PATH 2800 quiz 2: Membrane transport

Diffusion Gradient

uncharged molecules at Higher Con → Low Con Gradient

Diffusion must reach?

Equilibrium

Diffusion Determined by ?

Ficks First law of Diffusion = Diffusion Coefficient + Permeability coefficient =

Diffusion how is movement dictated ?

By concentration gradient + electrochemical gradient

Osmosis function?

The flow of water across the membrane

Osmosis Gradient

High water concentration → Low water concentration

or

Low solute concentration → High solute concertation

Osmosis reaches?

equilibrium in solid (ISOTONIC STATE)

Osmosis: Isotonic

The osmotic pressure of 2 solutions is EQUAL

Osmosis: Hypertonic

The osmotic pressure of one solution is LOWER than the other.

Osmosis: Hypertonic

The osmotic pressure of one solution is HIGHER than the other

Osmosis: for water to cross the bilayer they need?

Proteins: Aquaporins (membrane water channels)

Osmosis: Donnan Effect

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Facilitated diffusion gradient?

High concentration to low concentration

ex: bind glucose to the cell

Facilitated diffusion follows?

Ficks law and did necessary need

Active transport?

An active transport mechanism that need ATP energy to transport particals AGAINST the gradient.

Types of Active transport?

2:

• Primary Active transport

• Secondary Active transport

Primary Active transport

• Molecules move against (low→high) con gradient

• Energy comes from HYDROLYSIS of ATP

• ex : Sodium/Potassium pump

Secondary Active Transport

• uses 2 cotransport particles where 1 particle moved down (high to low) while the other moves against (Low to high)

• Sometimes the particles can move in the same direction (symport) or opposite direction (antiport)

• ex: absorption of AA + glucose in the GI tract.

ion channels

Because ions have a hard time during diffusion due to hydrophobic effect of the fatty acid chains, ion channels fix their problem and allow ions to travel at a significantly faster rate 100-1000x than FD.

• Direction is determined by the gradient and electrical potential

ions determine?

Ions determine rate but not direction

Comp of ion channels

• There must have hydrophilic regions that interact w/ an aq environments (to form the channel) + a hydrophobic area that are all over the bilayers core.

Acetylcholine receptor

• On a Neuron

• A type of ion channel synapse that has hydrophobic a-helix (changes the confirmational state of channel) and hydrophilic residues that point to aq region

• Hydrophobic region can withstand rich core

• No ach no enter

4 gates

• Voltage-gated

• Ligand-gated

• Mechanical gated

• Gap junction

Voltage gated

• Change in electrical gradient (in nerves + muscle)

Ligand Gated

• The reversable binding of a chemical ligand to the ion channel

  • ex : ach w/ out a synapse

Mechanical gated

• The opening needs changes/deformation of cytoskeleton in cell of gate

Gap Junction

• Allows ions to flow between cells

• Just direct transport from one side to another

• stimulus = Ca+ of H+ concentration

Membrane potential

• in all mammalian cells but unique in nerve + muscle cells

• w/ K+ leak channels