1.3a Movement of molecules across membranes Flashcards
How are integral membrane proteins held within the phospholipid bilayer?
Regions of hydrophobic R groups allow strong hydrophobic interactions
Integral membrane proteins interact extensively with the hydrophobic region of membrane phospholipids
What are one kind of integral membrane proteins?
Transmembrane
How are peripheral proteins held withing the phospholipid bilayer?
They are hydrophilic R groups on their surface and are bound to the surface of membranes, mainly by ionic and hydrogen bond interactions.
Describe how integral and peripheral membrane proteins interact
many peripheral membrane proteins interact with the surfaces of integral membrane proteins.
What is the phospolipid bilayer a barrier to?
ions and most uncharged polar molecules
Give examples of molecules that can pass through the bilayer by simple diffusion
-oxygen
-carbon dioxide
What is facilitated diffusion?
the passive transport of substances across the membrane through specific transmembrane proteins
Why do different cell types have different channel and transporter proteins?
to perform specialized functions
Describe most channel proteins in animal and plant cells
they are highly selective
Describe the structure of channels
they are multi-subunit proteins with the subunits arranged to form water-filled pores that extend across the membrane
How do some channel proteins allow or prevent diffusion?
- gated
- change conformation
How are ligand gated channels controlled?
By the binding of signal molecules
How are voltage gated channels controlled?
changes in ion concentration
Describe the function of transporter proteins
- bind to the specific substance being transported
- and undergo a conformational change to transfer the solute across the membrane
- They 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 type of membrane protein does active transport use?
pump proteins
