1. Cell – the basic unit of life

2. Cells Smallest living unit Most are microscopic

3. Discovery of Cells Robert Hooke (mid-1600s) –Observed bark of oak tree –Saw “row of empty boxes” –Coined the term cell

4. Cell theory (1839)Theodor Schwann & Matthias Schleiden “ all living things are made of cells” (50 yrs. later) Rudolf Virchow “all cells come from cells”

5. Principles of Cell Theory All living things are made of cells Smallest living unit of structure and function of all organisms is the cell All cells arise from preexisting cells

6. Cell Size

7. The origin and evolution of cells On the basis of presence of nucleus cells are divided into two groups: –Prokaryotic cells: lack a nuclear envelope –Eukaryotic cells: have a nucleus in which the genetic material is separated from the cytoplasm. Prokaryotic cells are generally smaller and simpler than eukaryotic cells; their genomes are less complex and they do not contain cytoplasmic organelles.

8. Cell Types Prokaryotic Eukaryotic

9. Prokaryotic Cells First cell type on earth Cell type of Bacteria and Archaea

10. Prokaryotic Cells No membrane bound nucleus Nucleoid = region of DNA concentration Organelles not bound by membranes

11. Prokaryotic Cells Features shared by all prokaryotic cells: –All have a plasma membrane. –All have a region called the nucleoid where the DNA is concentrated. –The cytoplasm (the plasma-membrane enclosed region) consists of the nucleoid, ribosomes, and a liquid portion called the cytosol.

12. Prokaryotic Cells Specialized features of some prokaryotic cells: –A cell wall just outside the plasma membrane. –Some bacteria have an outermost slimy layer made of polysaccharides and referred to as a capsule.

13. Some bacteria have flagella, locomotory structures. Some bacteria have cillia, threadlike structures that help bacteria adhere to one another during mating or to other cells for food and protection.

14. Figure 4.5 A Prokaryotic Cell

15. Eukaryotic Cells Nucleus bound by membrane Include fungi,, plant, and animal cells Possess many organelles Protozoan

16. Eukaryotic Cells Eukaryotes, animals, plants, fungi have a membrane-enclosed nucleus in each of their cells. Eukaryotic cells: –tend to be larger than prokaryotic cells. –have a variety of membrane-enclosed compartments called organelles. –have a protein scaffolding called the cytoskeleton.

17. Eukaryotic Cells Compartmentalization is the key to eukaryotic cell function. Each organelle has a specific role defined by chemical processes. Membranes surrounding these organelles keep away inappropriate molecules and also act as traffic regulators for raw materials into and out of the organelle.

18. Representative Animal Cell

20. StructureAnimal cellsPlant cells cell membraneYesyes nucleusYesyes nucleolusyes ribosomesyes ERyes Golgiyes centriolesyesno cell wallnoyes mitochondriayes cholorplastsnoyes One big vacuolenoyes cytoskeletonyesYes

21. How did organelles evolve? many scientists theorize that eukaryotes evolved from prokaryote ancestors. in 1981, Lynn Margulis popularized the “endosymbiont theory.”

22. Endosymbiont theory: a prokaryote ancestor “eats” a smaller prokaryote the smaller prokaryote evolves a way to avoid being digested, and lives inside its new “host” cell kind of like a pet.

23. the small prokaryotes that can do photosynthesis evolve into chloroplasts, and “pay” their host with glucose. The smaller prokaryotes that can do aerobic respiration evolve into mitochondria, and convert the glucose into energy the cell can use. Both the host and the symbiont benefit from the relationship