Ch3 Ppt Lect


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Ch3 Ppt Lect

  1. 1. Chapter 3 Cells
  2. 2. You are responsible for the following figures and tables : Fig. 3.1 - The cells of the human body. Fig. 3.2 - Specialized cells. Fig. 3.42. Fig. 3.3 - Generalized diagram of a universal animal cell. Fig. 3.6 - Phospholipid bilayer Fig. 3.7 - Embedded in this cell membrane are transmembrane proteins. Fig. 3.8 - cells communicate with each other Fig. 3.12 - representation of a cell. Fig. 3.12, 3.29, 3.30, 3.31 – endocytosis and exocytosis. Fig. 3.21 - Passive transport does not require energy. Tab. 3.4 - summary of transport mechanisms in and out of the cell. Fig. 3.36 - cell cycle - Name the phases. Fig. 3.37 - Name the phases of cell division, describe them. Define ' cancer'. Tab. 3.6.
  3. 3. Cells <ul><li>The adult human body consists of about 75 million cells, the basic units of the human body. </li></ul><ul><li>All precursor cells, also called stem cells , are alike and omnipotent . They only differentiate into specialized cells as they mature (Fig. 3.42). </li></ul><ul><li>Whether precursor or specialized, all body or somatic cells have 46 chromosomes. </li></ul><ul><li>Mature cells vary in size, shape, and function (Figs. 3.1 and 3.2). </li></ul>
  4. 4. Cells – They consist of: Cell membrane Cytoplasm Cytoplasmic organelles Nucleus
  5. 5. Cell Membrane <ul><li>Outermost limit of the cell consisting of a phospholipid bilayer (Fig. 3.6). </li></ul><ul><li>Thin, flexible, elastic </li></ul><ul><li>Maintains integrity of the cell </li></ul><ul><li>Controls entrance and exit of substances, selectively semipermeable </li></ul><ul><li>Receives and responds to messages, signal transduction </li></ul>
  6. 6. Cell Membrane Structure <ul><li>It is a phospholipid bilayer. </li></ul><ul><li>It contains lipids, proteins, and glycolipids or glycoproteins with some carbohydrates. </li></ul><ul><li>The surface of the membrane is formed by water-soluble heads made up of phosphate groups ( hydrophilic or polar ) </li></ul><ul><li>The interior of the membrane is formed by water-insoluble tails composed of fatty acids ( hydrophobic or nonpolar ) </li></ul>
  7. 7. Membrane Transport <ul><li>Molecules that are soluble in lipids can easily pass through the membrane. </li></ul><ul><li>Molecules that are water-soluble do not move through the membrane. </li></ul><ul><li>Cholesterol molecules embedded inside of the lipid bilayer make the cell membrane even more impermeable and make it inflexible. </li></ul>
  8. 8. Membrane Proteins <ul><li>Fibrous proteins that span the membrane function as receptors. </li></ul><ul><li>Globular, integral proteins spanning the membrane allow passage of certain molecules or ions such as the cystic fibrosis transporter protein (CFTR) that transports chlorine across the cell membrane. </li></ul><ul><li>Globular, peripheral proteins that do not span the membrane function as enzymes or signal transducers. These often aid in cell recognition and cell binding of ‘growth factors’. </li></ul>
  9. 9. Figure 3.7
  10. 10. Cytoplasm <ul><li>The cytoplasm is a clear gel called cytosol . </li></ul><ul><li>It contains a network of membranes around organelles that are suspended in the cytosol. </li></ul><ul><li>Protein rods and microtubules form the cytoskeleto n, a supportive framework. </li></ul><ul><li>The many different organelles perform specific cellular functions that aid in the growth of cells and the body. </li></ul>
  11. 11. Cell Components and Organelles CELL COMPONENT/ ORGANELLES DESCRIPTION/STRUCTURE FUNCTION(S) CELL or PLASMA MEMBRANE a phospholipid bilayer with transmembranous proteins / protein channels dispersed throughout it semipermeable cell boundary ( controls active/passive Transport ) CYTOPLASM jelly-like plasma / fluid (70% H 2 O) suspends organelles in cell; translation of m-RNA into protein using t-RNA NUCLEUS control center of the cell; bound by phospholipid bilayer = nuclear membrane; contains DNA DNA replication = synthesis of DNA double strand; DNA transcription into mRNA m-RNA synthesis r-RNA synthesis NUCLEOLUS dense spherical body within nucleus; area of r-RNA synthesis / protein synthesis of ribosomes RIBOSOMES consist of r-RNAs / proteins; dispersed throughout cytoplasm and on RER protein synthesis using m-RNA as template and t-RNA adding on amnio acids to the growing protein = translation ROUGH ER ( RER ) Membranous network studded with ribosomes protein synthesis = translation SMOOTH ER ( SER ) Membranous network lacking ribosomes lipid / cholesterol synthesis GOLGI Membrane stacks looking like “Stack of Pancakes”; cisternae posttranslational modification transport and packaging of proteins in vesicles = endocytosis / exocytosis LYSOSOMES Membranous sac of digestive enzymes degradation of worn cell parts (“autolysis) and foreign particles PEROXISOMES Membranous sacs filled with catalase enzymes (catalase) detoxification of harmful substances(i.e.ethanol,drugs) MITOCHONDRIA “ Powerhouse” kidney shaped; inner membrane is folded into “cristae”; cellular respiration ; uses O 2 , releases CO 2 ; makes 38 ATP = energy CYTOSKELETON protein filaments=microtubules intracellular transport along the protein filaments
  12. 12. Nucleus <ul><li>Large, spherical structure </li></ul><ul><li>Enclosed in a phospholipid bilayer called nuclear envelope , composed of an inner and outer lipid bilayer </li></ul><ul><li>Layers are joined at openings, the nuclear pores </li></ul><ul><li>Nuclear pores are channels made up of more than 100 different proteins that allow movement in and out of the nucleus </li></ul>
  13. 13. Nucleolus and Chromatin <ul><li>The nucleolus is a small, dense body composed of RNA and protein. </li></ul><ul><li>It is the site of ribosome production, that is, ribosomal RNA or r-RNA is synthesized . </li></ul><ul><li>Chromatin fibers are composed of continuous DNA strands. </li></ul><ul><li>Around these DNA molecules are wrapped eight proteins called histones . </li></ul>
  14. 14. Figure 3.12
  15. 15. <ul><li>Fig. 3.12 shows some specific functions of organelles: </li></ul><ul><li>Nucleus - transcription of DNA into mRNA </li></ul><ul><li>Ribosomes on Rough ER – translation of mRNA into protein </li></ul><ul><li>Rough ER – modification of proteins </li></ul><ul><li>Golgi Apparatus – modification of proteins and lipids by </li></ul><ul><li>addition of carbohydrates to the structure </li></ul><ul><li>Vesicles – transport of products outside the cell by exocytosis </li></ul><ul><li>Exocytosis is an active energy requiring process </li></ul><ul><li>Smooth endoplasmic reticulum ( Smooth ER ) lacks ribosomes (Fig. 3.10) </li></ul>
  16. 16. Mitochondria <ul><li>Fluid-filled sacs that contain their own DNA and can divide on their own. </li></ul><ul><li>There are two layers, an outer membrane and an inner membrane. </li></ul><ul><li>The inner membrane is folded into cristae. </li></ul><ul><li>Enzymes of the mitochondrion control reactions of energy release from nutrients. </li></ul>
  17. 17. Figure 3.13b
  18. 18. Lysosomes <ul><li>Tiny, membranous sacs containing enzymes that break down proteins, carbohydrates, and nucleic acids </li></ul><ul><li>White blood cells contain lysosomes which aid in the digestion of bacteria and degradation of bacterial components with lysosomal enzymes </li></ul><ul><li>Lysosomes dismantle worn cells and cell parts </li></ul>
  19. 19. Peroxisomes <ul><li>Membranous sacs found in all cells, but abundant in liver and kidneys that break down lipidic/fatty toxins, drugs and alcohol </li></ul><ul><li>Enzymes, peroxidases, catalyze these metabolic degradative reactions that release hydrogen peroxide as a byproduct </li></ul><ul><li>Catalase decomposes hydrogen peroxide (H 2 O 2 ) </li></ul>
  20. 20. Other Cell Components Figure 3.3 – Hypothetical Composite Cell
  21. 21. Other Cell Components Figure 3.3 Figure 3.3 – Hypothetical Composite Cell
  22. 22. CELL COMPONENTS that modify cell surface Or are specialized during mitosis DESCRIPTION/STRUCTURE FUNCTION(S) FLAGELLA long, tail-like extension; sperm locomotion CILIA short, eyelash-like extensions; respiratory tract & fallopian tube to push substances through passageways MICROVILLI microscopic folds of cell membrane increase surface area CENTRIOLES paired cylinders of microtubules at right angles near nuclear poles; they function during cell division; synthesis and resorption of protein filaments called microtubules aid in chromosome movement during mitosis
  23. 23. Figure 3.16 – cilia move mucus or eggs in tubes
  24. 24. Microfilaments and Microtubules <ul><li>Threadlike structures in the cytoplasm </li></ul><ul><li>Microfilaments are tiny rods of the protein actin. They function in cellular movements </li></ul><ul><li>Microtubules are long, slender tubes composed of the protein tubulin. They form the cytoskeleton and help move organelles within the cells </li></ul>
  25. 25. Cells Also Contain Inclusions <ul><li>Chemicals stored temporarily in the cell. </li></ul><ul><li>Nutrients such as glycogen and lipids can be stored. </li></ul><ul><li>Pigments such as melanin can be stored. </li></ul>
  26. 26. Movements Into and Out of the Cell <ul><li>The cell membrane controls the movement of substances into and out of the cell. </li></ul><ul><li>Movements involve physical or passive processes such as diffusion, facilitated diffusion, osmosis, and filtration. </li></ul><ul><li>Movements can be physiological or active processes such as active transport, endocytosis, and exocytosis. </li></ul>
  27. 27. Diffusion <ul><li>Diffusion is the tendency of molecules, and ions in solution to move from areas of higher concentration to areas of lower concentration . </li></ul><ul><li>The difference in concentration is the concentration gradient . </li></ul><ul><li>Diffusion occurs because particles are in constant motion attempting to equilibrate across a membrane or inside an organelle. </li></ul>
  28. 28. Diffusion <ul><li>Diffusion progresses until there is no net movement any longer called diffusional equilibrium . </li></ul>
  29. 29. Diffusion in Living Systems <ul><li>Diffusional equilibrium is more correctly referred to as seeking of a physiological steady state . </li></ul><ul><li>Diffusion of substances occurs if the membrane is permeable to that substance and if a concentration gradient exists </li></ul><ul><li>Examples: oxygen, carbon dioxide, cholesterol </li></ul>
  30. 30. Facilitated Diffusion <ul><li>Substances that are insoluble in lipids and too large to move through pores move by facilitated diffusion. </li></ul><ul><li>Facilitated diffusion includes protein channels and protein carriers. </li></ul><ul><li>Molecules fit into the carrier and are transported across the membrane. </li></ul><ul><li>The number of carriers limits the rate of movement. </li></ul>
  31. 31. Figure 3.24
  32. 32. Osmosis <ul><li>Osmosis is the diffusion of water molecules from a region of higher water concentration to a region of lower water concentration across a selectively permeable membrane. </li></ul>
  33. 33. Osmosis <ul><li>One might also say : Osmosis is the diffusion of water molecules from a region of low solute concentration to a region of high solute concentration across a selectively permeable membrane. </li></ul><ul><li>Red Blood Cells (RBC) exhibit how osmosis works nicely: when in isotonic or plasma solution, they appear donut shaped. </li></ul><ul><li>When they are placed into a hypotonic solution, they take up water and swell and might even burst. </li></ul><ul><li>When they are placed into a hypertonic solution, they loose water and shrink in size. </li></ul>
  34. 34. Figure 3.26a
  35. 35. Figure 3.26b
  36. 36. Figure 3.26c
  37. 37. Filtration <ul><li>Molecules can be filtered by force (such as pressure differences) through membranes as is done in the kidney nephrons. </li></ul>
  38. 38. Active Transport <ul><li>Active transport occurs when the net movement of particles passing through membranes is in the opposite direction, from a region of lower concentration to one of higher concentration. </li></ul>
  39. 39. Active Transport <ul><li>Active transport utilizes protein carriers. </li></ul><ul><li>This process requires energy from cell metabolism. </li></ul>
  40. 40. Endocytosis <ul><li>Endocytosis moves particles too large to move by diffusion or active transport. </li></ul><ul><li>Pinocytosis is the intake of liquid droplets. </li></ul>
  41. 41. Endocytosis <ul><li>Phagocytosis is the intake of solids, often with the fusion of lysosomes which digest the material. </li></ul><ul><li>Pinocytosis and phagocytosis bring material indiscriminately into the cell. </li></ul>
  42. 42. Exocytosis <ul><li>Exocytosis often expels the residue after lysosomal enzymes have digested solids brought in through phagocytosis. </li></ul><ul><li>Exocytosis allows cells to secrete material produced by the cell, for example, neurotransmitters. </li></ul>
  43. 43. Other Functions of Cells: Growth. The Cell Cycle <ul><li>The series of changes that a cell undergoes from the time it forms until it divides is called the cell cycle. </li></ul>
  44. 44. The Cell Cycle: Interphase <ul><li>Interphase is the period of cell growth and function. </li></ul><ul><li>Interphase is composed of G1, S Phase, and G2. </li></ul>
  45. 45. Interphase <ul><li>G 1 is the first Gap or Growth phase. During this period, cell growth occurs. </li></ul><ul><li>S phase is the period of DNA synthesis as the cell prepares for cell division. </li></ul>
  46. 46. <ul><li>G 2 is the second Gap or Growth phase. During this period, the cell replicates organelles in preparation for cell division. </li></ul>Interphase
  47. 47. Mitosis <ul><li>Mitosis occurs in somatic cells, all body cells with the exception of sex cells. </li></ul><ul><li>Cell division results in two genetically identical daughter cells with 46 chromosomes each . </li></ul><ul><li>Karyokinesis is nuclear division. </li></ul><ul><li>Cytokinesis or the movement of the daughter cells apart from each other is the division of the cytoplasm. </li></ul>
  48. 48. Figure 3.37
  49. 49. Mitosis: Prophase <ul><li>Prophase : chromosomes condense from chromatin and centrioles move to the poles. The nuclear envelope disintegrates . The spindle apparatus forms. </li></ul>
  50. 50. Mitosis: Metaphase <ul><li>Metaphase : spindle fibers attach to centromeres and chromosomes align in the center or equatorial plate of the cell. </li></ul>
  51. 51. Mitosis: Anaphase <ul><li>Anaphase : Spindle fibers contract and the chromosomes move to the opposite poles of the future daughter cells. </li></ul>
  52. 52. Mitosis: Telophase <ul><li>Telophase : Nuclear envelope reforms and chromosomes unwind into chromatin. </li></ul>
  53. 53. Last Stage Of The Cell Cycle: Cytokinesis <ul><li>Cytokinesis or cytoplasmic division begins in anaphase when the cell membrane starts to constrict in the middle. </li></ul><ul><li>Cytoplasmic inclusions and organelles are divided between the two new cells. </li></ul>
  54. 54. Control of the Cell Cycle <ul><li>How often cells divide is strictly controlled. </li></ul><ul><li>Cells appear to keep track of their divisions, the “mitotic clock”. </li></ul><ul><li>DNA at the tips of chromosomes, telomeres, wear down as the cell divides and may be a signal for the cell to stop dividing. </li></ul><ul><li>Size, space, hormones, and growth factors influence cell division. </li></ul>
  55. 55. Abnormal Cell Growth <ul><li>Abnormal growth or a neoplasm can produce a disorganized mass called a tumor . Tumors often are initially benign becoming malignant only later by additional signals </li></ul><ul><li>Benign tumors remain in place and grow, interfering with function of healthy tissue. </li></ul><ul><li>Malignant (cancerous) tumors are invasive or metastatic and extend into surrounding tissue. </li></ul><ul><li>Cancer or uncontrolled cell cycling , can affect different tissues. </li></ul>
  56. 56. Genes and Cancer <ul><li>Environmental factors may induce cancer by altering oncogenes and tumor suppressor genes in cells. </li></ul>Figure 3.40
  57. 57. Cellular Differentiation <ul><li>The process by which stem cells develop different structures and specialized functions is called cellular differentiation . </li></ul><ul><li>Differentiation begins in the first weeks after fertilization in the embryo. </li></ul><ul><li>It reflects genetic control of development. Special proteins (hormones, growth factors) activate some genes and repress others. </li></ul>
  58. 58. Figure 3.42
  59. 59. <ul><li>Clinical Applications 3.1 – Cloning to produce </li></ul><ul><li>therapeutic stem cells </li></ul><ul><li>In this as yet hypothetical scenario, embryonic cells can be altered to contain the normal unmutated genes. </li></ul><ul><li>When these cells mature and start to specialize, they can then synthesize normal proteins. </li></ul>Cloning