Chapter 8 Notes

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Chapter 8 Notes
Mr. Granderson

• Cellular Transport and Cell Cycle

Photo credit to Visuals Unlimited (VU) and
Glencoe Biology Text
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• Diffusion Movement of particles from higher to
  lower concentration (via kinetic theory, a
  general word.)
• Osmosis Diffusion of water across a selectively
  permeable membrane (across cell boundaries to
  make amount of water on each side even).
• Regulating osmosis is important part of cell
  homeostasis.
• Generally, strong sol. of sugars or salts placed
  with weak one sugar/salt diffusing into weaker
  (where less of them) and water into sugar/salt
  sol. (where there is fewer water molecules.
• In cell, selectively permeable membrane only
  water can move.
• Thus, water ? to where concentration is lower
  (until ).
• Most cells experience osmosis (in water solution).

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• Isotonic solution conc. of dissolved stuff in
  solution around cell is same as in cell (water
  likewise). Water diffuses in and out at same
  rate.
• Cell stay same shape.
• Might include body fluid solution and
  immunization shots, etc.

Water enters and leaves the cells at about the
same rate because concentration is about equal in
and out.
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• Hypotonic solution concentration of dissolved
  stuff is lower in the solution around the cell.
  Thus, more water outside the cell than in and
  water diffuses into the cell.
• With osmosis, cell swells and pressure increases.
• Cells may burst (lyse).
• Plant cells, cell wall, dont burst, but become
  firm. (Crisp fresh vegetables when in water).

Water flows in, because the cell interior is
comparatively low in H2O concentration.
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• Hypertonic solution Dissolved stuff outside
  cell is higher in concentration than in.
• Water flows out to equalize distribution.
• Cells may shrivel (animal) due to decreased
  pressuresalted meat dries and toughens.
• Plant cells lose water/pressure and wilt.

Water flow out of cell, b/c Concentration is
lower there b/c of large amounts of other
Stuff.salts, etc.
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• Passive transport- movement of particles across
  membrane without energy (simply by diffusion).
  Water, lipids, and lipid-solubles.
• Transport proteins can also allow passive
  transport.facilitated diffusion. (p.204)
  (Convenient openingsreaching normal
  concentration, no energy required.
• Active Transport- (p.205) requires energy, moving
  against gradient. Bonds to carrier protein in
  membrane, specifically shaped for molecule to
  fit chemical energy used to alter carrier
  protein and released inside membrane (open/shut
  door system). Releasing molecule restoring
  original protein shape for next molecule.
• Endocytosis- for moving large particles (requires
  energy). Cell actively surrounds a particle with
  cell membrane and engulfs it (ends up in vacuole
  inside cell). P. 206, Amoebas eat food this way.
  Reverse to rid wastes is called exocytosis.

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8.2 Cell growth and reproduction

• Cells varysmall, long with limited diameter
  (nerves) or large (ostrich egg yolk) with food
  supply.
• Usually 2-200micrometers in diameter.
• A. Nutrients and wastes ? membrane via diffusion.
• Inefficient over larger distances.
• B. DNA limits size b/c must be blueprint for
  proteins to be madenot enough DNA for cell
  protein synthesis may partly solve with
  multi-nucleated cells.
• C. Surface to volume ratio as size increases,
  volume increases faster than surface area
  (p.208).
• 1X1X1mm cellS.A.-6, V-1 2X2X2mm cellS.A.-24,
  V-8 .see next slide for comparison.
• Rapid decrease in relative surface means unable
  to diffuse nutrients in and wastes out.
  Typically reproduce when get past a certain size.

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Cell size comparison
As cell size increases, surface area
increases more slowly than does the volume (power
of 3).
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Cell Reproduction

• All cells from preexisting cells, reproduction
  via cell divisiontwo cells identical to first
  one.
• For growth, also daily maintenance of
  fast-shedding skin/intestinal lining and healing.
• Nucleus, structures of DNA during division, stain
  darkchromosomes.
• Chromosomes carry genetic info that is copied and
  passed from cell to cellcell identity and
  accurate reproduction is critical to cell.
• DNA long strands or loops wrapped around some
  proteinschromatin. Mess of spaghetti.
• Proteins are able to be made from this loosened
  DNA.
• To reproduce, must be organized, looped tightly,
  and forms specific chromosome structures so wont
  be tangled/lost/damaged.

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• Cell cycle
• Sequence-growth
• and cell division.
• Interphase Prd.
• of growth (most
• of cells life)
• growth in size,

• metabolism, chromosomes duplicated for later
  division.
• After Inter., cell goes thru nuclear division
  called mitosis.
• Last, division of cytoplasm occursthus complete
  life and division into two cells occurs.
  Cytokinesis cytoplasm divides.

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• Stages see p.211 also
• G1 start interphase. Uncoiled chromosomes,
  proteins made, cell growing.
• S Stage Chromosome replicated in nucleus and
  sister chromatids connected by a centromere.
• G2 Chrom. shorten, coil rapid protein
  syn.(needed for mitosis), cell organizes and
  preps (makes mitochondria), in animals,
  centrioles pair replicates and prepares for
  spindle.
• Mitosis When interphase complete 4 stages?
  After, cytoplasm dividestwo daughter cells
  w/identical DNA.

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Mitosis cycle (nuclear division)
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• Cells do mitosis as near maximum size (can still
  produce patterns for proteins and transport
  nutrients/wastes).
• 4 distinct phases Prophase, metaphase,
  anaphase, telophase (see previous slide).
• Prophase 1st and longest. Chromatin coils into
  visible chromosomes (still fuzzy), two halves of
  doubled chromosomes called sister chromatids.
• Exact copies of each other (from interphase).
  Centromere holds them together, helps in movement
  (and IDs some of them for scientists).
• Nuclear envelope and nucleolus dissolve. In
  animals, centrioles (dark cylindrical microtubule
  structures for chromosome separation) form and
  separate.
• As pairs of centrioles move to opposite ends of
  cell, spindle (football-shaped cage-like
  structure of thin microtubule fibers for
  chromosome attachment and separation) form
  between them.

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• Metaphase short 2nd phase doubled chrom. attach
  to spindle fibers by centromeres pulled by
  spindle fibers and lined up on midline (equator)
  of spindle.
• Each sister chromatid is hooked onto its own
  spindle fiber one sister chromatid attached to
  one pole, the other to the opposite pole ensure
  each new cell gets identical set of info from own
  set of chromosomes.

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• Anaphase marked by separating chromatid pairs.
  Centromeres split apart and chro.pairs from each
  chromosome separate and go to opposite poles,
  pulled by shortening microtubule fibers.
• Telophase Final phase. Chromatids reach poles.
  Many of prophase changes reversed. Chromosome
  windings loosen, spindle begins to go away,
  nucleolus reappears, new nuclear membrane begins
  to form.

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• After telophase Cytokinesis (division of
  cytoplasm). In animals, plasma membrane pinches
  in along equator and splits. In plants, rigid
  wall, so cell plate is laid down between, and new
  cell membranes and cell walls form on either side
  of this division line.
• Mitosis guarantees a clean copy. In unicellular
  organisms, equals reproduction (cells separate).
  In multicellular, identical daughter cells with
  same functions eventually form a group of
  like-functioning cells-a tissue for a specific
  use. Tissues are organized to form organs that
  perform organism tasks (muscle cells combine to
  make muscle tissues, that are groups to form
  heart tissue to pump blood. Organs may work
  together in an organ system to with general
  function of circulation and O2 distribution, and
  organ systems together form and aid survival of
  the organism. Complex specialization, but all
  based off the individual cell as the unit.
• Staggering organization and complexity! ?

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Control of the Cell Cycle

• We know what happens, how on earth does it work?
• Some clues series of enzymes control cell
  progression. Control rate and steps involved.
• Cells can lose control of thisuncontrolled
  growth and division. Failure to produce,
  overproduction or wrong timing of enzymes.
• Cancer-uncontrolled cell division. Environmental
  factors or changes in production.
• Enzyme production directed by genes (segment of
  DNA controlling a protein production) located on
  the chromosomes.

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• Interphase just before DNA replication is
  important-several enzymes control this.
• Cancer-changes in genes that produce enzymes
  controlling cell cycle. Something starts them,
  they fail to control cycle properly, and form
  masses of tissue called tumors.
• Deprive normal cells of nutrients metastasis
  process-enter circulation system, spread thru
  body, form new tumors, interfering with tissues
  and killing organism.

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• Cancer-2nd leading cause of death after heart
  disease. Many types/tissues. In US, lung,
  colon, breast and prostate most prevalent. (p.218
  activity for numbers).
• Causes both genetic and environmental.
• People in different countries have different
  rates, and change to local type when move to
  other countriesindicates environment causesbut
  heritable too.
• Healthy lifestyle lowers risk. Low fat, high
  fiber reduces many risks high fat increases
  colon, breast, prostate risks, higher fiber
  content reduces colon risk. Fruits, vegetables,
  grains help, for previous reasons.
• Vitamins and minerals may help also. Key
  Carotenoids, Vit.A, C, and E, and Calcium. Daily
  exercise, avoiding known carcinogens, and not
  using tobacco also are known to reduce cancer
  risks.

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The End

• The split ends, that is.
• of human hair, that is ?