How Cells are Put Together, part three  

I.  Prokaryotic Cells

Prokaryotic cells are all bacterial cells.  Only bacteria are prokaryotic in cell type, they are the only prokaryotes.  Bacteria are diverse and include such organisms as blue-green algae (seen in lab) and E. coli, the colon bacillus (and many others).  These all share a simple cell construction in which a nucleus or other membrane bound organelles do not occur.  Bacteria have cell walls and some have bacterial flagella.

II.  Eukaryotic Cells

Eukaryotic cells are more complex internally than prokaryotic cells.  All organisms except bacteria are eukaryotes.  Some components of the eukaryotic cell are listed below.

1. Cytoplasm - a chemical solution with floating “chemical factories” or organelles 

2. Cytoskeleton - internal system of microfilaments in cytoplasm:  These move objects through cytoplasm [ex. chromosomes during cell division; packages of chemicals (vesicles) are moved about within the cell with help from the cytoskeleton] 

3.  Membranous Organelles - specialized compartments

                      A. Vesicles - packages of molecules transported w/in cell or secreted outside cell, ex.  hormones, components of  mucus 

                       B.  Lysosomes - vesicles w/digestive enzymes, digest foreign invaders, recycle cell parts, & digest carbohydrates, 
                proteins, and other types of molecules 

           C.  Golgi apparatus (also called Gogi bodies or Golgi complex) - A PACKAGING CENTER consists of folded membranes (like stacks of  pita bread), creates vesicles 

                      D.  Endoplasmic Reticulum (ER) - SYNTHESIS CENTER, consists of folded  membranes that create pockets isolated from rest of cytoplasm.

                          Rough ER - w/ribosomes, for protein synthesis                    Smooth ER - w/out ribosomes, for lipid synthesis 

                        E.  Mitochondria – “power houses,” produce ATP through cellular respiration (in all live eukaryotic cells) 

                        F.  Chloroplasts - in plants and some algae; photosynthesis

Mitochondria and chloroplasts are thought to have arisen by endosymbiosis (one cell lives inside another in a mutually beneficial relationship).  According to the theory of endosymbiosis, after many, many millions of years the endosymbiont lost much of its autonomy and former structure.  Today these once free living organisms remain as vestiges of their former complexity and are known as chloroplasts and mitochondria and exists in mutual dependency with their "hosts."  

4.   Nucleus – holds genetic information, sends instructions to cytoplasm 

5.  Other Cells Structures

            A.  Central vacuole - large water-filled vacuole in plant cells. (f) turgor pressure. 

            B.  Cell walls - bacteria, plants, fungi, algae (NOT FOUND IN ANIMAL CELLS)  rigid or flexible, for support. 

            C.  Flagella (sing. flagellum) - whip-like, hair-like projections, occur singly or few: ex. sperm  &  Euglena  pull vs. push, for motility. 

            D.  Cilia - short, numerous, ex. protozoa, fallopian tubes, wind pipe.  For movement of fluid. 

6.         Plasma membrane and other membranes consist of a phospholipid bilayer with a mosaic of embedded proteins.  Membranes help regulate movement of chemicals across their boundary.