Transporters, Ion channels and Pores Flashcards
what does passive transport rely on
- permeability
- conc gradient
rate is proportional to conc gradient
molecules that can pass through bilayer
- small
- uncharged
- hydrophobic (02, C02, N2, H20 - EXCEPTION)
how to increase permeability of membrane
add protein carriers
name some important roles of transport processes
-maintain ionic composition
-maintain pH
-regulate cell volume
-generic ion gradient
conc of metabolic fuels and building blocks
describe how f.d via ion channels can work
eg, acetylcholine binds to protein and it forms a passage
ATP sensitive K channel
when there is a high ATP channel closes so stops K passing through
voltage sensor carrier
cells are always negative on the inside relative to the outside
so when there is a change in voltage the channel opens
where does energy come from for Active transport
ATP hydrolysis
channels
form a hydrophilic pore for ions to move across
difference between K and NA in intracellular and extracellular fluid
K in high in intracellular
K low in extracellular
conc gradient of Na
higher on outside of cells (145-12) mM
conc gradient of K
higher on inside the outside (140-4) mM
conc gradient of Ca
higher on the outside (1.5mM-0.1uM)
conc gradient of Cl
higher on outside (123-4.2)mM
osmole
solutions ability to create osmotic pressure and thus affect movement of water
what does 1 mol of glucose equate to
1 osmolar in 1L
what does 1 mol of NaCl equate to
2 osmolar in 1L
what does 1 mol of CaCl2 equate to
3 osmolar in 1L
osmolality
conc of solution expressed in osmoses per kg
osmole/kg
1 osmole/kg = 1 osmole/L = 1000milliosomole/L
diffusion of water
hypertonic - hypotonic across semi permeable membrane
how to stop flow of water
add pressure
Plasma membrane Ca2+ ATPase
(PMCA)
primary active transporter
energy released the reaction ATP –> ADP + Pi releases Ca against its conc gradient and moves it out the cell H into the cell
(Can also get Mg)
its a high affinity, low capacity transport
ATP synthetase
F1F0-ATPase
uses proton gradient in electron transport chain and energy to allow protons to re enter matrix to drive synthesis of ATP
so is a primary active transporter in reverse mode
Uniport
where there is one transported molecule through a protein
Symport
2 proteins travelling through a protein in the same direction
(example of cotransport)
antiport
2 molecules pass through protein in different directions
(example of cotransport)
Na/K pump
uses energy from hydrolysis of ATP to pump
- 3 NA out of cells
- 2 K into cells
both against conc gradient
antiport
what is a primary active transporter
uses ATP to pump ions
Describe this sodium pump
there is a P-type ATPase phosphorylated on the aspartate
alpha subunit - contains binding site for Na/K/ATP
beta subunit - needed for alpha subunit to be tranported to the plasma membrane. it is a glycoprotein
this is needed to create an ion gradient for secondary active transport
secondary active transport
driven indirectly by the energy released by hydrolysis of ATP to ADP
what part of the Na/K pump is responsible for membrane potential
diffusion of K through channels
Na - Ca exchanger
secondary active transport
dissapation of the Na gradient drives transport of Ca out of the cell
antiport ( Ca out of cell and Na in)
low affinnifty, high capacity - removes most of the Ca
Na - H exchanger
uses the Na / K pump to move H ions out of the cell
Na- Glucose co transport
glucose moves into the cell against ints conc gradient
symport
Cystic Fibrosis transport
the Cl receptor is damaged ao Cl cand move out of the cell and water cant move with it so there is a bbuild up of mucus
SERCA
similar to PMCA but the Ca enters the endoplasmic recticulum
high affinity, low capacity
mitochondrial Ca uniports
facilitated transport
operates at a high Ca conc to buffer potentially damaging levels of Ca
Na/Ca exchanger
