page 5
 CELL COMPONENTS
1) cell wall (see next page for structure of primary and secondary cell wall & middle lamella) 
    a) polysaccharide - a polymer or chain of sugars 
      1) cellulose- forms a matrix of microfibrils (chains of b-1,4-linked glucose,see below) 
      2) hemicellulose - filler between cellulose microfibrils (chains of misc. sugar) 
      3) pectin - cementing agent or filler; high in middle lamella and fruit; (chains 
                       of galacturonic acid) 
    b) lignin - tough polymer of phenolic compounds; high in secondary cell wall. 
    c) protein - mainly structural (most commonly hydroxyproline) 
2) plasmalemma or plasma membrane - a double membrane that surrounds the cytoplasm;
    composed of a bilayer of phospholipids and proteins; it is selectively permeable and
    regulates absorption into cells and leakage from cells. 

3) plasmodesmata- tubular plasma membrane extensions through cell walls that connect
                               adjacent cells. 

4) cytoplasm - cytosol plus organelles; most metabolism occurs in the cytosol or its organelles. 

    a) cytosol - much of the cytoplasm is a water solution of dissolved compounds 
    b) organelles - specialized structures in cytoplasm, each with specific functions. 
      1) nucleus - location of DNA and some of the RNA 
        a) chromosome - strands or coils of DNA 
        b) nucleolus - spherical, dense body; site of ribosome synthesis.
      2) mitochondria - major site of respiration; called the "power house" of the cell. 
      3) plastid - double membrane-bound bodies for storage and photosynthesis 
         a) leucoplast - colorless plastids 
          1) amyloplast- starch storage (chains of a-1,4-linked glucose, below) 
          2) elaioplast- fat and oil storage 
        b) chromoplast- colored plastids for storage of carotenoids(orange and 
                                   yellow pigments) 
        c) chloroplast - green plastids that contains chlorophyll; the site of
                                      photosynthesis 
      4) endoplasmic reticulum - tubular membranes for communication across the 
                                                        cytoplasm; site of protein & membrane synthesis 
      5) ribosome - dense spheres of RNA; protein synthesis occurs on their surface 
      6) vacuole- storage of organic acids, salts, anthocyanins (blue, red and purple
                             pigments), metabolic wastes, enzymes and metabolites. 
        a) tonoplast- membrane that surrounds the vacuole 
      7) Golgi body ordictyosome - disk-shaped membranes for membrane and
                                                               polysaccharide synthesis 
      8) microbody- membrane-bound storage bodies with various functions.
      9) microtubule - tubular rods used in mitosis & cellulose orientation in cell walls
Structure of starch vs. cellulose