4.1 Introduction to the Cell ·Smallest unit of matter that can carry on all processes of life
Robert Hooke (1635) *Examined slice of cork under a microscope and saw things that reminded him of small rooms in which Monks lived so he called them cells. *Development of the microscope lead to the discovery of the cell
Cell Theory *All living things are composed of 1 or more cells *Cells are the basic unit of structure and function in an organism *Cells come only from the reproduction of existing cells
3 Characteristics of Cells 1. Size 2. Shape 3. Internal organization
1. Size * Not all cells are alike, they have a different structure to fit their function * Body has 200- different types of cells *Most cells are only visible to microscope *Most plant and animal cells measure only 0.002 inches in diameter *They are limited in size by the ratio of their surface area to their volume. The larger this ratio then the better the cell can survive which means the smaller the cell the better for survival.
2. Cell Shape *Nerve cells have long extensions to pick up impulses *Shape relates to its function *Nerve cells have long extensions to pick up impulses
2. Cell Shape *Skin cells are flat shape to help in covering body surface
2. Cell Shape · White blood cells can change form which allows them to leave the blood and go to areas where infection is, engulf the infection (bacteria) and destroy it.
3. Internal organization ·Organelles are cell components which perform specific functions. ·Organs in a multicellular organism carry on functions of life just like organelles carry on life within a cell.
2 Types of Cells 1. Eukaryotic cells 2. Prokaryotic cells
1. Eukaryotic Cells *Has cell membrane *First discovered about 1.5 billion years ago *Has membrane bound nucleus which contains the genetic information and directs most of cell’s activities *Has membrane bound organelles *Has cell membrane *Has cytoplasm (liquid portion inside cell that nourishes the organelles)
Eukaryotic Cells
2. Prokaryotic Cells *Has cell membrane * First discovered about 3.5 billion years ago *Does not have a membrane bound nucleus *Does not have membrane bound organelles *First cells on earth which did not make their own food *Has cell membrane *Examples are bacteria and all unicellular (one-celled) organisms.
Prokaryotic Cells