Foundations of General Biology: Structure, Function, and Chemistry of Life

Five Fundamental Characteristics of Living Organisms

Overview

All living organisms share five essential characteristics that define life. These characteristics are foundational to the study of biology and help distinguish living things from non-living matter.

• Cells: All organisms are composed of membrane-bound cells, which serve as the basic unit of life.

• Replication: All organisms are capable of reproduction, ensuring the continuation of their species.

• Information: Organisms process hereditary information encoded in genes and respond to environmental information.

• Energy: All organisms acquire and use energy to maintain life processes.

• Evolution: Populations of organisms are continually evolving through genetic changes over time.

Hierarchy of Biological Organization

Levels of Organization

Biological systems are organized into a hierarchy, from the largest scale to the smallest. Each level represents increasing complexity and specialization.

• Biosphere: All environments on Earth.

• Ecosystem: All living and nonliving things in a particular area.

• Community: All organisms in an ecosystem.

• Population: All individuals of a species in a particular area.

• Organism: An individual living thing.

• Organ and organ system: Specialized body parts made up of tissues.

• Tissue: A group of similar cells.

• Cell: Life's fundamental unit of structure and function.

• Organelle: A structural component of a cell.

• Molecule: A chemical structure consisting of atoms.

The Central Dogma of Molecular Biology

Flow of Genetic Information

The central dogma describes how genetic information flows from DNA to RNA to protein, ultimately determining physical traits.

• DNA: Codes for ribonucleic acid (RNA), which codes for proteins.

• RNA: Molecules that carry out specialized functions in cells. Messenger RNA (mRNA) is read to make proteins (transcription).

• Proteins:

  • Crucial to tasks required by cells.

  • Form structural components and promote chemical reactions.

  • Proteins determine physical traits of organisms.

• Base Pairing: A pairs with T, G pairs with C. This pairing preserves genetic information and permits DNA copying.

End result of central dogma: An organism's traits are determined by the flow of genetic information.

Cell Theory

Principles of Cellular Life

Cell theory is a fundamental concept in biology, stating:

• All organisms are made up of cells.

• All cells come from preexisting cells.

Classification of Organisms: Plants and Bacteria

Types of Cells

Organisms can be classified based on their cell type and method of energy acquisition.

• Eukaryotes: Domain Eukarya includes all eukaryotic organisms.

  • Plants: Produce their own food by photosynthesis.

  • Fungi: Absorb nutrients.

  • Animals: Ingest their food.

  • All have membrane-bound organelles.

• Prokaryotes: Usually single-celled organisms, including bacteria and archaea.

Key Terminology in Biology

Essential Definitions

• Biology: The scientific study of life and living organisms.

• Cell: The smallest and most fundamental unit of life.

• Organism: Any individual form of life.

• Multicellular: Organisms composed of many cells with specialized functions.

• Microscope: Instrument used to visualize cells and small structures.

• Adaptations: Traits that enhance an organism's ability to survive and reproduce.

• Alleles: Different versions of a gene.

• Abiotic: Non-living chemical and physical parts of the environment.

• Acclimatization: The process by which an organism adjusts to changes in its environment.

Atomic Structure and Subatomic Particles

Atoms and Their Components

Atoms are the basic units of matter, composed of subatomic particles with distinct properties.

Subatomic Particle	Electric Charge	Atomic Mass Unit	Location
Proton	+1	1	Nucleus
Neutron	0	1	Nucleus
Electron	-1	0	Orbiting Nucleus

• Atomic Number: Number of protons in the nucleus. Determines the element.

• Mass Number: Sum of protons and neutrons.

• Electron Orbitals: 3D regions around the nucleus where electrons are found. Shells closer to the nucleus are lower in energy; outer shells (valence shells) are higher in energy and more reactive.

Isotopes and Radioactive Isotopes

Variation in Atomic Structure

Isotopes are atoms of the same element with different numbers of neutrons, resulting in different mass numbers.

• All atoms of an element have the same number of protons, but not necessarily the same number of neutrons.

• Radioactive Isotopes: Unstable isotopes that break down and emit energy as rays or particles.

• Half-life: Time it takes for half of the radioactive atoms in a sample to decay.

• Radioactive isotopes are used in medicine and radiometric dating of fossils.

Chemical Bonds and Molecules

Types of Chemical Bonds

Chemical bonds are attractive forces that hold atoms together to form molecules and compounds.

• Molecules: Substances containing two or more chemically bound atoms (e.g., O2).

• Compounds: Molecules composed of at least two different elements (e.g., H2O).

• Chemical Formula: Reveals the number and type of atoms in a molecule (e.g., C6H12O6).

Intramolecular vs. Intermolecular Bonds

• Intramolecular Bonds: Bonds within the same molecule.

• Intermolecular Bonds: Bonds between atoms of different molecules.

Covalent vs. Noncovalent Bonds

• Covalent Bonds: Interaction between two atoms resulting from the sharing of electrons.

  • Nonpolar: Equal sharing of electrons.

  • Polar: Unequal sharing, leading to partial charges.

• Electronegativity: Measure of an atom's attraction to electrons (scale: 0-4).

• Noncovalent Bonds: Interactions from full or partial charges; no sharing of electrons.

  • Ionic Bonds: Electrostatic interactions between ions (charged atoms or molecules).

    • Anions: Negatively charged ions (gain electrons).

    • Cations: Positively charged ions (lose electrons).

  • Hydrogen Bonds: Interaction between a highly electronegative atom (F, O, N) and a hydrogen atom. Collectively strong, important in water and macromolecules.

  • Van der Waals: Weak interactions due to transient charges.

Properties of Water

Structure and Emergent Properties

Water is a small polar molecule with unique properties due to hydrogen bonding.

• Cohesion: Ability of water molecules to stick together.

• Adhesion: Ability of water molecules to stick to other substances.

• Surface Tension: Difficulty in breaking the surface of water.

• High Specific Heat: Energy required to raise temperature; water resists temperature changes.

• Heat of Vaporization: Energy to convert liquid water to gas; sweating cools the body.

• Low Density of Ice: Ice floats on water due to lower density.

• Universal Solvent: Water dissolves many substances, especially polar and ionic compounds.

• Hydrophilic: Water-loving molecules (ions, polar).

• Hydrophobic: Water-fearing molecules (nonpolar).

Water in Acid-Base Reactions

Dissociation and pH

Water can dissociate into ions, affecting acidity and basicity.

• $H_2O \rightarrow H^+ + OH^-$

• Acids: Give up protons ($H^+$), increase proton concentration.

• Bases: Accept protons ($H^+$), decrease proton concentration.

• Concentrations:

  • Mole: $6.022 \times 10^{23}$

  • Molecular weight: Sum of atomic weights.

  • Molarity (M): mol/L solution.

Additional info: These notes provide a comprehensive overview of foundational topics in general biology, including cellular structure, molecular genetics, atomic theory, chemical bonding, and the unique properties of water essential for life.