1. Carbon and the Molecular Diversity of Life3
Carbon and the Molecular Diversity of Life

2. Overview: The Molecules of Life
Another level in the hierarchy of biological organization is reached when small organic molecules are joined together
Macromolecules
Are large molecules composed of smaller molecules
Are complex in their structures
Figure 5.1

3. Concept 5.1: Most macromolecules are polymers, built from monomers
Three of the classes of life’s organic molecules are polymers
Carbohydrates
Proteins
Nucleic acids
A polymer
Is a long molecule consisting of many similar building blocks called monomers

4. The Synthesis and Breakdown of Polymers
Monomers form larger molecules by condensation reactions called dehydration reactions
(a) Dehydration reaction in the synthesis of a polymer HO H 1 2 3 4
H2O
Short polymer
Unlinked monomer
Longer polymer
Dehydration removes a water molecule, forming a new bond
Figure 5.2A

5. (b) Hydrolysis of a polymer
Polymers can disassemble by
Hydrolysis
(b) Hydrolysis of a polymer HO 1 2 3 H 4
H2O
Hydrolysis adds a water molecule, breaking a bond
Figure 5.2B

6. The Diversity of Polymers
Each class of polymer
Is formed from a specific set of monomers
Although organisms share the same limited number of monomer types, each organism is unique based on the arrangement of monomers into polymers
An immense variety of polymers can be built from a small set of monomers 1 2 3 H HO

7. Concept 5.2: Carbohydrates serve as fuel and building material
Include both sugars and their polymers

8. Sugars Monosaccharides Can be used for fuel Are the simplest sugars
Can be converted into other organic molecules
Can be combined into polymers

9. Examples of monosaccharides
Triose sugars (C3H6O3)
Pentose sugars (C5H10O5)
Hexose sugars (C6H12O6)
H C OH
H C OH
HO C H
H C OH
C O
HO C H H C O
Aldoses
Glyceraldehyde
Ribose
Glucose
Galactose
Dihydroxyacetone
Ribulose
Ketoses
Fructose
Figure 5.3

10. Monosaccharides May be linear Can form rings 4C 3 2 OH Figure 5.4
H C OH
HO C H
H C O C 1 2 3 4 5 6 OH 4C
6CH2OH 5C
H OH
2 C 1C
3 C 2C
1 C
CH2OH HO
(a) Linear and ring forms. Chemical equilibrium between the linear and ring
structures greatly favors the formation of rings. To form the glucose ring,
carbon 1 bonds to the oxygen attached to carbon 5.
Figure 5.4

11. Disaccharides Consist of two monosaccharides
Are joined by a glycosidic linkage

12. Examples of disaccharides
Dehydration reaction in the synthesis of maltose. The bonding of two glucose units forms maltose. The glycosidic link joins the number 1 carbon of one glucose to the number 4 carbon of the second glucose. Joining the glucose monomers in a different way would result in a different disaccharide.
Dehydration reaction in the synthesis of sucrose. Sucrose is a disaccharide formed from glucose and fructose. Notice that fructose, though a hexose like glucose, forms a five-sided ring.
(a)
(b) H HO
H OH OH O
CH2OH
H2O 1 2 4
1– 4 glycosidic linkage
1–2 glycosidic linkage
Glucose
Fructose
Maltose
Sucrose
Figure 5.5

13. Polysaccharides Polysaccharides Are polymers of sugars
Serve many roles in organisms

14. Storage Polysaccharides
Starch
Is a polymer consisting entirely of glucose monomers
Is the major storage form of glucose in plants
Chloroplast
Starch
Amylose
Amylopectin
1 m
(a) Starch: a plant polysaccharide
Figure 5.6

15. Storage Polysaccharides
Glycogen
Consists of glucose monomers
Is the major storage form of glucose in animals
Mitochondria
Giycogen granules
0.5 m
(b) Glycogen: an animal polysaccharide
Glycogen
Figure 5.6

16. Structural Polysaccharides
Cellulose
Is a polymer of glucose

17. Has different glycosidic linkages than starch
(c) Cellulose: 1– 4 linkage of  glucose monomers H O
CH2OH OH HO 4 C 1
(a)  and  glucose ring structures
(b) Starch: 1– 4 linkage of  glucose monomers
 glucose
 glucose
Figure 5.7 A–C

18. Is a major component of the tough walls that enclose plant cells
Cell walls
Cellulose microfibrils
in a plant cell wall 
Microfibril
CH2OH OH O
Glucose monomer
Parallel cellulose molecules are
held together by hydrogen
bonds between hydroxyl
groups attached to carbon
atoms 3 and 6.
About 80 cellulose
molecules associate
to form a microfibril, the
main architectural unit
of the plant cell wall.
A cellulose molecule
is an unbranched 
glucose polymer.
Cellulose
molecules
Figure 5.8

19. Cellulose is difficult to digest
Cows have microbes in their stomachs to facilitate this process
Figure 5.9

20. Structural Polysaccharides
Chitin, another important structural polysaccharide
Is found in the exoskeleton of arthropods
Can be used as surgical thread
(a) The structure of the
chitin monomer. O
CH2OH OH H NH C
CH3
(b) Chitin forms the exoskeleton
of arthropods. This cicada
is molting, shedding its old
exoskeleton and emerging
in adult form.
(c) Chitin is used to make a
strong and flexible surgical
thread that decomposes after
the wound or incision heals.
Figure 5.10 A–C

21. Concept 5.3: Lipids are a diverse group of hydrophobic molecules
Are the one class of large biological molecules that do not consist of polymers
Share the common trait of being hydrophobic

22. (a) Dehydration reaction in the synthesis of a fat
Fats
Fats
Are constructed from two types of smaller molecules, a single glycerol and usually three fatty acids H O H H H H H H H H H H H H H H H H
O H C OH
Glycerol
Fatty acid
(palmitic acid) HO O
(a) Dehydration reaction in the synthesis of a fat
Ester linkage
Figure 5.11
(b) Fat molecule (triacylglycerol)

23. Fatty acids
Vary in the length and number and locations of double bonds they contain

24. (a) Saturated fat and fatty acid
Saturated fatty acids
Have the maximum number of hydrogen atoms possible
Have no double bonds
(a) Saturated fat and fatty acid
Stearic acid
Figure 5.12

25. (b) Unsaturated fat and fatty acid
Unsaturated fatty acids
Have one or more double bonds
(b) Unsaturated fat and fatty acid
cis double bond
causes bending
Oleic acid
Figure 5.12

26. Phospholipids Phospholipids Have only two fatty acids
Have a phosphate group instead of a third fatty acid

27. (a) Structural formula (b) Space-filling model
Phospholipid structure
Consists of a hydrophilic “head” and hydrophobic “tails”
CH2 O P CH C
Phosphate
Glycerol
(a) Structural formula
(b) Space-filling model
Fatty acids
(c) Phospholipid
symbol
Hydrophobic tails
Hydrophilic
head
Hydrophobic
tails –
Hydrophilic head
Choline +
Figure 5.13
N(CH3)3

28. The structure of phospholipids
Results in a bilayer arrangement found in cell membranes
Hydrophilic
head
WATER
Hydrophobic
tail
Figure 5.14

29. Steroids
Steroids
Are lipids characterized by a carbon skeleton consisting of four fused rings
One steroid, cholesterol
Is found in cell membranes
Is a precursor for some hormones HO
CH3
H3C
Figure 5.15

30. Proteins
Concept 5.4: Proteins have many structures, resulting in a wide range of functions
Proteins
Have many roles inside the cell
An overview of protein functions
Table 5.1

31. Enzymes
Are a type of protein that acts as a catalyst, speeding up chemical reactions
Substrate
(sucrose)
Enzyme
(sucrase)
Glucose OH
H O
H2O
Fructose
3 Substrate is converted
to products.
1 Active site is available for
a molecule of substrate, the
reactant on which the enzyme acts.
Substrate binds to
enzyme. 2
4 Products are released.
Figure 5.16

32. Polypeptides Polypeptides A protein Are polymers of amino acids
Consists of one or more polypeptides

33. Amino Acid Monomers Amino acids
Are organic molecules possessing both carboxyl and amino groups
Differ in their properties due to differing side chains, called R groups

34. 20 different amino acids make up proteinsH
H3N+ C
CH3 CH
CH2 NH
H2C
H2N
Nonpolar
Glycine (Gly)
Alanine (Ala)
Valine (Val)
Leucine (Leu)
Isoleucine (Ile)
Methionine (Met)
Phenylalanine (Phe)
Tryptophan (Trp)
Proline (Pro)
H3C
Figure 5.17 S

35. Polar Electrically chargedOH
CH2 C H
H3N+ O
CH3 CH SH
NH2
Polar
Electrically
charged –O
NH3+
NH2+
NH+ NH
Serine (Ser)
Threonine (Thr)
Cysteine
(Cys)
Tyrosine
(Tyr)
Asparagine
(Asn)
Glutamine
(Gln)
Acidic
Basic
Aspartic acid
(Asp)
Glutamic acid
(Glu)
Lysine (Lys)
Arginine (Arg)
Histidine (His)

36. Amino Acid Polymers Amino acids Are linked by peptide bondsOH
DESMOSOMES OH
CH2 C N H O
Peptide bond SH
Side chains
H2O
Amino end (N-terminus)
Backbone
(a)
Figure 5.18
(b)
Carboxyl end (C-terminus)

37. Determining the Amino Acid Sequence of a Polypeptide
The amino acid sequences of polypeptides
Were first determined using chemical means
Can now be determined by automated machines

38. Protein Conformation and Function
A protein’s specific conformation
Determines how it functions
Two models of protein conformation
(a) A ribbon model
(b) A space-filling model
Groove
Figure 5.19

39. Four Levels of Protein Structure
Primary structure
Is the unique sequence of amino acids in a polypeptide
Figure 5.20 –
Amino acid subunits
+H3N Amino end o
Carboxyl end c
Gly
Pro
Thr
Glu
Seu
Lys
Cys
Leu
Met
Val
Asp
Ala
Arg
Ser
lle
Phe
His
Asn
Tyr
Trp
Lle

40. Secondary structure
Is the folding or coiling of the polypeptide into a repeating configuration
Includes the  helix and the  pleated sheet O C
 helix
 pleated sheet
Amino acid subunits N H R H
Figure 5.20

41. Is the overall three-dimensional shape of a polypeptide
Tertiary structure
Is the overall three-dimensional shape of a polypeptide
Results from interactions between amino acids and R groups
CH2 CH
O H O C HO
NH3+ -O S
CH3
H3C
Hydrophobic interactions and van der Waals interactions
Polypeptide backbone
Hyrdogen bond
Ionic bond
Disulfide bridge

42. Quaternary structure
Is the overall protein structure that results from the aggregation of two or more polypeptide subunits
Polypeptide chain
Collagen
 Chains
 Chains
Hemoglobin
Iron
Heme

43. The four levels of protein structure
+H3N
Amino end
Amino acid
subunits
helix

44. Sickle-Cell Disease: A Simple Change in Primary Structure
Results from a single amino acid substitution in the protein hemoglobin

45. Sickle-cell hemoglobin
Hemoglobin structure and sickle-cell disease
Primary structure
Secondary and tertiary structures
Quaternary structure
Function
Red blood cell shape
Hemoglobin A
Molecules do not associate with one another, each carries oxygen.
Normal cells are full of individual hemoglobin molecules, each carrying oxygen  
10 m
Hemoglobin S
Molecules interact with one another to crystallize into a fiber, capacity to carry oxygen is greatly reduced.
 subunit 1 2 3 4 5 6 7
Normal hemoglobin
Sickle-cell hemoglobin
. . .
Figure 5.21
Exposed hydrophobic region
Val
Thr
His
Leu
Pro
Glul
Glu
Fibers of abnormal hemoglobin deform cell into sickle shape.

46. What Determines Protein Conformation?
Depends on the physical and chemical conditions of the protein’s environment
Most proteins
Probably go through several intermediate states on their way to a stable conformation

47. Denaturation
Is when a protein unravels and loses its native conformation
Denaturation
Renaturation
Denatured protein
Normal protein
Figure 5.22

48. Chaperonins
Are protein molecules that assist in the proper folding of other proteins
Hollow cylinder
Cap
Chaperonin (fully assembled)
Steps of Chaperonin Action: An unfolded poly- peptide enters the cylinder from one end.
The cap attaches, causing the cylinder to change shape in such a way that it creates a hydrophilic environment for the folding of the polypeptide.
The cap comes off, and the properly folded protein is released.
Correctly folded protein
Polypeptide 2 1 3
Figure 5.23

49. X-ray crystallography
Is used to determine a protein’s three-dimensional structure
X-ray diffraction pattern
Photographic film
Diffracted X-rays
X-ray source
X-ray beam
Crystal
Nucleic acid
Protein
(a) X-ray diffraction pattern
(b) 3D computer model
Figure 5.24

50. Concept 5.5: Nucleic acids store and transmit hereditary information
Genes
Are the units of inheritance
Program the amino acid sequence of polypeptides
Are made of nucleic acids

51. The Roles of Nucleic Acids
There are two types of nucleic acids
Deoxyribonucleic acid (DNA)
Ribonucleic acid (RNA)

52. Synthesis of mRNA in the nucleus
DNA
Stores information for the synthesis of specific proteins
Directs RNA synthesis
Directs protein synthesis through RNA 1 2 3
Synthesis of mRNA in the nucleus
Movement of
mRNA into cytoplasm
via nuclear pore
Synthesis
of protein
NUCLEUS
CYTOPLASM
DNA
mRNA
Ribosome
Amino acids
Polypeptide
Figure 5.25

53. The Structure of Nucleic Acids
Exist as polymers called polynucleotides
3’C
5’ end
5’C
3’ end OH
Figure 5.26 O
(a) Polynucleotide,
or nucleic acid

54. Each polynucleotide Consists of monomers called nucleotides
Nitrogenous
base
Nucleoside O O O P
CH2
5’C
3’C
Phosphate
group
Pentose
sugar
(b) Nucleotide
Figure 5.26

55. (c) Nucleoside components
Nucleotide Monomers
Nucleotide monomers
Are made up of nucleosides and phosphate groups CH
Uracil (in RNA) U
Ribose (in RNA)
Nitrogenous bases Pyrimidines C N O H
NH2 HN
CH3
Cytosine
Thymine (in DNA) T HC NH
Adenine A
Guanine G
Purines
HOCH2 OH
Pentose sugars
Deoxyribose (in DNA) 4’ 5” 3’ 2’ 1’
Figure 5.26
(c) Nucleoside components

56. The sequence of bases along a nucleotide polymer
Nucleotide Polymers
Nucleotide polymers
Are made up of nucleotides linked by the–OH group on the 3´ carbon of one nucleotide and the phosphate on the 5´ carbon on the next
The sequence of bases along a nucleotide polymer
Is unique for each gene

57. The DNA Double Helix Cellular DNA molecules
Have two polynucleotides that spiral around an imaginary axis
Form a double helix
The nitrogenous bases in DNA
Form hydrogen bonds in a complementary fashion (A with T only, and C with G only)
The DNA double helix
Consists of two antiparallel nucleotide strands
3’ end
Sugar-phosphate backbone
Base pair (joined by hydrogen bonding)
Old strands
Nucleotide about to be added to a new strand A
5’ end
New strands
Figure 5.27

58. DNA and Proteins as Tape Measures of Evolution
Molecular comparisons
Help biologists sort out the evolutionary connections among species

59. The Theme of Emergent Properties in the Chemistry of Life: A Review
Higher levels of organization
Result in the emergence of new properties
Organization
Is the key to the chemistry of life