Facilitated and Active Transport Flashcards
What are the three main classes of membrane protiens
- Channels
- transporters
- ATP powered pumps
What are channels
They are ion small hydrphilic molecules flow down their concentration gated and they can either be non gated or gated
What are the three transporters
You have three types a uniporter symporter and antiporters
all moving one molecule down the gradient
What are channels (gates) and transporters called
Facilitated transports
What does a uniporter do
Just has one molecule moving down the gradient
What does a symporter do
Move one molecule agaisnt the gradient and one down the gradient but in the same direction
what does an antiporter do
Moves one molecule against the gradient and one down the gradient but in opposite directions
What is an ATP-powered pump
Uses the energy of ATP hydrolis to move a variety of ions and small molecules agianst their concentration
What is the driving force of facilitated transporters
Concentration gradient atp is not required but could be used to set up concentration gradient
What are the two things facilitated transporters are
Specific
Saturable (have a limit to how fast they can do things)
What are the two ways channels can be
Either open
or gated so that they are closed or open but this is not due to ligand binding but due to chemical or electrica signals
What is an example of a voltage gated channel
SR calicum is released when the muscles sends a shock the calcium rushes out and contributes to muscle contraction
What make the potassium channel specefic
There are integral membrane protiens which create holes in the membrane large enough for solutes to pass through
Size-based exclusion- Hydrophilic interior to channel
Specificity can lead to membrane potential
Why does only potassium interact with these channels
Because of the spacing the potassium is happy when it is surrounded by water it needs the energy withing the CG for it to want to go through the membrane because it is a similar energy state within the pore and the spacing of the oxygens line up perfectly so they are touching it will continue through
Why won’t sodium go through the K pore
Because it is too small and it wont have enough interactions with the water that it will want to leave its natural state
What is the potassium resting channel
The plasma membrane is freely permeable to potassium due to open resting channels not permeable to Na or Cl this is due to size based exclusion
What is the resting channel like in resting state
There is no charge gradient but there is more potassium in the cytosol then the extracellular medium
What happens once potassium flows inside the cell
There than becomes more potassium in the extracellular medium the cell
What is the charge inside the membrane
Negative
Why does the cell have a negative charge in a resting channel
Because potassium is leaking out and chlorine cant cross so it stays inside the cell
What changes the shape of the transporter
Normally closed but open when the ligand bind which causes a confirmational change
What is a v class pump
Pumps only hydrogen atoms
What is an F class pump
Also pumps only hydrogen atoms from exoplasmic to cytosolic side
What does a ABC pump
Many small molecules
What does a P class pump
H, Na, K, Ca
What are ABC pumps not restricted to
Ions they can export sugars,amino acids, peptides, protiens, phospholipids , cholesterol, toxin and foreign substances across a membrane not just plasma membrane
What does Flippase do
Can flip fatty acids from one leaflet to the other leaflet this does not usally happen but flippase can make this happen
What are the concentrations of inside and outside the cell
High concentration of potassium inside the cell
High concentration of sodium outisde the cell
What is the P-class pump, Muscle Ca2+ - ATPase
It has reversible phosphorylation= conformational change
2 Ca out of the Cytosol per ATP releases calcium and get rid of calcium by ATPase out of the cytoplasm inot the SR membrane
What does the P-class Pump, Na/K ATPase do
- All cells have low cytoplasmic NA and high cytoplasmic K levels
Pumps potassium into the cell and sodium outside the cell
3 sodium out and 2 potassium in per ATP
How does the secondary active transport work
Use ion gradients genertaed by ATP-powered pumps then couple the free engery associated with these ions going back along their concentration gradient to the import or export of other molecules agaisnt their concentration gradient
What makes up secondary active transport
- Antiporters and symporters
Couples transport between two different-molecules not just ions
What is the glucose symporter
There is energy available from the Na/K ATPase and the K resting channel
2 Na down the gradient one glucose against the gradient
Where is the energy coming from in the transporting glucose
Sodium going down the concentration and coupled with the free enrgy coming from the electerical charge
What makes the electerical gradient
Potassium resting channel
