Cells

• Cell Theory


  • Cells represent the basic structural and functional unit of life
  • All organisms are composed of one or more cells
  • All tissues & organs are composed of cells
  • There is no life without cells
• Cell Theory


  Cells come from preexisting cells
• Prokaryotic vs Eukaryotic Cells


  • All cells have DNA
  • Use the same genetic code
  • Synthesize proteins
  • Use ATP in similar ways
• Prokaryotic Cells


  No nucleus or other membrane-bound organelles
• Kingdoms of Prokaryotic Cells


  • Archaebacteria
  • Eubacteria
• Eukaryotic Cells


  Do have nucleus and membrane-bound organelles
• Kingdoms of Eukaryotic Cells


  • Protista
  • Fungi
  • Plantae
  • Animalia
• Plasma Membrane


  Surrounds the cell
• Nucleus


  • Largest organelle
  • Double layered nuclear envelope
• Cytoplasm


  Cellular material between cell membrane and nuclear envelope
• Organelles found in Cytoplasm


  • Mitochondria
  • Golgi Complex
  • Centrioles
  • Endoplasmic Reticulum
• Plasma Membrane Structure


  Fluid mosaic model
• Plasma Membrane


  • Two layers of phospholipid molecules with hydrophilic heads toward outside and hydrophobic tails inside
  • Nonpolar nature of hydrophobic ends prohibit polar substances from crossing
  • Glycoproteins embedded function in transport of molecules across
• Nuclear Envelope


  Contains pores to allow molecules to move between nucleus and cytoplasm
• Chromosomes


  • Contained in the nucleus
  • Chromatin refers to loosely condensed DNA and proteins
• Nucleoli


  Specialized parts of certain chromosomes that carry multiple copies of DNA used to synthesize ribosomal RNA
• Ribosomes


  • Combine with ribosomal RNA to form two subunits
  • Leave the nucleus through pores in nuclear envelope
• Endoplasmic Reticulum (ER)


  • Nuclear envelope joins with a cytoplasmic membranous system
  • Rough ER is covered with ribosomes, Smooth ER is not
• Endoplasmic Reticulum

  • Ribosomes on RER synthesize proteins that enter ER to be incorporated into plasma membrane, exported from cell, or bound for lysosomes
  • Lipids and phospholipids are synthesized in SER
• Golgi Complex


  Stack of membranous vesicles where storage, modification, and packaging of protein products occurs
• Lysosomes


  • Contain enzymes that can breakdown foreign material or worn out cellular components
  • Contents would kill cell if membrane ruptured
  • May pour enzymes into food vacuoles
• Mitochondria


  • Powerhouses of cells, contain enzymes that carry out energy-yielding steps of aerobic metabolism, produce ATP
  • Composed of double membrane with inner membrane folded into cristae
  • Self-replicating, contain own circular DNA
• Cilia and Flagella


  Motile extensions of the cell surface
• Pseudopodia


  • Cytoplasmic streaming through action of actin microfilaments extends them outward
  • Some have specialized pseudopodia with microtubules assembled and disassembled to allow movement
• Tight Junctions


  Form when cell membranes of adjacent cells fuse, function as seals
• Adhesion Junctions


  Occur under tight junctions, transmembrane proteins link across small space and connect to microfilaments
• Desmosomes


  Act as spot welds and increase strength of tissue
• Hemidesmosomes


  Found at base of cells and anchor them to connective tissue
• Gap Junctions


  Canals between cells that provide intercellular communication
• Microvilli


  Small fingerlike projections with bundles of actin microfilaments, serve to increase surface area
• Centromere


  Also known as primary constriction, location where kinetochore proteins attach
• Kinetochore Proteins


  Site of spindle fiber attachment
• Telomeres


  Provide chromosome stability
• Chromomeres


  Knoblike regions along length of chromosome
• Chromatin


  Interphase and early prophase form, two forms: heterochromatin (tightly coiled/condensed) and euchromatin (non-condensed)
• Chromosome Types


  • Metacentric
  • Submetacentric
  • Acrocentric
  • Telocentric
• Chromosomes in Cells


  All nonreproductive cells in a species have the same number, half from each parent resulting in two sets (diploid)
• Homologous Chromosomes


  Chromosome 1 from mom and chromosome 1 from dad
• Cell Cycle


  Cells come from preexisting cells through cell division, which occupies a small portion of the cycle
• Interphase


  Includes G1 growth phase, S DNA replication phase, and G2 growth phase