Membrane Proteins Flashcards
How are integral membrane proteins held within the PLB
Strong hydrophobic interactions
between R groups and phospholipids
Peripheral Membrane proteins
How they bind
interactions
hydrophilic R groups on their surface, and are bound to the surface of membranes.
By Ionic and hydrogen bonds
Many interact with integral proteins
What cant and can pass through the
Phospholipid Bilayer
Barrier to ions and most uncharged molecules
Oxygen and carbon dioxide can by simple diffusion
What is
Facilitated Diffusion
Passive transport of substances across the membrane through specific transmembrane proteins
Channel proteins
Multi sub unit proteins with the subunits arranged to form water-filled pores that extend across the membrane
Some are gated and change conformation
Ligand-gated channel proteins
Controlled by binding of signal molecules
Voltage gated
Controlled by changes in ion concentration.
whaT DO
Transporter proteins
do
Bind to specific substance to be transported and undergo a confromational change to transfer solute across membrane
Transporter proteins alternating
They alternate between two conformations so that the binding site for a solute is sequentially exposed on one side of bylayer and then the other
Active Transport
And whats required
Uses pump proteins that transfer substances across the membrane against their concentration gradient
A source of metabolic energy is required
Hydrloysis of ATP
ATPases hydrolyse ATP to provide the energy for conformational change.
What forms the electrochemical gradient
Concentration gradient and elecitrical potential difference.
Membrane potetntial [EPD]
How is
Membrane potential
Created
With a difference in electrical charge on two sides of the membrane
Sodium potassium Ion pump
How does it transport ions
And where
It transports ions against a steep Concentration gradient using enerrgy directly from ATP hydrolysis
It transports Na+ ions out the cell and K+ ions into the cell
How
Na/K ATPase pumps ions
The pump has a high affinity for Na+ inside cell, binding occurs, phosphorylarion by ATP, Conformation changes, affinity for NA+ decreases and are released outside cell, K+ binds otside cell, dephosphorylation occurs and conformational change occurs, K+ ions taken in, affinity for Na+ returns
