Cells

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