Objective: 4(A) Compare and contrast prokaryotic and eukaryotic cells.

 1665 English scientist Robert Hooke made simple microscope and looked at cork.  He called tiny structures cells – the basic structural unit of all living organisms.  1683 Anton Leeuwenhoek designed his own microscope and sees living organisms in pond water, milk, and other substances.  1838 Matthias Shleiden, German scientist, concludes all plants are made of cells

 1839 Theodore Schwann reported that all animal tissues consisted of living cells.  The observations and conclusions of these and other scientists are summarized as the cell theory.

Cell Theory  A fundamental idea in modern biology that includes three principles:  All living things are composed of one or more cells.  Cells are the basic unit of structure and organization of all living organisms.  Cells arise only from previously existing cells, with cells passing copies of their genetic material on to their daughter cells.

 Cells were so small their existence was not known before the invention of microscopes. Compound Light Microscopes  Use a series of glass lenses and visible light to magnify images  Magnifies images up to 1000x actual size.

Electron Microscopes  Can magnify objects up to x.  Uses a beam of electrons instead of a beam of light.  Several types:  TEM  SEM  STM  AFM

 All cells have at least one physical trait in common: a plasma membrane.  A plasma membrane is a special boundary that helps control what enters and leaves the cell.  Cells generally have a number of functions in common.  They contain genetic material that provides instructions for making materials in the cell.  Most cells break down molecules to generate energy.

Two Basic Kinds of Cells: Eukaryotes and Prokaryotes  Eukaryotic cells contain a nucleus and other organelles.  Organelles are specialized structure that perform specific cell functions.  The nucleus is the distinct central organelle that contains the cell’s genetic material.  Eukaryotic cells are generally much larger than prokaryotic cells.

 Prokaryotic cells are cells without a nucleus or other membrane-bound organelles.  Smaller and simpler than eukaryotes  Probably similar to the first organism that lived on earth 3.5 bya.

Origin of Cell Diversity  Eukaryotic cells may have evolved from prokaryotic cells.  The endosymbiont theory proposes that a symbiotic relationship formed between two prokaryotic cells, one of which lived inside the other.  Eventually the symbiotic relationship led to the two cells becoming one.

 Because eukaryotic cells are larger and more complex, they developed specific functions.  These specific functions led to cell diversity, and thus organismal diversity.