2All organisms are made of cells The cell is the basic unit of structure & functionThe cell is the smallest unit that can still carry on all life processesBoth unicellular (one celled) and multicellular (many celled) organisms are composed of cells
3Before the 17th century, no one knew cells existed Most cells are too small to be seen with the unaided eyeIn the early 17th century microscopes were invented & cells were seen for the 1st timeAnton Von Leeuwenhoek, a Dutchman, made the 1st hand-held microscope & viewedmicroscopic organisms in water &bacteria from his teeth
4In 1665, an English scientist named Robert Hooke made an improved microscope and viewed thin slices of cork viewing plant cell walls and named what he saw "cells"
5In the 1830’s, Matthias Schleiden (botanist studying plants) & Theodore Schwann (zoologist studying animals) stated that all living things were made of cells
6In 1855, Rudolf Virchow stated that cells only arise from pre-existing cells Virchow’s idea contradicted the idea of spontaneous generation (idea that nonliving things could give rise to organisms)
7The combined work of Schleiden, Schwann, & Virchow is known as the Cell Theory
8Principles of the Cell Theory All living things are made of one or more cellsCells are the basic unit of structure & function in organismsCells come only from the reproduction of existing cells
9Prokaryotes and Eukaryotes Cells come in a variety of shapes and sizes.All cells:are surrounded by a barrier called a cell membrane.at some point contain DNA.
10Cells are classified into two categories, depending on whether they contain a nucleus. The nucleus is a large membrane-enclosed structure that contains the cell's genetic material in the form of DNA.
11Eukaryotes are cells that contain nuclei Eukaryotes are cells that contain nuclei. Prokaryotes are cells that do not contain nuclei.
12Prokaryotes Prokaryotic cells are less complex Unicellular Do not have a nucleus & no membrane-bound organelles; many have ribosomes though (which aren’t membrane bound)Most have a cell wall surrounding the cell membrane & a single, looped chromosome (genetic material) in the cytoplasmInclude bacteria & blue-green bacteria
13Eukaryotes More complex cells Includes both unicellular & multicellular organismsDo have a true nucleus & membrane-bound organellesOrganelles are internal structures in cell’s that perform specific functionsOrganelles are surrounded by a single or double membrane
14Entire eukaryotic cell surrounded by a thin cell membrane that controls what enters & leaves the cellNucleus is located in the center of the cellThe nucleus contains the genetic material (DNA) & controls the cell’s activities
15Cytoplasm includes everything between the nucleus and cell membrane and is composed of organelles & a jellylike material consisting of mainly water along with proteins.Eukaryotes include plant cells, animal cells, fungi, algae, & protists