determine properties of organic molecules  React in predictable ways with other molecules  Hydrophilic molecules: molecules that are attracted water  Hydrophobic molecules: molecules that do not mix with water

10. FUNCTIONAL GROUPS  4 most common functional groups: 1) hydroxyl group: (OH) 2) carbonyl group: (C=O) 3) carboxyl group: (O=C-OH) 4) amino group: (H-N-H)

11. HYDROCARBONS  Organic molecules composed only of carbon and hydrogen  Many are important fuels  Methane found in natural gas is used to heat homes.

12. MONOMERS & POLYMERS  Most biological molecules are large and are made up of smaller subunits  Monomer: molecular subunit that is building block of a larger molecule  Polymer: long chain of monomers

13. DEHYDRATION REACTION  Also called condensation reaction  Links monomers together forming polymers or making polymer chains longer  Water molecule is removed in forming a polymer or making it longer  Same type of reaction occurs regardless of type of monomers being linked or type of polymer produced

14. DEHYDRATION REACTION

15. HYDROLYSIS REACTION  Chemical reaction where polymers are broken down to their monomers  Large polymers must be broken down to make monomers available to cells  Hydrolysis breaks the chemical bonds in polymers by adding water molecules  reverse of dehydration/condensation

16. HYDROLYSIS REACTION

17. Short polymer Monomer Hydrolysis Dehydration Longer polymer

18. DEHYDRATION vs. HYDROLYSIS  Summary :  Dehydration: water is removed to build a polymer  Hydrolysis: Water is added to break down a polymer

19. CARBOHYDRATES ARE MADE UP OF SUGAR MOLECULES  Sugars contain carbon, hydrogen, and oxygen in the following ratio: 1 carbon : 2 hydrogen : 1 oxygen  Molecular formula of any carbohydrate is a multiple of the basic formula CH 2 O

20. HOW CELLS USE SUGARS  Main fuel supply for cellular work  Other uses: - Provide raw material to make other organic molecules such as fats - Used to make energy stockpiles - Serve as building materials

21. MONOSACCHARIDES  Sugars that contain just one sugar unit or monomer  Carbohydrate Monomer Unit monosaccharides  Examples: - glucose - fructose - galactose

22. DISACCHARIDES  “double sugars”  Produced in dehydration reactions from two monosaccharides  Most common disaccharide is sucrose – table sugar—formed by linking glucose and fructose molecules

23. DISACCHARIDE

24. POLYSACCHARIDES  3 common types  all glucose polymers:  Starch: found in plant cells—glucose storage molecule  Glycogen: found in animal cells—glucose storage—abundant in muscle and liver cells  Cellulose: used by plant cells for building material—makes up cell walls—not digestible by humans  forms “bulk” in our diet

25. POLYSACCHARIDES

26. LIPIDS  Commonly known as fats and oils  Are hydrophobic  do not mix with water  Lipid Base Unit Glycerol  Simplest fats are triglycerides  Chain of 3 fatty acids ( hydrocarbon molecules ) bonded to a glycerol molecule

27. Lipids Are Not Polymers Polymer: repeating monomer Macromolecule: The lipid base unit is not a monomer

28. TRIGLYCERIDES

29. FUNCTIONS OF LIPIDS  Act as a boundary—they are a major component of cell membranes  Circulate in the body acting as chemical signals to cells—some are hormones  Used to store energy in the body  Act to cushion and insulate the body

30. SATURATED FATS  All the carbon atoms in fatty acid chains contain only single bonds  Include animal fats such as butter  Solids at room temperature

31. UNSATURATED FATS  Have at least one double bond between the carbon atoms in one of the fatty acid chains  Found in fruits, vegetables, fish, corn oil, olive oil, and other vegetable oils  Liquids at room temperature

32. SATURATED vs. UNSATURATED

34. STEROIDS  Carbon skeleton forms four fused rings  Classified as lipids  are hydrophobic  Some act as chemical signals or hormones  estrogen and testosterone  Some form structural components of cells  cholesterol

35. EXAMPLES OF STEROIDS

36. CHOLESTEROL  Essential molecule found in all cell membranes  Serves as base molecule from which other steroids are produced  Has bad reputation  cholesterol containing substances in blood are linked to cardiovascular disease

37. FUNCTIONS OF PROTEINS  Form structures—hair, fur, muscles  Provide long-term nutrient storage  Circulate and defend the body against microorganisms (antibodies)  Act as chemical signals—hormones  Help control chemical reactions in cells-- enzymes

38. PROTEIN STRUCTURE  Polymers formed from monomers called amino acids  Amino acids bond together to form chains called a polypeptides  Sequence of amino acids makes each polypeptide unique  Each protein is composed of one or more polypeptides

39. Formation of a Peptide Bond

40. AMINO ACID STRUCTURE Figure 5-12: All amino acids consist of a central carbon bonded to an amino group, a carboxyl group, and a hydrogen atom. The fourth bond is with a unique side group – called the “R” group. Differences in side groups convey different properties to each amino acid.

41. PROTEIN SHAPE  Functional proteins consist of precisely twisted, coiled, and shaped polypeptides  Proteins cannot function correctly if shape is altered  Sequence and types of amino acids in the polypeptides affect protein shape  Surrounding environment—usually aqueous—plays a role in protein shape

42. DENATURATION  Denaturation: loss of normal protein shape  Changes in temperature, pH, or other environmental conditions may cause proteins to become denatured  If the protein shape is changed, protein cannot function normally

43. ENZYMES  Provide a way for reactions to occur at cell’s normal temperature  Enzymes lower energy requirement for a chemical reactions in cells so they can occur at normal cell temperatures  Enzymes are highly selective catalysts

44. ACTIVATION ENERGY  Activation energy: minimum energy required to start chemical reaction  Chemical bonds in reactants must be weakened to start most reactions  Catalysts: compounds that speed up chemical reactions without getting involved in the reaction.

45. Activation Energy

46. HOW ENZYMES WORK  Substrate: specific reactant acted on by an enzyme  Active site: specific region of the enzyme that the substrate fits into  Substrate binds to enzyme’s active site where the substrate undergoes a change

47. HOW ENZYMES WORK  Shape of an enzyme fits the shape of only specific reactant molecules  As substrate enters, active site of enzyme changes slightly to form snug attachment  Attachment weakens chemical bonds in substrate lowering activation energy required for reaction to proceed

48. ACTIVE SITE MODEL

49. HOW ENZYMES WORK  Once products of chemical reaction are released, enzyme’s active site is ready to accept another reactant molecule  Recycling is a key characteristic of enzymes—they are not “used up” catalyzing a single reaction

50. Nucleic Acids  Nucleic acids are molecules that store information for cellular growth and reproduction  There are two types of nucleic acids: - deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)  These are polymers consisting of long chains of monomers called nucleotides  A nucleotide consists of a nitrogenous base, a pentose sugar and a phosphate group:

51. Nitrogen Bases  The nitrogen bases in nucleotides consist of two general types: -Purines: adenine (A) and guanine (G) -Pyrimidines: cytosine (C), thymine (T) and Uracil (U)

52. Phosphodiester Bond  Nucleotides are linked together in a nucleic acid by a strong covalent bond called a phosphodiester bond.

53. DNA and RNA