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Cells

Cells . Basic unit of structure and function of all living things Microscopic in size Body is made of trillions of cells Live for few weeks or months, then die Reproduce duplicate cells Made up of: Cell or plasma membrane Nucleus and other organelles. Cell/Plasma Membrane .

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Cells

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  1. Cells • Basic unit of structure and function of all living things • Microscopic in size • Body is made of trillions of cells • Live for few weeks or months, then die • Reproduce duplicate cells • Made up of: • Cell or plasma membrane • Nucleus and other organelles

  2. Cell/Plasma Membrane • Surrounds every cell • Separates cell from external environment • Regulates transport of certain molecules in/out of cell • Selective semipermeable • Prevents passage of some molecules • Composed of double phospholipid layer • Looks like a balloon with tails • Hydrophilic (attracts water) – balloon-like part • Hydrophobic (repels water) – double tails • Allows for easy passage of water by osmosis

  3. Nucleus • Most important organelle within the cell • Spherical and usually located near center of cell • 2 vital functions • Control the activities of the cell • Facilitate cell division • Contains DNA and protein • Arranged loosely in a state called chromatin • When cell is ready to divide, it condenses to form chromosomes • Chromosomes – short, rod-like structures • Humans have 46 (23 pairs) • Store hereditary material of DNA

  4. Functions of Organelles • Nuclear membrane or nuclear envelope • Double-layered structure with pores (openings) • Outer layer continuous with endoplasmic reticulum • Regulates transport of substances into and out of the cell • Nucleoplasm • A clear, semi-liquid medium that fills the spaces around the chromatin and the nucleoli

  5. Functions of Organelles • Nucleolus • May be one or more nucleoli inside nucleus • Reservoir for ribosomes and RNA • Ribosomes • Composed of RNA and protein • Passes from nucleus into cytoplasm • Serves at site for protein synthesis • May be attached to walls of endoplasmic reticulum

  6. Functions of Organelles • Cytoplasm • Sticky, semi-fluid material found between nucleus and membrane • Consists of proteins, lipids, carbs, minerals, salts, water • Environment in which life functions take place by the organelles • Protein synthesis • Cellular respiration • Centrosome • Contains two centrioles, functional during animal cell division • Centrioles • Cylindrical; found near nucleus and perpendicular to each other • Separate during mitosis and form spindle fibers • Fibers attach to chromosomes to help separate into 2 daughter cells

  7. Functions of Organelles • Endoplasmic reticulum • Provides passage through which transport of substances occurs in cytoplasm • Rough ER • Ribosomes studding the outer membrane – site for protein synthesis • Smooth ER • Role in cholesterol synthesis, fat metabolism, and drug detoxification • Mitochondria • Spherical or rod-shaped; vary in number from one to > 1,000 • Serves as sites of cellular respiration and energy production • Known as the “powerhouses” of the cell • Stores energy as adenosine triphosphate (ATP)

  8. Functions of Organelles • Golgi apparatus (Golgi bodies or complex) • Arranged in layers of membranes resembling a stack of pancakes • Manufactures carbohydrates and packages secretions for discharge from the cell • Lysosomes • Oval or spherical bodies containing powerful digestive enzymes • Serve as center for cellular digestion • Digests old, worn out cells, bacteria, and foreign matter • Known as “suicide bags” • If ruptures, starts digesting cell proteins causing it to die

  9. Functions of Organelles • Perioxisomes • Contain oxidase enzymes • Help digest fats and detoxify harmful substances • Cytoskeleton • Forms internal framework of cell • Consists of: • Microtubles • Aid in movement of substances through cytoplasm • Intermediate filaments and microfilaments • Provide support for the cells

  10. Functions of Organelles • Pinocytic vesicles • Method by which large molecules can enter the cell • Cell membrane folds inward, creating a pocket • Edges of pocket then close and pinch away from cell membrane • Cilia and flagella • Long, hair-like protrusions from the cell membrane • Create movement • Cilia • Move materials across surface of cell (respiratory tract) • Flagellum • Propels cell (sperm cell)

  11. Cellular Metabolism • Chemical reactions occur within the cells • Energy supplied by ATP • Stored in mitochondria • ATP created from CHO, proteins, and fats we eat • Calories released from food used to make ATP • ATP is then available to be used for cell maintenance

  12. Cell Division • Meiosis • Involves reproduction • Mitosis • Involves growth and maintenance of cells

  13. Meiosis • Process of cell division of the sex cell or gamete • Ovum and spermatozoa reduce chromosomes from 46 to 23 • Fertilization occurs • Zygote is formed from two sex cells to obtain full set of 46 chromosomes (23 from each parent cell) • See page 36, Figure 3-3

  14. Mitosis • Cell division divided into two distinct processes • Division of the nucleus • Division of the cytoplasm • Orderly series of steps by which DNA in nucleus of cell is equally distributed to 2 daughter, or identical nuclei • Nuclear material distributed to each of 2 new nuclei • Followed by division of cytoplasm into 2 equal parts through formation of a new membrane between the 2 nuclei • All cells do not reproduce at same rate • Blood, skin, and intestinal cells reproduce continuously • Muscle cells reproduce every few years • Nerve cells do not reproduce after birth

  15. Mitosis Stages • Phase I – Interphase (resting stage) • Chromosomes have replicated • Each strand of replicated chromosome is called a chromatid • Chromatid strands are joined by a structure called centromere • Phase II – Prophase • Centrioles separate, move toward poles of cell, form spindle fibers • Nuclear membrane begins dissolving, nucleolus dissappears • DNA in chromosomes condenses and forms rod-like structures • Phase III – Metaphase • Nuclear membrane dissolved completely • Chromatid pairs arrange themselves in single file (equatorial plate)

  16. Mitosis Stages • Phase IV – Anaphase • Chromatid pairs separate, pulled by spindle fibers toward centrioles • Two chromatids of each replicated chromosome are fully separated • Phase V – Telophase • Chromosomes migrate to opposite poles of cell • Chromosomes uncoil to become loose chromatin material • Nuclear membrane and nucleolus reappear • Cytoplasmic division completes the division process • Cycle back to interphase

  17. Cell Death • Necrosis • Unprogrammed death of cells and living tissue • Causes of necrosis include: • Injury • Infection • Cancer • Infarction • Toxins • Inflammation • May release harmful chemicals that damage other cells

  18. Cell Death • Apoptosis • Orderly process by which cells intentionally die • Cell itself initiates, regulates, and executes its death • AKA “programmed cell death” • Confers advantages during organism’s life cycle • Example: differentiation of fingers and toes • In a developing human embryo, the cells in the tissues between the fingers and toes initiate apoptosis so that fingers and toes can separate • In other words: no webbed hands and feet

  19. Protein Synthesis • Review from chapter 2 • Cells produce proteins • DNA determines the kinds of proteins produced • Blueprint for protein contained within specific gene in DNA • Messenger (m-RNA) carries instruction for protein synthesis from DNA to ribosome • Transport (t-RNA) picks up amino acid in cytoplasm and takes it to ribosome, where they combine to form specific protein

  20. Movement of MaterialsAcross Cell Membranes • Cell membrane controls passage of substances into and out of the cell • Fluid inside and outside of cell must maintain a proper balance to maintain homeostasis • Cells must be able to acquire materials from surroundings • It also secretes synthesized substances and excretes waste • Two types of transport • Passive transport • Do not require an energy source • Active transport • Require an energy source

  21. Passive Transport • Diffusion • Physical process whereby molecules of gasses, liquids, or solid particles spread or scatter themselves evenly through a medium • When solid particles are dissolved in solution, known as solutes • Movement from area of high concentration to low concentration • Examples: • Air freshener/room deodorizer • Lump of sugar placed into a glass of water • Oxygen/Carbon Dioxide in blood • Once molecules are evenly distributed, a state of equilibrium occurs • Ways to increase diffusion process: stir, shake, heat, wind current

  22. Passive Transport • Osmosis • Diffusion of water or other solvent through selective membrane • Process continues until equilibrium occurs • Pressure exerted called osmotic pressure • Types of solutions: • Isotonic – equal osmotic pressure • Example: human blood serum (0.9% NaCl) • Hypotonic – less osmotic pressure • Example: freshwater (< 0.9% NaCl) • Hypertonic – more osmotic pressure • Example: seawater (> 0.9% NaCl)

  23. Passive Transport • Osmosis (continued) • Health care worker must know which type of solutions are used • Patient’s condition will determine what type of solution • Most IV fluids are isotonic • Hypertonic solutions are used for patients with edema • Hypotonic solutions are used for patients with dehydration • Filtration • Movement of solutes and water across semipermeable membrane • Results from some mechanical force, such as BP or gravity • Move from area of higher pressure to area of lower pressure • Allows for separation of large and small molecules • Example: kidneys filtering blood for excretion of waste

  24. Active Transport • Molecules move from an area of lower concentration against a concentration gradient, to an area of higher concentration – HOW? • Process requires high-energy compound (ATP) • Theory suggests molecule is picked up by carrier molecule • Both molecules bound shuttle across membrane • Molecule released in cell, carrier molecule returns outside cell • Phagocytosis • “Cell eating” – think PacMan • Pinocytosis • “Cell drinking” – discussed previously

  25. Specialization • Nerve cells • Specialize in response • Red blood cells • Specialize in oxygen transport • May lose some functions, such as reproduction • Interdependence among cells • Certain cells depend on others to aid in carrying on life activities

  26. Aging • Aging is a phase of normal development • Older person may have 30% fewer cells • Cells may change in ability to perform specialized tasks • Physiologic changes are universal and progressive • Aging is not a disease

  27. Disorders of Cell Structure • Atrophy • Decrease in size, usually due to aging or disease • Example: contractures • Hypertrophy • Increase in size, usually the result of an increased workload • Example: left ventricular hypertrophy of the heart from high BP • Hyperplasia • Increase in number, which is related to hormonal stimulation • Example: Grave’s disease due to large amounts of TSH

  28. Disorders of Cell Structure • Metaplasia • Transformation of one cell into another • Example: Barrett’s Esophagus • May be result of protective response • Example: respiratory tract from smoking • Dysplasia • Change in size, shape & organization of cell as result of stimulus • Usually progresses to neoplasia • Example: cervical dysplasia • Neoplasia • Change in cell structure with an uncontrolled growth pattern

  29. Tumor • When cell division does not occur in the usual pattern • Also called neoplasms • Two types: • Benign tumors – confined to a local area • Non-cancerous • Examples: wart, papilloma • Malignant tumors – AKA cancer • Continue to grow, crowd out health cells, interferes with body functions, drawing nutrients away from body tissues • Spreads to other parts of body through process called metastasis • 2nd most common cause of death in the United States

  30. Cancer • Early indicating symptoms • Changes in bowel or bladder habits • Sores that do not heal • Obvious changes in a mole or wart • Unusual bleeding or discharge • A new lump or thickening in the breast or elsewhere • Difficulty in swallowing or frequent indigestion • Persistent cough • Hoarseness

  31. Cancer • Diagnostic tests to detect early stages • X-ray • Mammogram • Sonogram • Biopsy • Biomarkers – norm substances found in blood/tissue in small amts • Cancer classification • Tumor, node, and metastasis (TNM) system used • Treatment • Radiation • Chemotherapy • Surgery

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