Explain how it is possible for an enzyme to catalyze a chemical reaction in two different directions.
What will be an ideal response?
Both the substrate and product have a 3 -D shape complementary to the active site of the enzyme. In a synthesis reaction between two organic monomers, the enzyme holds the substrates in a position that greatly increases the likelihood of bond formation between them, and as the bond forms to produce a dimer, the affinity of the enzyme
for the substrates increases. The dimer is also complementary to the active site of the enzyme, and if a dimer molecule happens to bind to the enzyme, becoming the substrate, the bond between the monomers becomes strained as the intermediate is formed and can break. If this happens, the reaction is a degradation and the products are the monomers. The tightest binding is between the enzyme and the intermediate form, different in structure compared to either the substrates or the product. Thus it is equally likely that the reaction will be a synthesis or a degradation, if no other factors are considered.
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Identify the muscular ridges that are found on the anterior wall of the right atrium and extend into the auricles
a) Pectinate muscles b) Trabeculae carneae c) Coronary sulci d) Papillary muscles e) Chordae tendinae
When plasma glucose concentration exceeds the renal plasma threshold,
A) the glomerular filtration rate increases. B) glucose is secreted into the peritubular capillary. C) the volume of urine decreases. D) glucose appears in the urine.
Blood is moved through the vascular system by
A. valves in the wall of the blood vessels. B. peristalsis caused by smooth muscle in the blood vessel walls. C. pressure gradients created by the heart. D. osmotic pressure. E. viscosity of the blood.
What is the term used for wavelike contractions that move the bolus along the length of the esophagus?
A. Peristalsis B. Deglutition C. Mastication D. None of these are correct.