1. Dinitrophenol (DNP) is a compound that allows hydrogen ions to leak across a
ID: 2 • Letter: 1
Question
1. Dinitrophenol (DNP) is a compound that allows hydrogen ions to leak across a membrane. This leakage prevents the maintenance of an H+ gradient. How would this impact a cell?
A. It would permit a greater growth rate, since the cell would no longer have to spend energy pumping H+
across the membrane.
B. It would permit a greater growth rate, because the equalization of H+ on both sides of a membrane would help the cell cope
with an acidic environment.
C. If the cell were a neuron, it would have no impact, because the charge differential on the surface of the neuron membrane is
based on Na+ and K+, not on H+.
D. It would slow the growth rate slightly, but the cell would compensate by maintaining the function of proton pumps.
E.The cell would lose the bulk of its energy production because of DNP%u2019s interference with chemiosmosis.
2. cell is composed of thousands of molecules that range in size from very small to very large. Select the sequence of molecular size from the smallest to the largest.
A. Carbon dioxide%u2014DNA polymerase%u2014phospholipid%u2014ribosome
B. Phospholipid%u2014DNA polymerase%u2014ribosome%u2014carbon dioxide
C. Phospholipid%u2014carbon dioxide%u2014ribosome%u2014DNA polymerase
D. Carbon dioxide%u2014phospholipid%u2014DNA polymerase%u2014ribosome
E. DNA polymerase%u2014ribosome%u2014carbon dioxide%u2014phospholipid
Explanation / Answer
E. This question is designed to ascertain your understanding of the functioning of mitochondria.Chemiosmosis is the process whereby hydrogen ions are pumped across a membrane. In the mitochondria, these proton pumps are powered by the energy extracted from electrons harvested from glycolysis and the TCA cycle. Because of the gradient, the ions will rush back through the membrane via a molecule of ATP synthase, thereby manufacturing ATP. If DNP is present, then the electron-transport system is still functioning, and H+ ions are being pumped across the membrane, but the leakage prevents the maintenance of the gradient required to power ATP synthase. Thus, no energy is produced by the cell, and the cell ceases to be able to maintain homeostasis.
Answer D
Carbon dioxide is a gas that consists of three atoms with a molecular weight of 76 Da. A phospholipid consists of a phosphate group attached to a glycerol head that is connected to two fatty acid chains of about 20 carbon atoms in length each for a total less than 30 carbon atoms; its molecular weight is 700%u2013800 Da. DNA polymerase is an enzyme complex of between 50 and 150 kDa, or about 2S. The bacterial ribosome consists of about 55 proteins plus rRNA strands that total 70S.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.