3.1 The Cellular Level of Organization

1. 3.1 The Cellular Level of Organization • All life is “cellular” • Unicellular organisms like Archaea, Bacteria, protists • Multicellular eukaryotes like fungi, plants, and animals • Exceptions: Viruses are ‘acellular’ but exhibit life qualities when acting as a parasite within host cells

2. 3.1 The Cellular Level of Organization • The cell is the structural and functional unit of an organism, the smallest structure capable of performing all the functions necessary for life.

3. 3.1 The Cellular Level of Organization • Prokaryotic cells lack membrane enclosed structures. No nucleus or “organelle” compartments • Eukaryotic cells possess membrane enclosed structures. Prominent nucleus and distinct compartments - organelles

4. The Cell Theory • All organisms are composed of one or more cells. • Robert Hooke, Louis Pasteur, Leuwenhoek, Virchow and others helped form the “cell theory”

5. The Cell Theory • All organisms are composed of one or more cells. • Cells are the basic living unit of structure and function in organisms.

6. The Cell Theory • All organisms are composed of one or more cells. • Cells are the basic living unit of structure and function in organisms. • All cells come only from other cells.

7. Sizes of Living Things

8. Surface Area / Volume Ratio • The amount of surface area affects the ability to get materials in and out of a cell. • Cells are “small”. Their size is limited. Size is limited by S/V ratio.

9. Surface Area / Volume Ratio • The amount of surface area affects the ability to get materials in and out of a cell. • A cells increase in volume, the proportionate amount of surface area decreases.

10. Surface Area / Volume Ratio

11. Plasma Membrane and Cytoplasm • All cells are surrounded by a plasma membrane (AKA cytoplasmic memb., cell memb.). • The material inside of a cell is the cytoplasm. • The plasma membrane regulates what enters and exits a cell.

12. 3.2 Prokaryotic Cells • Smaller in size than Eukaryotes (1 – 10 microns) • Unicellular, no nucleus or organelles • Archaea • Bacteria

13. 3.2 Prokaryotic Cells

14. 3.2 Prokaryotic Cells • Cell Wall - Unique Polysaccharide, Peptidoglycan • Capsule- Sugar coat • Flagellum - Motor • Nucleoid - DNA • Ribosomes

15. 3.2 Prokaryotic Cells • Cell Wall • Capsule • Flagellum • Nucleoid • Ribosomes

16. Prokaryotes are: • Structurally simple • Metabolically diverse • Adapted to most types of environments

17. 3.2 Prokaryotic Cells

18. 3.3 Eukaryotic Cells • Larger in size than Prokaryotes (10 to 50 microns) • Membrane bound organelles (compartments with specialized functions)

19. 3.3 Eukaryotic Cells • Eukaryotic cells: • Are structurally complex • Have a nucleus • Possess membrane-bound organelles • May have a cell wall

20. 3.3 Eukaryotic Cells

21. 3.3 Eukaryotic Cells – Review these for assessment test, particularly the animal cell

22. The Nucleus • Stores DNA

23. The Nucleus • Stores DNA • Nucleolus - rRNA

24. The Nucleus • Stores DNA • Nucleolus - rRNA • Nuclear Envelope • Nuclear pores

25. Ribosomes • Site of protein synthesis • Two subunits (large and small) • Subunits consist of rRNA and protein molecules • Polyribosomes • Several ribosomes with a single mRNA molecule

26. Endoplasmic Reticulum • Consists of membranous channels and saccules

27. Endoplasmic Reticulum • Rough ER • Processing and modification of proteins • Smooth ER • Synthesizes phospholipids • Various other functions

28. Golgi Apparatus • The Golgi apparatus collects, sorts, packages, and distributes materials such as proteins and lipids.

29. Lysosomes • Lysosomes contain digestive enzymes that break down unwanted, foreign substances or worn- out parts of cells

30. Vacuoles • Vacuoles are membranous sacs that store substances. • For example: Water Pigments Toxins

31. Peroxisomes • Membrane bound vesicles containing enzymes. • The enzymes break down molecules and as a result produce hydrogen peroxide. • Toxic oxygen waste products – free radicals, can cause serious problems • Detoxification by special enzymes like SOD to less toxic hydrogen peroxide • Hydrogen peroxide is broken down to water and oxygen by the enzyme catalase

32. Energy-Related Organelles • Chloroplasts • Mitochondria

33. Energy-Related Organelles Photosynthesis Cellular Respiration

34. Chloroplasts • Site of photosynthesis • Structure: • Double-membrane • Stroma • Grana • Thylakoids • Chloroplasts contain: • Their own DNA • Ribosomes • Enzymes

35. Mitochondria • Found in all eukaryotic cells • Site or cellular respiration • Structure: • Double-membrane • Matrix • Crista

36. The Cytoskeleton • Maintains cell shape • Assists in movement of cell and organelles • Assemble and disassemble as needed • Three types of macromolecular fibers • Actin Filaments • Intermediate Filaments • Microtubules

37. Actin Filaments • Anchored to the plasma membrane • Allows intestinal microvilli to expand and contract • Found in pseudopods allowing amoeboid movement • Play a role in animal cell division

38. Actin Filaments • Actin interacts with motor molecules such as myosin. • In the presence of ATP, myosin pulls actin along • Example: muscle cells

39. Intermediate Filaments • Intermediate in size between actin filaments and microtubules • Functions: • Support nuclear envelope • Cell-cell junctions, such as those holding skin cells tightly together

40. Microtubules • Hollow cylinders made of two globular proteins • Assembly: • Under control of Microtubule Organizing Center (MTOC) • Most important MTOC is centrosome • Interacts with specific proteins to cause movement of organelles

41. Microtubule Operation

42. Centrioles • Short cylinders with a 9 + 0 pattern of microtubule triplets

43. Centrioles • Help organize microtubules during animal cell division • May be involved with microtubule formation and in the organization of cilia and flagella

44. Cilia and Flagella • Hairlike projections that aid in cell movement • In eukaryotic cells, cilia are much shorter than flagella • They are membrane-bound cylinders enclosing a matrix area • The matrix consists of microtubules in a 9 + 2 pattern

45. Cilia and Flagella