Membrane Proteins Flashcards
(12 cards)
what makes up the central region of the phospholipid bilayer?
the highly hydrophobic parts of phospholipid bilayer
how are integral proteins held so tightly within the bilayer?
the R groups of their amino acids have strong hydrophobic interactions with the phospholipid bilayer
what is facilitated diffusion?
the passive transport of substances across the membrane through specific transmembrane proteins called channels
why are peripheral proteins attracted to the surface of membranes and exposed integral proteins?
have hydrophilic R groups on their surface which have ionic and hydrogen bond interactions.
what is the purpose of channels and transporters?
to control ion concentrations and concentration gradients
how are ligand gated channels controlled?
by signal molecules that act as ligands
voltage-gated channels:
rely on changes in ion concentrations
how is a membrane potential created?
when there is an electrical potential difference between the two sides of the membrane
how does the sodium-potassium pump establish and maintain ion gradients?
uses energy from the hydrolysis of ATP
summary of sodium-potassium pump:
three sodium ions bind to the transporter protein, it is phosphorylated by splitting ATP and changes conformation, releasing the sodium ions outside the cell. The change in conformation gives the protein a high affinity for potassium ions outside the cell and two K+ ions bind. Dephospho-rylation occurs and reverts to original conformation releasing two potassium ions into the cell.
what is the purpose of the sodium-potassium pump in intestinal epithelial cells?
Generates a sodium ion gradient across the plasma membrane so that there is always a low concentration of sodium inside the cell.
glucose symport channel:
sodium ions enter cell down their concentration gradient through a glucose symport channel. The energy from the flow allows the simultaneous transport of glucose into the cell against its concentration gradient-from where it can diffuse into the blood
