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Cell Structure and Function

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found in the hydrophobic region of ... fluid mosaic model of cell membranes ... Neoplasm- new growth either benign or malignant (cancer) Cellular disease ... – PowerPoint PPT presentation

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Title: Cell Structure and Function


1
Cell Structure and Function
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ANATOMY AND PHYSIOLOGY I LECTURE NOTES
  • CELL BIOLOGY
  • CELL THEORY
  • Schleiden and Schwann (1830)
  • all living things are composed of cells

3
CELLS IN HUMANS
  • size variation
  • red blood cells ( 7.5 micrometers)
  • female 'egg' cell 300 micrometer
  • structural variations
  • muscle cells-very long
  • nervous cells- conduct impulses
  • red blood cells- transport gases

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THE TYPICAL CELL
  • CELL STRUCTURES AND FUNCTIONS
  • Nucleus-
  • nuclear membrane has nuclear pores
  • double layered
  • function of nucleus
  • contains genetic material of cell
  • controls all functions in cell

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CELL STRUCTURES AND FUNCTIONS
  • nucleolus
  • contains RNA
  • site of synthesis of mRNA, rRNA, tRNA

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Cell membrane ( plasma membrane)
  • phospholipid bilayer
  • cholesterol
  • found in the hydrophobic region of phospholipid
    bilayer
  • glycolipids
  • lipid portion faces to outside

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Cell membrane, cont.
  • membrane proteins
  • channels
  • enzymes
  • glycoproteins
  • proteins with added carbohydrates

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fluid mosaic model of cell membranes
  • movement of proteins and glycoproteins within in
    the membrane (pattern pieces)
  • movement of phospholipids , into and out of the
    membrane and within membrane ( background pieces)

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ESSENTIAL FUNCTIONS OF CELL MEMBRANES
  • maintains integrity of cell or organelle
  • transports water soluble molecules
  • contains receptors for hormones

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FUNCTIONS OF CELL MEMBRANES
  • regulation of metabolic reactions ( membrane
    enzymes)
  • support and shape of cell ( cytoskeleton)
  • identification of cells or organelles (
    glycoprotein)

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CYTOPLASM ORGANELLES
  • Endoplasmic reticulum
  • rough endoplasmic reticulum
  • protein synthesis for exported proteins
  • smooth endoplasmic reticulum
  • no ribosomes , synthesis of carbohydrate of
    glycoproteins

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CYTOPLASM ORGANELLES, cont.
  • ribosomes
  • site of synthesis of proteins
  • some exist attached to RER
  • some ribosomes synthesize proteins used by the
    cell which makes the protein ( non export)
  • NOTE RIBOSOMES ARE ESSENTIAL FOR ALL PROTEIN
    SYNTHESIS

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CYTOPLASM ORGANELLES, cont.
  • Golgi apparatus
  • membranous stack plus vesicles
  • package and post process products from the
    endoplasmic reticulum

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Synthesis of exported proteins
  • 1. Protein synthesis starts in the rough
    endoplasmic reticulum (RER)
  • 2. The protein makes it way to the smooth
    endoplasmic reticulum (SER)
  • 3. Next the protein is transported to the Golgi
    apparatus where it is packaged for export
  • 4. Secretory vesicles pinch of the the Golgi and
    migrate to the plasma membrane
  • 5. Fusion- vesicle fuses with the plasma membrane
    and releases protein(s) to the extracellular
    space ( secretion occurs)

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CYTOPLASM ORGANELLES, cont.
  • Lysosomes
  • membrane bound sac contains hydrolytic enzymes
  • digest old organelles
  • digest pathogens ( bacteria, fungi, viruses)

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CYTOPLASM ORGANELLES
  • Peroxisomes
  • membrane bound sac contains peroxidase and
    catalase
  • important in metabolic reactions involving
    hydrogen peroxide
  • used to detoxify harmful chemicals

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CYTOPLASM ORGANELLES, cont.
  • Mitochondria
  • oval shaped, double membranes and cross
    membranes called cristae
  • site of synthesis of ATP used for energy in the
    cell

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CYTOPLASM ORGANELLES, cont.
  • cytoskeleton
  • microtubules
  • hollow , 25nm largest
  • also found in centrioles, flagella
  • intermediate filaments
  • 3 strands- 10 nm
  • attaches to ribosomes, mitochondrion and other
    organelles

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CYTOPLASM ORGANELLES, cont.
  • cytoskeleton
  • microfilaments
  • smallest- 7 nm
  • used in mitosis also

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CYTOPLASM ORGANELLES, cont.
  • centrosome
  • a pair of centrioles
  • plays a role in cell division
  • composed of microtubules

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CELL EXTENSIONS
  • microvilli ( brush border)
  • increases surface area
  • found on epithelial cells
  • cilia
  • hair like structures
  • found in respiratory tract epithelial
  • flagella
  • tail like structure found on sperm

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cell connections
  • desmosomes
  • spot weld type ( intermediate filaments
  • gap junction channels
  • tight junctions -plastic collar

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TRANSPORT PROCESSES or how things get into and
out of cells
  • simple diffusion
  • passive
  • movement of solute
  • From higher solute concentration to lower

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TRANSPORT PROCESSES, cont.
  • dialysis
  • passive
  • peritoneal dialysis

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TRANSPORT PROCESSES, cont.
  • facilitated diffusion
  • passive
  • membrane protein carrier
  • example- transport of glucose into cells

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TRANSPORT PROCESSES, cont.
  • osmosis
  • diffusion of WATER through a selectively
    permeable membrane
  • movement of water is from higher to lower

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More on osmosis
  • if red blood cells are put into WATER they will
    swell and burst.
  • The water is HYPOTONIC in relationship to the
    internal environment of the RBC.
  • Water moves into the cell

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More on osmosis
  • if red blood cells are put into 2.5 NaCl, the
    cells will shrink.
  • Water leaves the cell.
  • The solution is HYPERTONIC

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More on osmosis
  • if red blood cells are put into a solution of
    0.9 NaCl, they will stay the same size.
  • Amount of water going into and out of the cell is
    equal.
  • This solution (0.9 NaCl) is ISOTONIC.

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TRANSPORT PROCESSES, cont.
  • active transport
  • uses ATP
  • from low to high possible
  • muscle- pumps calcium ions, Na/K pump

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ENDOCYTOSIS( vesicles formed)
  • phagocytosis
  • active
  • cell eating- intake of bacteria
  • pinocytosis
  • active
  • cell drinking- intake of fluid and dissolved
    solutes

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ENDOCYTOSIS , cont.
  • membrane mediated endocytosis.
  • intake of specific molecules
  • membrane receptors bind with specfic molecules
  • example- uptake of hormones into target cells

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EXOCYTOSIS
  • excretion- waste products put out of cell
  • vesicle fuses with plasma membrane and releases
    waste to outside
  • secretion- product put out of cell
  • same as above, except product released is used

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CELL CYCLE
  • INTERPHASE
  • growth 1 G1
  • synthesis- DNA replication takes place
  • growth 2

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MITOSIS
  • I. prophase-
  • nuclear membrane disappears
  • chromosomes supper coil
  • II. metaphase
  • double stranded chromosomes migrate to the
    equatorial plane

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MITOSIS, cont.
  • III. anaphase-
  • single stranded chromosomes form
  • and migrate towards poles

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MITOSIS, cont.
  • IV. telophase
  • cytokinesis occurs
  • nuclear membrane reforms

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MEIOSIS
  • meiosis I and meiosis II
  • synthesis of sperm and ovum

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Cell activities
  • DNA REPLICATION
  • the doubling of genetic material ( single
    stranded chromosome to double stranded chromosome
  • TRANSCRIPTION
  • synthesis of mRNA
  • TRANSLATION
  • synthesis of protein molecule

74
Diseases and cells
  • Cell growth and reproduction problems
  • Atrophy- decrease cell size
  • Hypertrophy- increase in cell size
  • Hyperplasia- increase cell numbers ( nor normal)
  • Neoplasm- new growth either benign or malignant
    (cancer)

75
Cellular disease
  • Cystic fibrosis- Cl- transport affected
  • Duchenne muscular dystrophy- Ca ion in muscle
    cells affected
  • NIDDM- membrane receptors for insulin are
    reduced
  • Disorders that affect protein synthesis
  • Sickle cell anemia
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