06-04-2007, 07:10 PM
d?
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who i s awake?? - ros2
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06-04-2007, 07:11 PM
Familial hypercholesterolemia results in elevated serum cholesterol by as much as 2 to 3 times normal, all due to increased LDL. The LDL elevation is due to an inherited deficiency in LDL receptors resulting in delayed LDL clearance.
E. Familial hypertriglyceridemia is due to a genetic deficiency in lipoprotein lipase which impairs the ability to clear chylomicrons from the blood. This is not a risk factor for atherosclerosis, but pancreatitis is common. A. Mixed hypertriglyceridemia shows elevated chylomicron and triglyceride levels, and modest increases in cholesterol. Lipoprotein lipase activity is normal. B. Endogenous hypertriglyceridemia, as the term implies, is characterized by elevated serum triglycerides contained in VLDL. Elevated cholesterol is also seen with the increased VLDL levels, but LDL and HDL concentrations tend to be lowered. C. Type III hyperlipoproteinemia is caused by a block in the conversion of triglyceride rich VLDL to LDL. Like mixed hypertriglyceridemia, it is characterized by elevated triglyceride and cholesterol levels, but differs in having a much stronger increase in cholesterol and the appearance of a broad beta-migrating VLDL band on electrophoresis (hence the name broad beta disease)
06-04-2007, 07:11 PM
The extraction of energy from carbohydrates requires that each reaction in the process be coupled. In order for two reactions to be coupled, which of the following is absolutely necessary?
A. The reactions should be in the same metabolic pathway. B. One should have a positive standard free energy and the other a negative standard free energy. C. The rate of one reaction should be significantly faster than the other. D. An intermediate should be common to both reactions. E. The activation energies of both reactions do not exceed the total free energy change.
06-04-2007, 07:15 PM
Answer D.
A common intermediate, such as a metabolite that is the product of one reaction and the substrate for another, is the essential requirement for coupling of two reactions. A. While a metabolic pathway is comprised of reactions which are coupled together, this is a result and not a cause of coupling. B. While free energy changes describe spontaneity and are additive when determining the spontaneity for coupled reactions, they do not form the basis for coupling. C. The concept of coupling does not concern reaction rates. E. The activation energies of individual reactions are unrelated either to coupling or to the total free energy change.
06-04-2007, 07:16 PM
Many therapeutic drugs act as noncompetitive inhibitors. The addition of a noncompetitive inhibitor to an enzyme catalyzed reaction leads to:
A. both an increase in the Vmax and an increase in the Km. B. a decrease in the observed Vmax. C. a decrease in Km and in Vmax. D. an increase in Km but no change in Vmax. E. irreversible inhibition. |
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