1. Copyright 2009 John Wiley & Sons, Inc. Chapter 3 The Cellular Level of Organization

2. Copyright 2009 John Wiley & Sons, Inc. A Generalized Cell 1. Plasma membrane - forms the cell’s outer boundary - separates the cell’s internal environment from the outside environment - is a selective barrier - plays a role in cellular communication

3. Copyright 2009 John Wiley & Sons, Inc. A Generalized Cell 2. Cytoplasm - all the cellular contents between the plasma membrane and the nucleus - cytosol - the fluid portion, mostly water - organelles - subcellular structures having characteristic shapes and specific functions

4. Copyright 2009 John Wiley & Sons, Inc. A Generalized Cell 3. Nucleus - large organelle that contains DNA - contains chromosomes, each of which consists of a single molecule of DNA and associated proteins - a chromosome contains thousands of hereditary units called genes

5. Fig. 3.1 Generalized Body Cell

6. Copyright 2009 John Wiley & Sons, Inc. Plasma Membrane Flexible yet sturdy barrier The fluid mosaic model - the arrangement of molecules within the membrane resembles a sea of lipids containing many types of proteins The lipids act as a barrier to certain substances The proteins act as “gatekeepers” to certain molecules and ions

7. Copyright 2009 John Wiley & Sons, Inc. Structure of a Membrane Consists of a lipid bilayer - made up of phospholipids, cholesterol and glycolipids Integral proteins - extend into or through the lipid bilayer Transmembrane proteins - most integral proteins, span the entire lipid bilayer Peripheral proteins - attached to the inner or outer surface of the membrane, do not extend through it

8. Copyright 2009 John Wiley & Sons, Inc. Structure of the Plasma Membrane

9. Copyright 2009 John Wiley & Sons, Inc. Structure of a Membrane Glycoproteins - membrane proteins with a carbohydrate group attached that protrudes into the extracellular fluid Glycocalyx - the “sugary coating” surrounding the membrane made up of the carbohydrate portions of the glycolipids and glycoproteins

10. Copyright 2009 John Wiley & Sons, Inc. Functions of Membrane Proteins Some integral proteins are ion channels Transporters - selectively move substances through the membrane Receptors - for cellular recognition; a ligand is a molecule that binds with a receptor Enzymes - catalyze chemical reactions Others act as cell-identity markers

11. Copyright 2009 John Wiley & Sons, Inc. Figure 3.3

12. Copyright 2009 John Wiley & Sons, Inc.

13. Membrane Permeability The cell is either permeable or impermeable to certain substances The lipid bilayer is permeable to oxygen, carbon dioxide, water and steroids, but impermeable to glucose Transmembrane proteins act as channels and transporters to assist the entrance of certain substances, for example, glucose and ions

14. Copyright 2009 John Wiley & Sons, Inc. Passive vs. Active Processes Passive processes - substances move across cell membranes without the input of any energy; use the kinetic energy of individual molecules or ions Active processes - a cell uses energy, primarily from the breakdown of ATP, to move a substance across the membrane, i.e., against a concentration gradient

15. Copyright 2009 John Wiley & Sons, Inc. Diffusion Steepness of concentration gradient Temperature Mass of diffusing substance Surface area Diffusion distance

16. Copyright 2009 John Wiley & Sons, Inc. Simple Diffusion, Channel-mediated Facilitated Diffusion, and Carrier-mediated Facilitated Diffusion

17. Copyright 2009 John Wiley & Sons, Inc. Channel-mediated Facilitated Diffusion of Potassium ions through a Gated K + Channel

18. Copyright 2009 John Wiley & Sons, Inc. Carrier-mediated Facilitated Diffusion of Glucose across a Plasma Membrane

19. Glucose transporter Glucose gradient Glucose Extracellular fluid Plasma membrane Cytosol 1 Glucose transporter Glucose gradient Glucose Extracellular fluid Plasma membrane Cytosol 1 2 Glucose transporter Glucose gradient Glucose Extracellular fluid Plasma membrane Cytosol 1 2 3

20. Copyright 2009 John Wiley & Sons, Inc. Osmosis Net movement of water through a selectively permeable membrane from an area of high concentration of water (lower concentration of solutes) to one of lower concentration of water Water can pass through plasma membrane in 2 ways: 1. through lipid bilayer by simple diffusion 2. through aquaporins, integral membrane proteins

21. Copyright 2009 John Wiley & Sons, Inc.

22. Tonicity and its effect on RBCS

23. Copyright 2009 John Wiley & Sons, Inc. Active Transport Solutes are transported across plasma membranes with the use of energy, from an area of lower concentration to an area of higher Concentration Sodium-potassium pump 1 3 Na + K + gradient Na + gradient Na + /K + ATPase Extracellular fluid Cytosol 1 3 Na + expelled 3 Na + ADP P K + gradient Na + gradient Na + /K + ATPase Extracellular fluid Cytosol ATP 21 3 Na + expelled 3 Na + ADP P P K + gradient Na + gradient Na + /K + ATPase Extracellular fluid Cytosol 2K + ATP 23 1 3 Na + expelled 3 Na + ADP P P 2 K + imported K + gradient Na + gradient Na + /K + ATPase Extracellular fluid Cytosol 2K + ATP 234

24. Copyright 2009 John Wiley & Sons, Inc. Transport in Vesicles Vesicle - a small spherical sac formed by budding off from a membrane Endocytosis - materials move into a cell in a vesicle formed from the plasma membrane three types: receptor-mediated endocytosis phagocytosis bulk-phase endocytosis (pinocytosis) Exocytosis - vesicles fuse with the plasma membrane, releasing their contents into the extracellular fluid Transcytosis - a combination of endocytosis and exocytosis

25. Copyright 2009 John Wiley & Sons, Inc. Receptor-Mediated Endocytosis

26. 1 Clathrin-coated pit Binding Receptor Receptor-LDL complex LDL particle Plasma membrane Invaginated plasma membrane 1 Clathrin-coated vesicle Clathrin-coated pit Binding Vesicle formation Receptor Receptor-LDL complex LDL particle Plasma membrane Invaginated plasma membrane 2 1 Clathrin-coated vesicle Clathrin-coated pit Binding Vesicle formation Receptor Receptor-LDL complex Uncoated vesicle Uncoating LDL particle Plasma membrane Invaginated plasma membrane 2 3 1 Clathrin-coated vesicle Clathrin-coated pit Binding Vesicle formation Receptor Receptor-LDL complex Uncoated vesicle Fusion with endosome Uncoating LDL particle Plasma membrane Invaginated plasma membrane Endosome 2 3 4 Transport vesicle 1 Clathrin-coated vesicle Clathrin-coated pit Binding Vesicle formation Receptor Receptor-LDL complex Uncoated vesicle Transport vesicle Fusion with endosome Recycling of receptors to plasma membrane Uncoating LDL particle Plasma membrane Invaginated plasma membrane Endosome 2 3 4 5 Transport vesicle 1 Clathrin-coated vesicle Clathrin-coated pit Binding Vesicle formation Receptor Receptor-LDL complex Uncoated vesicle Degradation in lysosome Lysosome Transport vesicle Transport vesicle Fusion with endosome Recycling of receptors to plasma membrane Uncoating LDL particle Plasma membrane Invaginated plasma membrane Endosome Digestive enzymes 2 3 4 5 6

27. Copyright 2009 John Wiley & Sons, Inc. Phagocytosis

28. Copyright 2009 John Wiley & Sons, Inc. Bulk-phase Endocytosis

29. Copyright 2009 John Wiley & Sons, Inc. Cytoplasm - 2 components 1. Cytosol - intracellular fluid, surrounds the organelles - the site of many chemical reactions - energy is usually released by these reactions - reactions provide the building blocks for cell maintenance, structure, function and growth 2. Organelles Specialized structures within the cell The cytoskeleton - network of protein filaments throughout the cytosol -provides structural support for the cell -three types according to increasing size: microfilaments, intermediate filaments, and microtubules

30. Copyright 2009 John Wiley & Sons, Inc. The Cytoskeleton

31. Copyright 2009 John Wiley & Sons, Inc. Organelles Centrosome - located near the nucleus, consists of two centrioles and pericentriolar material (Fig. 2.7) Cilia - short, hair-like projections from the cell surface, move fluids along a cell surface Flagella - longer than cilia, move an entire cell; only example is the sperm cell’s tail (Fig. 2.8)

32. Copyright 2009 John Wiley & Sons, Inc. The Centrosome

33. Copyright 2009 John Wiley & Sons, Inc. Cilia and Flagella

34. Copyright 2009 John Wiley & Sons, Inc. Organelles Ribosomes - sites of protein synthesis Endoplasmic reticulum - network of membranes in the shape of flattened sacs or tubules - Rough ER - connected to the nuclear envelope, a series of flattened sacs, surface is studded with ribosomes, produces various proteins -Smooth ER - a network of membrane tubules, does not have ribosomes, synthesizes fatty acids and steroids, detoxifies certain drugs

35. Copyright 2009 John Wiley & Sons, Inc. Ribosomes

36. Copyright 2009 John Wiley & Sons, Inc. Endoplasmic Reticulum

37. Copyright 2009 John Wiley & Sons, Inc. Organelles Golgi complex - consists of 3-20 flattened, membranous sacs called cisternae - modify, sort, and package proteins for transport to different destinations - proteins are transported by various vesicles Lysosomes - vesicles that form from the Golgi complex, contain powerful digestive enzymes

38. Copyright 2009 John Wiley & Sons, Inc. Golgi Complex

39. Copyright 2009 John Wiley & Sons, Inc. Processing and Packaging

40. Transport vesicle Ribosome Synthesized protein 1 Rough ER Transport vesicle Ribosome Synthesized protein Rough ER 2 1 Transport vesicle Ribosome Entry face cisterna Exit face cisterna Medial cisterna Synthesized protein Rough ER 3 2 1 Transport vesicle Ribosome Entry face cisterna Exit face cisterna Medial cisterna Synthesized protein Transfer vesicle Rough ER Transfer vesicle 4 3 2 1 4 Transport vesicle Ribosome Entry face cisterna Exit face cisterna Medial cisterna Synthesized protein Transfer vesicle Rough ER Transfer vesicle 5 4 3 2 1 4 Transport vesicle Ribosome Entry face cisterna Exit face cisterna Medial cisterna Synthesized protein Transfer vesicle Rough ER Transfer vesicle 6 5 4 3 2 1 4 Transport vesicle Ribosome Entry face cisterna Exit face cisterna Medial cisterna Synthesized protein Transfer vesicle Rough ER Transfer vesicle Secretory vesicle 7 6 5 4 3 2 1 4 Proteins exported from cell by exocytosis Plasma membrane Proteins in vesicle membrane merge with plasma membrane Proteins exported from cell by exocytosis Plasma membrane Transport vesicle Ribosome Entry face cisterna Exit face cisterna Medial cisterna Synthesized protein Transfer vesicle Rough ER Transfer vesicle Membrane vesicle Secretory vesicle 8 7 6 5 4 3 2 1 4 Proteins in vesicle membrane merge with plasma membrane Proteins exported from cell by exocytosis Plasma membrane Transport vesicle Ribosome Entry face cisterna Exit face cisterna Medial cisterna Synthesized protein Transport vesicle (to lysosome) Transfer vesicle Rough ER Transfer vesicle Membrane vesicle Secretory vesicle 9 8 7 6 5 4 3 2 1 4

41. Copyright 2009 John Wiley & Sons, Inc. Lysosomes

42. Copyright 2009 John Wiley & Sons, Inc. Organelles Peroxisomes - smaller than lysosomes, detoxify several toxic substances such as alcohol, abundant in the liver Proteasomes - continuously destroy unneeded, damaged, or faulty proteins, found in the cytosol and the nucleus

43. Copyright 2009 John Wiley & Sons, Inc. Organelles Mitochondria - the “powerhouses” of the cell  Generate ATP  More prevalent in physiologically active cells: muscles, liver and kidneys  Inner and outer mitochondrial membranes  Cristae - the series of folds of the inner membrane  Matrix - the large central fluid-filled cavity  Self-replicate during times of increased cellular demand or before cell division

44. Copyright 2009 John Wiley & Sons, Inc. Mitochondria

45. Copyright 2009 John Wiley & Sons, Inc. Organelles - Nucleus Spherical or oval shaped structure Usually most prominent feature of a cell Nuclear envelope - a double membrane that separates the nucleus from the cytoplasm Nuclear pores - numerous openings in the nuclear envelope, control movement of substances between nucleus and cytoplasm Nucleolus - spherical body that produces ribosomes Genes - are the cell’s hereditary units, control activities and structure of the cell Chromosomes - long molecules of DNA combined with protein molecules

46. Copyright 2009 John Wiley & Sons, Inc.

47. Packing of DNA into a Chromosome of a Dividing Cell

48. Copyright 2009 John Wiley & Sons, Inc. Overview of Gene Expression

49. Copyright 2009 John Wiley & Sons, Inc. Transcription

50. Copyright 2009 John Wiley & Sons, Inc. Translation

51. 1 Key: Initiator tRNA attaches to a start codon. Amino acid (methionine) Anticodon mRNA binding site Initiator tRNA Start codon Small subunit = Adenine = Guanine = Cytosine = Uracil U U U G G G G G G A A A A A U A C C U C U A A C U C 1 Key: Initiator tRNA attaches to a start codon. Large and small ribosomal subunits join to form a functional ribosome and initiator tRNA fits into P site. Amino acid (methionine) Anticodon mRNA binding site Initiator tRNA Start codon Small subunit Initiator tRNA Small subunit Large subunit P site A site = Adenine = Guanine = Cytosine = Uracil U U U G G G G G G A A A A A U A C C U C U A A C U C G A U U U G G A A A A A C C G G U C U A C U U A C G 2

52. Copyright 2009 John Wiley & Sons, Inc. Somatic Cell Division - Mitosis The cell cycle is a sequence of events in which a body cell duplicates its contents and divides in two Human somatic cells contain 23 pairs of chromosomes (total = 46) The two chromosomes that make up each pair are called homologous chromosomes (homologs) Somatic cells contain two sets of chromosomes and are called diploid cells

53. Copyright 2009 John Wiley & Sons, Inc. Cell Division Interphase - the cell is not dividing - the cell replicates its DNA - consists of three phases, G 1, S, and G 2, replication of DNA occurs in the S phase Mitotic phase - consists of a nuclear division (mitosis) and a cytoplasmic division (cytokinesis) to form two identical cells

54. Copyright 2009 John Wiley & Sons, Inc. The Cell Cycle

55. Copyright 2009 John Wiley & Sons, Inc. DNA Replication

56. Copyright 2009 John Wiley & Sons, Inc. Nuclear Division: Mitosis Prophase - the chromatin fibers change into chromosomes Metaphase - microtubules align the centromeres of the chromatid pairs at the metaphase plate Anaphase - the chromatid pairs split at the centromere and move to opposite poles of the cell; the chromatids are now called chromosomes Telophase - two identical nuclei are formed around the identical sets of chromosomes now in their chromatin form

57. Copyright 2009 John Wiley & Sons, Inc. Cytoplasmic Division: Cytokinesis Division of a cell’s cytoplasm to form two identical cells Usually begins in late anaphase The plasma membrane constricts at its middle forming a cleavage furrow The cell eventually splits into two daughter cells Interphase begins when cytokinesis is complete

58. 1 Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol (a) INTERPHASE Centrioles Centrosome: all at 700x LM 1 Late Early Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol Chromosome (two chromatids joined at centromere (a) INTERPHASE (b) PROPHASE Centrioles Centrosome: Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore 2 all at 700x LM Centromere 1 Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol Metaphase plate (a) INTERPHASE Centrioles Centrosome: (c) METAPHASE 2 3 Late Early (b) PROPHASE Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore all at 700x LM Chromosome (two chromatids joined at centromere Centromere 1 Early Late (d) ANAPHASE Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol Chromosome (a) INTERPHASE Centrioles Centrosome: (c) METAPHASE 2 3 4 Cleavage furrow Late Early (b) PROPHASE Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore Metaphase plate all at 700x LM Chromosome (two chromatids joined at centromere Centromere 1 Early Late (d) ANAPHASE Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol (a) INTERPHASE Centrioles Centrosome: Cleavage furrow (e) TELOPHASE (c) METAPHASE 2 3 4 5 Cleavage furrow Late Early (b) PROPHASE Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore Metaphase plate Chromosome all at 700x LM Chromosome (two chromatids joined at centromere Centromere 1 Early Late (d) ANAPHASE Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol (a) INTERPHASE Centrioles Centrosome: (f) IDENTICAL CELLS IN INTERPHASE Cleavage furrow (e) TELOPHASE (c) METAPHASE Cleavage furrow 2 3 4 5 6 Late Early (b) PROPHASE Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore Metaphase plate Chromosome all at 700x LM Centromere Chromosome (two chromatids joined at centromere

59. Copyright 2009 John Wiley & Sons, Inc. Reproductive Cell Division During sexual reproduction each new organism is the result of the union of two gametes (fertilization), one from each parent Meiosis - reproductive cell division that occurs in the gonads (ovaries and testes) that produces gametes with half the number of chromosomes Haploid cells - gametes contain a single set of 23 chromosomes Fertilization restores the diploid number of chromosomes (46)

60. Copyright 2009 John Wiley & Sons, Inc. Reproductive Cell Division Meiosis occurs in two successive stages: meiosis I and meiosis II Each of these two stages has 4 phases: prophase, metaphase, anaphase, and telophase Summary - Meiosis I begins with a diploid cell and ends with two cells having the haploid number of chromosomes; in Meiosis II, each of the two haploid cells divides, the net result is four haploid gametes that are genetically different from the original diploid starting cell

61. Copyright 2009 John Wiley & Sons, Inc.

63. Cellular Diversity The average adult has nearly 100 trillion cells There are about 200 different types of cells Cells come in a variety of shapes and sizes Cellular diversity permits organization of cells into more complex tissues and organs

64. Copyright 2009 John Wiley & Sons, Inc. End of Chapter 3 Copyright 2009 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of theses programs or from the use of the information herein.