Chapter 8 Review Quiz

Carbohydrate Metabolism

. Which of the following activates glycolysis?

. The body requires backup stores of reduced carbon. We have two forms, lipids and starch or glycogen. Our immediate source of reduced carbon is glucose, which we access by several pathways such as glycolysis. We normally have about 90 mg of glucose per dL of blood, but need to have an immediate backup source of glucose. Which of these is the source?

. As molecules move through metabolism, some are oxidized through glycolysis and several other pathways, but a few may be taken out of the pathways to form special molecules needed for synthesis of other metabolites. In order to synthesize triglycerides (triacylglycerols or TAGs, which are esters of fatty acids and the polyhydroxy alcohol glycerol), animals obviously must have a supply of glycerol. Which intermediate in glycolysis would be the best candidate for a starting material for glycerol formation?

. Cyclic-3',5'-AMP (cAMP) acts as a second messenger for protein hormones, but also has other important functions, undoubtedly including many which have not yet been discovered. It's possible, with luck and skill, to grow some cells in tissue culture, which is probably more of an art than a science. Under normal circumstances, these cells divide and fill the usable space in the medium, and then, when they near the stationary phase of their growth cycle (contact inhibition usually causes the cells to slow division when they begin to encounter other cells, a strange phenomenon occurs: the activity of adenyl cyclase in the medium increases, [cAMP] increases, and the cells cease dividing. It's possible to add some substances to the medium, transforming the cell culture from normal cells into an out-of-control mixture of cells which have no contact inhibition and pile up on top of each other, exhausting the growth medium. If you were experimenting with these cells, and had observed the events described, what should be your next experiment?

. During metabolism in a certain tissue, glucose is oxidized, ATP is generated, and NAD+ is reduced to NADH. At the same time, CO2 is released. The most likely type of metabolism here is:

. The process of glycogenolysis is accelerated by:

. During glycolysis, energy in the form of ATP is produced at the substrate level, and reduced NADH is also produced and can later be oxidized to yield more energy. If each NADH were equivalent in energy to 2.5 mols of ATP, then during aerobic conditions, the maximum number of mols of ATP which could be produced by passage of one mole of glucose through aerobic glycolysis would be:

. Production of alcoholic beverages by fermentation is probably among the first chemical processes employed by humans. Alcohol concentration is commonly described as the proof number. Nineteenth-century fur traders lacking testing equipment could determine proof of spirit. They would pour a small amount of black gunpowder onto a stump, add some of the alcohol, and set it afire. If the alcohol were at least 50% (v/v), the gunpowder would ignite after the liquid burned off and the preparation was described as 100 proof. Suppose that a certain whiskey were 45% (v/v). The alcohol proof number would be:

. A major physiological function of the pentose phosphate pathway is formation of:

. If a person were exercising vigorously and unable to take in sufficient oxygen, his or her tissues would probably accumulate excess amounts of:

. We consume some fructose in our diet. The fructose can provide energy by:

. The Pasteur effect showed that:

. Both insulin and glucagon affect glycogenesis and glycogenolysis. Glucagon could be classified as this type of hormone:

. Under some circumstances (sometimes referred to as the futile cycle), fructose-1,6-biphosphate may be hydrolyzed to form fructose-6-phosphate and phosphoric acid nearly as rapidly as it is formed. When this is happening, the major effect noticed would be:

. One of the early steps in glycogenesis is formation of UDP-glucose from glucose-1-phosphate and UTP according to the reaction:
Glucose-1-phosphate + UTP UDP-glucose + PPi
One would expect this reaction to occur spontaneously if ΔG were large and negative, but in fact, ΔG for this reaction is nearly zero. What, then, drives the reaction?

. Glycogenolysis is controlled by a system which relies on a series of events. First, epinephrine in muscle or glucagon in liver activates adenyl cyclase, a few molecules of which convert many ATP molecules to many more cAMP molecules. These cAMP molecules activate many more protein kinase molecules, which in turn convert a great deal of glycogen phosphorylase from inactive to active forms which in turn rapidly convert a very, very large number of glycogen molecules to glucose-1-phosphate molecules. This process of enzyme activation represents a strategy for control of enzyme activity known as:

. Which of the following decreases the rate of glycolysis in a tissue?

. The process of fermentation of glucose is favored in systems which:

. It seems that if we can convert glucose to pyruvic acid and to other metabolites, we should be able to simply reverse glycolysis and form new glucose from pyruvic acid. What prevents this?

. The process of gluconeogenesis not only clears cells of some molecular debris, but can also provide glucose for these cells which need a constant supply:

. The end product of glycolysis under anaerobic conditions is:

. The first step in glycolysis is phosphorylation of glucose to form glucose-6-phosphate. This action serves to:

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