CHAPTER 5

1. CHAPTER 5 THE MOLECULES OF LIFE

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

3. CONCEPT 5.1 CARBON IS THE MAIN INGREDIENT OF ORGANIC MOLECULES

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

5. 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 Atomic Structure of Carbon

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

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. 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

12. 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

13. DEHYDRATION REACTION

14. HYDROLYSIS REACTION • Chemical reaction where polymers are broken downto 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

15. HYDROLYSIS REACTION

16. DEHYDRATION & HYDROLYSIS

17. Dehydration Hydrolysis Monomer Longer polymer Short polymer

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

19. CONCEPT 5.2 CARBOHYDRATES PROVIDE FUEL AND BUILDING MATERIAL

20. 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 CH2O

21. 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

22. MONOSACCHARIDES • Sugars that contain just one sugar unit or monomer • Examples: - glucose - fructose - galactose

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

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. CONCEPT 5.3 LIPIDS INCLUDE FATS AND STEROIDS

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

28. TRIGLYCERIDE: SIMPLE LIPID

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 roomtemperature

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. CONCEPT 5.4 PROTEINS PERFORM MOST FUNCTIONS IN CELLS

38. 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

39. 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

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. CONCEPT 5.5 ENZYMES ARE PROTEINS THAT SPEED UP SPECIFIC REACTIONS IN CELLS

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 • Enzymes: proteins that act as catalysts for chemical reactions in organisms

45. 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 • Each enzyme catalyzes a specific kind of chemical reaction

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 ofenzymes—they are not “used up” catalyzing a single reaction

50. HOW ENZYMES WORK