 Questions:  What is a cell?  What is the difference between Prokaryotic & Eukaryotic cells?  Vocabulary: Continue today’s vocabulary on the “Cells” page. Define the following terms on that page:  Cell wall  Cytoskeleton (top of pg. 58)  ribosome  Endoplasmic reticulum  Mitochondrion  Golgi complex  Lysosome You may use Chapter 2, section 2, the index, or the glossary to define the words. If you did not finish the vocabulary or the foldable from yesterday, finish that within the first 5 minutes!

 Robert Hooke was the first person to describe cells. In 1665, he built a microscope to look at tiny objects. He named the little boxes he saw when looking at cork, cells.  In 1673, Anton van Leeuwenhoek made his own microscope. He observed pond scum and animal blood. First person to see bacteria.  Cell Theory:  All organisms are made of one or more cells.  The cell is the basic unit of all living things.  All cells come from existing cells.

 Most cells are too small to be seen without a microscope, but some are big.  The yolk of a chicken egg is one big cell.  Most cells are small b/c cells take in food and get rid of wastes through their outer surface. The area of a cell’s surface limits its size.

 Cell membrane is a protective layer that covers the cells’ surface and acts as a barrier. It controls materials going into and out of the cell.  Cytoplasm is the fluid inside of the cell that holds all of its parts.  Organelles are structures that perform specific functions within the cell.  DNA (deoxyribonucleic acid) is the genetic material that carries information needed to make new cells and new organisms. Controls the activities of the cell.  Nucleus contains DNA and plays a role in cell growth and reproduction- control center.

PROKARYOTIC  Cells with NO nucleus.  Single-celled organisms  Bacteria is the smallest cells known; no nucleus, but does have DNA  Archaea is a single-celled organism with no nucleus  3 types: heat-loving, salt- loving, & methane loving EUKARYOTIC  Cells with a nucleus  Largest cells  10x larger than most bacteria  All living things that are not bacteria or archaea are made up of one or more eukaryotic cells  Most are multicellular (many cells)  Multicellular organisms are larger than single-celled  Animals & plants