Study material
Basic biology
The Foundations of Life and Biological Chemistry
Analyze the defining characteristics of living organisms, understand the structural organization of biological systems, and evaluate the chemical properties of water and the four fundamental biological macromolecules.
Biology is the empirical study of life and living organisms. Living systems obey the fundamental laws of chemistry and physics while exhibiting emergent properties that arise from complex structural organization.
Characteristics of Life
All known living systems share a core set of distinct biological characteristics:
- Cellular Organization: All organisms consist of one or more membrane-bound units called cells.
- Metabolism: Organisms acquire and transform energy through coordinated chemical reactions to sustain cellular processes.
- Homeostasis: The maintenance of a stable internal environment despite fluctuations in external conditions.
- Reproduction: The transmission of genetic information from parent to offspring via asexual or sexual mechanisms.
- Growth and Development: Directed change and enlargement controlled by encoded genetic instructions.
- Response to Stimuli: Dynamic physiological or behavioral adjustments to environmental cues.
- Evolutionary Adaptation: Changes in hereditary characteristics across populations over successive generations via natural selection.
Hierarchical Organization of Life
Biological complexity is structured hierarchically, from subatomic particles to the global biosphere.
- Atom and Molecule: Smallest units of matter participating in biochemical compounds.
- Organelle: Functional subcellular structure (e.g., mitochondrion, nucleus).
- Cell: Fundamental structural and functional unit of life.
- Tissue: Integrated group of cells working collaboratively toward a shared function.
- Organ and Organ System: Specialized groupings of tissues integrated into distinct physiological entities.
- Organism: An individual biological entity.
- Population: Conspecific individuals occupying a specified spatial area simultaneously.
- Community: Interacting assemblage of diverse populations inhabiting a common habitat.
- Ecosystem: Dynamic network comprising the living biological community and nonliving physical factors.
- Biosphere: The entire global aggregate of living ecosystems on Earth.
Chemical Principles and Macromolecules
Biological matter consists primarily of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur (CHNOPS). The high electronegativity of oxygen relative to hydrogen causes water () to form a polar covalent molecule capable of establishing hydrogen bonds. These bonds grant water high specific heat capacity, cohesion, adhesion, and solvent capabilities necessary for physiological processes.
Biological macromolecules are large, carbon-based polymers assembled from repeating subunit molecules called monomers via dehydration synthesis (condensation) reactions, and disassembled through hydrolysis reactions.
| Macromolecule Class | Monomer Unit | Primary Chemical Linkage | Biological Roles |
|---|---|---|---|
| Carbohydrates | Monosaccharide (e.g., glucose) | Glycosidic bond | Short-term energy storage, structural support |
| Lipids | Fatty acids + glycerol | Ester linkage | Membrane composition, long-term energy reserves |
| Proteins | Amino acid (20 variations) | Peptide bond | Enzymatic catalysis, structural support, transport |
| Nucleic Acids | Nucleotide (sugar, phosphate, base) | Phosphodiester bond | Storage and transmission of genetic data |
Which level of biological organization is the lowest tier capable of performing all activities required for life?
All living entities rely on chemical energy and coordinated carbon-based macromolecules to sustain homeostatic order against entropic decay.
