BIO189 - CH.4

CELL STRUCTURE AND FUNCTION

LECTURE LEARNING OBJECTIVES

  • Describe three types of microscopy and their appropriate uses.

  • Identify components found in all cells.

  • Compare prokaryotic and eukaryotic cells.

  • Describe the structure and function of cellular components such as membranes, organelles, and cytoskeleton.

  • Explain the endosymbiont theory and its supporting characteristics.

MICROSCOPY

  • Light Microscopy: Uses visible light; can view living cells.

  • Electron Microscopy: Uses electrons; cannot view living cells; includes:

    • Scanning Electron Microscopy (3D surface structures)

    • Transmission Electron Microscopy (2D interior structures)

CELL

  • Basic unit of structure and function; may be unicellular or multicellular.

  • All cells have:

    • Plasma membrane

    • Cytosol

    • Chromosomes/DNA

    • Ribosomes (70S in prokaryotes, 80S in eukaryotes)

PROKARYOTIC CELLS

  • Unicellular, no membrane-bound organelles, no nucleus; DNA in nucleoid.

  • May have a peptidoglycan cell wall.

EUKARYOTIC CELLS

  • Membrane-bound organelles; DNA in nucleus; larger than prokaryotes.

  • Cell walls: cellulosic in plants, chitin in fungi.

CELLULAR COMPONENTS

  • Nucleus: Double membrane, regulates molecule movement; stores genetic info.

  • Ribosomes: Two subunits (protein + RNA); site of protein synthesis.

  • Rough ER: Membrane-bounded sacs; synthesizes proteins, glycoproteins.

  • Smooth ER: Membrane-bounded sacs; synthesizes lipids, detoxifies, stores ions.

  • Golgi Apparatus: Membrane sacs; processes and packages proteins/lipids.

  • Mitochondria: Two membranes; site of cellular respiration.

  • Peroxisome: Single membrane; catalyzes reactions producing hydrogen peroxide.

  • Lysosome: Membrane sac with hydrolytic enzymes; intracellular digestion.

  • Centrosome: Animal cells; organizes microtubules during cell division.

  • Chloroplasts: Plant cells; site of photosynthesis.

ENDOSYMBIONT THEORY

  • Eukaryotes engulfed prokaryotes:

    • Mitochondria from aerobic prokaryotes

    • Chloroplasts from photosynthetic prokaryotes

  • Supporting traits:

    • Double membranes

    • 70S ribosomes

    • Circular DNA

    • Independent reproduction

CYTOSKELETON

  • Microtubules: Hollow tubes, movement of organelles, cell division support.

  • Microfilaments: Actin filaments; function in muscle contraction and cell movement.

  • Intermediate Filaments: Fibrous proteins; structural support and anchor organelles.

EXTRACELLULAR COMPONENTS

  • Plasma membrane in all cells; cell wall present in plants (cellulose) and fungi (chitin).

  • Extracellular Matrix: Composed of glycoproteins, collagen; functions in communication.

CELL JUNCTIONS

  • Plasmodesmata: Membrane-lined channels in plant cells for transport/communication.

  • Gap Junctions: Pores in animal cells for molecular transport.

  • Desmosomes: Anchor cells together using intermediate filaments.

  • Tight Junctions: Proteins uniting plasma membranes to prevent fluid leakage.