And now for something completely different' NATURE' Deep Jungle: New Frontiers' Jungle Dancers PBS i

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• And now for something completely different.
  NATURE. Deep Jungle New Frontiers. Jungle
  Dancers PBS ( if this wont open go to next
  one)
• Video Gratuit Gratis Moonwalking bird Video Clip
  Spot Pub TV de Moonwalking bird - Video Spot Clip
  TV Reportage - Moonwalking bird

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Cell Membrane/pg 8 sg

• separate the cell from the outside world
• separate compartments inside the cell to protect
  important processes and events.

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Functions of Membrane

• be protective
• regulate transport in and out of cell or
  subcellular domain
• allow selective receptivity and signal
  transduction by providing transmembrane receptors
  that bind signaling molecules
• allow cell recognition

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• 5. provide anchoring sites for cytoskeletal
  filaments or components of the extracellular
  matrix. This allows the cell to maintain its
  shape and perhaps move to distant sites.
• 6. help compartmentalize subcellular domains or
  microdomains

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• 7. provide a stable site for the binding and
  catalysis of enzymes.
• 8.regulate the fusion of the membrane with other
  membranes in the cell via specialized junctions
  (click here for electron micrographs of
  junctions).

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• 9. provide a passageway across the membrane for
  certain molecules, such as in gap junctions.
• 10 allow directed cell or organelle motility

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Structure of the plasma membrane

• Page 8 study guide
• The membrane has built into it
• Hormone binding sites,
• enzymes,
• electron carriers,
• channels for passive transport
• pumps for active transport.

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A historical perspective

• 1930's-40's, Danielli and Davson
• studied triglyceride lipid bilayers over a water
  surface. They found that they arranged themselves
  with the polar heads facing outward. However,
  they always formed droplets (oil in water) and
  the surface tension was much higher than that of
  cells. The Structure of the Cell Membrane
• However, if you added proteins, the surface
  tension was reduced and the membranes flattened
  out.  

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Sandwich Model

• What membrane functions might be allowed by this
  model?

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• In the 1960s, freeze-fracturing () and the
  electron microscope showed that the proteins were
  actually deeply embedded or penetrating the lipid
  bilayer.

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EM of cell membrane
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1972, S. Jonathan Singer and Garth Nicolson

• proposed a new model, the fluid-mosaic model
  (sometimes referred to as the Singer-Nicolson
  model).
• In addition to knowing that the proteins
  penetrated the lipid bilayer, they showed that
  the positions of the proteins were not fixed on
  the membrane - they move about like a fluid.

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• You must be able to draw a cell membrane. The IB
  Study Guide lists the parts which must be
  included. Look at page 8 of your study guide
• Essential Biochemistry - Membrane Transport

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Points to remember

• Proteins are embedded in the membrane not coating
  the outside as in the sandwich model

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• Hydrophilic portions of both proteins and
  phospholipids are maximally exposed
• to water resulting
• in a stable membrane structure

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• Hydrophobic portions of proteins and
  phospholipids are in the non aqueous environment
  inside the bilayer

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• The membrane is a mosaic of proteins bobbing in a
  fluid bilayer of phospholipids

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The fluid quality of membranes

• 1. most membrane lipids and some proteins can
  drift laterally within the membranes
• 2. molecules rarely flip due to hydrophobic and
  hydrophilic regions
• 3. Phospholipids move quickly along the
  membranes plane.
• Biology Animations

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• 4. membrane proteins drift more slowly than
  lipids. Proteins drift laterally and this was
  established by fusing a human and mouse cell
  (Frye and Edidin 1970)
• Protein Diffusion (Frye and Edidin) (animation)

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• 5. some membrane proteins are tethered to the
  cytoskeleton and cannot move far.
• Teachers' Domain Cell Membrane Just Passing
  Through

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• The presence of the double ( unsaturated) bond (
  unsaturated) prevents tight packing and makes the
  bilayer difficult to freeze.
• (compare unsaturated and saturated)

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Effect of temperature on the packing of the
hydrocarbons

• low temperatures, bilayer is in a gel state and
  tightly packed. 
• higher (body) temperatures, the bilayer actually
  "melts' interior is fluid - lipid molecules move
  around, rotate, exchange places. 
• Biology Animations

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• Another type of lipid in the membrane is
  cholesterol.
• The amount of cholesterol may vary with the type
  of membrane.
• Plasma membranes have nearly one cholesterol per
  phospholipid molecule. Other membranes (like
  those around bacteria) have no cholesterol.

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• same orientation as the phospholipid molecules.
• polar head of the cholesterol is aligned with the
  polar head of the phospholipids.

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Cholesterol molecules have several functions in
the membrane

• makes the lipid bilayer less deformable and
  decreases its permeability to small water-soluble
  molecules. Without cholesterol (such as in a
  bacterium) a cell would need a cell wall.
• prevents crystallization of hydrocarbons and
  phase shifts in the membrane.

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Membrane Glycolipids

• Glycolipids are also a constituent of membranes.
  In this  figure, they are shown as blue sugar
  groups projecting into the extracellular space.

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Membrane proteins

• More than 50 types of proteins have been found on
  RBC.
• The purple spot in the middle is a white blood
  cell

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• Membrane proteins determine most of the membranes
  function.

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Two major types of membrane proteins

• Look at the picture and notice the integral
  proteins and the peripheral proteins.

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Integral proteins

• Transmembrane or embedded proteins allowing for
  passage through the membranes hydrophobic region

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Peripheral proteins

• Appendages to the membrane or may be found
  attached to integral proteins

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Attachment to cytoskeleton

• Cytoskeleton may be bonded to membrane proteins.
  This allows for cell shape and fixes the location
  for some proteins

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The fluid mosaic model
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Practice identification

• Membrane Structure and Function
• Biomembranes I Introduction
• cell membrane

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Traffic

• The molecular organization of the membrane allows
  for selective permeability.
• Remember hydrophobic region and hydrophilic
  regions.

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Types of Membranes and Transport

• Membrane is selectively permeable
• Small non charged lipid molecules (alcohol and
  oxygen pass through freely
• Small polar molecules (water carbon dioxide) pass
  following their concentration gradient
• Macromolecules cannot freely cross

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• Ions and charged particles have difficulty due to
  hydrophobic area of membrane
• Passive and active transport move molecules

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• The following substances can pass through the
  cell membrane
• Nonpolar molecules (example lipids)
• Small polar molecules such as water
• The following substances cannot pass through the
  cell membrane
• Ions and charged molecules (example salts
• dissolved in water)
• Large polar molecules (example glucose)
• Macromolecules

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Passive transport is diffusion across a membrane
(pg9)

• Shockwave (we will go through each section)
• Beginning with diffusion the movement of
  molecules from a high concentration gradient to a
  lower gradient.

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• Diffusion
• Is the tendency for molecules of any substance to
  spread out evenly into the available space

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• Substances diffuse down their concentration
  gradient, the difference in concentration of a
  substance from one area to another

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• In facilitated diffusion
• Transport proteins speed the movement of
  molecules across the plasma membrane
• Animation How Facilitated Diffusion Works

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Facilitated Diffusion

• Passive diffusion requires no ATP
• Uses transport proteins in membrane, which may
  have a subtle change in shape.
• Some of these proteins are gated channels where a
  stimulus causes them to open and close

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• Channel proteins
• Provide corridors that allow a specific molecule
  or ion to cross the membrane

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• Carrier proteins
• Undergo a subtle change in shape that
  translocates the solute-binding site across the
  membrane

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• Active transport
• the mediated process of moving
• particles across a biological membrane
• against a concentration gradient. If the
• uses chemical energy ATP

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Active Transport requires ATP

• Shockwave (go to active transport intro)
• Tutorial 5.2 Active Transport
• ATP is required due to transporting against the
  concentration gradient or going uphill
• http//www.wiley.com/legacy/college/boyer/04700037
  90/animations/membrane_transport/membrane_transpor
  t.swf

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Ion Pumps

• The sodium potassium pump is an example of an ion
  pump
• Sodium potassium pump
• Animations (go to NA K pump)
• http//www.stolaf.edu/people/giannini/flashanimat/
  transport/secondary active transport.swf

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Osmosis is the passive transport of water

• Osmosis

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• Osmosis
• Is the movement of water across a semipermeable
  membrane
• BIOL 230 Lecture Guide - Osmosis Animation

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• Tonicity
• Is the ability of a solution to cause a cell to
  gain or lose water
• Has a great impact on cells without walls

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• If a solution is isotonic
• The concentration of solutes is the same as it is
  inside the cell
• There will be no net movement of water

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• If a solution is hypertonic
• The concentration of solutes is greater than it
  is inside the cell
• The cell will lose water

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• If a solution is hypotonic
• The concentration of solutes is less than it is
  inside the cell
• The cell will gain water

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Terms to know when thinking about osmosis and
plants

• Hypotonic Water enters, Turgor develops
• Isotonic No net change (no growth possible)
• Hypertonic Water leaves, Turgor lost, Wilts
• Celery wilted in refrigerator...what to do?
• Hydroponics water culture without soil

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Some Basic Principles

• Water always moves from high water potential to
  low water potential.
• Water potential is a measure of the tendency of
  water to move from high free energy to lower free
  energy.
• Distilled water in an open beaker has a water
  potential of 0(zero).
• The addition of solute decreases water potential

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• The addition of pressure increases water
  potential.
• In cells, water moves by osmosis to areas where
  water potential is lower.
• A hypertonic solution has lower water potential.
• A hypotonic solution has higher water potential.

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• Water potential (Y, the Greek letter psi,
  pronounced "sy") is a measure of the water
  molecule potential for movement in a solution
• measured in units of pressure (Pa, or usually
  kPa), and the rule is that water always moves by
  osmosis from less negative to more negative water
  potential
• 100 pure water has Y  0, which is the highest
  possible water potential, so all solutions have
  Y lt 0 (i.e. a negative number), and you cannot
  get Y gt 0.

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• Osmosis and Membrane Permeability Tutorials

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Water balance in cells without walls
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Plant cells

• Turgor pressure swelling of plant cell in
  hypotonic solution. How plants maintain erect
  position.

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Water balance cells without walls

• Animals Osmoregulation Introduction
• A cell without rigid walls can not tolerate
  either excessive uptake nor excessive loss of
  water .
• Osmoregulation is the control of water balance.

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• Animals and other organisms without rigid cell
  walls living in hypertonic or hypotonic
  environments
• Must have special adaptations for osmoregulation

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Contractile vacuole
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Animal Cells

• Solutions which cause cells to shrink are
  hypertonic solutions . This condition is called
  crenation

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Note differences in plant and animal cells
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Endocytosis and Exocytosis

• Transport large molecules into and out of cell
• Animations (go to endo and exo )

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• In exocytosis
• Transport vesicles migrate to the plasma
  membrane, fuse with it, and release their
  contents
• In endocytosis
• The cell takes in macromolecules by forming new
  vesicles from the plasma membrane

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• Three types of endocytosis

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• Phagocytosis Endocytosis - Animation of
  Phagocytosis
• pinocytosisEndocytosis - Animation of Pinocytosis
• Receptor mediated endocytosisTutorial 5.3
  Receptor-Mediated Endocytosis

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• Plasma membrane is boundary
• Cells produce components and place them outside
  the plasma membrane by exocytosis
• Examples
• from plant (cellulose)
• From animal is glycoproteins

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• Synthesis of cellulose put into vesicles and laid
  down as cell wall. Functions include
• Maintaining shape
• Allowing high pressure without lysing cell
• Prevents over input of water
• Allows for high turgor pressure
• Animation enzyme puts together glucoses to make
  cellulose

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Extracellular componentsnew material for 09 test
page 10sg

• Cell Wall

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Glycoproteins in animals

• Protein with carbohydrate attached
• Tissues one cell layer think produce a think
  matrix called the basement membrane
• Matrix is gel
• Functions include supporting single layers of
  cells (do not tear or perforate)
• And cell to cell adhesion

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• Osmosis and Membrane Permeability Tutorials

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• http//www.wiley.com/legacy/college/boyer/04700037
  90/animations/membrane_transport/membrane_transpor
  t.swf

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More sites for review

• Cell Membranes Problem Set
• Cell Organelles Membrane and CytosolCellnotes
  (you will have to scroll down to cell membrane.)
• Membranes - How Things Get In and Out of Cells

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AP Lab Osmosis

• Quick review LabBench
• Answers to questions AP Biology - Lab 1 Answers
• Typical data ( need to scroll down )ap lab1
  osmosis sample4