Characteristics of Life

Five Fundamental Characteristics of Living Organisms

• Cells: All organisms are made up of membrane-bound cells.

• Replication: All organisms are capable of reproduction.

• Information: All organisms process hereditary information encoded in genes as well as information from the environment.

• Energy: All organisms acquire and use energy to stay alive.

• Evolution: Populations of organisms are continually evolving.

Hierarchy of Biological Organization

• 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

• 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. Permits DNA copying and preserves genetic information.

• End Result: An organism's traits are determined by the flow of genetic information from DNA to RNA to protein.

Theories in Biology

• Cell Theory:

  • All organisms are made up of cells.

  • All cells come from preexisting cells.

Cells: Eukaryotes and Prokaryotes

• Eukaryotes: Organisms with membrane-bound organelles, including a nucleus.

  • Domain Eukarya: Includes all eukaryotic organisms.

  • Three Kingdoms:

    • Plants: Produce their own food by photosynthesis.

    • Fungi: Absorb nutrients.

    • Animals: Ingest their food.

• Prokaryotes: Organisms without a nucleus or membrane-bound organelles.

  • Usually single-celled organisms.

  • Includes Bacteria and Archaea.

Key Terminology

• Biology: The scientific study of life, encompassing all living organisms and their interactions.

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

• Organism: Any individual form of life.

• Multicellular: Organisms composed of many cells that often specialize and work together.

• Microscope: Instrument used to visualize cells and other 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 over time.

Atoms and Subatomic Particles

Structure of the Atom

• Atoms are composed of protons, neutrons, and electrons.

Atomic Number and Mass

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

• Mass Number: Sum of protons and neutrons.

• Atomic Mass: Average mass of all isotopes of an element.

Electron Orbitals

• Electrons occupy orbitals around the nucleus.

• Shells closer to the nucleus are lower in energy; outer shells are higher in energy and more reactive.

• Valence Electrons: Electrons in the outermost shell, important for chemical bonding.

• 1st shell holds up to 2 electrons; 2nd shell up to 8 electrons.

Isotopes

• Atoms of the same element with the same number of protons but different numbers of neutrons.

• Isotopes have different mass numbers.

• Radioactive Isotopes: Unstable isotopes that break down and emit energy.

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

  • Used in medicine and radiometric dating of fossils.

Chemical Bonds

Types of Bonds

• Covalent Bonds: Atoms share electrons.

  • Nonpolar Covalent: Equal sharing of electrons.

  • Polar Covalent: Unequal sharing, leading to partial charges.

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

• Noncovalent Bonds: No sharing of electrons.

  • Ionic Bonds: Attraction between oppositely charged ions (cations and anions).

  • Hydrogen Bonds: Weak attraction between a hydrogen atom and an electronegative atom (F, O, N).

  • Van der Waals Interactions: Weak attractions due to transient charges.

Properties of Water

• Polarity: Water is a polar molecule with partial positive and negative charges.

• Hydrogen Bonding: Water molecules form hydrogen bonds with each other.

• Emergent Properties:

  1. Cohesion: Water molecules stick together (surface tension).

  2. Adhesion: Water molecules stick to other substances.

  3. High Specific Heat: Water resists temperature change.

  4. High Heat of Vaporization: Energy required to convert water from liquid to gas.

  5. Low Density of Ice: Ice floats on liquid water.

  6. Universal Solvent: Water dissolves many substances.

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

     • Hydrophobic: Water-fearing (nonpolar molecules).

Water in Acid-Base Reactions

• Water dissociates:

• Acids: Donate protons (), increase proton concentration.

• Bases: Accept protons (), decrease proton concentration.

• Concentrations:

  • Mole: molecules.

  • Molecular Weight: Sum of atomic weights.

  • Molarity (M): Moles per liter of solution.

Example: The Central Dogma in Action

• Example: The gene for hemoglobin in DNA is transcribed into mRNA, which is then translated into the hemoglobin protein, determining the trait of oxygen transport in red blood cells.