Cell Organelles, Cell Membrane, Cell Transport

• Cell theory


  • Cells are the building blocks of all organisms
  • All cells come from the division of preexisting cells
  • Cells are the smallest units that carry out life’s essential physiological functions
• Each cell maintains homeostasis at the cellular level
• Homeostasis at the tissue, organ, organ system, and organism levels results from the combined feedback of many cells
• Cytology


  The study of the structure (anatomy) of cells
• Types of cells in the human body

  • Sex cells
  • Somatic cells
• Sex cells


  Germ cells or reproductive cells that allow for reproduction
• Sex cells


  • Male sperm
  • Female oocyte
• Somatic cells


  All body cells except sex cells
• Plasma membrane


  Forms the outer boundary of the cell and allows for selective transport of substances
• Main components of the plasma membrane

  • Lipids
  • Proteins
• Functions of the plasma membrane

  • Physical isolation
  • Regulation of exchange with the environment
  • Sensitivity to the environment
  • Structural support
• Physical isolation


  Separates the inside of the cell (or cytoplasm) from the surrounding extracellular fluid
• Regulation of exchange with the environment


  Controls the entry of ions and nutrients, the elimination of wastes, and the release of secretions
• Sensitivity to the environment

  Contains receptors that allow the cell to respond to chemical signals
• Structural support


  Anchors cells to each other and to extracellular materials and provides stability to tissues
• Membrane lipids


  The plasma membrane is a phospholipid bilayer
• Hydrophilic heads


  Face outward to the watery environments of the extracellular fluid and the intracellular fluid (cytosol)
• Hydrophobic tails


  Form the inside core of the membrane and act as a barrier to ions and water-soluble compounds
• Other lipids in the membrane

  • Cholesterol
  • Other steroids
  • Glycolipids
• Cholesterol


  Makes the plasma membrane less fluid and less permeable
• Integral proteins


  Proteins within the membrane
• Transmembrane proteins


  Integral proteins that span the entire width of the membrane
• Peripheral proteins


  Bound to inner or outer surface of the membrane
• Types of membrane proteins by function

  • Anchoring proteins
  • Recognition proteins
  • Enzymes
  • Receptor proteins
  • Carrier proteins
  • Channels
• Anchoring proteins


  Attach to inside or outside structures and stabilize membrane position
• Recognition proteins


  Label cells as normal or abnormal
• Enzymes


  Catalyze reactions
• Receptor proteins


  Bind and respond to ligands (ions, hormones)
• Carrier proteins


  Bind and transport specific solutes through the membrane
• Channels


  Integral proteins with a central pore which permits water and small solutes to flow through
• Gated channels


  Open or close to regulate the passage of substances
• Membrane carbohydrates


  • Proteoglycans
  • Glycoproteins
  • Glycolipids
• Glycocalyx


  Sticky “sugar coat” formed by membrane carbohydrates
• Functions of the glycocalyx

  • Lubrication and protection
  • Anchoring and locomotion of specialized cells
  • Specificity in binding
  • Recognition (immune response)
• Cytosol


  A colloid which contains water and dissolved nutrients, ions, proteins, and waste products
• Organelles


  Internal structures with specific functions
• Inclusions


  Masses of insoluble materials inside cells
• Types of organelles


  • Nonmembranous organelles
  • Membranous organelles
• Nonmembranous organelles


  • Cytoskeleton
  • Centrioles
  • Ribosomes
  • Proteasomes
  • Microvilli
  • Cilia
  • Flagella
• Membranous organelles


  • Endoplasmic reticulum (E R)
  • Golgi apparatus
  • Lysosomes
  • Peroxisomes
  • Mitochondria