Membrane Proteins Flashcards
What are integral membrane proteins ?
They are proteins found in the cell membrane within the phospholipid bilayer.
What allow these integral proteins to hold to the phospholipid bilayer ?
Regions of hydrophobic R groups allow strong hydrophobic interactions that hold the proteins within the phospholipid bilayer , integral proteins interact extensively with the hydrophobic regions of the membrane phospholipids.
What are some integral proteins ?
Transmembrane proteins
What are peripheral membrane proteins ?
They are proteins which are found on the the surface of the membranes.
How are peripheral membrane proteins bond there ?
Peripheral membrane proteins have hydrophilic R groups on their surface and are bound to he surface of membranes mainly by ionic and hydrogen bond interactions .
What do they bind to ?
Many peripheral membrane proteins interact with the surfaces of integral memberane proteins .
What is the phospholipid bilayer?
It is a barrier to ions and most uncharged polar molecules
What can pass the phospholipid bilayer and how ?
Some small molecules such as oxygen and c02 can pass the bilayer by diffusion.
What is facilitated diffusion?
Is the passive transport of substances across the membrane through specific transmembrane proteins
How do they preform specific functions ?
To perform specialised functions, different cell types have different channel and transporter proteins
How selective are channel proteins?
They are highly selective.
What are channels ?
Channels are multi-subunit proteins with the subunits arranged to form water-filled pores that extend across the membrane. They are highly selective
What can some channel proteins do ?
Some channel proteins are gated and change confirmation to allow of prevent diffusion
What are ligand gated channels ?
Ligand-gated channels are controlled by the binding of signal molecules, when a molecule binds a gate opens and ions are allowed to flow through. and voltage- gated channels are controlled by changes in ion concentration
What are transporter proteins ?
They bind to the specific substance to be transported and undergo a confirmational change to transfer the solute across the membrane.
Why do transporters alternate between 2 conformations ?
So that the binding sight for a solute is sequentially exposed on one side of the bilayer , then on the other
What are protein pumps ?
Active transport uses proteins that transfers substances across the membrane against their concentration gradient. Pumps mediate active transport are transporter proteins
What is required for active transport ?
A source of metabolic energy
What do some transport proteins hydrolyse ?
ATP . this directly provides the energy for the conformational change required to move the substances across the membrane.
What hydrolyses ATP
ATPases
What is an ion gradient and how is it come by ?
For a solute carrying a net charge , the concentration gradient and electrical potential difference combine to form The electrochemical gradient that determines the transport of the solute
What are ion pumps ?
Examples - sodium potassium pump
They use energy from hydrolysis of atp to establish and maintain ion gradients.
How are membrane potentials made ?
When there is a difference in electrical charge and the two sides of the membrane
What does the sodium potassium pump do ?
They transport ions against the concentration gradient using energy from hydrolysis
It actively transports 3 sodium’s out and 2 potassium in, This establishes both concentration gradients and an electrical gradient.
