Cellular Transport Notes (Text 7.2 p 175-178

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Cellular Transport Notes(Text 7.2 p 175-178
8.1 p 194-200)
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Cell Membrane Solutions

• Cell membranes are completely permeable to water.
• The environment the cell is exposed to can have a
  dramatic effect on the cell.
• Solutions are made of solute and a solvent
• Solvent - the liquid (water) into which the
  solute is poured and dissolved.

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Solute

• Solute substance that is dissolved or put into
  the solvent (water).
• Common cell solutes include salts, sugars, some
  minerals (iron ions and calcium ions) and protons
  (electrons from acids).
• Eg. Sodium chloride dissolved in water makes a
  saline solution. The sodium chloride is the
  solute. The water is the solvent.

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Concentration

• Amount of solute per unit volume of solution.
• expressed in mass/volume (g/100ml - percentage),
  ppm (parts per million), and moles/volume
  (molarity).
• The greater the mass or moles per unit volume,
  the more concentrated the solution.

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Concentration Gradient

• Difference in concentration between solute
  molecules from area high concentration to area of
  low concentration.
• The greater the difference the faster the rate of
  diffusion and vice versa
• i.e. the steeper the hill

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Cellular MembraneStructure and Function

• All cells have a cell membrane
• Chiefly responsible for maintaining homeostasis
  inside a living cell using different methods to
  transport molecules in and out of the cell.

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Cellular MembraneStructure and Function

• Too much water can burst the cell
• Too many wastes can poison the cell
• The cell cannot tolerate any great variations in
  ion conditions.

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Function

• Provides protection and support for the cell
• Regulate the exchange of substances (gases and
  ions)
• Communicates with other cells
• Immune System Identification (proteins and
  carbohydrates on its surface)

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http//www.goldiesroom.org/AP20Biology/AP20Lectu
re20Notes20pdf/LN014--Ch05--Cell20Transport.pdf
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http//www.goldiesroom.org/AP20Biology/AP20Lectu
re20Notes20pdf/LN014--Ch05--Cell20Transport.pdf
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Fluid Mosaic Model of the cell membrane
Polar heads love water dissolve

• Plasma Membrane Animation

Non-polar tails hide from water
Carbohydrate cell markers
Proteins
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Fluid Portion

• Lipid Bilayer
• - 2 phospholipid layers
• Phosphate head is polar (hydrophilic water
  loving)
• Fatty acid tails non-polar (hydrophobic water
  fearing)
• Proteins embedded in membrane

Phospholipid
Lipid Bilayer
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Cell Membrane Pores

1. Selectively permeable Allows some molecules in
   and keeps other molecules out
2. The structure helps it be selective!

Pores
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Lipid Bilayer
Outside of cell (interstitial)
Carbohydrate chains
Proteins
Transport Protein
Phospholipids
Inside of cell (cytoplasm)
Go to Section
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http//www.goldiesroom.org/AP20Biology/AP20Lectu
re20Notes20pdf/LN014--Ch05--Cell20Transport.pdf
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• The different components of a plasma membrane are
  integral proteins, peripheral proteins,
  glycoproteins, phospholipids, glycolipids, and in
  some cases cholesterol, and lipoproteins.
• Construction of the Cell Membrane - Learning
  Activity
• detailed cell membrane animation

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Transport Proteins

• Regulate movement of substance
• 1. Channel Proteins
• form small openings for molecules to diffuse
  through like water
• 2. Carrier Proteins
• binding site on protein surface "grabs" certain
  molecules and pulls them into the cell animation

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Gated Channels

• similar to carrier proteins, not always
  "open"eg. Bind and pull in calcium ions when
  needed. This requires cell energyactive
  transport.

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Receptor Proteins

• molecular triggers that set off cell responses
  (such as release of hormones or opening of
  channel proteins)
• e.g. The junction between nerve cells requires
  the transmission of neurotransmitters between
  synaptic gapsthese chemicals bind onto receptor
  proteins.

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• Recognition Proteins - ID tags, to identify cells
  to the body's immune system (called antigens)

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TRANSPORT MECHANISMS

1. PASSIVE TRANSPORT
2. ACTIVE TRANSPORT
3. ENDOCYTOSIS
4. EXOCYTOSIS

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Types of Cellular Transport

• Transport Animations

• Passive Transport
• doesnt use energy
• Diffusion
• Facilitated Diffusion
• Osmosis
• Active Transport
• uses energy
• Protein Pumps
• Endocytosis
• Exocytosis

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Passive Transport (p 198)

• cell uses no energy
• molecules move randomly
• Molecules spread out from an area of high
  concentration to an area of low concentration.
• i.e. down a concentration gradient
• (High ? Low)
• Passive Transport Animation

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3 Types of Passive Transport

• Diffusion high conc. to low conc.
• Facilitative Diffusion diffusion with the help
  of transport proteins
• Osmosis diffusion of water

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1. Diffusion
Animation

• random movement of particles from an area of high
  concentration to an area of low concentration.
• (High to Low)
• Diffusion continues until all molecules are
  evenly spaced (equilibrium is reached)
• Note molecules will still move around but stay
  spread out.

http//bio.winona.edu/berg/Free.htm
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1. Diffusion
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2. Facilitated Diffusion
A
B

• diffusion that is enabled by proteins (channel or
  carrier proteins) which bind onto required
  molecules so that they flow into the cell.
• Transport Proteins are specific they select
  only certain molecules to cross the membrane
• Transports larger or charged molecules
• Animation How Facilitated Diffusion Works

Facilitated diffusion (Channel Protein)
Diffusion (Lipid Bilayer)
Carrier Protein

• http//bio.winona.edu/berg/Free.htm

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2. Facilitated Diffusion
Glucose molecules
Cellular Transport from an area of
High
High Concentration

• Channel Proteins animations

Cell Membrane
Protein channel
Low Concentration
Low
Transport Protein
Through a ?
Go to Section
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Animations
3. Osmosis

• Diffusion of water through a selectively
  permeable membrane
• From high to low concentrations

• Water moves freely through pores.
• Solute (green) too large to move across.

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3. Osmosis
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Factors Affecting Rate of Diffusion
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1. Size

• small molecules diffuse faster than large
  molecules
• slip through phospholipids bilayer easier
• very large molecules may not be able to diffuse
  at all

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2. Concentration

• concentration gradient - diffusion rate
• Steeper hill

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3. Temperature

• temperature diffusion rate
• molecules move faster

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4. Polarity of molecules

• Polar molecules (water-soluble) dont move easily
  through membrane
• stopped by middle water-insoluble (nonpolar) layer

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5. Surface Area

• surface area - diffusion rate
• As a cells size increases its volume increases
  much quicker than its surface area.
• If you double individual lengths (1 cm to 2 cm)
  the surface areas increases 4 times, and the
  volume increases 8 times.

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5. Surface Area

• If cells size is doubled, it would require 8
  times more nutrients and have 8 times s much
  waste.
• SA only increases by a factor of 4 not enough
  surface area through which nutrients and wastes
  could move.
• Cell would either starve or be poisoned (waste
  products)
• Cells divide before they come too large to
  function.

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Active Transport

• Involves moving molecules "uphill" against the
  concentration gradient, which requires energy.
• Uses carrier protein molecules as receptors.
• One may transport calcium ions another glucose
  molecules.
• Hundreds of these types of protein molecules.
• Each one changes shape to accommodate a specific
  molecule.
• (Low ? High)

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2. Active Transport (contd)

• Their activity can be stopped from transporting
  molecules with inhibitors (unfortunately, these
  are usually poisons) which
• either destroy the membrane protein
• or just plug it up
• (e.g. for your neurons tetanus
• botulinum-B secrete a poison that
• suppress the Na/K pump)
• Three types
• active transport animation

http//www.biology4kids.com/files/cell2_activetran
.html
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1. Protein Pumps
Sodium Potassium Pumps

• transport proteins that require energy to do work
• Example Na/K pumps are important in nerve
  responses.

Protein changes shape to move molecules this
requires energy!
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Sodium-Potassium Pump

• Pumps out 3 sodium atoms for ever 2 potassium
  atoms taken in against gradient in the cell.
• ATP and the Na/K Pump
• Animation How the Sodium Potassium Pump Works

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The H/K ATPase

• The parietal cells of your stomach (lining) use
  this pump to secrete gastric juice.
• These cells transport hydrogen ions (H) from a
  concentration of about 4 x 10-8 M within the cell
  to a concentration of about 0.15 M in the gastric
  juice (giving it a pH close to 2).
• Recall pH power of the H ion
• Small wonder that parietal cells are stuffed with
  mitochondria and use huge amounts of energy as
  they carry out this three-million fold
  concentration of protons.

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The H/K ATPase
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2. Endocytosis

• taking bulky material into a cell
• Uses energy
• Cell membrane in-folds around food particle
• cell eating
• forms food vacuole digests food
• This is how white blood cells eat bacteria!

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Endocytosis

• Endocytosis moves large particles (huge molecules
  or molecular conglomerates) into a cell.

• endo exocystosis animations

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Phagocytosis

• solids
• Phagocytosis is another type of endocytosis used
  for massive transport.
• Cell membrane extends out forming pseudopods
  (fingerlike projections) that surround the
  particle.
• Membrane pouch encloses the material pinches
  off inside the cell making a vesicle.
• Vesicle can fuse with lysosomes(digestive
  organelles) or release their contents (enzymes)
  into the vesicle, breaking it down
• Animation Phagocytosis
• HowStuffWorks "Phagocytosis"

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• Used by ameba to feed white blood cells to kill
  bacteria.Known as killer cells"

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Pinocytosis

• Cell membrane surrounds fluid droplets
• Fluids taken into membrane-bound vesicle
• Known as cell drinking

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3. Exocytosis
Endocytosis Exocytosis animations

• Moves large, complex molecules such as proteins
  out of the cell membrane.
• Large molecules, food, or fluid droplets are
  packaged in membrane-bound sacs called vesicles.
• Cell changes shape requires energy
• Ex Hormones or wastes released from cell

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• Exocytosis is used to remove large products from
  the cell such as wastes, mucus, cell products
  such as hormones and antibodies.
• Exocytosis is the process used by our memory
  cells (white blood cells that produce antibodies
  to fight infection).
• It is also used by our gland cells to secrete
  hormones when needed.
• Phagocytosis
• animation

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In Summary

• Essential Biochemistry - Membrane Transport

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Membrane Transport Flowchart
Active
Passive
Ion Pump
Simple Diffusion
Endocytosis
Exocytosis
Facilitated Diffusion
Osmosis
Phagocytosis
Pinocytosis
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Osmosis and Tonicity

• Tonicity is a relative term
• Water molecules are so small, and there is so
  much of it, that the cell cant control its
  movement through the cell membrane.

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Hypotonic Solution

• Osmosis Animations for isotonic, hypertonic, and
  hypotonic solutions

Hypotonic The solution has a lower
concentration of solutes and a higher
concentration of water than inside the cell. (Low
solute High water)
Result Water moves from the solution to inside
the cell) Cell Swells and bursts open
(cytolysis)!
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Hypertonic Solution

• Osmosis Animations for isotonic, hypertonic, and
  hypotonic solutions

Hypertonic The solution has a higher
concentration of solutes and a lower
concentration of water than inside the cell.
(High solute Low water)
shrinks
Result Water moves from inside the cell (out)
into the solution Cell shrinks (Plasmolysis)!
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Isotonic Solution

• Osmosis Animations for isotonic, hypertonic, and
  hypotonic solutions

Isotonic The concentration of solutes in the
solution is equal to the concentration of solutes
inside the cell.
Result Water moves equally in both directions
and the cell remains same size! (Dynamic
Equilibrium)
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What type of solution are these cells in?
C
B
A
Hypertonic
Isotonic
Hypotonic
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Plant and Animal Cells put into various
solutions
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How Organisms Deal with Osmotic Pressure

• Salt water fish pump salt out of their
  specialized gills so they do not dehydrate.
• Animal cells are bathed in blood. Kidneys keep
  the blood isotonic by remove excess salt and
  water.
• Blood brain barrier allows some substances into
  the brain, but screens out toxins and bacteria
• Allows water, CO2, glucose, AAs, alcohol,
  antihistamines
• HIV and bacterial meningitis can also cross this
  barrier

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How Organisms Deal with Osmotic Pressure

• Bacteria and plants have cell walls that prevent
  them from over-expanding.
• In plants the pressure exerted on the cell wall
  by the central vacuole is called turgor pressure.
  (bike tire analogy)
• A protist like paramecium has contractile
  vacuoles that collect water flowing in and pump
  it out to prevent them from over-expanding.

• Paramecium (protist) removing excess water video

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Review

• Transport Animations
• endo exo animation
• Assignment
• P 174 2, 4
• P 178 1-5
• P 200 1-5
• P 224 1-6