1. The Molecules of Cells
Chapter Three

2. Classes of Compounds Inorganic compounds Organic compounds
Water, salts, and many acids and bases
Do not contain carbon
Organic compounds
Carbohydrates, fats, proteins, nucleic acids
Contain carbon, usually large, covalently bonded
Life’s molecular diversity is based on the properties of carbon

3. Characteristic chemical groups help determine the properties of organic compounds
Functional Groups: affect a molecules function by participating in chemical reactions in a characteristic way

4. Cells make a huge number of large molecules from a small set of small molecules
Monomers: Building blocks of polymers
Polymers: Large molecules formed from smaller monomers
There are four classes of Biological macromolecules, three are polymers:
Carbohydrates
Lipids (not polymers)
Proteins
Nucleic Acids

5. Polymers Around Us

6. Making and Breaking Polymers
Dehydration (synthesis) reactions: Form polymers by removing a molecule of water
Hydrolysis: Polymers are broken down using water
The reverse of dehydration reactions

8. Carbohydrates Functions Major source of cellular fuel (glucose)
Sugars and starches
Contain C, H, and O [(CH20)n]
Three classes
Monosaccharides-Simple sugars containing three to seven C atoms
Disaccharides-Double sugars/too large to pass through cell membranes
Polysaccharides-Polymers of simple sugars, e.g., starch and glycogen
Functions
Major source of cellular fuel (glucose)
Structural molecules (ribose sugar in RNA)

9. (a) Monosaccharides
Monomers of carbohydrates
Example
Hexose sugars
Example
Pentose sugars
Glucose
Fructose
Galactose
Deoxyribose
Ribose

10. (b) Disaccharides
Consist of two linked monosaccharides
Example
Sucrose, maltose, and lactose
Glucose
Fructose
Glucose
Glucose
Galactose
Glucose
Sucrose
Maltose
Lactose

12. Lipids Contain C, H, O (less than in carbohydrates), and sometimes P
Insoluble in water
Several Classes of Lipids:
Triglycerides
Phospholipids
Steroids

13. Triglycerides Triglycerides—solid fats and liquid oils
Composed of three fatty acids bonded to a glycerol molecule
Main functions
Energy storage
Insulation
Protection

14. Phospholipids Modified triglycerides:
Glycerol + two fatty acids and a phosphorus (P)-containing group
“Head” and “tail” regions have different properties
Main component of cellular membranes

15. Steroids Lipids composed of fused ring structures
Cholesterol, vitamin D, steroid hormones, and bile salts

16. Proteins Contain C, H, O, N, and sometimes S Polymers of amino acids
All 20 amino acids have same basic structure
Amino acids are held together by peptide bonds (polypeptides)

17. Proteins are made from amino acids linked by peptide bonds

18. Natural
Folding
Denaturing

19. Nucleic Acids DNA and RNA Contain C, O, H, N, and P
Building block = nucleotide, composed of N-containing base, a pentose sugar, and a phosphate group

20. Sugar-phosphate backbone
Nucleotide
Base
pair
Base pair
Figure 3.16C DNA double helix.
Sugar-phosphate backbone

21. Deoxyribonucleic Acid (DNA)
Four bases:
adenine (A), guanine (G), cytosine (C), and thymine (T)
Double-stranded, helical
Replicates before cell division, ensuring genetic continuity
Provides instructions for protein synthesis

22. Ribonucleic Acid (RNA)
Four bases:
adenine (A), guanine (G), cytosine (C), and uracil (U)
Uracil replaces thymine in RNA
Single-stranded
Mainly active outside of nucleus