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CELLS AND TISSUES

CELLS AND TISSUES. PART I: AN OVERVIEW OF THE CELLULAR BASIS OF LIFE. Cells are the ultimate example of organization and division of labor Chemical analysis of cells: Primary elements: carbon, oxygen, hydrogen and nitrogen trace elements: iron, sodium, potassium, calcium, iodine

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CELLS AND TISSUES

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  1. CELLS AND TISSUES

  2. PART I: AN OVERVIEW OF THE CELLULAR BASIS OF LIFE • Cells are the ultimate example of organization and division of • labor • Chemical analysis of cells: • Primary elements: carbon, oxygen, hydrogen and nitrogen • trace elements: iron, sodium, potassium, calcium, iodine • Over 60% of living matter is water • The major building substance of the cell is protein • Cells vary in size, shape and function Appear as electrolytes

  3. ANATOMY OF A GENERALIZED CELL 3 MAJOR REGIONS Plasma membrane Nucleus Cytoplasm

  4. PLASMA MEMBRANE

  5. THE PLASMA MEMBRANE REGULATES ENTRY INTO AND • EXIT OUT OF THE CELL • PERMEABILITY MEANS FREE (PASSIVE) PASSAGE OF • SUBSTANCES • WHAT ARE THE DETERMINING FACTORS FOR WHAT • IS ALLOWED TO PASS THROUGHT THE PLASMA MEMBRANE? • - LIPID SOLUBILITY – NONPOLAR AND HYDROPHOBIC • MOLECULES EASILY PASS THROUGH • - SIZE– MOST LARGE PARTICLES CANNOT PASS • THROUGH • - CHARGE – MOST IONS CANNOT PASS THROUGH; SOME • ARE ALLOWED TO PASS THROUGH CHANNEL PORES • PROTEINS IN THE MEMBRANE HELP “FERRY” SUBSTANCES • ACCROSS

  6. FUNCTIONS OF PLASMA MEMBRANE PROTEINS Anchors membrane to cytoskeleton and cell membrane-to- cell membrane for cell recognition Important for allowing entry and exit of certain materials Into and out of cell Cell surface receptors “sense” materials needed by cells and initiate enzyme reactions within cell May be an enzyme with its active site inside the cell to catalyze cellular reactions

  7. Cell Connections • Gap Junctions • Gap junctions are one type of cell connection. When two cells are right next to each other, their cell membranes may actually be touching. A gap junction is an opening from one cell to another. It's not a big opening, but it is large enough for cytoplasm to move from one cell to another. The connections are called channels and they act like tunnels for the movement of molecules. Desmosomes • Desmosomes are a second type of cell connection. They physically connect cells like the gap junction, but no opening is created. Proteins that bond the membrane of one cell to its neighbor create the desmosomes. You will find desmosomes in your skin cells. All of those proteins hold your skin together. The distance between the cells, however small, is about 10 times wider than the gap junction connections. Tight Junction • The last type of connection we will introduce is the tight junction. Tight junctions happen when two membranes actually bond into one. It makes a very strong barrier between two cells. Cells have some distance with a desmosome. Gap junctions allow molecules to pass. Tight junctions form solid walls. These types of connections are often found where one area needs to be protected from the contents of other areas. Example: Found in the stomach wall. They do not allow Fluids to leak out.

  8. PASSIVE TRANSPORT THROUGH THE PLASMA MEMBRANE • DIFFUSION: The free movement of particles from an area of high • concentration to an area of lower concentration. This type of • transport is carried out by almost every cell in the body and is • and important means of passive membrane transport. The driving force for diffusion is the kinetic energy of the molecules . . . This factor is influence by particle size and temperature

  9. Differentiations of Diffusion • Simple diffusion – nonpolar and lipid-soluble substances diffuse • directly through the lipid layer (oxygen, carbon dioxide, fat- • soluble vitamins, alcohol) • Facilitated diffusion – certain molecules like glucose, amino • acids and ions may bind to protein carriers and “ferried” across • or move through water-filled protein channels • Osmosis – the diffusion of water molecules through the • plasma membrane

  10. More Types of Passive Transport • Dialysis – The diffusion of small solute particles, but not larger solute particles through a selectively permeable membrane. -- separates large from small solutes. • Filtration - The passing of water and permeable solutes through a membrane by the force of hydrostatic pressure.

  11. IMPORTANCE OF OSMOTIC PRESSURE IN OUR CELLS NORMAL RBC’S TURGID RBC’S CRENATED RBC’S In an isotonic solution, the [H2O] is the same inside the cell as outside; water flows freely into & out of cells (homeostasis) In a hypotonic solution. the [H2O] is greater on the outside of the cell; water flows into the cell causing it to swell, become bloated and eventually burst (lysis) In a hypertonic solution, the [H2O] is greater inside the cell than outside; water flows out of the cell, and it shrivels or becomes crenated

  12. ACTIVE TRANSPORT ACROSS PLASMA MEMBRANE Process of moving solutes across the membrane against a concentration gradient. . . This requires the bond energy of ATP • The sodium-potassium pump is the primary active transport • pump for the cell. It transports Na+ out of the cell and K+ • into the cell to maintain ionic homeostasis in cells

  13. LARGE PARTICLES, MACROMOLECULES AND FLUIDS ARE TRANSPORTED ACROSS PLASMA MEMBRANES BY VESICULAR TRANSPORT (FORMATION OF VESICLES) ENDOCYTOSIS: moving substances from the extracellular environment into the cell • Pinocytosis (cell “drinking”) – a bit of infolding plasma membrane • surrounds a very small volume of extracellular fluid containing • dissolved molecules and pinches it off into a vesicle.

  14. Phagocytosis (cell “eating”) – relatively large or solid material • (clump of bacteria or cell debris) binds to the cellular surface; • cytoplasmic extensions called pseudopods flow around the • clump and engulf it.

  15. EXOCYTOSIS – THE REMOVAL OF WASTE MATERIALS • FORM THE CELL BY THE FORMATION OF VESICLES • The waste material is first enclosed in a vesicle and moved • through the cytoplasm to the membrane. It is “docked” there, • binding to the membrane proteins. The lipid layers of • the plasma membrane “corkscrew” to “spit out” the water • material

  16. A LOOK INSIDE THE CELL . . . BELOW THE PLASMA MEMBRANE, LIES A THICK FLUID IN WHICH MANY TINY STRUCTURES CARRY ON THE FUNCTION OF THE CELL. EACH ORGANELLE OPERATES MUCH LIKE A PART OF A LARGE MANUFACTURING PLANT . . . WE’VE ALREADY DISCUSSED THE “SECURITY” ROLE OF THE PLASMA MEMBRANE THERE’S ALSO THE OFFICE OF THE “CEO”, THE POWER SUPPLY TO OPERATE THE MACHINERY, THE PHYSICAL “SCAFFOLDING” OF THE PLANT ITSELF, THE ASSEMBLY LINES, RECEIVING DEPARTMENT FOR ORDERS, PACKAGING AND SHIPPING DEPARTMENTS

  17. CYTOPLASM CYTOPLASM IS A COLLOIDAL SUBSTANCE CONTAINING WATER, ORGANIC AND INORGANINC SUBSTANCES AND ORGANELLES THE FLUID PART OF THE CYTOPLASM IS CALLED CYTOSOL INCLUSIONSARE CHEMICAL SUBSTANCES MAY OR MAY NOT BE PRESENT GLYCOGEN MOLECULES (LIVER & MUSCLE CELLS) LIPID DROPLETS (ADIPOSE, OR FAT, CELLS PIGMENTS (MELANIN IN CERTAIN HAIR & SKIN CELLS CRYSTALS OF VARIOUS TYPES CYTOPLASMIC ORGANELLES ARE THE METABOLIC MACHINERY OF THE CELL, EACH WITH A SPECIFIC FUNCTION:

  18. CYTOSKELETON • AN ELABORATE SERIES OF RODS RUNNING THROUGH THE • CYTOSOL, ACTING AS THE “BONES”, “MUSCLES” AND • “LIGAMENTS” TO SUPPORT CELLULAR STRUCTURES AND • PROVIDE THE MACHINERY TO GENERATE CERTAIN CELLULAR • MOVEMENTS • THESE INCLUDE: • MICROTUBULES – HELP DETERMINE THE OVERALL SHAPE OF • THE CELL • MICROFILAMENTS – STRANDS OF ACTIN INVOLVED IN CELL • MOTILITY AND CHANGES IN CELL SHAPE • CENTROSOMES AND CENTRIOLES – FORM SPINDLE FIBERS • FOR THE ATTACHMENT OF CHROMOSOMES • DURING MITOTIC DIVISION

  19. CELLULAR PROJECTIONS THESE PROJECTIONS RESULTS WHEN THE CYTOSKELETON EXTENDS BEYOND THE PLASMA MEMBRANE Cilia are “eyelash-like” extensions that are short and numerous. Their purpose is to move substances along the surface of the membrane . . . Particularly, in the respiratory tract to move debis away from the lungs Flagella are “whip-like” structures that result when the cytoskeletal extensions are longer and thicker. . . The only example in the human body is the sperm

  20. THE NUCLEUS – CONTROL CENTER OF THE CELL Nuclear envelope – outer layer continuous with the rough ER; inner membrane is lined with protein filaments that give the nucleus its shape Nuclear pores – proteins through which RNA, water and other molecules pass Nucleolus – dark-staining body within the nucleus; site for synthesis of ribosome subunits (cells may have multiple nucleoli) DNA material (in this case it is condensing in preparation for cell division)

  21. MITOCHONDRIA – THE “POWER PLANTS” OF THE CELL Cristae – inner membrane folds protruding into the gel matrix of mitochondria. . . These folds provide increased surface area for reactions Mitochondria contain their own DNA and RNA and are able to reproduce themselves • In living cells, mitochondria squirm, elongate and change shape • continuously • they provide most of the ATP supply for the cell • mitochondria are abundant in cells requiring a great deal of energy • (kidney and liver cells have many; inactive lymphocytes, few) • Here, through the process of aerobic respiration, metabolites • are broken down and oxidized . . . Some of the energy is captured • and used to attach phosphate groups to ADP to form ATP

  22. RIBOSOMES : SITES OF PROTEIN SYNTHESIS • Small, dark-staining granules composed of proteins and a variety of • of RNA called ribosomal RNA • Free ribosomes float freely in the cytoplasm to make soluble • proteins that function in the cytosol • Membrane-bond ribosomes are attached to the rough ER and synthesize • proteins for incorporation into the cell membranes or for export • from the cell Each ribosome has two globular subunits that fit together like the body and cap of an acorn

  23. ENDOPLASMIC RETICULUM: “NETWORK WITHIN THE CYTOPLASM” • an extensive system of interconnected tubes and parallel membranes • enclosing fluid-filled cavities or cisternae that coils and twists througout • the cytosol; about half the cell’s membranes • the ER is continuous with the nuclear membrane • ER is of two distinct varieties in the cell: Rough Endoplasmic Reticulum • external surface studded with ribosomes • all proteins produced here are secreted from the cell (especially numerous in secretory cells and in antibody-producing cells and in the liver) • the “membrane factory” since the proteins and phospholipids of the cellular membrane are formed here

  24. SMOOTH ENDOPLASMIC RETICULUM • Tubules continuous with the rough ER, but play no part in protein synthesis • Abundant in some cells, absent in others • They catalyze reactions involved in the following processes: - lipid metabolism, cholesterol synthesis and synthesis of the lipid components of lipoproteins (liver cells - synthesis of steroid-based hormones, such as sex hormones (abundant in testicle cells producing testosterone) - absorption, synthesis and transport of fats (intestinal cells) - detoxification of drugs, certain pesticides and carcinogens (liver and kidney cells) - breakdown of stored glycogen to form free glucose (specifically, liver cells)

  25. GOLGI APPARATUS : “PACKING & SHIPPING” DEPARTMENT • stacked and flattened membranous sacs associated with • swarms of tiny membranous vesicles • major function: modify, concentrate and package proteins for • export from the cell “receiving” side transport vesicles bud off rough ER and fuse with Golgi at convex surface “shipping” side various proteins are “tagged” for delivery to a specific site, sorted and packaged in vesicles that bud from the concave surface

  26. LYSOSOMES: “DEMOLITION CREW” • spherical membranous organelles • containing digestive enzymes • abundant in phagocytes ( cells that • dispose of invading bacteria • and cell debris • Functions: • digest particles taken in by endocytosis (bacteria, viruses, toxins) • degrade worn-out or nonfunctional organelles • perform metabolic functions (glycogen breakdown and release) • break down nonuseful tissues (webs between human fingers and • toes of the developing fetus and uterine lining during menstruation) • break down bone to release calcium ions into the blood

  27. PeroxisomesGlorified lysosomes Detoxify harmful Substances which May enter cells Contain the enzymes Peroxidase and Catalase which break Down hydrogen peroxide.

  28. CELL DIVISION: MITOSIS • Cell division is essential for body growth and tissue repair • Some cells reproduce themselves continually (skin, • intestinal lining) while others lose their ability to divide • when they are fully mature (nervous tissue, skeletal and • heart muscle) • What makes cells divide? • Ratio of volume to surface area – increase efficiency

  29. STAGES OF MITOSIS

  30. Interphase • Nucleus is intact • Individual chromosomes are not visible yet. • G1, S, and G2 occur as the cell prepares to divide.

  31. Prophase • Chromatin is darkening, shortening, and forming Individual chromosomes • Nuclear envelope is breaking down. • Mitotic spindles are forming

  32. Metaphase • Visible chromosomes line up at the equator of the cell. Each attached to a spindle fiber.

  33. Anaphase • Centromeres divide and spindles contract pulling each Chromatid toward opposite poles/ends. • Cytokinesis begins.

  34. Telophase • Chromatids reach their opposite poles • Cytockinesis continues

  35. Daughter Cells-Interphase • Cytokinesis is complete. • G1, S and G2 begin again.

  36. Quiz 1 4 • Daughter • cells • Interphase • Prophase • Metaphase • Anaphase • Telophase 5 2 3 6

  37. ANATOMY & PHYSIOLOGY • COMPLETE ALL PARTS OF CELL LAB TODAY, INCLUDING • MITOSIS PHASE-COUNT AND QUESTIONS • TURN IN COLOR PLATES: GENERAL CELL & MITOSIS • COMPLETE STUDY GUIDE ON CELLS

  38. Another type of Cell Division • Meiosis is the type of cell division that produces sex cells. EGG and SPERM • It reduces the number of chromosomes in the resulting cells by ½ = haploid • Only sex cells are haploid. • All cells begin cell division as diploid.

  39. Sexual Reproduction • Fertilization restores the chromosome number to diploid and mitosis begins.

  40. Spermatogenesis

  41. Oogenesis

  42. What if cells divide too often? • Hyperplasia-the excessive formation of new cells hyper- excessive -plasia- formation Example: Milk producing glands of breast during pregnancy. Cancer cells also result from hyperplasia forming a tumor called a neoplasm.

  43. Hyperplasia may also happen in the uterus which results in the lining becoming too thick causing excessive bleeding.

  44. Cell Size • Hypertrophy- Cells increase in size. • Atrophy- Cells decrease in size.

  45. BODY TISSUE . . . “The Living Fabric” • The millions of cells in our body • become specialized for particular • functions . . . • Groups of cells that are similar in • structure and function are called • Tissues result from MITOSIS. • There are 4 primary tissue types • Based on function: • Epithelium (covering) • Connective (support) • Muscle (movement • Nervous (control)

  46. EPITHELIUM • Epithelial tissue is the lining, covering and glandular tissue of the body • - Lining and covering epithelia covers all free • body surfaces (versatile) • Glandular Epithelium forms various glands in the body • Special functions: protection, absorption, filtration and secretion • Special charactistics: • cells fit closely together to forma continuous sheet; cells • connected by desmosomesand tight-junctions • membranes always have one “free” (unattached) surface – apical surface • lower surface rests on a basement membrane (secreted by cells) • epithelial tissue is avascular (no blood supply) and depends upon diffusion • from capillaries in the underlying connective tissue for nourishment and • oxygen • Epithelial cells (if properly nourished) regenerate themselves

  47. CLASSIFICATION OF EPITHELIUM Epithelial tissue is classified according to shapeand arrangement of component cells

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