Functional zoology

• Cells


  The basic unit of all living matter, enormously complex structures that form tissues and organs
• In human beings an estimated 60 trillion cells interact, each performing its specialized role in an organized community
• In single-celled organisms all the functions of life are performed within the confines of one microscopic package
• There is no life without cells
• Cells are mostly small and microscopic, with the exception of eggs which are the largest cells (in volume) known
• Cell theory


  A theory stating that all living organisms are composed of cells
• Anthony Leeuwenhoek (Dutch scientist; 1632-1723) produced microscopes which were able to magnify up to 270X and saw bacteria, yeast, blood cells and many tiny animals swimming about in a drop of water
• Anthony Leeuwenhoek has since been called the "Father of Microscopy"
• Prokaryotes


  Bacteria having a single chromosome comprising a single, large molecule of DNA not located in a membrane-bound nucleus, but found in the nuclear region, or nucleoid
• Eukaryotes


  Cells with membrane-bound nuclei containing chromosomes composed of chromatin
• Eukaryotes are generally larger than prokaryotes, contain much more DNA, and are usually divided by some form of mitosis
• Organelles found in eukaryotic cells

  • Mitochondria
  • Golgi bodies
  • Ribosomes
  • Plastids
• Cell membrane


  An extremely thin membrane, 75-105 Å thick, that encloses the protoplasm
• Phospholipid bilayer


  The basic structure of the plasma membrane, consisting of a matrix in which other molecules are attached
• Fluid-mosaic model


  The view of the membrane as a phospholipid bilayer in which a variety of protein molecules are embedded, in which they can move about
• Nuclear envelope


  The membrane that bounds the nucleus, consisting of two membranes with a space of about 15nm between them
• Chromatin


  The complex of DNA and histone and nonhistone protein that carries the genetic information of the cell
• Nucleolus


  A specialized part of certain chromosomes that carries multiple copies of the DNA information to synthesize ribosomal RNA
• Cytoplasm


  The content of the cell, containing many organelles such as mitochondria, golgi complexes, and centrioles
• Endoplasmic reticulum


  A system of parallel-flattened cavities (called cisternae) lined in a thin membrane, continuous with the nuclear membrane
• Rough endoplasmic reticulum


  The bulk of the endoplasmic reticulum encrusted in ribosomes, where proteins are synthesized
• Smooth endoplasmic reticulum


  The endoplasmic reticulum not encrusted in ribosomes, involved in the synthesis and transport of lipids
• Golgi apparatus


  Consists of stacks of flattened cavities (cisternae) lined by smooth endoplasmic reticulum, involved in the modification, and packaging of protein products
• Ribosomes


  Granules attached to the matrix side of the endoplasmic reticulum membranes, the sites where proteins are synthesized in the cell
• Endoplasmic reticulum


  • Encrusted in ribosomes (rough endoplasmic reticulum)
  • Not encrusted in ribosomes (smooth endoplasmic reticulum)
• Smooth endoplasmic reticulum


  • Not continuous with the rough endoplasmic reticulum
  • Cavities are tubular rather than flattened sacs
  • Involved in the synthesis and transport of lipids
• Golgi body


  • Consists of stacks of flattened cavities (cisternae)
  • Lined by smooth endoplasmic reticulum
  • Has numerous vesicles containing secretory granules
  • Functions in the modification, and packaging of protein products especially secretory products
  • Does not synthesize protein but may add polysaccharide to the complex
• Ribosomes


  • Small (about 0.015um in diameter)
  • Lie freely in the cytoplasm or on the surface of the endoplasmic reticulum
  • Contain a significant proportion of the cell's RNA
  • When in groups, are called polyribosomes
• Mitochondria


  • Sausage shaped, round or threadlike
  • Largest are 1.0um wide and 3-6um long
  • Covered by a double membrane, the inner being folded to form projections (cristae)
  • Site of oxidative phosphorylation and electron transport, and enzymes of the TCA cycle
• Lysosomes


  • Simple spherical sacs about 0.25-0.8um in diameter
  • Bounded by a single membrane
  • Contain digestive (hydrolytic) enzymes
  • Pinched off from the Golgi bodies
  • Digest worn-out organelles and can destroy the entire cell
• Centrioles


  • Barrel-shaped organelles
  • 0.3-0.5um long and 0.2um in diameter
  • Contain 9 triplets of microtubules
  • Occur in pairs (centrosomes)
  • Involved in assembling microtubules, influencing cell shape, moving chromosomes in cell division, and providing structure for flagella and cilia
• Microtubules


  • Hollow tubes about 25 nanometers in diameter
  • Composed of a ring of 13 protein protofilaments
  • Form from MTOC nucleation centers and radiate toward the cell periphery
  • In a constant state of flux, polymerizing and depolymerizing
  • Stabilized by the binding of GTP
  • Allow for cellular movement and transport of materials within the cell
• Passive transport


  1. Diffusion

  2. Facilitated diffusion

  3. Osmosis

  4. Filtration
• Diffusion


  The net movement of material from an area of higher concentration to an area of lower concentration
• Facilitated diffusion


  Carrier-mediated transport of large molecules through the cell membrane using transport proteins
• Osmosis


  The movement of water between two solutions with different concentrations when separated by a semi-permeable membrane
• Filtration


  The movement of molecules and water across a membrane based on the size of the membrane pores
• Active transport


  1. Movement of molecules across cell membrane or membrane of a cell organelle, from low to high concentration

  2. Requires cellular energy
• Active transport using transport proteins

  • Movement directly across the cell membrane with assistance from transport proteins (transporters or permeases)
  • Permeases form a passageway through the membrane, enabling solute molecules to cross
• Sodium-potassium pump


  Example of active transport using transport proteins, helps nerve cells pass electrical impulses