Introduction to physiology lecture


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Introduction to physiology lecture

  1. 1. Cell Physiology
  2. 2. Cell: <ul><li>Basic living unit of structure & function of the body. </li></ul><ul><ul><li>> 100 trillion cells in body. </li></ul></ul><ul><ul><li>Very small (10 -5 m in diameter). </li></ul></ul><ul><ul><li>Highly organized. </li></ul></ul><ul><ul><li>Variety of shapes & sizes. </li></ul></ul><ul><ul><li>Each type of cells has a special function. </li></ul></ul>
  3. 3. Cell (continued) <ul><li>All Cells share certain characteristics: </li></ul><ul><ul><li>General cell structure & components. </li></ul></ul><ul><ul><li>General mechanisms for changing nutrients to Energy . </li></ul></ul><ul><ul><li>Deliver end products into their surrounding fluid. </li></ul></ul><ul><ul><li>Almost all have the ability to reproduce. </li></ul></ul>
  4. 4. General Cell structure: <ul><li>3 principal parts: </li></ul><ul><ul><li>Plasma (cell) membrane. </li></ul></ul><ul><ul><li>Cytoplasm & organelles. </li></ul></ul><ul><ul><li>Nucleus. </li></ul></ul><ul><li>The cell has two major compartments: the nucleus & the cytoplasm. </li></ul><ul><li>The cytoplasm contains the major cell organelles & a fluid called cytosol. </li></ul>
  5. 5. General Cell Structure & Function Function Structure Component Surrounds, holds cell together & gives its form; controls passage of materials into & out of cell Membrane composed of double layer of phospholipids in which proteins are embedded Plasma (cell) membrane Serves as matrix substance in which chemical reactions occur. Fluid, jellylike substance b/w cell membrane & nucleus in which organelles are suspended Cytoplasm Supports nucleus & controls passage of materials b/w nucleus & cytoplasm Produces ribosomal RNA for ribosomes Contains genetic code that determines which proteins (including enzymes) will be manufactured by the cell Double-layered membrane that surrounds nucleus, composed of protein & lipid molecules Dense nonmembranous mass composed of protein & RNA molecules Fibrous strands composed of protein & DNA Nucleus: - Nuclear envelope - Nucleolus - Chromatin
  6. 6. <ul><li>Plasma (cell) membrane </li></ul>
  7. 7. Plasma membrane: <ul><li>Surrounds, holds cell together & gives its form. </li></ul><ul><li>75 to 111 Å thickness. </li></ul><ul><li>Not solid. </li></ul><ul><li>Separates cell ’ s internal structures from extracellular </li></ul><ul><li>environment. </li></ul><ul><li>Is selectively permeable, & controls passage of materials into & out of cell. </li></ul><ul><li>Participates in intracellular communication. </li></ul>
  8. 8. Plasma (Cell) Membrane <ul><li>Composed of: </li></ul><ul><ul><li>Double layer of phospholipids (hydrophobic/ hydrophilic parts). </li></ul></ul><ul><ul><li>Proteins span, or partially span the membrane. </li></ul></ul><ul><ul><li>Negatively charged carbohydrates attach to the outer surface. </li></ul></ul>
  9. 9. Plasma Membrane (continued)
  10. 10. General composition of cell membrane <ul><li>Proteins …………………… . 55% </li></ul><ul><li>Lipids ……………………… .. 41% </li></ul><ul><li>- Phospholipids … 25% </li></ul><ul><li>- Cholesterol …… . 12% Lipids </li></ul><ul><li>- Glycolipids …… .. 4% </li></ul><ul><li>Carbohydrates …………… 3% </li></ul>
  11. 11. Cell membrane phospholipids <ul><li>Consists of: </li></ul><ul><li>a. Glycerol head that contains phosphate group </li></ul><ul><li>(polar & hydrophilic). </li></ul><ul><li>b. 2 fatty acid ‘ tails ’ (nonpolar & hydrophobic). </li></ul><ul><li>The hydrophobic parts restricts the passage of H 2 0 & H 2 0- soluble ions. </li></ul>
  12. 12. <ul><li>1. Integral proteins : / Internal or intrinsic proteins </li></ul><ul><li>- span the membrane. </li></ul><ul><li>- transport proteins. </li></ul><ul><li>- provide structural channels or pores. </li></ul><ul><li>2. Peripheral proteins : / external or extrinsic proteins </li></ul><ul><li>- embedded in one side (face) of the membrane. </li></ul><ul><li>- carrier proteins. </li></ul><ul><li>- bind with substances to be transported. </li></ul><ul><li>- include hormone receptors & cell surface antigens. </li></ul>Cell membrane proteins
  13. 13. General functions of cell membrane proteins <ul><li>1. Provide structural support. </li></ul><ul><li>2. Transport molecules across the membrane. </li></ul><ul><li>3. Enzymatic control of chemical reactions at cellular </li></ul><ul><li>surface. </li></ul><ul><li>4. Some function as receptors for hormones. </li></ul><ul><li>5. Some function as regulatory molecules, that arrive at outer surface of the membrane. </li></ul><ul><li>6. Some act as antigens and induce the process of antibody formation. </li></ul>
  14. 14. Cell membrane carbohydrates <ul><li>Primarily attached to the outer surface of the membrane as: </li></ul><ul><li>- Glycoproteins … (most of it). </li></ul><ul><li>- Glycolipids …… (1/10). </li></ul>
  15. 15. <ul><li>1. Attach cells to each other. </li></ul><ul><li>2. Act as receptor substances. </li></ul><ul><li>3. Some enter in immune reactions. </li></ul><ul><li>4. Give most of cells overall – ve surface charge, which affects the interaction of regulatory molecules with the membrane. </li></ul>General functions of cell membrane carbohydrates
  16. 16. <ul><li>Cytoplasm & Organelles </li></ul>
  17. 17. Cytoplasm, Organelles, Nucleoli (continued)
  18. 18. Cytoplasm <ul><li>T he aqueous content of a cell (fluid, jellylike </li></ul><ul><li>substance), that lies b/w cell membrane & nucleus </li></ul><ul><li>in which organelles are suspended. </li></ul><ul><li>Serves as matrix substance in which chemical </li></ul><ul><li>reactions occur. </li></ul><ul><li>‘ cytosol ’ is the term used to describe fluid portion of </li></ul><ul><li>the cytoplasm. </li></ul>
  19. 19. Organelles (excluding nucleus) <ul><li>Subcellular structures within the cytoplasm that perform specific functions. </li></ul><ul><li>Generalized view of a mammalian cell showing organelles common to all cells (such as the Golgi </li></ul><ul><li>complex) as well as specialized structures (e.g., cilia) found only in some cells. </li></ul>
  20. 20. Cytoplasmic Organelles: Structure & Function Function Structure Component Agranular (smooth) ER metabolizes nonpolar compounds & stores Ca 2+ in striated muscle cells; granular (rough) ER assists in protein sysnthesis System of interconnected membrane-forming canals & tubules Endoplasmic reticulum Synthesize proteins Granular particles composed of protein & RNA Ribosomes Synthesizes carbohydrates & packages molecules for secretion. Secretes lipids & glycoproteins Cluster of flattened membranous sacs Golgi complex Release energy from food molecules & transform energy into usable ATP Membranous sacs w folded inner partitions Mitochondria Digest foreign molecules & damaged organelles Membranous sacs Lysosomes
  21. 21. <ul><li>An illustration of the processing of proteins by the granular endoplasmic reticulum & Golgi complex. Notice the formation of vesicles at the ends of some of the flattened sacs of the Golgi complex. </li></ul>
  22. 22. <ul><li>The endoplasmic reticulum. Agranular ER has ribosomes </li></ul><ul><li>attached to its surface, whereas granular ER lacks ribosomes. </li></ul>
  23. 23. <ul><li>A model structure of a ribosome. It is composed of two subunits: smaller (lighter) & larger (darker) subunits. The space between the two subunits accommodates a molecule of transfer RNA, needed to bring amino acids to the growing polypeptide chain. </li></ul>
  24. 24. <ul><li>The structure of a mitochondria. The outer mitochondrial membrane & the infoldings of the inner membrane. The fluid in the center is the matrix. </li></ul>
  25. 25. Cytoplasmic Organelles: Structure & Function (continued) Function Structure Component Contain enzymes that detoxify harmful molecules & break down hydrogen peroxide Spherical membranous vesicles Peroxisomes Helps to organize spindle fibers & distribute chromosomes during mitosis Nonmembranous mass of 2 rodlike centrioles Centrosome Store & release various substances within the cytoplasm Membranous sacs Vacuoles Support cytoplasm & function as cytoskeleton, transport materials within the cytoplasm Thin, hollow tubes Microfilaments & microtubules Move particles along cell surface, or move the cell Minute cytoplasmic projections that extend from the cell surface Cilia & flagella
  26. 26. <ul><li>The formation of the cytoskeleton by microtubules. Microtubules are also important in the motility (movement) of the cell, & movement of materials within the cell. </li></ul>
  27. 27. <ul><li>Nucleus </li></ul>
  28. 28. Cell Nucleus <ul><li>Is a large spheroid body. </li></ul><ul><li>Largest of organelles. </li></ul><ul><li>Contains the genetic material (DNA). </li></ul><ul><li>Most cells have a single nucleus. </li></ul><ul><li>Enclosed by inner & outer membrane (nuclear envelope). </li></ul><ul><ul><li>Outer membrane is continuous with ER. </li></ul></ul><ul><li>Nuclear pore complexes fuse inner & outer membranes together. </li></ul><ul><ul><li>Selective active transport of proteins & RNA. </li></ul></ul>
  29. 29. Cell Nucleus
  30. 30. <ul><li>(a) The cell nucleus is enclosed in a double membrane called the nuclear envelope. Pores in the envelope permit the passage of molecules in & out of the nucleus. The outer layer of the nuclear envelope is continuous with the endoplasmic reticulum, so that the lumen of the ER is continuous with the perinuclear space. In the nondividing nucleus, DNA is visible as chromatin. The nucleolus plays a role in the synthesis of ribosomes from RNA. (b) A nuclear pore is formed from the fusion of the two layers of the nuclear envelope. Proteins are thought to be located in the pores. </li></ul>
  31. 31. Cell Nucleus (continued) <ul><li>Nucleoli: </li></ul><ul><ul><li>Dark areas within the nucleus, not surrounded by membrane. </li></ul></ul><ul><ul><li>Centers for production of ribosomes. </li></ul></ul><ul><li>Chromatin: </li></ul><ul><ul><li>Threadlike material that makes up chromosomes. </li></ul></ul>
  32. 32. Intercellular Junctions <ul><li>Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact </li></ul><ul><li>Intercellular junctions facilitate this contact </li></ul><ul><li>There are several types of intercellular junctions </li></ul><ul><ul><li>1.Tight junctions </li></ul></ul><ul><ul><li>2.Desmosomes </li></ul></ul><ul><ul><li>3. Gap junctions </li></ul></ul>
  33. 33. Tight Junctions, Desmosomes, and Gap Junctions <ul><li>-At tight junctions , membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid </li></ul><ul><li>-Desmosomes (anchoring junctions) fasten cells together into strong sheets </li></ul><ul><li>-Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells </li></ul>
  34. 34. Tight junction 0.5 µm 1 µm Desmosome Gap junction Extracellular matrix 0.1 µm Plasma membranes of adjacent cells Space between cells Gap junctions Desmosome Intermediate filaments Tight junction Tight junctions prevent fluid from moving across a layer of cells