Membrane Transport Flashcards
What are the 3 fundamentally diff mechanisms involved in
the movement of solutes across membranes?
(S.F.A)
1 - Simple diffusion (passive transport)
2 - Facilitated diffusion (passive transport)
3- Active transport
How is the movement of a molecule w/ no net charge determined?
- By the concentration gradient of that
molecule across the membrane.
What is Passive Transport/ Facilitated Diffusion?
- Movement of molecules through the membrane
- No energy is required
- Molecules move in response to a concentration gradient
What is Diffusion?
- movement of molecules from high concentration to low concentration.
What is simple diffusion?
Is the movement of many small molecules across the cell membrane.
- Each substance (molecule) diffuses independently of others present.
What is the rate of diffusion affected by?
- Concentration gradient – faster when steep
- Size of molecule – smaller molecules like O2 will diffuse faster than large molecules like carbs.
What is the permeability of the cell wall?
cell wall is selectively permeable
What does the selectively permeable cell wall let through?
- Small Molecules
- water
- non charged molecules pass easily through the phospholipid bilayer of the membrane.
What is Osmosis in relation to passive transport? (see pics slide 9)
Is the passive movement of water across a semi - permeable membrane in response to the conc gradient.
It is the movement of water from a region of high water conc to a region of low water conc.
- movement of water toward an
area of high solute
concentration (dissolved
substances are the solutes)
What is Tonicity?
the relative concentration of solutes between both extracellular and intracellular fluid.
If one fluid has a higher solute concentration (hypertonic) than the other
(hypotonic) then H2O moves from the hypotonic fluid to hypertonic one.
Read.
What is Isotonic?
If the conc of solute is equal in both fluids then they will have the same osmotic pressure and water will diffuse in and out of the cell at the same rate.
What are Integral Membrane Proteins?
They are transport proteins that recognize substances w/ great specificity and speed their movement across the membrane.
What is Facilitated Diffusion?
- movement of a molecule from high to low concentration w/ the help of a protein.
- Specific bc each protein transports a
specific molecule. - Passive bc no energy needed
- saturated when all carriers are occupied.
What are transport proteins? examples
- Are specific bc each protein transports a specific molecule.
e. g. Chanel + carrier proteins
What are Channel Proteins?
see pics slide 17
- Forms a pore extending across the lipid bilayer.
- When pore is open, the Specific molecule enters and passes through lipid bilayer.
What are Carrier Proteins?
see pics slide 17
Binds the specific molecule to be transported and the protein undergoes a change in shape in order to transfer the bound molecule across the membrane.
What are the 2 Channel Proteins?
- Ion Channels.
- Gated Channels.
What is an Ion Channel?
- Allow the passage of ions (charged atoms or molecules) which are associated with water.
What is the Gated Channel?
- Is opened or closed in response to a stimulus.
the stimulus may be chemical or electrical
What are the 3 carrier proteins called in order? (U.S.A)
- Uniports
- Symports
- Antiports
What is the Uniport?
see pics slide 19
- Transport a single particle in one direction.
e. g. Facilitated diffusion of glucose.
What is the Symport?
see pics slide 19
- Transport requires the binding of more than one substance to the transport protein
- The substances are transported across the membrane together.
What is the Antiport?
see pics slide 19
- The transport proteins exchange one substance for another.
Eg: Na, K ATPase
