100 Anatomy, Histology, and Cell Biology
33.Band 3 protein exists as a 95-kDa multipass membrane protein that
functions as the primary anion exchanger in erythrocytes. Within the red
blood cell (RBC) membrane, band 3 binds to spectrin dimers and tetramers
indirectly through ankyrin. The spectrin tetramers are bound together by
actin and band 4.1 protein, which also binds to band 3 and glycophorin.
Null mutations in band 3 occur in the human population. Which of the fol-
lowing is most likely to decrease in the absence of band 3 protein?
a. Osmotic fragility
b. Destruction of RBCs in the spleen
c. Bile production
d. Erythroid production in the bone marrow
e. Blood pH
34.A 56-year-old man who drinks a six-pack of beer a day, with higher
alcoholic intake on weekends, holidays, and “special days,” presents to the
internal medicine clinic. He has an abnormal plasma lipoprotein profile. It
is known that erythrocyte fluidity is altered in liver disease. Which of the
following would increase membrane fluidity in the hepatocytes of this
patient’s liver?
a. Restriction of rotational movement of proteins and lipids in the membrane
b. Transbilayer movement of phospholipids in the plasma membrane
c. Increased cholesterol/phospholipids ratio in the plasma membrane
d. Binding of integral membrane proteins with cytoskeletal elements
e. Binding of an antibody to a cell-surface receptor
35.The asymmetry of the cell membrane is established primarily by which
of the following?
a. Membrane synthesis in the endoplasmic reticulum
b. Membrane modification in the Golgi apparatus
c. Presence of carbohydrates on the cytoplasmic surface
d. The distribution of cholesterol
e. Flipping proteins between the leaflets of the lipid bilayer