Cellular Foundations - Biochemistry

Cellular Foundations

  • Cellular Unity and Diversity

    • Organisms can be single-celled or multicellular.
    • All cells share fundamental biochemical properties despite their differences.

  • Fundamental Properties of Cells

    • Cells are the structural and functional units of all living organisms.
    • Plasma Membrane:
    • Defines the cell's boundary.
    • Composed of lipids and proteins.
    • Functions as a barrier to ions and polar molecules; transport proteins facilitate selective passage.
    • Cytoplasm:
    • Contains cytosol, organelles, and various particles.
    • Cytosol is a concentrated solution of enzymes, RNA, metabolites, and ions.
    • Cells must have either a nucleus or nucleoid where genetic material is stored.

  • Cell Size Limits

    • Cell size is defined by the relationship between surface area and volume.
    • Surface-to-Volume Ratio: For spherical cells, surface area = 4πr24 \pi r^2 and volume = 43πr3\frac{4}{3} \pi r^3, leading to decreased ratio as size increases.
    • Small cells maintain efficient transport processes.

  • Three Domains of Life

    • Bacteria: Live in diverse environments; typically smaller.
    • Archaea: Thrive in extreme conditions; biochemically distinct from bacteria.
    • Eukarya: Include organisms with complex cells featuring membrane-bound organelles.

  • Energy and Nutritional Strategies

    • Organisms classified by energy sources:
    • Phototrophs: Use sunlight.
    • Chemotrophs: Use chemicals.
    • Autotrophs synthesize compounds from CO₂, while heterotrophs depend on organic nutrients from others.

  • Bacterial and Archaeal Cells

    • Bacteria: Defined cell structure with a protective outer membrane and peptidoglycan cell wall.
    • Archaeal membranes differ significantly in composition but share structural similarities.

  • Eukaryotic Cell Structure

    • Larger than prokaryotes, possessing intricate organelles.
    • Organelles include mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and for plants, chloroplasts and vacuoles.

  • Cytoplasmic Organization

    • The cytoskeleton aids in cell shape, structure, and intracellular transport.
    • Filaments: Actin filaments, microtubules, and intermediate filaments work dynamically, regulated by various proteins.

  • Supramolecular Structures

    • Higher-order structures arise from noncovalent interactions among macromolecules.
    • These interactions stabilize complex structures that can be essential for cellular function.

  • In Vitro vs In Vivo Studies

    • Research on purified biomolecules (in vitro) may overlook crucial interactions present in living cells (in vivo).

  • Summary of Cellular Foundations

    • Cells are supported by a plasma membrane, contain cytosol rich in biomolecules and are organized around genetic material.
    • Size constraints relate to efficient nutrient delivery.

Key Concepts

  • Physical and Chemical Laws: Both living organisms and inanimate matter conform to the same laws, revealing the biochemistry underlying life.

  • Nuclear Structure: Bacterial cells have a nucleoid with non-membrane-bound DNA, while eukaryotic cells contain a membrane-bound nucleus.

  • Evolution: Fundamental evolutionary connections shared across diverse life forms are revealed at the molecular level through genetics and biochemistry.

  • Diversity of Life: Biological diversity in habitats leads to various biochemical adaptations that align with environmental needs.