Lecture 3
THE CHEMISTRY OF LIVING
THINGS
III. Atoms Combine to Form
Molecules
C. Three types of Bonds
Table 2.1
III. Atoms Combine to Form
Molecules
Covalent Bond
Figure 2.6
Covalent Bonds
III. Atoms Combine to Form
Molecules
Ionic Bond
Figure 2.7
Ionic Bonds
Hydrogen Bonds
IV. Elements of Living Organisms
Table 2.2
V. Life Depends on Water
A. Water molecules are polar
B. Water is liquid at body temperature
C. Water can absorb & hold heat energy
V. Life Depends on Water
D. Two Important Biological Functions
of Water
1. Water is the biological Solvent
2. Water helps regulate body temperature
Water Keeps Ions in Solution
Figure 2.9
VI. The Importance of Hydrogen Ions
A. Acids are proton (hydrogen ion) donors,
1. Bases accept hydrogen ions
B. pH Scale = hydrogen ion concentration
C. Buffers: minimize pH change
1. Carbonic acid & bicarbonate act as one of
body’s most important buffer pairs
The pH Scale
Figure 2.11
VII. The Organic Molecules of Living
Organisms
A. Carbon, the building block of living things:
1. Comprises 18% of body by weight
2. Forms four covalent bonds
3. Can form single or double bonds
4. Can build micro- or macromolecules
Carbon Can Bond in Many Ways
Figure 2.13
VIII. Making & Breaking Biological
Macromolecules
Figure 2.14
VIII. Making & Breaking Biological
Macromolecules
A. Dehydration synthesis
1. Removes equivalent of a water molecule to
link molecular units
2. Requires energy
B. Hydrolysis
1. Adds the equivalent of a water molecule to
break apart macromolecules
2. Releases energy
IX. Carbohydrates
Figure 2.15
IX. Carbohydrates
A. Oligosaccharides: short chains of
monosaccharides
Disaccharides: sucrose, maltose, lactose
IX. Carbohydrates
B. Polysaccharides: thousands of
monosaccarides joined in chains & branches
1. Starch: made in plants; stores energy
2. Glycogen: made in animals; stores energy
3. Cellulose: undigestible polysaccharide made in
plants for structural support
X. Lipids: Insoluble in Water
A. Triglycerides: energy storage molecules
Ex: Fatty acids: saturated and unsaturated
B. Phospholipids: cell membranes
C. Steroids: carbon-based ring structures
Ex: Cholesterol: used in making estrogen and
testosterone
Triglycerides
Figure 2.17
Phospholipids & Steroids
Figure 2.19
Figure 2.18
Protein Structure
Figure 2.18
XI. Proteins: Complex Structures
Constructed of Amino Acids
A. Structure
1. Primary: amino acid sequence
2. Secondary: describes chain’s orientation in
space; e.g., alpha helix, beta sheet
XI. Proteins: Complex Structures
Constructed of Amino Acids
A. Structure
3. Tertiary: describes three-dimensional shape
created by disulfide and hydrogen bonds
Creates polar and nonpolar areas in molecule
4. Quaternary: describes proteins in which
two or more tertiary protein chains are
associated
Protein Structure
Figure 2.18
XI. Proteins: Complex Structures
Constructed of Amino Acids
XII. Enzyme Function
A. Enzymes:
1. proteins
2. function as catalysts
3 facilitate chemical reactions
B. The functional shape of an enzyme is
dependent on:
1. temperature of reaction medium
2. pH
3. ion concentration
4. presence of inhibitors
XII. Structure and Function of
Nucleic Acids
A. Functions
1. Store genetic information
2. Provide information used in making
proteins
B. Structure
1. Nucleotides consist of a phosphate group, a
sugar, and a nitrogenous base
2. DNA structure is a double helix: two
associated strands of nucleic acids
3. RNA is a single-stranded molecule
XII. Structure and Function of
Nucleic Acids
C. DNA: double-stranded
1. Sugar: deoxyribose
2. Nitrogenous bases: adenine, thymine,
cytosine, guanine
3. Pairing: adenine-thymine and cytosineguanine
XII. Structure and Function of
Nucleic Acids
D. RNA: single-stranded
1. Sugar: ribose
2. Nitrogenous bases: adenine, uracil,
cytosine, guanine
3. Pairing: adenine-uracil, cytosine-guanine
Structure and Function of Adenosine
Triphosphate (ATP)
Figure 2.26