Membrane Transport Flashcards
How does downhill transport occur?
By diffusion, simple or facilitated, and required no input of metabolic energy
How does uphill transport occur?
Primary or secondary active transport
What is the difference between primary and secondary active transport?
Primary requires a direct input of energy, secondary uses indirect energy
What is the only form of transport that is not carrier mediated?
Simple diffusion
What are features of carrier-mediated transport?
Saturation, stereospecificity, and competition
What is osmosis?
The flow of water across a semipermeable membrane from a solution with high concentration to a solution with low class concentration
Will a potential difference affect the rate of diffusion of a non-electrolyte?
No
Will a potential difference alter the rate of diffusion of a electrolyte?
Yes, it will alter the net rate of diffusion of a charged solute
(K+ will be slowed in a positive area and faster in a negative area)
What is diffusion potential?
A potential difference across a membrane generated by a charged solute diffusing down its concentration gradient
What is membrane permeability determined by?
Charge, polarity, size
What are some examples of hydrophobic molecules?
O2, CO2, N2, steroid hormones
What are some examples of small, uncharged polar molecules?
H2O, urea, glycerol, NH3
List molecules groups from easiest to hardest to move across a membrane.
Hydrophobic molecules, small uncharged polar molecules, large uncharged polar molecules, ions
How does low solute concentration affect facilitated diffusion?
Facilitiatated diffusion typically proceeds faster than simple diffusion
How does high solute concentrations affect facilitated diffusion?
The membrane carrier proteins will become saturated and facilitated diffusion will level
What are some examples of primary active transport?
Sodium/potassium pump, calcium pump, hydrogen/potassium pump
Describe how secondary active transport works.
One solute moves down (downhill) its electrochemical gradient and the other solute moves up its electrochemical gradient (uphill)
What is an example of facilitated diffusion?
The transport of d-glucose into skeletal muscle and adipose cells by the GLUT4 transporter
What are the two types of secondary active transport?
Co-transport/symport and counter-transport/antiporter/exchange
What is co-transport/symport?
A type of secondary active transport in which both solutes travel in the same direction
Provide and example of co-transport/symport
Sodium and glucose binding to a transporter, and the transporter rotating and releasing both inside the cell
What is counter-transport/antiport/exchange?
Secondary active transport where the solutes move in opposite directions
Provide an example of counter-transport/antiport/exchange
Sodium moving down its gradient established by the sodium/potassium pump and calcium moving uphill
How can you maintain osmotic balance?
Increase osmotic pressure on the external medium or continuously pump ions out to reduce the number of molecules in the cell and osmotic pressure
What would happen to a RBC in a hypertonic, isotonic, hypotonic or very hypnotic solution?
Crenated, normal, swollen, lysed
What is a channel?
Simple hole, often selective, often gated. May undergo conformational changes to open/close, but not for each substrate translocation reaction. Does not require energy input
What does a carrier alter?
Accessibility to binding sites through conformational changes
What is the ABC transporter superfamily?
2 highly conserved ATP binding cassette that fuel uphill substrate transport across cellular membrane through conformational changes
How can cells becomes resistant to drugs?
Non-specific ABC transporters transport relatively hydrophobic molecules, most drugs are highly hydrophobic, cells that over-express an MDR protein can become resistant
What is CFTR?
An ABC transporter activated by cAMP that’s a passive ATP-gated chloride channel. Chloride flows out, followed by sodium and water
What are ion channels?
Pores that allow passive movement of ions across a membrane and can exploit ionic gradients to generate electrical signals
If the concentrations are vastly different, the molecules will move _____, if the concentrations are similar, the molecules will move _____.
Quickly/slowly
Sodium ions are usually more concentrated ___ of the cell, and potassium ions are usually more concentrated ____ of the cell.
Outside/inside
