Flashcards in Membrane Proteins Deck (17)
Give two membrane proteins by which ions and molecules can progress through a membrane.
Describe the two types of channel proteins.
Ligand-gated: signal molecules bind to channels causing a conformational change, opening the channel and allowing ions/molecules to pass through.
Voltage-gated: change in ion concentrations causes a conformational change, opening the channel and allowing ions/molecules to pass through.
Describe transporter proteins
Ions/molecules bind to transporter protein, this causes a conformational change and the protein passes the molecules through to membrane.
State the definition of the term 'facilitated diffusion'
The process of passive movement across a membrane through specific membrane proteins.
What is signal transduction?
Extracellular hydrophobic signal molecules bind to receptor proteins, triggering a signal-transduction pathway. This causes a specific intracellular response, involving cascades occur to amplify the signal.
This can change the uptake or secretion of molecules or rearrange the cytoskeleton.
What is the role of the Sodium Potassium pump?
Moving sodium ions out of the cell and moving potassium ions into the cell to generate a new ion gradient.
Describe 4 reasons the Na/K pump is important.
Maintains osmotic balance in animal cells -low ion concentration increases water concentration
Generation of sodium ion gradient for glucose symport
Generation of sodium ion gradient in kidney tubules - gradient created between lumen of tubule to cell
Maintain ion gradient for resting potential.
State the two stable conformational states of the Na/K pump
Open towards inside of cell with high affinity for Na+ ions
Open towards outside of cell with high affinity for K+ ions
Describe the 6 stages of how the Na/K pump works
1. 3 Na+ ions bind
2. ATP hydrolyses, phosphorylation occurs, conformational change occurs.
3. Na+ ions released
4. 2 K+ ions bind, triggering dephosphorylation
5. Conformational change occurs to original state
6. K+ ions are released
Explain what the resting potential of a cell is.
Imbalance in electrical charge in a cell. K channels allow K+ to leak back out pf the cell causing a net positive charge outside of cell
How does a nerve impulse pass along a neuron?
As a wave of depolarisation
Describe the 5 stages of triggering a nerve impulse.
1. Neurotransmitter binds to ligand gates channel
2. Channel opens to allow Na+ to diffuse into neuron
3. Na+ movement causes depolarisation
4. Depolarisation reaches critical level
5. Voltage gated channel opens to allow Na+ to diffuse into cell, creating a domino effect
Describe the 5 stages of resetting the resting potential
1. Voltage gated channel opens to allow Na+ to pass through
2. Voltage builds up so Na+ channel closes and K+ channel opens
3. K+ diffuses out of neuron to reverse depolarisation
4. Resting potential is restored so K+ channel closes
5. Na/K pump resets ion gradient
Describe the term 'coupled transport'
movement of one material down a concentration gradient, causing another material to move up against the concentration gradient
Describe active transport.
The protein conformational change requires the binding of ATP
State 3 examples of specific transmembrane proteins