Membrane Transport Flashcards
What factors affect permeability? 4
Size, shape, electrical charge, and lipid solubility
What 7 factors affect diffusion?
- Distance: closer is faster
- Size: smaller is faster
- Temperature: higher is faster
- Concentration: higher is faster
- Electrical Forces: opposite charges attract
- Solubility
- Permeability
What are the 4 modes of transport?
Diffusion, filtration, carrier-mediated, and vesicular
What modes of transport require energy?
Carrier mediated (passive or active), vesicular (active)
What modes of transport do not require energy?
Diffusion (passive), filtration (passive), carrier mediated (active or passive)
What is diffusion?
Passive transport
Movement of ions across a membrane through a channel from [high] to [low] (down a concentration gradient)
it is believed that some lipid-soluble molecules can diffuse directly across the plasma membrane
What is osmosis?
Passive transport; diffusion of water
Movement of water across a membrane using aquaporins until water and solute concentrations are equal on both sides
rate depends on #
What molecules are lipid soluble and which are lipid insoluble?
Fatty acids, steroids, alcohol, O2, and CO2 are lipid soluble
H2O, Na+, and Ca2+ are lipid insoluble
In what environments does osmotic flow occur?
Isotonic, hypotonic, hypertonic solutions
What happens if a cell is placed in an isotonic solution?
No osmotic flow occurs and the cell appears normal in size and shape
What happens if a cell is placed in a hypotonic solution? (lower solute concentration than within the cell)
Water flows into the cell and will swell and continue until the plasma membrane ruptures or lyses
What happens if a cell is placed in a hypertonic solution? (higher solute concentration than within the cell)
Water flows out of the cell and will crenate (shrivel)
What type of open channels do red blood cells have?
Aquaporins
What is filtration?
Passive transport
Hydrostatic pressure (HP, blood pressure) forces water and small molecules across a membrane
about 80% of fluid entering tissues on arteriole end are reabsorbed on venous side of an artery
What is carrier-mediated transport: facilitated transport?
Passive movement of molecules along a concentration gradient, requiring a transporter (a protein) to facilitate this movement across the membrane
different from diffusion because the maximum transport rate is determined by the number of transporters
What is carrier-mediated transport: primary active transport?
Active movement of molecules against the concentration gradient across the membrane requiring energy (from low to high)
energy is supplied in the form of ATP and required specialized proteins called ion pumps
ex. Na+/K+ pump which actively pumps Na+ out and K+ into cells
this protein is present in most cells in the body and uses 25% of all ATP produced at rest
What is the difference between diffusion and facilitated transport?
Facilitated transport is different from diffusion because the maximum transport rate is determined by the number of transporters
What is carrier-mediated transport: secondary active transport?
Occurs when the Na+ concentration created by the Na+/K+ pump is used to aid in the transport of other molecules
ATP is still used but is used indirectly, or secondary to the transportation of the molecule
ex. sodium dependent glucose transporter where glucose is absorbed along with the Na+ entering the channel to go through the cycle
What are antiporters and symporters?
Antiporters: one comes in, the other goes out
Symporters: going in the same direction/together
What are the types of vesicular transportation?
Endocytosis, phagocytosis, pinocytosis, and exocytosis
What is endocytosis?
The process of transporting substances across the plasma membrane into the cell by forming a vesicle
substances that are transported in this way are too large or complex to use a transporter or channel
What is phagocytosis?
Cell eating, type of endocytosis where cells or debris are consumed and destroyed
white blood cells do this to invading bacteria
What is pinocytosis?
Cell drinking, type of endocytosis where small particles are absorbed into the cell
What is exocytosis?
Occurs when a substance is exported from a cell using a vesicle. The vesicle fuses with the plasma membrane and expels the vesicle contents into the extracellular fluid
hormones and extracellular proteins are transported in this manner
-mucus and waste
