1. PowerPoint ® Lecture Slides prepared by Karen Dunbar Kareiva Ivy Tech Community College © Annie Leibovitz/Contact Press Images Chapter 3 Part C Cells: The Living Units © 2016 Pearson Education, Inc.

2. Part 2 – Cytoplasm All cellular material that is located between the plasma membrane and the nucleus –Composed of: Cytosol: gel-like solution made up of water and soluble molecules such as proteins, salts, sugars, etc. Inclusions: insoluble molecules; vary with cell type (examples: glycogen granules, pigments, lipid droplets, vacuoles, crystals) Organelles: metabolic machinery structures of cell; each with specialized function; either membranous or nonmembranous © 2016 Pearson Education, Inc.

3. 3.7 Cytoplasmic Organelles Membranous –Mitochondria –Endoplasmic reticulum –Golgi apparatus –Peroxisomes –Lysosomes © 2016 Pearson Education, Inc. Membranes allow compartmentalization, which is crucial to cell functioning Nonmembranous –Ribosomes –Cytoskeleton –Centrioles

4. Mitochondria Called the “power plant” of cells because they produce most of cell’s energy molecules (ATP) via aerobic (oxygen-requiring) cellular respiration Enclosed by double membranes; inner membrane has many folds, called cristae –Cristae are embedded with membrane proteins that play a role in cellular respiration Mitochondria contain their own DNA, RNA, and ribosomes Resemble bacteria; capable of same type of cell division bacteria use, called fission © 2016 Pearson Education, Inc.

5. Figure 3.15 Mitochondrion. © 2016 Pearson Education, Inc. Ribosome Mitochondrial DNA Outer mitochondrial membrane Inner mitochondrial membrane Cristae Matrix Enzymes

6. Ribosomes Nonmembranous organelles that are site of protein synthesis Made up of protein and ribosomal RNA (rRNA) Two switchable forms found in cell: –Free ribosomes: free floating; site of synthesis of soluble proteins that function in cytosol or other organelles –Membrane-bound ribosomes: attached to membrane of endoplasmic reticulum (ER); site of synthesis of proteins to be incorporated into membranes or lysosomes, or exported from cell © 2016 Pearson Education, Inc.

7. Endoplasmic Reticulum (ER) Consists of series of parallel, interconnected cisterns—flattened membranous tubes that enclose fluid-filled interiors ER is continuous with outer nuclear membrane Two varieties: –Rough ER –Smooth ER © 2016 Pearson Education, Inc.

8. Figure 3.16 The endoplasmic reticulum. © 2016 Pearson Education, Inc. Smooth ER Nuclear envelope Rough ER Ribosomes Nucleus Diagrammatic view of smooth and rough ER Electron micrograph of smooth and rough ER (25,000  )

9. Endoplasmic Reticulum (ER) (cont.) Rough ER –External surface appears rough because it is studded with attached ribosomes Site of synthesis of proteins that will be secreted from cell Site of synthesis of many plasma membrane proteins and phospholipids –Proteins enter cisterns as they are synthesized and are modified as they wind through fluid-filled tubes –Final protein is enclosed in vesicle and sent to Golgi apparatus for further processing © 2016 Pearson Education, Inc.

10. Endoplasmic Reticulum (ER) (cont.) Smooth ER –Network of looped tubules continuous with rough ER –Enzymes found in its plasma membrane (integral proteins) function in: Lipid metabolism; cholesterol and steroid-based hormone synthesis; making lipids for lipoproteins Absorption, synthesis, and transport of fats Detoxification of certain chemicals (drugs, pesticides, etc.) Converting of glycogen to free glucose Storage and release of calcium –Sarcoplasmic reticulum is specialized smooth ER found in skeletal and cardiac muscle cells © 2016 Pearson Education, Inc.

11. Golgi Apparatus Stacked and flattened membranous cistern sacs Modifies, concentrates, and packages proteins and lipids received from rough ER Three steps are involved: 1.Transport vesicles from ER fuse with cis (inner) face of Golgi 2.Proteins or lipids taken inside are further modified, tagged, sorted, and packaged 3.Golgi is “traffic director,” controlling which of three pathways final products will take as new transport vesicles pinch off trans (outer) face © 2016 Pearson Education, Inc.

12. Figure 3.17 Golgi apparatus. © 2016 Pearson Education, Inc. Cisterns New vesicles forming Transport vesicle from trans face Cis ­­face—­ “receiving” side of Golgi apparatus Transport vesicle from rough ER Trans face— “shipping” side of Golgi apparatus Newly secreted proteins Secretory vesicle New vesicles forming Golgi apparatus Transport vesicle at the trans face Electron micrograph of the Golgi apparatus (90,000  ) Many vesicles in the process of pinching off from the Golgi apparatus

13. Golgi Apparatus (cont.) Depending on its contents, final transport vesicle can take one of three pathways: –Pathway A: Secretory vesicles containing proteins to be used outside of cell fuse with plasma membrane and exocytosis contents –Pathway B: Vesicles containing lipids or transmembrane proteins fuse with plasma membrane or organelle membrane, inserting contents directly into destination membrane –Pathway C: Lysosomes containing digestive enzymes remain in cell, holding contents in vesicle until needed © 2016 Pearson Education, Inc.

14. Figure 3.18 The sequence of events from protein synthesis on the rough ER to the final distribution of those proteins. © 2016 Pearson Education, Inc. Proteins in cisterns ER membrane Phagosome Plasma membrane Vesicle becomes lysosome Pathway C: Lysosome containing acid hydrolase enzymes Rough ER Golgi apparatus Secretory vesicle Secretion by exocytosis Extracellular fluid Pathway B: Vesicle membrane to be incorporated into plasma membrane Pathway A: Vesicle contents destined for exocytosis Protein-containing vesicles pinch off rough ER and migrate to fuse with membranes of Golgi apparatus. 1 Proteins are modified within the Golgi compartments. 2 Proteins are then packaged within different vesicle types, depending on their ultimate destination. 3 Slide 1

15. Figure 3.18 The sequence of events from protein synthesis on the rough ER to the final distribution of those proteins. © 2016 Pearson Education, Inc. Proteins in cisterns ER membrane Plasma membrane Rough ER Golgi apparatus Extracellular fluid Protein-containing vesicles pinch off rough ER and migrate to fuse with membranes of Golgi apparatus. 1 Slide 2

16. Figure 3.18 The sequence of events from protein synthesis on the rough ER to the final distribution of those proteins. © 2016 Pearson Education, Inc. Proteins in cisterns ER membrane Phagosome Plasma membrane Rough ER Golgi apparatus Extracellular fluid Protein-containing vesicles pinch off rough ER and migrate to fuse with membranes of Golgi apparatus. 1 Proteins are modified within the Golgi compartments. 2 Slide 3

17. Figure 3.18 The sequence of events from protein synthesis on the rough ER to the final distribution of those proteins. © 2016 Pearson Education, Inc. Proteins in cisterns ER membrane Phagosome Plasma membrane Vesicle becomes lysosome Pathway C: Lysosome containing acid hydrolase enzymes Rough ER Golgi apparatus Secretory vesicle Secretion by exocytosis Extracellular fluid Pathway B: Vesicle membrane to be incorporated into plasma membrane Pathway A: Vesicle contents destined for exocytosis Protein-containing vesicles pinch off rough ER and migrate to fuse with membranes of Golgi apparatus. 1 Proteins are modified within the Golgi compartments. 2 Proteins are then packaged within different vesicle types, depending on their ultimate destination. 3 Slide 4

18. Peroxisomes Membranous sacs containing powerful detoxifying substances that neutralize toxins –Free radicals: toxic, highly reactive molecules that are natural by-products of cellular metabolism; can cause havoc to cell if not detoxified –Two main detoxifiers: oxidase uses oxygen to convert toxins to hydrogen peroxide (H 2 O 2 ), which is itself toxic; however, peroxisome also contains catalase, which converts H 2 O 2 to harmless water Peroxisomes also play a role in breakdown and synthesis of fatty acids © 2016 Pearson Education, Inc.

19. Lysosomes Spherical membranous bags containing digestive enzymes (acid hydrolases) –Considered “safe” sites because they isolate potentially harmful intracellular digestion from rest of cell Digest ingested bacteria, viruses, and toxins Degrade nonfunctional organelles Metabolic functions: break down and release glycogen; break down and release Ca 2+ from bone Intracellular release in injured causes cells to digest themselves (autolysis) © 2016 Pearson Education, Inc.

20. Figure 3.19 Electron micrograph of lysosomes (20,000  ). © 2016 Pearson Education, Inc. Light green areas are regions where materials are being digested. Lysosomes

21. Clinical – Homeostatic Imbalance 3.4 Lysosomal storage diseases result when one or more lysosomal digestive enzymes are mutated and do not function properly Tay-Sachs disease is a condition in which the patient lacks a lysosomal enzyme needed to break down glycolipids in brain cells –Glycolipids build up as a result of this defect, interfering with nervous system functioning –Seen predominantly in infants of Central European Jewish descent –Causes seizures, mental retardation, blindness, and death before age 5 © 2016 Pearson Education, Inc.

22. Endomembrane System Consists of membranous organelles discussed so far (ER, Golgi apparatus, secretory vesicles, and lysosomes), as well as the nuclear and plasma membranes These membranes and organelles work together to: 1.Produce, degrade, store, and export biological molecules 2.Degrade potentially harmful substances © 2016 Pearson Education, Inc.

23. Figure 3.20 The endomembrane system. © 2016 Pearson Education, Inc. Nucleus Smooth ER Nuclear envelope Rough ER Lysosome Secretory vesicle Plasma membrane Golgi apparatus Transport vesicle

24. Cytoskeleton Elaborate network of rods that run throughout cytosol Hundreds of different kinds of proteins link rods to other cell structures Also act as cell’s “bones, ligaments, and muscle” by playing a role in movement of cell components Three types: –Microfilaments –Intermediate filaments –Microtubules © 2016 Pearson Education, Inc.

25. Cytoskeleton (cont.) Microfilaments –Thinnest of all cytoskeletal elements –Semi-flexible strands of protein actin –Each cell has a unique arrangement of strands, although share common terminal web Dense, cross-linked network of microfilaments attached to cytoplasmic side of plasma membrane Strengthens cell surface and helps to resist compression –Some are involved in cell motility, changes in cell shape, or endocytosis and exocytosis © 2016 Pearson Education, Inc.

26. Figure 3.21a Cytoskeletal elements support the cell and help to generate movement. © 2016 Pearson Education, Inc. 7 nm Actin subunit Strands made of spherical protein subunits called actin Microfilaments Microfilaments form the blue batlike network in this photo.

27. Cytoskeleton (cont.) Intermediate filaments –Size is in between microfilaments and microtubules –Tough, insoluble, ropelike protein fibers –Composed of tetramer (4) fibrils twisted together, resulting in one strong fiber –Help cell resist pulling forces Filaments attach to desmosome plaques and act as internal guy-wires –Some have special names Called neurofilaments in nerve cells and keratin filaments in epithelial cells © 2016 Pearson Education, Inc.

28. Figure 3.21b Cytoskeletal elements support the cell and help to generate movement. © 2016 Pearson Education, Inc. 10 nm Tetramer subunits Tough, insoluble protein fibers constructed like woven ropes composed of tetramer (4) fibrils Intermediate filaments Intermediate filaments form the lavender network surrounding the pink nucleus in this photo.

29. Cytoskeleton (cont.) Microtubules –Largest of cytoskeletal elements; consist of hollow tubes composed of protein subunits called tubulins, which are constantly being assembled and disassembled Most radiate from centrosome area of cell –Determine overall shape of cell and distribution of organelles Many organelles are tethered to microtubules to keep organelles in place Many substances are moved throughout cell by motor proteins, which use microtubules as tracks © 2016 Pearson Education, Inc.

30. Figure 3.21c Cytoskeletal elements support the cell and help to generate movement. © 2016 Pearson Education, Inc. 25 nm Tubulin subunits Hollow tubes of spherical protein subunits called tubulin Microtubules Microtubules appear as gold networks surrounding the cells’ pink nuclei in this photo.

31. Cytoskeleton (cont.) –Motor proteins: complexes that function in motility Can help in movement of organelles and other substances around cell Use microtubules as tracks to move their cargo on Powered by ATP © 2016 Pearson Education, Inc.

32. Centrosome and Centrioles Centrosome, which is located near the nucleus, means “cell center” It is a microtubule organizing center, consisting of a granular matrix and centrioles—a pair of barrel-shaped microtubular organelles that lie at right angles to each other Newly assembled microtubules radiate from centrosome to rest of cell –Some microtubules aid in cell division, and some form cytoskeletal track system Centrioles form the basis of cilia and flagella © 2016 Pearson Education, Inc.

33. Figure 3.22a Centrioles. © 2016 Pearson Education, Inc. Centrosome matrix Centrioles Microtubules

34. Figure 3.22b Centrioles. © 2016 Pearson Education, Inc.

35. 3.8 Cellular Extensions Certain cells have structures extending from the cell surface: –Cilia and flagella aid in the movement of the cell or of materials across the surface of the cell –Microvilli are fingerlike projections that extend from the surface of the cell to increase surface area © 2016 Pearson Education, Inc.

36. Cilia and Flagella Cilia are whiplike, motile extensions on surfaces of certain cells (such as respiratory cells) –Thousands of cilia work together in sweeping motion to move substances (example: mucus) across cell surfaces in one direction Flagella are longer extensions that propel the whole cell (example: tail of sperm) Both structures are made up of microtubules synthesized by centrioles that are called basal bodies because they form the base of each cilium and flagellum © 2016 Pearson Education, Inc.

37. Cilia and Flagella (cont.) Cilia and flagella have “9 + 2” pattern of microtubules (9 sets of double tubes surrounding a central pair of doublets). –Slightly different from 9 + 0 pattern of centriole (9 triplets with no tubules in center) Cilia movements alternate between power stroke and recovery stroke; this alteration produces a current at cell surface that moves substances forward © 2016 Pearson Education, Inc.

38. Figure 3.23 Structure of a cilium. © 2016 Pearson Education, Inc. Triplet Plasma membrane Radial spoke Cross-linking proteins between outer doublets Radial spoke Cross-linking protein between outer doublets Central microtubule Dynein arms Outer microtubules doublet Cilium Basal body (centriole) The “9  2” pattern: microtubule doublets encircle two central microtubules. Microtubules are held together by cross-linking proteins and radial spokes. The doublets also have attached motor proteins, the dynein arms. A cross section through the cilium shows the “9  2” arrangement of microtubules. A cross section through the basal body. The nine outer doublets of a cilium extend into a basal body where each doublet joins another microtubule to form a ring of nine triplets.

39. Figure 3.24 Ciliary function. © 2016 Pearson Education, Inc. Layer of mucus Cell surface Power, or propulsive, stroke Recovery stroke, when cilium is returning to its initial position Phases of ciliary motion. Traveling wave created by the activity of many cilia acting together propels mucus across cell surfaces. 7 6 5 4 3 2 1

40. Microvilli Minute, fingerlike extensions of plasma membrane that project from surface of select cells (example: intestinal and kidney tubule cells) Used to increase surface area for absorption Have a core of actin microfilaments that is used for stiffening of projections © 2016 Pearson Education, Inc.

41. Figure 3.25 Microvilli. © 2016 Pearson Education, Inc. Microvillus Actin filaments Terminal web

42. Part 3 – Nucleus Largest organelle; contains the genetic library of blueprints for synthesis of nearly all cellular proteins –Responds to signals that dictate the kinds and amounts of proteins that need to be synthesized Most cells are uninucleate (one nucleus), but skeletal muscle, certain bone cells, and some liver cells are multinucleate (many nuclei) –Red blood cells are anucleate (no nucleus) © 2016 Pearson Education, Inc.

43. 3.9 Structure of the Nucleus The nucleus has three main structures: –Nuclear envelope –Nucleoli –Chromatin © 2016 Pearson Education, Inc.

44. Figure 3.26a The nucleus. © 2016 Pearson Education, Inc. Nucleolus Chromatin (condensed) Nuclear envelope Nuclear pores Nucleus Cisterns of rough ER

45. The Nuclear Envelope Double-membrane barrier that encloses the jelly-like fluid, the nucleoplasm –Outer layer is continuous with rough ER and, like the rough ER, is studded with ribosomes –Inner layer, called nuclear lamina, is a network mesh of proteins that maintains nuclear shape and acts as scaffolding for DNA Nuclear pores allow substances to pass into and out of nucleus; they are guarded by the nuclear pore complex, which regulates transport of specific large molecules © 2016 Pearson Education, Inc.

46. Figure 3.26b The nucleus. © 2016 Pearson Education, Inc. Fracture line of outer membrane Nuclear pores Nucleus Surface of nuclear envelope. Nuclear pore complexes. Each pore Is ringed by protein particles. Nuclear lamina. The netlike lamina composed of intermediate filaments formed by lamins lines the inner surface of the nuclear envelope.

47. Nucleoli Dark-staining spherical bodies within nucleus that are involved in ribosomal RNA (rRNA) synthesis and ribosome subunit assembly Associated with nucleolar organizer regions that contain the DNA that codes for rRNA Usually one or two per cell © 2016 Pearson Education, Inc.

48. Chromatin Consists of 30% threadlike strands of DNA, 60% histone proteins, and 10% RNA Arranged in fundamental units called nucleosomes, which consist of DNA wrapped around histones –Chemical alterations of histones have an effect on DNA and therefore can help regulate gene expression Chromosomes are condensed chromatin –Condensed state helps protect fragile chromatin threads during cell division © 2016 Pearson Education, Inc.

49. Figure 3.27b Chromatin and chromosome structure. © 2016 Pearson Education, Inc. Tight helical fiber (30-nm diameter) Chromatid (700-nm diameter) Metaphase chromosome (at midpoint of cell division) consists of two sister chromatids 3 4 5

50. Figure 3.26 The nucleus. © 2016 Pearson Education, Inc. Nucleolus Chromatin (condensed) Nuclear envelope Fracture line of outer membrane Nuclear pores Nucleus Cisterns of rough ER Surface of nuclear envelope. Nuclear pore complexes. Each pore is ringed by protein particles. Nuclear lamina. The netlike lamina composed of intermediate filaments formed by lamins lines the inner surface of the nuclear envelope.