Cell and Molecular Biology Notes

  • Living things: Organisms are intricate chemical factories that self-replicate using surrounding matter.
  • Cells: Fundamental units of life, enclosed by a membrane, containing chemicals in aqueous solution, and capable of self-replication through growth and division.
  • Cell Biology: Study of cell structure, function, and behavior, providing insights into life's nature and mechanisms. Pioneered by E.B. Wilson.
  • Biology's Themes: Balance between variety in details and constancy in fundamental mechanisms.
  • Heredity: Central to life definition; distinguishing it from non-biological processes through parent-offspring information transfer.
  • Universal Features of Life:
    • Hereditary information stored in double-strand DNA molecules.
    • DNA replicates via templated polymerization.
    • DNA transcribed into RNA.
    • Proteins act as catalysts.
    • RNA translates into proteins using same mechanism.
    • Genes encode specific proteins.
    • Life requires continual free energy input.
    • Cells function as biochemical factories.
    • Cells enclosed by a plasma membrane for nutrient and waste exchange.
    • Cells operate at a microscopic scale dominated by random thermal motion.
    • A living cell can exist with 500 genes.
  • All cells on Earth store their hereditary information in the form of double-strand molecules of DNA composed of nucleotides: A, T, C, G.
  • Templated Polymerization: Bases pair (A with T, C with G) to control monomer addition, creating a double-strand structure {(A=T, C=G)}.
  • Transcription: DNA sequence segments act as templates for synthesizing RNA.
  • Translation: RNA guides protein synthesis.
  • Proteins: Catalyze reactions and maintain cell structures; sequences selected for specific functions.
  • Catalyst: Speeds up reactions without being changed.
  • Living cell: Self-replicating collection of catalysts processing food for building blocks and energy.
  • Heredity Basis: Identified through the double-strand structure of DNA, revealing mechanisms for information translation.
  • Triplets/Codons: mRNA sequence read in three-nucleotide groups, each specifying an amino acid.
  • Free Energy & Life: Consumption of free energy is fundamental; unavailable energy leads to decay and chemical equilibrium.
  • All cells require phosphorylated nucleotide ATP (adenosine triphosphate) as a building block for DNA and RNA synthesis, as well as a carrier of free energy.
  • Plasma Membrane: Selective barrier for nutrient uptake and waste excretion.
  • Brownian motion: Drives diffusion impacting rates of biochemical reactions.
  • Brownian ratchet: Harnessing random thermal motions in a directed way, like membrane protrusion driven by actin polymerization.
  • Hereditary Information: Transmitted through DNA replication, where strands separate and are used as templates for new complementary strands.
  • Information Expression: The process of transcription (DNA to RNA) and translation (RNA to protein).
  • The "Tree of Life" consists of three primary lineages: Eukaryotes, Bacteria, and Archaea.
  • Diversity Quantification: Evolutionary relationships are determined through DNA sequence analysis.
  • Tree of Life Domains:
    • Eukaryotes: "Truly nucleated" cells with DNA in a nucleus, including plants, animals, fungi, and various microscopic forms.
    • Bacteria: Highly diverse, small, typically unicellular organisms lacking a nucleus.
    • Archaea: Less understood; outwardly resemble bacteria but genetically closer to eukaryotes.
  • Analysis via DNA genomes allows scientists to position a wide variety of organisms in an evolutionary tree of life.
  • Eukaryotic Cells: Distinguished by
    • nucleus enclosing DNA
    • membrane-bound organelles
    • cytoskeleton
    • size: Eukaryotic cells are typically larger than those of bacteria and archaea.
  • Genetic Information: Transmitted through DNA replication, where strands separate and serve as templates for new complementary strands.
  • Information Expression: RNA transcription and protein translation.
  • Eukaryotic cell's genetic information has a hybrid origin––from an ancestorial anaerobic archaeon and from captured bacteria (endosymbionts).