Chapter 11: Membrane Transport Flashcards
What are the 4 different groups of items that can be transported through the membrane via bilayer diffusion
- hydrophobic molecules
- small uncharged molecules
- large uncharged molecules
- ions
What are two types of passive transport proteins?
- transporters
- channels
This type of passive protein has a conformational change (opens/closes) when moving molecules across membranes
transporter
this type of passive protein is a (sometimes gated) pore that quickly moves molecules across membranes
channel
About what portion of a typical cell membrane consists of receptors?
1/15
What type of molecule movement across membranes produces a logarithmic curve of activity?
transporter-mediated
What type of molecule movement across membranes produces a linear curve of activity?
simple diffusion
What are the three types of active transport?
- coupled transport
- ATP-driven pumps
- Light-driven pumps
A type of transport where only a single molecule is moved across a membrane
uniport
A type of coupled transport where two molecules are moved in the same direction across a membrane
symport
a type of coupled transport where two molecules are moved in opposite directions across a membrane
anitport
(T/F) the molecules moved in coupled transport are always going against their gradients
False
What essential basal/lateral transport proteins are found in gut lumen cells?
- Na+/K+ pumps
- passive glucose channels
What essential apical transport proteins are found in the gut lumen cells?
Na+/glucose transporter
What is the purpose of the Na+/K+ pump in the basal/lateral portions of gut lumen cells?
maintains a low [Na+] inside the cell
What is the purpose of the passive glucose transporters found in the basal/lateral portions of gut lumen cells?
removes absorbed glucose from the cell into the blood
what is the purpose of Na+/glucose transporters found in the apical surface of gut lumen cells?
absorbs low [glucose] from the lumen
What are 4 types of ATP-driven pumps?
- P-type ATPase
- ABC transporters
- V-type H+ pump
- F-type ATP synthase
This type of ATP-driven pump undergoes conformational changes as it consumes ATP to move molecules against their concentration gradient
ABC transporters
This is a turbine-like protein machine that consumes ATP to transport H+ ions across membranes
V-type H+ pump
This is a turbine-like protein machine that conducts rotational catalysis to produce ATP while transporting H+ ions
F-type ATP synthase
In these proteins, the energy-providing ATP hydrolysis is coupled to the ion transport of one or two ion species across membranes (with the gradient)
P-type ATPase
[Na+] are typically higher where?
outside the cell
[K+] are typically higher where?
inside the cell
[H+] is typically higher where?
inside the cell
Where does the ATP-binding domain of ATP-driven pumps have to be located to function properly
inner membrane
[Na+] gradients aid in the maintenance of what?
pH
This ATP-driven pump brings in 2K+ and pushes out 3 Na+
Na+/K+ pump
what is the range of Na+/K+ pumps per cell?
80,000-30,000,000
About how many cycles does the Na+/K+ pump complete per minute
1,500-5,000 cycles/min
What are the levels of control for activity does the Na+/K+ pump undergo?
- gene expression (slow)
- regulatory domain (fast)
The initial state of the Na+/K+ pump cycle is called what?
E1
Once ATP binds to the Na+/K+ pump, what is the complex called?
E1 + ATP
How many ATP binding domains are present in ABC transporters?
2
How do bacterial cells uses ABC transporters?
bring large molecules into cell
How do eukaryotes use ABC transporters?
remove small molecules from cell
Whats an example of an ABC pump?
MDR (multiple drug resistant) pump
What 2 things are affected by [H+]?
- ATP synthase
- amino acids (proteins)
The functions of metabolism generally do what to pH?
decreases; more acidic
What are 3 examples of pH-regulating transporters?
- Sodium/proton exchanger
- Sodium-driven chloride ion/bicarbonate exchanger
- sodium-independent chloride/bicarbonate exchanger
This is a pH-regulating transporter that utilizes high exterior [Na+] to export H+ ions from the cell (antiport fashion)
sodium/proton exchanger
This is a pH-regulating transporter that uses Na+ to facilitate the transport of bicarbonate into the cell (symport). This then allows for the export of Cl- and H+ ions (symport)
Sodium-driven chloride ion/bicarbonate exchanger
How many bicarbonates are imported with a Na+ ion in a Sodium-driven chloride ion/bicarbonate exchanger?
2-3 bicarbonates
How many H+ ions are eliminated with one Na+ ion via the sodium-driven chloride ion/bicarbonate exchanger
2 H+ ions
This is a pH-regulating transporter that exports bicarbonate and imports Cl- ions
sodium-independent chloride/bicarbonate exchanger
Why is the chloride/bicarbonate exchanger not preferred?
removes buffering bicarbonate
When is the chloride/bicarbonate exchanger typically used?
with high pH environments (low [H+])
