1. The Chemistry of Living Things
Chapter 2
The Chemistry of Living Things

2. All Matter Consists of Elements Made of Atoms
Chemistry
The study of matter
Atoms, the smallest functional unit, consist of
Protons: positive charge, have mass
Neutrons: no charge, have mass
Electrons: negative charge, have no discernable mass

3. Isotopes
Same element, same atomic number = same number of protons and electrons
Different number of neutrons = different weight

4. Radioisotopes Are unstable (varies with isotope)
Emit energy (radiation)
Emit particles

5. Atoms Combine to Form Molecules
Joining atoms requires energy
Energy is the capacity to do work
Stored energy: potential energy
Energy in motion, doing work: kinetic energy
Electrons have potential energy
Shells: the energy levels of electrons
Orbitals describe the probable location of an electron
PLAY
Animation—Atoms, Ions, and Bonding

6. Three Types of Chemical Bonds
Table 2.1

7. Elements of Living Organisms
Table 2.2

8. Life Depends on Water Water molecules are polar
Water is liquid at body temperature
Water can absorb and hold heat energy

9. Two Important Biological Functions of Water
Water is the biological solvent
Water helps regulate body temperature
PLAY
Animation—Water and Chemistry

10. Water Keeps Ions in Solution
Figure 2.8

11. The Importance of Hydrogen Ions
Acids are proton (hydrogen ion) donors
Bases accept hydrogen ions
pH Scale
Hydrogen ion concentration
Buffers
Minimize pH change
Carbonic acid and bicarbonate act as one of the body’s most important buffer pairs

12. The pH Scale
Figure 2.10

13. The Organic Molecules of Living Organisms
Carbon, the building block of living things
Comprises 18% of the body by weight
Forms four covalent bonds
Can form single or double bonds
Can build micro- or macromolecules

14. Carbon Can Bond in Many Ways
Figure 2.12

15. Making and Breaking Biological Macromolecules: Dehydration Synthesis and Hydrolysis
Figure 2.13

16. Dehydration Synthesis Is the Reverse of Hydrolysis
Removes equivalent of a water molecule to link molecular units
Requires energy
Hydrolysis
Adds the equivalent of a water molecule to break apart macromolecules
Releases energy
PLAY
Animation—Monomers and Polymers

17. Carbohydrates are Composed of Monosaccharides
Figure 2.14

18. Carbohydrates are Used for Energy and Structural Support
Oligosaccharides
Short chains of monosaccharides
Disaccharides
Sucrose, fructose, lactose

19. Carbohydrates are Used for Energy and Structural Support
Polysaccharides: thousands of monosaccharides joined in chains and branches
Starch: made in plants; stores energy
Glycogen: made in animals; stores energy
Cellulose: indigestible polysaccharide made in plants for structural support

20. Lipids: Insoluble in Water
Triglycerides: energy storage molecules
Fatty acids: saturated and unsaturated
Phospholipids: cell membranes
Steroids: carbon-based ring structures
Cholesterol: used in making estrogen and testosterone
PLAY
Animation—Lipid Structure and Function

21. Proteins: Complex Structures Constructed of Amino Acids
Primary: amino acid sequence
Secondary: describes chain’s orientation in space (e.g., alpha helix, beta sheet)

22. Proteins: Complex Structures Constructed of Amino Acids
Tertiary: describes three-dimensional shape created by disulfide and hydrogen bonds
Creates polar and nonpolar areas in molecule
Quaternary: describes proteins in which two or more tertiary protein chains are associated
PLAY
Animation—Protein Structure

23. Proteins: Complex Structures Constructed of Amino Acids
Denaturation
Permanent disruption of protein structure
Can be damaged by temperature or changes in pH
Leads to loss of biological function

24. Enzyme Function Enzymes Are proteins Function as catalysts
Speed up chemical reactions
Are not altered or consumed by the reaction

25. Enzyme Function The functional shape of an enzyme is dependent on
Temperature of reaction medium pH
Ion concentration
Presence of inhibitors

26. Structure and Function of Nucleic Acids
Functions
Store genetic information
Provide information used in making proteins
Structure
Nucleotides consist of a phosphate group, a sugar, and a nitrogenous base
DNA structure is a double helix: two associated strands of nucleic acids
RNA is a single-stranded molecule
PLAY
Animation—Nucleic Acids

27. Structure of DNA DNA Deoxyribonucleic acid Double–stranded Sugar
Deoxyribose

28. Structure of DNA DNA Nitrogenous bases Adenine Thymine Cytosine
Guanine
Pairing
Adenine–thymine
Cytosine–guanine

29. Structure of RNA
RNA
Ribonucleic acid
Single–stranded
Sugar
Ribose

30. Structure of RNA RNA Nitrogenous bases Adenine Uracil Cytosine Guanine
Pairing
Adenine–uracil
Cytosine–guanine

31. Structure and Function of Adenosine Triphosphate (ATP)
Universal energy source
Bonds between phosphate groups contain potential energy
Breaking the bonds releases energy
ATP  ADP + P1 + energy

32. Structure and Function of Adenosine Triphosphate (ATP)
Figure 2.26