Human Anatomy Chapter 2

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amauerba
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307033
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Human Anatomy Chapter 2
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2015-08-29 22:02:37
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cells
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science,biology
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anatomy and functions of cells
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  1. the study of cells
    • - the study of cells : cytology
    •    -only visible by microscopy
    •    - measured in micrometers (μm)
    •          - 1 cm =10,000 μm
    •    - sizes vary 
    •           - from 7μm (RBC) to 120μm oocyte
    •    - shapes vary 
    •           - flat, cylindrical,oval, and irregular in shape
  2. types of microscopy
    • -light microscopy (LM)
    • - transmission electron microscopy (TEM)
    • - scanning electron microscopy (SEM)
  3. light microscopy
    visible light passes through the cell
  4. transmission electron microscopy
    • - a beam of electrons passes through the cell
    • - can magnify about 100x greater than LM
  5. scanning electron microscopy
    -beam of electrons bounces off the surface of the cell to provide a 3D study of the cell surface
  6. cellular functions
    • -covering
    • -lining
    • - storage
    • -movement-
    • -connection
    • -defense
    • -communication
    • -preproduction
  7. prototypical cell
    • -a generalized cell (not a real cell in the body)
    • -combines features from many different cells for teaching purposes
    • -most human cells have 3 basic parts:
    •       - plasma (cell) membrane
    •       - cytoplasm
    •       -  nucleus
  8. plasma (cell) membrane
    • -an extremely thin outer border on cell 
    • -serves as a selective physical and chemical barrier deciding what comes into and leaves the cell
    • -it is the "gatekeeper" that regulates the passage of gasses, nutrients and wastes between the internal and external environments of the cell
  9. composition and structure of membranes
    • - the plasma membrane and membranes within the cell have 2 molecular components  
    •        - lipids
    •        - proteins
  10. membrane lipids
    • - 2 layers: inner and outer
    • -insoluble in water.... prevents cells from dissolving in water
    • - 3 types of lipids in membranes
    •        - phospholipids
    •        - cholesterol
    •        -glycolipids
  11. phospholipids
    • - the majority of lipids in cell membranes
    • - each has a polar (chanrged) region and nonpolar (uncharged) region
    • - when exposed to aqueous (water)environment, they form a phospholipid bilayer
    •      - polar regions face outside and inside of the cell
    •      - nonpolar regions face each other  (form internal core of the membrane)
  12. cholesterol
    • - abut 20% of all membrane lipids
    • - strengthens and stabilizes membranes against extreme temperatures
  13. glycolipids
    • -about 5-10% of all membrane lipids
    • - have carbohydrate (sugar) molecules attached facing out and forming the glycocaylx
  14. membrane proteins
    • - lipids are majority if structure but proteins give membrane functions
    • - proteins: complex molecule made of amino acid chains
    • - 2 types of membrane protein
    •       - integral 
    •       - peripheral
  15. integral membrane proteins
    • · embedded in phospholipid  bilayer
    • · span the entire thickness if the membrane
    • · exposed to the outside and inside of the cell
    • · also termed transmembrane proteins
    • ·cam have carbohydrates (sugar) attached to outer surface = glycoproteins
    • · the glycoproteins and the glycolipids form the  glycocalyx on the external surface of the plasma membrane
    • · have many varied functions
  16. peripheral proteins
    • · not embedded in the lipid bilayer
    • · loosely attached to the external or internal surface if the plasma membrane
    • · have many varied function
  17. general function of the plasma (cell) membrane
    • · communication
    • · intercellular connection
    • · physical barrier
    • · selective permeability
  18. protein-specific functions of the plasma (cell) membrane
    • · transport
    • · intercellular connection
    • · anchorage for the cytoskeleton
    • · enzyme activity
    • · cell-cell recognition
    • · signal transduction
  19. crossing the membrane
    • · 2 general types of membrane transport
    •     - passive
    •     - active
  20. passive
    • · does not require energy from the cell
    • · materials move from area of higher concentration "down" to area of lower concentration = diffusion
  21. active
    • · requires energy fro the cell
    • ·materials are moved up or against concentration gradient
  22. passive transport
    • · all involve diffusion
    • · non require energy from the cell
    • · 4 types of diffusion
    •     -  simple diffusion
    •     - osmosis
    •     - facilitated diffusion
    •     - bulk filtration
  23. simple diffusion
    • · small and/ or nonpolar (uncharged) molecules
    • ·example
    •    - movement of O2 out of the lungs (higher concentration) into blood (lower concentration)
    •     - movement of O2 from blood (higher concentration) into lungs (lower concentration)
  24. osmosis
    • · applies only to movement of H2 O
    •     - same principle as simple diffusion
    •     - H2 O moves from region of higher concentration to region of lower concentration
  25. facilitated diffusion
    • · for large and/or polar (charged molecules)
    • · requires a specific transport protein (integral membrane protein that will bind to the molecule being transported
  26. bulk filtration
    · diffusion of both liquids (solvents) and dissolved molecules ( solutes)
  27. Active Transport
    • · movement of a molecule against the concentration gradient
    •     - opposite of passive transport
    • · requires energy form the cell
    • ·may involve a transport protein
    •     - example is an I pump
    •     - Na+ and K+ are moved in opposite directions against their concentration gradients
  28. active transport by ion pump
    • · Na+ is pumped out of the cell and K+ is pumped in to the cell
    • · requires energy
  29. Bulk transport
    • · moves large molecule or bulk structures across the plasma membrane
    • · requires energy from the cell
    • · can go in either direction
    •     1. exocytosis: out of the cell
    •     2. endocytosis: into the cell
  30. Excoytosis
    • ·materials to be secreted out of the cell and are packaged into vesicles
    • ·vesicles fuse with plasma membranes and materials are released
  31. endocytosis
    • · opposite of exocytosis
    • · materials are taken into the cell packaged in vesicles
  32. types of endocytosis
    • · phagocytosis
    • · pinocytosis
  33. phagocytosis
    · nonspecific uptake of particle by formation of membrane extensions (pseudopodia) that surround particles to be engulfed
  34. pinocytosis
    · nonspecific uptake of extracellular fluid
  35. types of endocytosis
    • · receptor-mediated endocytosis
    •   - engulfing of specific molecule bound to receptors on the surface of the plasma membrane
  36. cytoplasm
    • · all materials (solid and liquid ) between plasma membrane and nucleus
    •    - cytosol
    •    - inclusions
    •    - organelles
  37. cytosol
    • ·  a viscous, syrup- like fluid containing many different dissolved substances such as
    •    - ions
    •    - nutrients
    •    -  proteins
    •    -  carbohydrates
    •    - amino acids
  38. inclusions
    • · large storage aggregates of complex molecule found in the cytosol
    • · examples
    •     - melanin: brown pigment in the skin cells
    •     -  glycogen : long chins of sugars in the liver and skeletal muscles
  39. organelles
    • · means "little organs"
    • · many types of division of labor
    •     - a type and number of organelles within a cell is reflection of the cell's function
    • · membranes can be classified in 2 types
    •    - membrane-bound
    •    - non-membrane- bound
  40. membrane -bound organelles
    • · biochemical activity in organelle is isolated from cytosol and other organelles
    • · examples
    •     - endoplasmic reticulum
    •     - Golgi apparatus
    •     -  lysosomes
    •     - peroxisomes
    •     -  mitochondria
  41. endoplasmic reticulum (ER)
    • · a network of intercellular membrane-bound tunnels
    •    - enclosed spaces are called cisternae
    • · 2 types of ER
    •    - smooth endoplasmic reticulum (SER)
    •    - rough endoplasmic reticulum (RER)
  42. smooth endoplasmic reticulum
    • · walls have smooth appearance
    • · continuous with RER
    • · functions include
    •    1. synthesis , transportation, and storage of lipids including steroid hormones
    •    2. metabolism of carbohydrates
    •    3. detoxification of drugs, alcohol and poisons
  43. Rough endoplasmic retiulum
    • ·walls appear rough due to the attachment of ribosomes on outside of the RER membrane
    •    - ribosomes synthesis proteins
    • ·the RER functions to synthesize, transport or store proteins for
    •    1. secretion by the cell
    •    2.incroration in the plasma membrane
    •    3. creation of lysosomes
  44. Golgi apparatus
    • · stacked cisternae whose lateral edges bulge, pinch off and give rise to small transport and secretory vesicles
    • · function to receive proteins and lipids for the RER for modification, sorting and packing
    •     - receiving region- is the cis-face
    •     - shipping region is the trans-face
  45. protein flow through the Golgi apparatus
    • 1. proteins syntesizeed in RER get packaged in transport vesicles
    • 2. transport vsicles pinch off from RER and fuse with the receiving cis-face of the Golgi apparatus
    • 3. the protein move between and are modified in the cisternae of the Golgi apparatus
    • 4. modified proteins are packaged in secretory vesicles
    • 5 secretory vesicles either participate in exocytosis or become lysosomes in the cell
  46. lysosomes
    • · vesicles generated by the Golgi apparatus
    • · contain enzymes used to digest and remove waste products and damage organelles with in the cell (autophagy)
    • · when the cell is dying it releases lysosomal enzymes that digest the cell ( autolysis)
  47. peroxisomes
    • ·vesicle smaller than lysosomes
    • · use O2 and an enzyme (catalase) to detoxify harmful molecules taken into the cell
  48. mitochondria
    • · bean-shaped organelles with double membrane
    •    - inner membrane folded into shelf-like cristae
    •     - internal fluid: matrix
    • · function to produce a high energy containing molecule called ATP on the cristae
    • · cells that require more energy have more mitochondria than cells requiring less energy
  49. non-membrane bound organelles
    • · in direct contact with the cytosol
    • · examples
    •    - ribosomes
    •    - cytoskeleton
    •    - centrosomes and centrioles
    •    - cilia and flagella
    •    - microvilli
  50. ribosomes
    • · comprised of a large and small subunit
    • · responsible for protein synthesis
    • ·free ribosomes float unattached with in cytosol
    • · fixed ribosomes are attached to the outer surface of RER
  51. cytoskeleton
    • · proteins organized in the cytosol as solid filaments or hollow tubes
    • · 3 main types
    •   - microfilaments
    •   - intermediate filaments
    •   - microtubules
  52. microfilaments
    • · 7 nm (nanometer) think filaments
    •    - 1,000 nanometers =1μm
    • · maintain and change cell shape
    • · participate in muscle contraction and cell division
  53. intermediate filaments
    • · 8-12 nm thick filaments
    • · provide structural support and stabilize junctions between apposed cells
  54. microtubules
    • · 25 nm thick hollow tubes
    • · radiate from centrosomes
    • · fix organelles in place
    • · maintain cell shape and rigidity
    • · direct movement of organelles in the cell
    • · allow cell motility ( in cilia and flagella)
  55. centrosome
    · a pair of centrioles at right angle to each other
  56. centrioles
    • · 9 sets of microtubule triplets
    •   - involved in organizing microtubules
    •   - attached to chromosomes during cell division causing chromosomal migration
  57. cilia and flagella
    • · projections of the cell containing cytoplasm and microtubules capable of movement
    • · cilia : grouped on cells that move objects across their surface (i.e., cells if the respiratory tree and oviduct)]
    • · flagella: longer, usually singular, to propel a cell (e.g., sperm)
  58. microvilli
    • · extensions of cell, not capable of motion
    •   - much smaller than cilia
    • · increase the surface area to increase absorption of food
    •    - found on surface of cells of the small intestine
  59. Nucleus
    • · control center of cellular activity
    • · contains DNA, a complex molecule containing
    •    - when not dividing, nuclear DNA is unwound into fine filaments called chromatin
    •     - during cell division chromatin coils tightly to form chromosomes
  60. nuclear envelope
    • · double membrane structure
    • · controls entry and exit of molecule from nucleus and cytoplasm
    • ·outer membrane is continuous with endoplasmic reticulum
    • · nuclear pore are selectively permeable channels that allow some molecules in or out of the nucleus
  61. nucleoli
    • · dark staining bodies within the nucleus
    • · responsible for making  the components of small and units if the ribosomes
  62. life cycle of the cll
    • · cells are always in 1 of 2 stages
    •   - interphase: maintenance (resting) phase between cell divisions where the following activities occur
    •             - normal activities
    •             - prep for cell division
    •             -  cells spend the majority of life in this
    •   - mitotic phase: when the cell divides
  63. interphase stages
    • · G1 phase
    •     - cells grow, replicate organelles, produce proteins for replication and centrioles just prior to cell division
    • · S phase
    •   - "synthesis phase" where DNA replicate in preparation for cell division
    • · G2 phase
    •   - centriole replication is complete
    •   - other organelle production continues
    •   - enzyme needed for cell division are synthesized
  64. mitotic phase
    • · mitotic cell division is the process by which 2 daughter cells are produced hat are genetically identical to the original (mother) cell
    • · 2 distinct events occur in the phase
    •    - mitosis: duplication of DNA and division of the nucleus
    •    - cytokinesis: division of the cytoplasm and the mother cell
  65. stages of mitosis
    • · mitosis has 4 consecutive stages
    •   - takes less than 2 hours to complete all 4
    •      1. prophase
    •      2. metaphase
    •      3. anaphase
    •      4. telophase
  66. prophase
    • · chromatin supercoils forming chromosomes
    • · duplicate, identical sister chromatids are conjoined at a region called the centromere
    • · elongated microtubules called spindle fiber begin to grow from each centriole
    • · the end of prophase is marked by the dissolution of the nuclear envelope
  67. metaphase
    • · chromosomes line up along the equatorial plate
    • · spindle fiber attach to the centromere of sister chromatids and form an oval structure array called mitotic spindle
  68. anaphase
    · spindle fibers pull sister chromatids apart to opposite ends of the dividing cell
  69. telophase
    • · the nuclear envelope forms around each set of chromosomes
    • · chromosomes begin to uncoil and the mitotic spindle disappears
    • · a pinched area, the cleavage furrow, appears that will complete the physical division of the daughter cells
  70. aging and the cell
    · aging is a normal and continuous process   - indicated by changes in number of organelles or chromatin structure· cells can die in 2 general ways   1. harmful agents or mechanical damage   2. programmed cell death or apoptosis

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