1. Chapter 3
The Molecules of Cells

2. Got Lactose? Many people in the world suffer from lactose intolerance
Got Lactose?
Many people in the world suffer from lactose intolerance
Lacking an enzyme that digests lactose, a sugar found in milk

3. Lactose intolerance illustrates the importance of biological molecules
To the functioning of living cells and to human health

4. INTRODUCTION TO ORGANIC COMPOUNDS
Structural formula
Methane H
Ball-and-stick model
Space-filling model C
The 4 single bonds of carbon point to the corners of a tetrahedron.
3.1 Life’s molecular diversity is based on the properties of carbon
A carbon atom can form four covalent bonds
Allowing it to build large and diverse organic compounds
Figure 3.1A

5. Carbon chains vary in many ways
Carbon chains vary in many ways H
Ethane
Propane
Carbon skeletons vary in length. C
Butane
Isobutane
Skeletons may be unbranched or branched.
1-Butene
2-Butene
Skeletons may have double bonds, which can vary in location.
Cyclohexane
Benzene
Skeletons may be arranged in rings.
Figure 3.1A

6. Hydrocarbons
Are composed of only hydrogen and carbon
Some carbon compounds are isomers
Molecules with the same molecular formula but the atoms are arranged differently

7. 3.2 Functional groups help determine the properties of organic compounds
Examples of functional groups
Table 3.2

8. Functional groups are particular groupings of atoms that give organic molecules particular properties OH
Estradiol HO
Female lion OH O
Testosterone
Figure 3.2
Male lion

9. Sucrose, Sucralose, Saccharin, Aspartame

10. 3.3 Cells make a huge number of large molecules from a small set of small molecules
The four main classes of biological molecules
Are carbohydrates, lipids, proteins, and nucleic acids
Many of the molecules are gigantic
And are called macromolecules

11. Cells make most of their large molecules
Cells make most of their large molecules
By joining smaller organic molecules into chains called polymers
Cells link monomers to form polymers
By a dehydration reaction H OH
Unlinked monomer
Dehydration reaction
Longer polymer
Short polymer
H2O
Figure 3.3A

12. Polymers are broken down to monomers
Polymers are broken down to monomers
By the reverse process, hydrolysis H
H2O OH
Hydrolysis
Figure 3.3B

13. CARBOHYDRATES 3.4 Monosaccharides are the simplest carbohydrates
3.4 Monosaccharides are the simplest carbohydrates
The carbohydrate monomers
Are monosaccharides
Figure 3.4A

14. A monosaccharide has a formula that is a multiple of CH2O
And contains hydroxyl groups and a carbonyl group

15. The monosaccharides glucose and fructose are isomers
The monosaccharides glucose and fructose are isomers
That contain the same atoms but in different arrangements C H HO O OH
Glucose
Fructose
Figure 3.4B

16. Abbreviated structure
Monosaccharides can also occur as ring structures H O C OH HO
CH2OH
Structural formula
Abbreviated structure
Simplified structure 6 5 4 3 2 1
Figure 3.4C

17. 3.5 Cells link two single sugars to form disaccharides
3.5 Cells link two single sugars to form disaccharides
Monosaccharides can join to form disaccharides via a glycosidic bond
Such as sucrose (table sugar) and maltose (brewing sugar) H OH HO O
CH2OH
H2O
Glucose
Maltose
Figure 3.5

18. CONNECTION 3.6 How sweet is sweet?
3.6 How sweet is sweet?
Various types of molecules, including nonsugars
Taste sweet because they bind to “sweet” receptors on the tongue
Table 3.6

19. 3.7 Polysaccharides are long chains of sugar units
3.7 Polysaccharides are long chains of sugar units
Polysaccharides are polymers of monosaccharides
Linked together by dehydration reactions

20. Starch and glycogen are polysaccharides That store sugar for later use
Starch granules in potato tuber cells
Glycogen granules in muscle tissue
Cellulose fibrils in a plant cell wall
Glucose monomer
Cellulose molecules
STARCH
GLYCOGEN
CELLULOSE O OH
Figure 3.7
Starch and glycogen are polysaccharides
That store sugar for later use
Cellulose is a polysaccharide found in plant cell walls

21. LIPIDS 3.8 Fats are lipids that are mostly energy-storage molecules
3.8 Fats are lipids that are mostly energy-storage molecules
Lipids are diverse compounds
That consist mainly of carbon and hydrogen atoms linked by nonpolar covalent bonds

22. Lipids are grouped together Because they are hydrophobic
Lipids are grouped together
Because they are hydrophobic
Figure 3.8A

23. Fats, also called triglycerides
Fats, also called triglycerides
Are lipids whose main function is energy storage
Consist of glycerol linked to three fatty acids H
CH2 O
CH3 CH C
CH2
CH3
H2O H OH HO C O
Fatty acid
Glycerol
Figure 3.8B
Figure 3.8C

24. 3.9 Phospholipids, waxes, and steroids are lipids with a variety of functions
Phospholipids are a major component of cell membranes
Waxes form waterproof coatings
Steroids are often hormones HO
CH3
H3C
Figure 3.9

25. 3.10 Anabolic steroids pose health risks
CONNECTION
3.10 Anabolic steroids pose health risks
Anabolic steroids
Are synthetic variants of testosterone
Can cause serious health problems

26. NUCLEIC ACIDS
3.20 Nucleic acids are information-rich polymers of nucleotides
Nucleic acids such as DNA and RNA
Serve as the blueprints for proteins and thus control the life of a cell

27. DNA consists of two polynucleotides
DNA consists of two polynucleotides
Twisted around each other in a double helix C T A G
Base
pair
Figure 3.16C

28. RNA, by contrast
Is a single-stranded polynucleotide

29. The monomers of nucleic acids are nucleotides
The monomers of nucleic acids are nucleotides
Composed of a sugar, phosphate, and nitrogenous base
Sugar OH O P O
CH2 H N
Phosphate
group
Nitrogenous
base (A)
Figure 3.16A

30. The sugar and phosphate
The sugar and phosphate
Form the backbone for the nucleic acid or polynucleotide
Sugar-phosphate
backbone T G C A
Nucleotide
Figure 3.16B

31. Stretches of a DNA molecule called genes
Program the amino acid sequences of proteins

32. 3.11 Proteins are essential to the structures and activities of life
3.11 Proteins are essential to the structures and activities of life
A protein
Is a polymer constructed from amino acid monomers

33. Are involved in almost all of a cell’s activities As enzymes
Proteins
Are involved in almost all of a cell’s activities
As enzymes
They regulate chemical reactions.
Figure 3.11

34. 3.12 Proteins are made from amino acids linked by peptide bonds
3.12 Proteins are made from amino acids linked by peptide bonds
Protein diversity
Is based on different arrangements of a common set of 20 amino acid monomers

35. Each amino acid contains An amino group A carboxyl group
Each amino acid contains
An amino group
A carboxyl group
An R group, which distinguishes each of the 20 different amino acids H N C R O OH
Amino
group
Carboxyl (acid)
Figure 3.12A

36. Each amino acid has specific properties Based on its structure
Each amino acid has specific properties
Based on its structure H N C
CH2 CH
CH3 O OH
Leucine (Leu)
Serine (Ser)
Aspartic acid (Asp)
Hydrophobic
Hydrophilic
Amino Acids List
Figure 3.12B

37. Cells link amino acids together By dehydration synthesis
Cells link amino acids together
By dehydration synthesis
The bonds between amino acid monomers
Are called peptide bonds H N C O OH + R
H2O
Peptide
bond
Dipeptide
Amino acid
Dehydration
reaction
Amino
group
Carboxyl
Figure 3.12C

38. 3.13 A protein’s specific shape determines its function
3.13 A protein’s specific shape determines its function
A protein consists of one or more polypeptide chains
Folded into a unique shape that determines the protein’s function
Groove
Groove
Figure 3.13A
Figure 3.13B

39. 3.14 A protein’s shape depends on four levels of structure
Primary structure
Secondary structure
Tertiary structure
Quaternary structure

40. Levels of Protein Structure
Primary Structure
A protein’s primary structure
Is the sequence of amino acids forming its polypeptide chains
Levels of Protein Structure
Primary structure
Gly
Thr
Glu
Ser
Lys
Cys
Pro
Leu
Met
Val
Asp
Ala
Arg
Ile
Asn
His
Amino acids
Phe
Figure 3.14A

41. Secondary structure A protein’s secondary structure
Secondary structure
A protein’s secondary structure
Is the coiling or folding of the chain, stabilized by hydrogen bonding
Figure 3.14B
Secondary structure C N O H
Hydrogen
bond R
Alpha helix
Pleated sheet
Amino acids

42. Tertiary Structure A protein’s tertiary structure
Tertiary Structure
A protein’s tertiary structure
Is the overall three-dimensional shape of a polypeptide
Tertiary structure
Polypeptide
(single subunit
of transthyretin)
Figure 3.14C

43. Quaternary Structure A protein’s quaternary structure
Quaternary Structure
A protein’s quaternary structure
Results from the association of two or more polypeptide chains
Can be described as globular or fibrous
Polypeptide
chain
Collagen
Quaternary structure
Transthyretin, with
four identical
polypeptide subunits
Figure 3.14D

44. TALKING ABOUT SCIENCE
3.19 Linus Pauling contributed to our understanding of the chemistry of life
Linus Pauling made important contributions
To our understanding of protein structure and function
Figure 3.15