1. Molecules of Life Chapter 3
Biology Concepts and Applications, Eight Edition, by Starr, Evers, Starr. Brooks/Cole, Cengage Learning 2011.
Biology, Ninth Edition, by Solomon, Berg, Martin. Brooks/Cole, Cengage Learning 2011.

2. 3.1 Molecules of Life
Molecules of life are synthesized by living cells
Carbohydrates
Lipids
Proteins
Nucleic acids
Organic Compounds
In organic compounds, covalently bonded carbon atoms form the backbone of the molecule

3. Structure to Function
Molecules of life differ in three-dimensional structure and function
1. Carbon backbone
A carbon atom can complete its valence shell by forming a total of four covalent bonds
Carbon-to-carbon bonds are strong and not easily broken  Single, Double, Triple covalent bonds
2. Attached functional groups
Structures give clues to how they function

4. Organic Compounds Consist primarily of carbon and hydrogen atoms
Carbon atoms bond covalently with up to four other atoms, often in long chains or rings
Hydrocarbon  Hydrophobic
An organic compound or region of one that consists only of carbon and hydrogen atoms
Functional groups attach to a carbon backbone
Influence organic compound’s properties

5. Functional Groups

6. attached to an interior carbon of backbone
hydroxyl
In alcohols (e.g.,
sugars, amino acids);
water soluble
methyl
In fatty acid chains;
insoluble in water
carbonyl
In sugars, amino acids,
nucleotides; water
soluble. An aldehyde
if at end of a carbon
backbone; a ketone if
attached to an interior
carbon of backbone
(aldehyde)
(ketone)
carboxyl
In amino acids, fatty
acids, carbohydrates;
water soluble. Highly
polar; acts as an acid
(releases H+)
(non-ionized)
(ionized)
Fig. 3.3, p. 36

7. amino In amino acids and certain nucleotide bases; water soluble,
acts as a weak base
(accepts H+)
(non-ionized)
(ionized)
phosphate
In nucleotides (e.g.,
ATP), also in DNA,
RNA, many proteins,
phospholipids; water
soluble, acidic
icon
Fig. 3.3, p. 36

8. Functional Groups: The Importance of Position

9. Processes of Metabolism
All the enzyme-mediated chemical reactions by which cells acquire and use energy as they build and break down organic molecules.
Cells use energy to grow and maintain themselves
Enzyme-driven reactions build, rearrange, and split organic molecules
Enzymes  a compound (protein) that speeds a reaction without being changed by it.

10. Building Organic Compounds
Cells form complex organic molecules
Simple sugars → carbohydrates
Fatty acids → lipids
Amino acids → proteins
Nucleotides → nucleic acids
Condensation combines monomers to form polymers
Monomer  Molecules that are subunits of polymers
Polymers  Molecules that consists of multiple monomers

11. Polyethylene: A Simple Polymer

12. What Cells Do to Organic Compounds

13. Condensation (aka Dehydration Synthesis) and Hydrolysis

14. Key Concepts: STRUCTURE DICTATES FUNCTION
We define cells partly by their capacity to build complex carbohydrates and lipids, proteins, and nucleic acids
The main building blocks are simple sugars, fatty acids, amino acids, and nucleotides
These organic compounds have a backbone of carbon atoms with functional groups attached

15. 3.2 Carbohydrates – The Most Abundant Ones
Molecules that consists primarily of carbon, hydrogen, and oxygen atoms at a 1:2:1 ratio.
Three main types of carbohydrates
Monosaccharides (simple sugars)
Oligosaccharides (short chains)
Polysaccharides (complex carbohydrates)
Carbohydrate functions
Instant energy sources
Transportable or storable forms of energy
Structural materials

16. Monosaccharides (Simple Sugar): Glucose and Fructose

17. Glucose (C6H12O6) (an aldehyde) Fructose (C6H12O6) (a ketone)
Figure 3.6: Monosaccharides.
Shown are 2-D chain structures of (a) three-carbon trioses, (b) five-carbon pentoses, and (c) six-carbon hexoses. Although it is convenient to show monosaccharides in this form, the pentoses and hexoses are more accurately depicted as ring structures, as in Figure 3-7. The carbonyl group (gray screen) is terminal in aldehyde sugars and located in an internal position in ketones. Deoxyribose differs from ribose because deoxyribose has one less oxygen; a hydrogen (white screen) instead of a hydroxyl group (blue screen) is attached to carbon 2. Glucose and galactose differ in the arrangement of the hydroxyl group and hydrogen attached to carbon 4 (red box).
Glucose (C6H12O6) (an aldehyde)
Fructose (C6H12O6) (a ketone)
Galactose (C6H12O6) (an aldehyde)
(c) Hexose sugars (6-carbon sugars)
Fig. 3-6c, p. 52

18. Glucose
Glucose (C6H12O6), the most abundant monosaccharide, is used as an energy source in most organisms
During cellular respiration, cells oxidize glucose molecules, converting stored energy to a form used for cell work
Homeostatic mechanisms maintain blood glucose levels

19. Disaccharides: Sucrose

20. Disaccharides
A disaccharide (two sugars) contains two monosaccharide rings joined by a glycosidic linkage, consisting of a central oxygen covalently bonded to two carbons, one in each ring
Common disaccharides:
Maltose (malt sugar): 2 covalently linked glucose
Sucrose (table sugar): 1 glucose + 1 fructose
Lactose (milk sugar): 1 glucose + 1 galactose

21. Complex Carbohydrates (Polysaccharides): Bonding Patterns

22. Polysaccharides
A polysaccharide is a macromolecule (a single long chain or a branched chain) consisting of repeating units of simple sugars, usually glucose
Common polysaccharides:
Starches: Energy storage in plants
Glycogen: Energy storage in animals
Cellulose: Structural polysaccharide in plants

23. Starches starch Plant cells store starch as granules in amyloplasts
Form of carbohydrate used for energy storage in plants
Polymer consisting of glucose
Plant cells store starch as granules in amyloplasts

24. Starch: A Storage Polysaccharide

25. Amyloplasts
Figure 3.9: Starch, a storage polysaccharide.
(a) Starch (stained purple) is stored in specialized organelles, called amyloplasts, in these cells of a buttercup root.
Fig. 3-9a, p. 55

26. Complex Carbohydrates: Starch

27. Glycogen
glycogen
Form in which glucose subunits are stored as an energy source in animal tissues
Similar in structure to plant starch but more extensively branched and more water soluble
In vertebrates, glycogen is stored mainly in liver and muscle cells

28. c Glycogen. In animals, this
polysaccharide is a storage form for excess glucose. It is especially abundant in the liver and muscles of highly active animals, including fishes and people.
Structure of cellulose
Fig. 3.8, p. 39

29. Cellulose cellulose Some microorganisms digest cellulose to glucose
Insoluble polysaccharide composed of many joined glucose molecules
Structural component of plants (fibers)
The most abundant carbohydrate
Some microorganisms digest cellulose to glucose
Humans lack enzymes to hydrolyze β 1—4 linkages

30. Cellulose: A Structural Polysaccharide

31. Complex Carbohydrates: Chitin

32. Key Concepts: CARBOHYDRATES
Carbohydrates are the most abundant biological molecules
Simple sugars function as transportable forms of energy or as quick energy sources
Complex carbohydrates are structural materials or energy reservoirs

33. 3.3 Greasy, Oily – Must Be Lipids
Fats, phospholipids, waxes, and sterols
Don’t dissolve in water
Dissolve in nonpolar substances (other lipids)
Lipid functions
Major sources of energy
Structural materials
Used in cell membranes

34. Fats
Lipids with glycerol molecule and one, two, or three fatty acid tails
Fatty acids 
Organic compound with a chain of carbon atoms and an acidic carboxyl group at one end
Saturated
Unsaturated (cis and trans)
Triglycerides (neutral fats )
Three fatty acid tails
Most abundant animal fat (body fat)
Major energy reserves

35. Saturated and Unsaturated Fatty Acids
Contain the maximum number of hydrogen atoms
Found in animal fat and solid vegetable shortening
Solid at room temperature
unsaturated fatty acids
Include one or more pairs of carbon atoms joined by a double bond (not fully saturated with hydrogen)
Tend to be liquid at room temperature

36. Unsaturated Fatty Acids
Each double bond produces a bend in the hydrocarbon chain that prevents close alignment with an adjacent chains
monounsaturated fatty acids
Fatty acids with one double bond
Example: Oleic acid
polyunsaturated fatty acids
Fatty acids with more than one double bond
Example: linoleic acid

37. Fatty Acids

38. Trans and Cis Fatty Acids

39. Trans Fats
Food manufacturers hydrogenate or partially hydrogenate cooking oils (convert unsaturated fatty acids to saturated fatty acids) to make fat more solid at room temperature
In naturally-occurring unsaturated fatty acids
the hydrogens on each side of the double bond are on the same side of the hydrocarbon chain (cis configuration)
Artificial hydrogenation produces a trans configuration
solid at room temperature and increases risk of cardiovascular disease

40. Trans and Cis Isomers

41. Triglyceride Formation

42. Phospholipids Main component of cell membranes
Hydrophilic head, hydrophobic tails
A lipid with a phosphate group in its hydrophilic head and two nonpolar fatty acid tails

43. A Phospholipid

44. A Phospholipid Bilayer

45. Waxes
Firm, pliable, water repelling, lubricating

46. Cholesterol
Membrane components; precursors of other molecules (steroid hormones)

47. Steroids
steroid
Consists of carbon atoms arranged in four attached rings
Side chains distinguish one steroid from another
Synthesized from isoprene units
Steroids of biological importance include cholesterol, bile salts, reproductive hormones, cortisol and other hormones secreted by the adrenal cortex
Plant cell membranes contain molecules similar to cholesterol

48. Steroids
Lipid with four carbon rings
No fatty acid tails

49. Key Concepts: LIPIDS
Complex lipids function as energy reservoirs, structural materials of cell membranes, signaling molecules, and waterproofing or lubricating substances

50. 3.4 Proteins – Diversity in Structure and Function
Proteins have many functions
Structures
Nutrition
Enzymes
Transportation
Communication
Defense

51. Protein Structure Built from 20 kinds of amino acids
Amino acid  carboxyl group, amino group, and side group (R)

52. Fig. 3.15, p. 42

53. Fig. 3.15, p. 42

54. Protein Synthesis

55. Peptide Bonds

56. Four Levels of Protein Structure
1. Primary structure
Amino acids joined by peptide bonds form a linear polypeptide chain
2. Secondary structure
Polypeptide chains form sheets and coils
3. Tertiary structure
Sheets and coils pack into functional domains

57. Four Levels of Protein Structure
4. Quaternary structure
Many proteins (e.g. fs) consist of two or more chains
Other protein structures
Glycoproteins
Lipoproteins
Fibrous proteins

58. 1. Primary Structure

59. 2. Secondary Structure

60. Secondary Structure of a Protein

61. 3. Tertiary Structure

62. Tertiary Structure of a Protein

63. 4. Quaternary Structure

64. Quaternary Structure of a Protein

65. 3.5 Why is Protein Structure So Important?
Protein structure dictates function
Sometimes a mutation in DNA results in an amino acid substitution that alters a protein’s structure and compromises its function
Example: Hemoglobin and sickle-cell anemia

66. Normal Hemoglobin Structure

67. Normal Hemoglobin Structure

68. Sickle-Cell Mutation

69. VALINE HISTIDINE LEUCINE THREONINE PROLINE VALINE
GLUTAMATE
b One amino acid substitution results in the
abnormal beta chain in HbS molecules. Instead
of glutamate, valine was added at the sixth
position of the polypeptide chain.
sickle cell
c Glutamate has an overall negative charge; valine has no net charge. At low oxygen levels, this difference gives rise to a water-repellent, sticky patch on HbS molecules. They stick together
because of that patch, forming rodshaped clumps that distort normally rounded red blood cells into sickle shapes. (A sickle is a farm tool that has a crescent-shaped blade.)
normal cell
Fig. 3.19, p. 45

70. Clumping of cells in bloodstream
Circulatory problems, damage to brain, lungs, heart, skeletal muscles, gut, and kidneys
Heart failure, paralysis, pneumonia, rheumatism, gut pain, kidney failure
Spleen concentrates sickle cells
Spleen enlargement
Immune system compromised
Rapid destruction of sickle cells
d Melba Moore, celebrity spokes-person for sickle-cell anemia organizations. Right, range of symptoms for a person with two mutated genes for hemoglobin’s beta chain.
Anemia, causing weakness,fatigue, impaired development,heart chamber dilation
Impaired brain function, heart failure
Fig. 3.19, p. 45

71. Denatured Proteins
If a protein unfolds and loses its three-dimensional shape (denatures), it also loses its function
Caused by shifts in pH or temperature, or exposure to detergent or salts
Disrupts hydrogen bonds and other molecular interactions responsible for protein’s shape

72. Key Concepts: PROTEINS
Peptide bond joins amino acids in proteins
Polypeptides are a chain of amino acids linked by peptide bonds
Proteins are organic compounds that consists of one or more chains of amino acids
Structurally and functionally, proteins are the most diverse molecules of life
They include enzymes, structural materials, signaling molecules, and transporters

73. 3.6 Nucleotides, DNA, and RNAs
Nucleotide structure, 3 parts:
Sugar
Phosphate group
Nitrogen-containing base

74. Nucleotide Functions: Reproduction, Metabolism, and Survival
DNA and RNAs are nucleic acids, each composed of four kinds of nucleotide subunits
ATP energizes many kinds of molecules by phosphate-group transfers
Other nucleotides function as coenzymes or as chemical messengers

75. Nucleotides of DNA

76. DNA, RNAs, and Protein Synthesis
DNA (double-stranded)
Encodes information about the primary structure of all cell proteins in its nucleotide sequence
RNA molecules (usually single stranded)
Different kinds interact with DNA and one another during protein synthesis

77. The DNA Double-Helix

78. Key Concepts: NUCLEOTIDES AND NUCLEIC ACIDS
Nucleotides have major metabolic roles and are building blocks of nucleic acids
Two kinds of nucleic acids, DNA and RNA, interact as the cell’s system of storing, retrieving, and translating information about building proteins

79. Animation: Condensation and hydrolysis

80. Animation: Fatty acids

81. Animation: Functional group

82. Animation: Globin and hemoglobin structure

83. Animation: Nucleotide subunits of DNA

84. Animation: Peptide bond formation

85. Animation: Phospholipid structure

86. Animation: Secondary and tertiary structure

87. Animation: Sickle-cell anemia

88. Animation: Structure of an amino acid

89. Animation: Structure of ATP

90. Animation: Triglyceride formation