Biology: Tissues, Organs, and Systems of Living Things

ALL ABOUT CELLS

A Short History Lesson Robert Hooke (1665) first discovered cells - cork Schwann and Schleiden (1838) first hypothesized that all organisms are composed of cells First to distinguish between plant and animal cells 3

It has been estimated that there are 10 times more cells in the human body than stars in the Milky Way.

Cell Theory All living things composed of cells Cells are basic unit of living organisms All cells come from existing cells

Cell Theory The Human body is estimated to have 100 trillion cells. Cells are specialized to perform various tasks. Examples: Nerve Cells transmit electrochemical messages. Muscle Cells contract. All cells: Digest nutrients Excrete wastes Reproduce

Prokaryotic vs. Eukaryotic

Prokaryotic Cells No internal compartments No organelles 1-celled organisms Eg. bacteria

Prokaryotic Cells Smaller DNA located in nucleoid region May not need O2

Eukaryotic Cells Have internal compartments Have organelles 1-celled or multi- celled organisms Eg. Plant cell

Eukaryotic Cells Larger cells DNA located in the nucleus Usually need O2

Ticket out of Class! On a scrap piece of paper provided answer the following question: Are your cells prokaryotic or eukaryotic? Explain. Hand the paper in, with your name on it Homework: Textbook Page 32 Questions 1 and 3 13