1.1 Science and the Scientific Method
● an idea or experiment is within the realm of science if it adheres to four key elements
1. focuses on the natural universe ~ only what people can observe & measure
2. its results are reported honestly
3. its results are reproducible
4. it is carried out within a scientific context
ex. hypothesis → experiment → answer; serendipity; inspiration; exploration &
observation; model-building & deduction
1.2 Organisms, Cells, Chromosomes, and Genes
● cells are organized systems of molecules & macromolecules that fall into three broad
domains, distinguished by evolutionary, structural, and biochemical relationships
○ three domains → bacteria, archaea, eukarya
catalysis: a modification, especially an increase, in the rate of a chemical reaction induced by
material that is unchanged chemically at the end of the reaction
enzyme: a biomolecule, either protein or RNA, that catalyzes a specific chemical reaction by
providing a reaction path with a lower activation energy
● viruses are not members of the main domains, but are present in nature in great variety &
complexity
○ viruses are unable to reproduce unless they invade a living cell; reliant on
enzymes and resources present in the host
1.3 The Organic Chemistry of Biochemistry
● biochemistry conforms to the laws of chemistry & physics; involve chemical reactions
● hydrogen, oxygen, nitrogen, & carbon make up >99% of the mass of most cells
● the chemistry of living organisms is organized around carbon
○ carbon forms single bonds with hydrogen and double bonds with oxygen &
nitrogen
● types of bond cleavage
○ homolytic: involves breaking a bond so that each atom retains one electron,
forming free radicals
■ common in high-energy or oxidative environments
■ ex. lipid peroxidation, photosynthesis, cytochrome P450 reactions
○ heterolytic: breaks a bond unevenly, with both electrons going to one atom,
forming ions like carbocations, carbanions, hydrides, or protons
■ ex. ATP hydrolysis, enzyme catalysis, formation of NADH/NAD+
● functional groups give additional properties to molecules
● molecular mass, m, is expressed in daltons (Da)
● many biochemical reactions involve interactions between nucleophiles & electrophiles
● an idea or experiment is within the realm of science if it adheres to four key elements
1. focuses on the natural universe ~ only what people can observe & measure
2. its results are reported honestly
3. its results are reproducible
4. it is carried out within a scientific context
ex. hypothesis → experiment → answer; serendipity; inspiration; exploration &
observation; model-building & deduction
1.2 Organisms, Cells, Chromosomes, and Genes
● cells are organized systems of molecules & macromolecules that fall into three broad
domains, distinguished by evolutionary, structural, and biochemical relationships
○ three domains → bacteria, archaea, eukarya
catalysis: a modification, especially an increase, in the rate of a chemical reaction induced by
material that is unchanged chemically at the end of the reaction
enzyme: a biomolecule, either protein or RNA, that catalyzes a specific chemical reaction by
providing a reaction path with a lower activation energy
● viruses are not members of the main domains, but are present in nature in great variety &
complexity
○ viruses are unable to reproduce unless they invade a living cell; reliant on
enzymes and resources present in the host
1.3 The Organic Chemistry of Biochemistry
● biochemistry conforms to the laws of chemistry & physics; involve chemical reactions
● hydrogen, oxygen, nitrogen, & carbon make up >99% of the mass of most cells
● the chemistry of living organisms is organized around carbon
○ carbon forms single bonds with hydrogen and double bonds with oxygen &
nitrogen
● types of bond cleavage
○ homolytic: involves breaking a bond so that each atom retains one electron,
forming free radicals
■ common in high-energy or oxidative environments
■ ex. lipid peroxidation, photosynthesis, cytochrome P450 reactions
○ heterolytic: breaks a bond unevenly, with both electrons going to one atom,
forming ions like carbocations, carbanions, hydrides, or protons
■ ex. ATP hydrolysis, enzyme catalysis, formation of NADH/NAD+
● functional groups give additional properties to molecules
● molecular mass, m, is expressed in daltons (Da)
● many biochemical reactions involve interactions between nucleophiles & electrophiles
