Membrane Transport

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Membrane Transport

• There are many molecules on (peripheral), within
  (trans), and inside (intracellular) the cell
  membranes. These all aid in getting necessary
  molecules into and out of the cell. They also
  play a role in cell to cell communication.
• Most are proteins with or without carbohydrates
  or lipids attached

2
These structures make membrane Selectively
permeable

• The cell membrane acts like a wall around the
  cell but it does have pores that act like doors
  (see page 97)
• Some molecules are brought into the cell and it
  TAKES energy to do this. ACTIVE TRANSPORT
• Some molecules can flow through without costing
  the cell any energy. PASSIVE TRANSPORT

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Passive Transport examples

• Osmosis The movement of water from High to low
  concentrations.Aquaporins for diffusion of water,
  
• Filtration process that is driven by hydrostatic
  pressure (pressure from water) it drives
  particles in and out of cell
• Blood pressure forces fluid through gaps in
  capillary walls
• Water, salts, nutrients are transferred from
  blood to tissues .
• Diffusion of molecules from High to Low conc
• O2 from the air to blood
• Facilitated diffusion Uses carrier proteins but
  does not use energy.

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Active Transport and examples

• Carrier Mediated Transport TAKES energy to do
  this!!! Usually in the form of ATP
• This can pump a molecule AGAINST the gradient!!!
• Sodium/Potassium pump 3 Na out, 2K in
• Half your daily calories are used for this
  alone!!!!!! Why so important??
• THIS PUMP
• 1. Regulates cell volume
• 2. Provides secondary active transport via
  generating electricity to pump other
  things..kidney function or Sodium Glucose
  transport
• 3. Heat production(thyroid stimulates na/k pump
  production..raising heat
• 4. Maintenance of membrane potential(Imp. In
  nerve function)

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• Vesicular Transport TAKES energy
• Endocytosis, exocytosis, phagocytosis,
  pinocytosis

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Most important Pumps

• Sodium-potassium pumps(Na-K) this pump burns one
  ATP to push 3 Na out of cell and 2 K into the
  cell
• Sodium-glucose transport protein(SGLT) binds Na
  and glucose outside of cell. Uses ATP and Na
  gradient to push glucose into cell
• ATP synthetase As Na enters the cell ATP is
  made from ADP and P

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Diffusion

• Diffusion the process of particles, nutrients,
  molecules, salts moving from high to low
  concentration to achieve a balance
• Concentration Gradient when the concentration of
  a particle is higher in one area then another

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Osmolality

• Osmolality is the amount of solute (stuff) in a
  solution.
• HYPO-tonic solution has a LOW concentration of
  solute compared to that inside the cell High
  conc of water
• HYPER-tonic solution has a HIGH concentration of
  solute compared to that inside the cell Low conc
  of water
• ISO-tonic solution has equal conc of water is
  same as the cell.

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Movement of water

• Osmosis the process of water moving from low
  solute(High Water) to high solute (Low
  Water)through a selectively permeable membrane
• Osmotic Pressure the force that stops osmosis
  due to filtration.(the flow of water across the
  membrane due to its own weight the flow of
  water due to osmosis
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