Notes on Cells

1. Notes on Cells

2. Cell Theory • 1665: Hooke: British, first to look at magnified plant tissue (cork); named cells = basic unit of all life forms • 1674: Leuwenhoek: Dutch, first to magnify “nature” with a lens • 1838: Schleiden: German, (botanist) said all plants were made of cells • 1839: Schwann: German, (zoologist) said all animals were made of cells • 1855: Virchow: Stated that all cells come from other cells

3. Robert Hooke Hooke’s sketch of the cork cells he observed under his microscope.

4. Cell Theory: summary of these discoveries a. All living things are made up of cells b. Cells are the basic unit of structure and function in living things c. New cells are produced from existing cells

5. Prokaryotic Cells • No true nucleus • No membrane-bound organelles • Single-cell • No Mitochondria • Have cell wall and cell membrane • Grow, reproduce, respond to changes in the environment • Do contain ribosomes • DNA is circular (Plasmid) • Belong to the Kingdoms: Archaebacteria and Eubacteria & Cyanobacteria • Much smaller than Eukaryotic cells

6. Eukaryotic Cells • Do have a nucleus • Eu= true • Do contain anucleus: a structure that contains genetic information and controlscell functions • Have cell membrane: thin, flexible barrier around cell • Have cytoplasm: material inside cell membrane but not including organelles ex. Belong to the Kingdoms: Protista, Fungi, Plantae, Animalia

7. Cell Structures Cytoplasm Structure: • Jelly-like material inside the cell membrane which contains water, salts, and organic molecules Function: In constant movement Cytoplasmic streaming Surrounds organelles

8. Organelles – specialized structures that perform important cellular functions

9. Mitochondria“Powerhouse” • Has its own DNA and ribosomes! • evidence that the mitochondria evolved from a heterotrophic prokaryote • Function: Respiration centers for the release of energy • Use energy from food to make high-energy compounds that the cell can use to power growth, development, Movement • (ATP -adenosine triphosphate) - Most numerous organelle in cells that use a lot of energy (muscles) • Enclosed by 2 membranes • outer – smooth, forms boundary • inner – long folds (cristae) increase surface area

10. Mitochondria

11. 2. Endoplasmic reticulum (ER) • Membrane system of sacs and tunnels • covered with ribosomes- rough ER, place where proteins are modified • few or no ribosomes – smooth ER, contains enzymes that perform specialized tasks, like production of lipids • “intracellular highway”

12. Smooth and Rough ER

13. 3. ribosomes • “protein factories” • made of RNA and proteins • where proteins are made (most numerous organelle) – produces proteins following encoded instructions that come from the nucleus • granulated, attached to ER or float in cytoplasm

14. Ribosomes

15. 4. Golgi apparatus • processing, packaging, and secreting organelle • stack of membranes or sacs which package proteins produced by rough ER • “protein packagers”

16. 5. lysosomes • contain digestive enzymes • breakdown carbohydrates, lipids, and proteins into particles that can be used by the cell • breakdown of organelles that are no longer useful • remove debris that otherwise accumulate/clutters the cell • in animal cells and fungi • “suicide sacs” • lysis = breakdown • soma = body

17. Lysosomes“suicide sacs”

18. 6. centrioles • rod-shaped bodies close to the nucleus which guide the cell during division • animals cells only

19. 7. Vacuoles • cavities (containers) which store enzymes, waste products, water, salts, proteins, and carbohydrates • mainly in plant cells – plants have a large central vacuole filled with liquid • in mature plants – the vacuole takes up 90% of volume of the cell • smaller vacuoles are called vesicles

20. 8. plastids • chemical factories to store food • only in plants • can contain pigments • example: chloroplasts

21. Cytoskeleton: framework of cell (supports the cells) • network of protein filaments • used in cell movement 9. Microtubules • small hollow tubes of protein; maintains cell shape, forms tracks along which organelles are moved • assembled and broken down as needed (during cell division) • in some cells they form cilia and flagella that aid in movement • act as the “bones” in the cell

22. Flagella and Cilia

23. 10. microfilaments • protein threads of actin for cytoplasmic streaming • smaller than microtubules • act as “muscles” in the cell

24. Nucleus – identified in 1831 • control center of the cell • site of nucleic acid synthesis

25. Nucleus • nuclear envelope (membrane) • double membrane (phospholipids and proteins) • nuclear pores allow substances to enter and leave

26. Nucleus 2. nucleoplasm • protoplasm within the nucleus • dense, protein rich

27. Nucleus 3. nucleolus (singular), nucleoli (plural) • form ribosomes • composed of RNA

28. Nucleus 4. chromatin • fine strands of DNA and proteins • genetic material • chromosomes – coiled up chromatin when the cell is dividing

29. Differences in Plant Cells a. Cell wall – provides support and protection for plant cell • contain pores which allow H2O, CO2, and O2 to pass through • made from fibers of carbohydrates and proteins (cellulose) • cellulose – tough carbohydrate fibers, makes up wood and paper

30. Differences in Plant Cells: b. vacuoles – one large central vacuole - 90% of cell’s volume

31. Differences in Plant Cells: c. Plastids

32. Cell Membrane

33. Cell Membrane • forms outer boundary and separates the cell from its surroundings and other cells • composed of two layers of phospholipids and proteins – both move like a liquid called “fluid mosaic model”

34. Fluid Mosaic Model Phospholipid molecule (2-layers)

35. contains protein molecules that provide attachment points for carbohydrate molecules to form chains • some proteins in cell membrane form channels and pumps to help move materials • regulates what enters and leaves the cell – selectively permeable (semi-permeable) (Keeps out some molecules but allows others to enter)

36. Present day bacteria are divided into two groups Archaebacteria and Eubacteria Diverged early in evolutionary history Evolution of Cells

37. Endosymbiosis created Eukaryotic cells Symbiotic association with prokaryotes Mitochondria and chloroplasts evolved from prokaryotic organisms living inside larger cells

38. Chloroplasts and mitochondria have their own unique DNA that replicates independently Chloroplasts and mitochondria are similar in size to bacteria (prokaryotes) The ribosomes of chloroplasts and mitochondria are more closely related to bacterial ribosomes than those of eukaryotes Evidence of Endosymbiosis

39. Evolved from unicellular eukaryotes Colonies of algae are precursors to present day multicellular plants Increasing specialization led to the transition from colonies to multicellular organisms Evolution of Cells into Multicellular Organisms