Exploring the Intricate Cell Structures and Functions

1. Unit II: The Cell All organisms are made of cells, the organism’s basic unit of structure and function.

2. Size range of cells

3. How We Study Cells Microscopes - light microscope - electron microscope (TEM/SEM)

5. A Panoramic View of the Cell Prokaryotic Eukaryotic +only in bacteria/archaebacteria Protists, Fungi, Plantae, Animalia +no true nucleus/nuclear envelope true membrane-bound nucleus +genetic material in nucleoid region genetic material in nucleus +no organelles many organelles

6. Animal vs. Plant Cell • Unique to Plant Cells: • - cell wall • - large central vacuole • Chloroplasts • Plasmodesmata • Unique to Animal Cells: • Centrioles • Lysosomes • - flagella and/or cilia

11. How organelles are fractionated (isolated)

12. The Nucleus and Ribosomes Nucleus - enclosed by nuclear envelope - contains most of the genes that control the entire cell + DNA organized with proteins into chromatin - nucleolus Nuclear lamina – protein filaments that give structure to the inner nuclear membrane

13. The Nucleus and Ribosomes (con’t) Ribosomes - build proteins - RNA/protein complexes - free/bound

14. The Endomembrane System • Includes: • nuclear envelope • Endoplasmic reticulum • Golgi apparatus • Lysosomes • Vacuoles • Plasma membrane*

15. Endomembrane System (con’t) • Endoplasmic reticulum • manufactures membranes • two distinct regions • + smooth ER • - synthesis of lipids • - carbohydrate metabolism • - detoxify drugs/poisons • - stores calcium ions • + rough ER • - manufacture proteins for • secretion • - membrane production

16. Endomembrane System (con’t) • Golgi apparatus • finishes, sorts, and ships cell products • two poles • + cis face • + trans face Enzymes in the Golgi modify products of the ER in stages as they move through the Golgi stack from cis to trans face.

19. Endomembrane System (con’t) • Lysosomes – contain hydrolytic enzymes • digestive compartments • + intracellular digestion • + recycle cell material • + program cell destruction (apoptosis)

21. Apoptosis – programmed cell death

22. Endomembrane System (con’t) • Vacuoles • function in cell maintenance • + food vacuole • + contractile vacuole • + central vacuole (pictured) • - tonoplast

23. Endomembrane System Summary

24. Other Membranous Organelles • Peroxisomes • consume oxygen for • metabolism • + contain specialized • teams of enzymes • - peroxide-producing • oxidases and catalase • RH2 + O2 -oxidase-> R + H2O2 • 2H2O2 -catalase-> 2H2O + O2

25. Mitochondria and Chloroplasts • energy transformers of cells • + double membranes • + contain ribosomes/DNA • Mitochondrial DNA is only passed on • by mom

28. The Cytoskeleton • Cytoskeleton • provides structural support • for motility and regulation • + network of fibers • - microtubules • - microfilaments • - intermediate filaments

30. Cytoskeleton (con’t)

31. Centrosomes • Found in animal & plant cells • Produce microtubules during cell reproduction • Animal cells contain centrioles which contain 9 sets of 3 microtubules

32. F L A G E L L A C I L IA

33. Flagellum Structure

34. Cell Surfaces and Junctions • Cell Walls (1° & 2°) • cellulose fibers • Plasmodesmata • Middle lamella • Made of pectin • (sticky polysaccharide) • Pectin holds cell walls • together like concrete

35. Cell Surfaces and Junctions • ECM (Extra Cellular Matrix) • meshwork of macromolecules outside plasma membrane • + mostly glycoproteins (Collagen & proteoglycan) • + support/anchorage (Fibronectin & integrin)

36. Cell Surfaces and Junctions Tight junctions – prevent fluid from moving between cell layers in a tissue Desmosomes – anchor adjacent cells Gap junctions – allows the movement of cytoplasm, ions, sugars, amino acids from one cell to the next

37. Tight Junctions

38. Desmosomes

39. Gap junctions

41. Membrane Structure and Function Collagen proteoglycan Fibronectin

42. Membrane Structure and Function (con’t) • Plasma Membrane • boundary that separates living cell from • its non-living surroundings • + 8 nm thick • + selectively permeable • + unique structure relates to function

43. Phospholipid Glycerol Fatty Acid Chains Amphipathic molecule – has hydrophilic & hydrophobic regions

44. Hydrophilic vs Hydrophobic

47. Membrane Structure and Function (con’t) • Fluid Mosaic Model • The Fluid Quality of Membranes • + held together by hydrophobic interactions • - lipids/proteins drift about laterally • + unsaturated hydrocarbon tails • - maintain fluidity at low temperatures • + cholesterol • - stabilizes the membrane • restrains movement at high temp. • hinders close packing at low temp.

48. Membrane Structure and Function (con’t) • Fluid Mosaic Model • Membranes as Mosaics • + membrane is collage of proteins • - integral proteins • transmembrane • - peripheral proteins • appendages

49. Plasma membrane synthesis

50. Membrane Structure and Function (con’t) • Functions of Membrane Proteins • Transport • Enzymatic Activity • Signal Transduction • Intercellular joining • Cell-cell recognition • Attachment to the cytoskeleton and ECM