Cells and Tissues

1. Cells and Tissues

2. Cells and Tissues • Carry out all chemical activities needed to sustain life • Cells are the building blocks of all living things • Tissues are groups of cells that are similar in structure and function

3. Anatomy of the Cell • Cells are not all the same • All cells share general structures • All cells have three main regions • Nucleus • Cytoplasm • Plasma membrane Figure 3.1a

4. The Nucleus • Control center of the cell • Contains genetic material (DNA) • Three regions • Nuclear envelope (membrane) • Nucleolus • Chromatin

5. The Nucleus Figure 3.1b

6. The Nucleus • Nuclear envelope (membrane) • Barrier of the nucleus • Consists of a double membrane • Contains nuclear pores that allow for exchange of material with the rest of the cell

7. The Nucleus • Nucleoli • Nucleus contains one or more nucleoli • Sites of ribosome assembly • Ribosomes migrate into the cytoplasm through nuclear pores

8. The Nucleus • Chromatin • Composed of DNA and protein • Present when the cell is not dividing • Scattered throughout the nucleus • Condenses to form chromosomes when the cell divides

9. Plasma Membrane • Barrier for cell contents • Double phospholipid layer • Hydrophilic heads • Hydrophobic tails • Also contains proteins, cholesterol, and glycoproteins

10. Plasma Membrane Figure 3.2

11. Plasma Membrane Specializations • Microvilli • Finger-like projections that increase surface area for absorption

12. Plasma Membrane Specializations • Membrane junctions • Tight junctions • Impermeable junctions • Bind cells together into leakproof sheets • Desmosomes • Anchoring junctions that prevent cells from being pulled apart • Gap junctions • Allow communication between cells

13. Plasma Membrane Specializations Figure 3.3

14. Cytoplasm • Cytoplasm is the material outside the nucleus and inside the plasma membrane

15. Cytoplasm • Contains three major elements • Cytosol • Fluid that suspends other elements • Organelles • Metabolic machinery of the cell • “Little organs” that perform functions for the cell • Inclusions • Chemical substances such as stored nutrients or cell products

16. Cytoplasmic Organelles Figure 3.4

17. Cytoplasmic Organelles • Mitochondria • “Powerhouses” of the cell • Change shape continuously • Carry out reactions where oxygen is used to break down food • Provides ATP for cellular energy

18. Cytoplasmic Organelles • Ribosomes • Made of protein and RNA • Sites of protein synthesis • Found at two locations • Free in the cytoplasm • As part of the rough endoplasmic reticulum

19. Cytoplasmic Organelles • Endoplasmic reticulum (ER) • Fluid-filled tubules for carrying substances • Two types of ER • Rough endoplasmic reticulum • Studded with ribosomes • Synthesizes proteins • Smooth endoplasmic reticulum • Functions in lipid metabolism and detoxification of drugs and pesticides

20. As the protein is synthesizedon the ribosome, it migratesinto the rough ER cistern. Ribosome mRNA Rough ER In the cistern, the protein foldsinto its functional shape. Shortsugar chains may be attachedto the protein (forming aglycoprotein). Protein The protein is packaged in atiny membranous sac called atransport vesicle. Transportvesicle buds off The transport vesicle buds fromthe rough ER and travels to theGolgi apparatus for furtherprocessing or goes directly tothe plasma membrane where itscontents are secreted. Protein insidetransport vesicle Rough Endoplasmic Reticulum Figure 3.5

21. Cytoplasmic Organelles • Golgi apparatus • Modifies and packages proteins • Produces different types of packages • Secretory vesicles • Cell membrane components • Lysosomes

22. Secretion byexocytosis Proteins in cisterna Rough ER Lysosome fuses withingested substances Cisterna Membrane Transportvesicle Golgi vesicle containingdigestive enzymesbecomes a lysosome Pathway 3 Pathway 2 Golgiapparatus Secretory vesicles Pathway 1 Golgi vesicle containingmembrane componentsfuses with the plasmamembrane Proteins Golgi vesicle containingproteins to be secretedbecomes a secretoryvesicle Plasma membrane Extracellular fluid Figure 3.6

23. Proteins in cisterna Rough ER Cisterna Membrane Golgiapparatus Plasma membrane Extracellular fluid Figure 3.6, step 1

24. Proteins in cisterna Rough ER Cisterna Membrane Transportvesicle Golgiapparatus Pathway 1 Plasma membrane Extracellular fluid Figure 3.6, step 2

25. Proteins in cisterna Rough ER Cisterna Membrane Transportvesicle Golgiapparatus Pathway 1 Plasma membrane Extracellular fluid Figure 3.6, step 3

26. Proteins in cisterna Rough ER Cisterna Membrane Transportvesicle Golgiapparatus Secretory vesicle Pathway 1 Golgi vesicle containingproteins to be secretedbecomes a secretoryvesicle Plasma membrane Extracellular fluid Figure 3.6, step 4

27. Secretion byexocytosis Proteins in cisterna Rough ER Cisterna Membrane Transportvesicle Golgiapparatus Secretory vesicles Pathway 1 Proteins Golgi vesicle containingproteins to be secretedbecomes a secretoryvesicle Plasma membrane Extracellular fluid Figure 3.6, step 5

28. Proteins in cisterna Rough ER Cisterna Membrane Transportvesicle Pathway 2 Golgiapparatus Plasma membrane Extracellular fluid Figure 3.6, step 6

29. Proteins in cisterna Rough ER Cisterna Membrane Transportvesicle Pathway 2 Golgiapparatus Plasma membrane Extracellular fluid Figure 3.6, step 7

30. Proteins in cisterna Rough ER Cisterna Membrane Transportvesicle Pathway 2 Golgiapparatus Golgi vesicle containingmembrane componentsfuses with the plasmamembrane Plasma membrane Extracellular fluid Figure 3.6, step 8

31. Proteins in cisterna Rough ER Cisterna Membrane Transportvesicle Pathway 3 Golgiapparatus Plasma membrane Extracellular fluid Figure 3.6, step 9

32. Proteins in cisterna Rough ER Cisterna Membrane Transportvesicle Golgi vesicle containingdigestive enzymesbecomes a lysosome Pathway 3 Golgiapparatus Plasma membrane Extracellular fluid Figure 3.6, step 10

33. Proteins in cisterna Rough ER Lysosome fuses withingested substances Cisterna Membrane Transportvesicle Golgi vesicle containingdigestive enzymesbecomes a lysosome Pathway 3 Golgiapparatus Plasma membrane Extracellular fluid Figure 3.6, step 11

34. Secretion byexocytosis Proteins in cisterna Rough ER Lysosome fuses withingested substances Cisterna Membrane Transportvesicle Golgi vesicle containingdigestive enzymesbecomes a lysosome Pathway 3 Pathway 2 Golgiapparatus Secretory vesicles Pathway 1 Golgi vesicle containingmembrane componentsfuses with the plasmamembrane Proteins Golgi vesicle containingproteins to be secretedbecomes a secretoryvesicle Plasma membrane Extracellular fluid Figure 3.6, step 12

35. Cytoplasmic Organelles • Lysosomes • Contain enzymes that digest worn-out or nonusable materials within the cell

36. Cytoplasmic Organelles • Peroxisomes • Membranous sacs of oxidase enzymes • Detoxify harmful substances such as alcohol and formaldehyde • Break down free radicals (highly reactive chemicals) • Replicate by pinching in half

37. Cytoplasmic Organelles • Cytoskeleton • Network of protein structures that extend throughout the cytoplasm • Provides the cell with an internal framework Figure 3.7a

38. Cytoplasmic Organelles • Cytoskeleton • Three different types of elements • Microfilaments (largest) • Intermediate filaments • Microtubules (smallest) Figure 3.7b–d

39. Cytoplasmic Organelles • Centrioles • Rod-shaped bodies made of microtubules • Direct the formation of mitotic spindle during cell division

40. Cellular Projections • Not found in all cells • Used for movement • Cilia move materials across the cell surface • Located in the respiratory system to move mucus • Flagella propel the cell • The only flagellated cell in the human body is sperm

41. Cell Diversity Figure 3.8a

42. Cell Diversity Figure 3.8b

43. Cell Diversity Figure 3.8c

44. Cell Diversity Figure 3.8d

45. Cell Diversity Figure 3.8e

46. Cell Diversity Figure 3.8f

47. Cell Diversity Figure 3.8g