Human Immunodeficiency Virus (HIV) Infects Cells That Have Both CD4

question 19

Multiple Choice

Human immunodeficiency virus (HIV) infects cells that have both CD4 and CCR5 cell surface molecules. The viral nucleic acid molecules are enclosed in a protein capsid, and the protein capsid is itself contained inside an envelope consisting of a lipid bilayer membrane and viral glycoproteins. One hypothesis for viral entry into cells is that binding of HIV membrane glycoproteins to CD4 and CCR5 initiates fusion of the HIV membrane with the plasma membrane, releasing the viral capsid into the cytoplasm. An alternative hypothesis is that HIV gains entry into the cell via receptor-mediated endocytosis, and membrane fusion occurs in the endocytotic vesicle. To test these alternative hypotheses for HIV entry, researchers labelled the lipids on the HIV membrane with a red fluorescent dye.
-In an HIV-infected cell producing HIV virus particles, the viral glycoprotein is expressed on the plasma membrane. How do the viral glycoproteins get to the plasma membrane? They are synthesised ________.

• A) on ribosomes on the plasma membrane
• B) by ribosomes in the rough ER and arrive at the plasma membrane in the membrane of secretory vesicles
• C) on free cytoplasmic ribosomes and then inserted into the plasma membrane
• D) by ribosomes in the rough ER, secreted from the cell, and inserted into the plasma membrane from the outside

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