Cell Theory and Prokaryote vs. Eukaryote

1. Cell Theory and Prokaryote vs. Eukaryote Characteristics #1 of Living Things: -Living things are organized

2. What is a Cell? • Cell– Basic unit of living things. • Organisms are either: • Unicellular – made of one cell such as bacteria and amoebas. OR • Multicellular – made of many cells such as plants and animals.

3. tissue organ cell organism Multicellular Organization A group of similar cells is called a tissue. A group of similar tissues is called an organ. A group of organs working together form an organ system or organism

4. Scientists to Remember • Anton van Leeuwenhoek (1674) • Father of Microscopy • Saw tiny living things in pond water.

5. Scientists to Remember • Robert Hooke (1665) – Observed “cells” in cork • Named box-shaped structures as “cells”

6. Other Scientists • Matthias Schleiden (1838) – Plants are made of cells. • Theodor Schwann (1839) – Animals are made of cells. • Rudolf Virchow (1855) – New cells come from existing cells. • Janet Plowe (1931) – Cell membrane is a physical structure. • Lynn Margulis (1970) – Organelles were once free-living cells.

7. Cell Theory • Confirmed discoveries that all scientists believe to be true about cells: • All organisms (living things) are composed of one or more cells. • The cell is the basic unit of (life) structure and organization of organisms. • All (new) cells come from preexisting cells.

8. Microscopes • Light Microscope – magnifies tiny organisms up to 1,000 times. -Uses light and lenses. -We use these. • Electron Microscope – magnifies up to a million times. -Uses electrons.

9. before true nucleus nucleus The Discovery of Cells Prokaryotic Eukaryotic

10. Eukaryotes • Has a nucleus with a nuclear envelope • Bigger and more complex than prokaryotes • Have membrane bound Organelles(golgi, ER, lysosomes…etc) • DNA – double-stranded and forms chromosomes (highly organized) • Can be unicellularORmulticellular organisms • Sexual Reproduction by Meiosis • Ex: animals, plants, fungi

11. Prokaryotes • NOnucleus • NOmembrane bound organelles (just ribosomes) • ALL are unicellular • Smaller than eukaryotic cells • Forerunner to eukaryotic cells (smaller and more simple) • DNA – single strand and circular • Asexual Reproduction by Binary Fission • Ex: ALL Bacteria

12. Similarities • Contain all four macromolecules • lipids, carbohydrates, proteins, and nucleic acids • Both have ribosomes • Both have DNA • Similar Metabolism • Both can be unicellular • Have cell/plasmamembranes or cell wall

13. Eukaryote VS. Prokaryote Picture

14. Prokaryotic Cell Reproduction Binary Fission

15. Eukaryotic Cell Reproduction Mitosis: cell reproduction for growth and replacement of cells. This makes identical copies (clones) Meiosis: cell reproduction for the production of gametes, such as egg and sperm (sex cells)

16. How did organelles evolve? • Biologists generally believe that eukaryotes evolved from prokaryotes. • In 1981, Lynn Margulis popularized the “endosymbiont theory.”

17. Endosymbiotic Theory • The Endosymbiotic Theory states that present day eukaryotic cells evolved from the uniting of several types of primitive prokaryotic cells • Some organelles (mitochondria and chloroplasts) might have been were originally prokaryotes that were involved in a symbiotic relationship

18. Endosymbiotic 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.

19. Endosymbiotic Theory • Endo = insideSymbiont = friend

20. Endosymbiotic Theory • 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

21. Endosymbiotic Theory • Chlorella are tiny green cells that live inside some amoeba... endosymbiosis may still be evolving today!