Chapter 3 Sec. 2: Cell Features

1. Chapter 3 Sec. 2:Cell Features

2. Cell Theory • All living organisms are made of one or more cells. • Cells are the basic unit for both structure and function. • Cells come from preexisting cells. - not by spontaneous generation (mice from rags, worms from horse hairs) we believe in biogenesis

3. Robert Hooke • Englishman • Looked at cork • Saw cubicals • 1st person to see cells – but they were dead cells.

4. Scientists involved in cell theory • Schleiden – All plants are made of cells • Schwann – All animals are made of cells • Virchow – All cells come from other cells

5. Differences in Cells • Size – • biggest cell is ostrich egg • smallest is bacteria .002 mm • most are from 5 to 20 µm in diameter

6. Differences in Cells • The size of the cell is limited by the surface area to volume ratio. Surface area= amount of cell membrane available Volume= amount of material inside the cell

7. Surface Area to Volume Ratio Calculation Activity • Using 1 cm cubes, build a 2 cm x 2 cm x 2 cm block to symbolize a small cell. • Calculate the surface area by using the formula: (l x w x number of sides) • Calculate the volume by using the formula: (l x w x h) • Calculate the ratio by dividing the surface area by the volume. • Repeat using a 3 x 3 x 3 cell. • Repeat using a 4 x 4 x 4 cell.

8. What happens when the surface area to volume ratio gets too small? Cell division occurs!

9. Cells can be different by… • Internal organization (does it have a nucleus or not????)

10. Cell Internal Organization… Prokaryotes: Organisms without a nucleus or any membrane bound organelles (ex. Bacteria & simple algae) Eukaryotes: Have nuclei & membrane bound organelles (ex. Humans, fish, trees, sponges)

11. Prokaryote Characteristics: • First life forms on Earth (3.5 billion years ago) • May or may not need oxygen • Cytoplasm holds everything – enzymes, ribosomes, DNA, etc. • Have a cell wall surrounding cell membrane • Many have flagella for movement

12. Eukaryotes • All have a nucleus containing DNA • Have organelles outside the nucleus – internal compartments with specific functions to perform • Most organisms ARE eukaryotes!

13. Common Features of Cells… • Cell Membrane • Cytoplasm • Cytoskeleton • Ribosomes • DNA

14. Common Features of Cells… • Cell Membrane - gatekeeper of the cell - is selectively permeable (allows only certain substances to pass in or out)

15. Parts of a cell… • Structure of the Cell Membrane - made of lipids and proteins (mostly lipids) - two layers thick (phospholipid bilayer)

16. Model of the cell membrane is called the Fluid Mosaic Model

17. The Cytoskeleton: • Is the internal framework or support • Is composed of a protein fiber network • 3 different kinds of cytoskeleton fibers: • Microfilaments (fibers made of protein actin) • Microtubules (hollow – made of protein tubulin) • Intermediate fibers (thick protein ropes)

18. Section 3:Cell Organelles

19. Cell Parts-The Nucleus… • Is the Control Centerfor the cell • Contains DNA and RNA • Is filled with nucleoplasm and chromatin (dark grainy material that changes into chromosomes during cell division)

20. Cell Parts-The Nucleus… • Nucleus is contained by a nuclear membrane made of 2 layers • Nuclear membrane has pores to allow materials to leave nucleus

21. Cell Parts-The Nucleus… • Has a nucleolus (small dark oval inside) • Nucleolus produces ribosomes

22. Parts of the cell… • Endoplasmic Reticulum (E.R.) The cell’s subway system

23. Endoplasmic Reticulum • Materials (especially proteins) are transported from one area to another. • 2 kinds of ER – smooth and rough • Smooth has no ribosomes attached. • Rough has lots of ribosomes attached. • Vesicles form when ends of ER pinch off as a membrane sac

24. Parts of the cell… • Ribosomes • Are produced in the nucleolus • They produceproteins • Are located on the surface of endoplasmic reticulum and also free floating in the cytoplasm. • Are made of ribosomal-RNA

25. Parts of the cell… • Golgi Apparatus vesicle

26. Golgi Apparatus • Proteins packaged in vesicles move to Golgi apparatus - also called Golgi bodies or golgi complex • GA looks like stacks of flattened pancakes • GA areproteinprocessing centers – refined, processed & packaged.

27. Lysosomes: • Are small spherical structures that contain digestive enzymes that allow cells to recycle its materials. • Lysosomes act as the “recycling center” for the cell.

28. Protein Packaging & Distribution • Made at ribosomes on ER & packaged into vesicles • Travel from ER to Golgi Apparatus • Get processed & repackaged at GA • Move from GA to cell membrane for export

29. Mitochondria: (mighty mitochondria) • produce ATP energy by breaking down glucose • have double membranes • have in and out folds called Cristae • Have ring of DNA

30. Mitochondrion

31. Parts of the cell… • Which cells have the most mitochondria? High energy requiring cells like muscles!

32. Parts of the cell… • Cilia & Flagella • Used for movement of the cell • Cilia are short and numerous • Flagella are usually 1-2 in number and very long like a whip • Made of sets of microtubules

33. Structures of Plant Cells

34. Plant Cells • All plant cells have a Cell Wall - on the outside of cell membrane - provides cell support & strength - made of cellulose - a carbohydrate

35. Plant Cells… • Central Vacuole - are storage spots in cytoplasm - very large - may store water, enzymes, waste products, or even toxins

37. Plant Cells… • Contain Plastids - are membrane bound structures - have their own type of DNA 3 kinds: • Chloroplasts • Leucoplasts • Chromoplasts

38. Plant Cells… • Have Chloroplasts: - green - membrane bound structures - store chlorophyll (green pigment needed for photosynthesis) so… - chloroplasts are the sites of photosynthesis.

40. Plant Cells… • Leucoplasts: - are white structures inside cells - are storage areas for produced food. - Ex: Potato grains stained in lab. - may be other starchy materials like corn, wheat

41. Plant Cells… • Chromoplasts – are the colored pigments seen in petals of flowers or in leaves in fall.