Consider the molecule depicted below bond length, charges, lone pairs of electrons, what is the expected behavior of this molecule towards the PRMT enzyme. Considering electronegativity, chemical NH2 НО *H3Ñ HO NH2 ÕH

The following chemical reactants produce the ester ethyl ethanoate (C4H8O2): C2H6O + CH3COOH What type of reaction occurs to make ethyl ethanoate? condensation hydrolysis combustion acid-base reaction

Figure 27.3 illustrates the response of R (ATP-regenerating) and U (ATP-utilizing) enzymes to energy charge. a. Would hexokinase be an R enzyme or a U enzyme? Would glutamine: PRPP amidotransferase, the second enzyme in purine biosynthesis, be an R enzyme or a U enzyme? b. If energy charge = 0.5: Is the activity of hexokinase high or low? Is ribose-5-P pyrophosphokinase activity high or low? c. If energy charge = 0.95: Is the activity of hexokinase high or low? Is ribose-5-P pyrophosphokinase activity high or low?

PREDICT Do any of the amino acid side groups shown below have the potential to form an ionic bond with any of the other side groups shown? If so, which pair(s) could form such an association? (a)CH3 (b)CH2 COO (c)CH2 CH2 NH3+ (d)CH2 CH2 COO (e)CH2 OH

VISUALIZE The structures depicted are (a) enantiomers (b) different views of the same molecule (c) geometric (cistrans) isomers (d) both geometric isomers and enantiomers (e) structural isomers

In an enzymatic reaction: a. the enzyme leaves the reaction chemically unchanged. b. if the enzyme molecules approach maximal rate, and the substrate is continually increased, the rate of the reaction does not reach saturation. c. in the stomach, enzymes would have an optimal activity at a neutral pH. d. increasing temperature above the optimal value slows the reaction rate. e. the least important level of organization for an enzyme is its tertiary structure.

MATHEMATICAL A catalog in the lab has a recipe for preparing 1 L of a TRIS buffer at 0.0500 M and with pH 8.0: dissolve 2.02 g of TRIS (free base, MW=121.1 g/mol) and 5.25 g of TRIS hydrochloride (the acidic form, MW=157.6 g/mol) in a total volume of 1 L. Verify that this recipe is correct.

Energetic of Fructose-1 ,6-bis P Hydrolysis (Integrates with Chapter 3.) The standard free energy change (G) for hydrolysis of fructose-1. 6-bisphosphate (FBP) to fructose-S-phosphate (F-6-P) and P: is -16.7 KJ/mol: FBP + H2O fructose-6-P + Pi The standard free energy change (G) for ATP hydrolysis is -30.5 KJ/mol: ATP + H2O ADP + Pj What is the standard free energy change for the phosphofructokinase reaction: ATP + fructose-6-P ADP + FBP b. What is the equilibrium constant for this reaction? c. Assuming the intracellular concentrations of [ATP] and (ADP] are maintained constant at 4 mM and 1.6 mM, respectively, in a rat liver cell, what will be the ratio of [FBP]/[fructose-6-P] when the phosphofructokinase reaction reaches equilibrium?

In 1976, a team of chemists in the United Kingdom was developing new insecticides by modifying sugars with chlorine (Cl2), phosgene (Cl2CO), and other toxic gases. One young member of the team misunderstood his verbal instructions to test a new molecule. He thought he had been told to taste it. Luckily for him, the molecule was not toxic, but it was very sweet. It became the food additive sucralose. Sucralose has three chlorine atoms substituted for three hydroxyl groups of sucrose (table sugar): The altered sugar binds so strongly to the sweet-taste receptors on the tongue that the human brain perceives it as 600 times sweeter than sucrose. Sucralose was originally marketed as an artificial sweetener called Splenda, but it is now available under several other brand names. Researchers investigated whether the body recognizes sucralose as a carbohydrate by feeding sucralose labeled with 14C to volunteers. Analysis of the radioactive molecules in the volunteers urine and feces showed that 92.8 percent of the sucralose passed through the body without being altered. Some people are worried that the chlorine atoms impart toxicity to sucralose. How would you respond to that concern?

Understanding the Mechanisms of Reactions Related to Transketolase The mechanistic chemistry of the acetolactate synthase and phosphoketolase reactions (shown here) is similar to that of the transketolase reaction (Figure 22.30). Write suitable mechanisms for these reactions.