Cholesterol is transported in the bloodstream in lipoproteinparticles. There are several classes of lipoprotein particles, butone of the most important classes is called Low-densitylipoproteins (LDL). LDL particles are composed of a single moleculeof a large protein called apolipoprotein, as well as thousands ofcholesterols molecules and phospholipids. Part of theapolipoprotein forms the surface of the particles and faces theaqueous phase, while other parts face the hydrophobic interior ofthe particle where they interact with cholesterol and thehydrophobic tails of the phospholipids. When cells need additionalcholesterol, they produce a receptor protein on the surface oftheir plasma membrane that binds to the apolipoprotein andinitiates the uptake of LDL particles into the cell via a processcalled endocytosis.
1. What is the likely reason that LDL particles are used totransport cholesterol in the blood stream?
a. Cholesterol in LDL particles easily inserts into lipidbilayers
b. Cholesterol id largely insoluble in aqueous solutions
c. Cholesterol is synthesized within LDL particles
d. LDL particles can form lipid rafts in the lipid bilayer
2. What is the most likely location of phospholipids in LDLparticles?
a. Bound to the hydrophilic domain of apolipoprotein
b. In the lipid bilayer that surrounds LDL particles
c. On the surface interacting with the aqueous environment aswell as interacting with the hydrophobic core of the particle
d. Within the hydrophobic core of the particle
3. What best describes the class of protein that apolipoproteinbelongs to?
a. Amphipathic proteins
b. Cell surface proteins
c. Membrane associated protein
d. Multipass membrane proteins
4. What kind of molecule on the surface of the cell would bemost likely to serve as a receptor for LDL particles?
a. a cholesterol binding protein
b. a glycolipid
c. a phospholipid
d. trans membrane protein
5. What conditions would be most likely to trigger increaseduptake of LDL particles by cells?
a. increased glycolipid synthesis
b. increased plasma membrane growth
c. increased protein secretion
d. increase protein synthesis
