Movement Of Molecules Across Membranes Flashcards
What do regions of hydrophobic R groups allow?
Strong hydrophobic interactions that hold integral membrane proteins within the phospholipid bilayer
What do integral membrane proteins interact with?
They interact extensively with the hydrophobic region of membrane phospholipids
Are some integral membrane proteins transmembrane proteins?
Yes
What R groups do peripheral membrane proteins have?
They have hydrophobic R groups on their surface and are bound to the surface of membranes mainly by ionic and hydrogen bond interactions
What do many peripheral membrane proteins interact with?
The surfaces of integral membrane proteins
What is the phospholipid bilayer a barrier to?
Ions and most uncharged polar molecules
How do some small molecules such as oxygen and carbon dioxide pass through the phospholipid bilayer?
By simple diffusion
What is facilitated diffusion?
It is the passive transport of substances across the membrane through specific transmembrane proteins
To preform specialised functions what do different cell types have?
They have different channel and transporter proteins
Are most channel proteins in animal and plant cells highly selective or unselective?
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
Why are some channel proteins gated and change conformation?
To allow or prevent diffusion
How are ligand gated channels controlled?
By the binding of signal molecules
How are voltage gated channels controlled?
By changes in ion concentration
What do transporter proteins bind to and what happens after binding?
They bind to the specific substance to be transported and undergo a conformational change to transfer the solute across the membrane
Why do transporters alternate between two conformations?
So that the binding site for a solute is sequentially exposed on one side of the bilayer then the other
What does active transport use?
They use pump proteins that transfer substances across the membrane against their concentration gradient
What are pumps that mediate active transport?
They are transporter proteins coupled to an energy source
What is required for active transport?
A source of metabolic energy
Why do some active transport proteins hydrolyse ATP directly?
To provide the energy for the conformational change required to move substances across the membrane
What does ATPases do?
It hydrolyses ATP
