4-1 Introduction to the Cell

1. 4-1 Introduction to the Cell

2. Important events in the discovery of the cell and the development of the cell theory…..

3. 1665 – Robert Hooke Observed cells in cork. Coined the term "cells”. Cork Cells

4. 1673- Anton van Leeuwenhoek Created a powerful microscope

5. 1827-33 - Robert Brown -noticed that pollen grains in water jiggled around called “Brownian motion” -discovered the nucleus Nucleus Human Cheek Cell

6. 1838 - Matthias Schleiden A botanist who concluded that all plants are made of cells. Typical Plant Cell

7. 1839 - Theodor Schwann A zoologist who concluded that all animals are made of cells. Nerve Cells

8. 1855 - Rudolph Virchow A physician who did research on cancer cells and concluded “Omnis cellula e cellula”. “All cells are from other pre-existing cells.”

9. The Cell Theory 1. All living things are composed of one or more cells. 2. Cells are the basic units of structure and function in an organism. 3. Cells come only from existing cells.

10. Cells are Diverse… both in size, shape, and internal organization.

11. Why Are Cells So Small? • Transport- Cell volume to surface area ratios favor small size. • Control- Nucleus to cytoplasm consideration. • Metabolic requirements- ……..we’ll come back to this later.

12. How small can a cell be? Mycoplasmas - bacteria that are 0.1 to 1.0 mm. (1/10 the size of regular bacteria). Note: 1.0 mm = one millionth of a meter

13. All cells have…… • Plasma (cell) Membrane • Nucleus (eukaryotes only) • Cytoplasm (an area) • Organelles (structures with specialized functions)

14. Cell Types Prokaryotes- simple cells that do not have internal membranes example = bacteria Eukaryotes- more complex cells that do have internal, membrane-bound structures examples = plants and animals

15. Timeline Prokaryotic Organisms: First appeared 3.5 BYA include bacteria and cyanobacteria Eukaryotic Organisms: First appeared 2.0 BYA include protists, fungi, plants and animals

16. Key Differences: Eukaryotes • Have a nucleus and other membrane bounded structures. • Have large ribosomes • DNA is organized into chromosomes • Flagella are made of microtubules and have a 9+2 structure • Cell walls are made of cellulose • Prokaryotes • Lack a nucleus and other membrane bounded structures. • Have small ribosomes • DNA is not organized into chromosomes • Flagella are not made of microtubules and does not have a 9+2 structure • Cell walls are made of peptidoglycan, not cellulose

17. Examples Prokaryotic Eukaryotic Nucleus

18. Eukaryotic Prokaryotic