Module 11 Summary Quiz

Which is a viable path that a carbon atom could take as it moves through metabolic pathways in a cell? - Fatty acid → amino acid → pyrimidine → purine → glycerol → acetyl CoA → amino acid - Amino acid → purine → DNA → purine → amino acid → acetyl CoA → fatty acid → triglyceride - Pyrimidine → fatty acid → purine → amino acid → acetyl CoA → glucose → pyruvate → lactic acid - Amino acid → acetyl CoA → purine → pyrimidine → glycerol → fatty acid → lactic acid → glucose - Glucose → glycerol → triglyceride → fatty acid → purine → DNA → pyrimidine → amino acid

Amino acid → purine → DNA → purine → amino acid → acetyl CoA → fatty acid → triglyceride

Which statement could be used as part of a description of how carbohydrate, lipid, and protein are linked through catabolic and anabolic pathways? - Metabolic pathways are compartmentalized in the cell, which allows physical boundaries to organize the large numbers of metabolic interconversions taking place at any one time in a cell. - Metabolic pathways for lipids, proteins, and carbohydrates all share the same characteristic, in that they represent a series of separate chemical reactions that together accomplish a complex chemical transformation. - Metabolism is a cyclical process of energy conversion in which chemical energy is harvested from nutrients in catabolic reactions and used to synthesize new molecules in anabolic reactions. - Glycolysis and fermentation only partially oxidize glucose, while the citric acid cycle and oxidative phosphorylation allow for full oxidation of glucose and transfer of its free energy to ATP. - Glycolysis and the citric acid cycle occupy a central position in cell metabolism, connecting to lipid, protein, and carbohydrate breakdown and synthesis through small molecule intermediates.

Glycolysis and the citric acid cycle occupy a central position in cell metabolism, connecting to lipid, protein, and carbohydrate breakdown and synthesis through small molecule intermediates.

Which effector of enzyme activity is least likely to be utilized by cells? - Noncompetitive inhibitors - Allosteric activators - Allosteric inhibitors - Irreversible inhibitors - Competitive inhibitors

Irreversible inhibitors

Refer to the figure showing allosteric regulation of glycolysis and the citric acid cycle. If a cell is fed a large supply of fatty acids, which outcome can be expected? - The excess fatty acids will deplete the oxygen supply, causing everything except glycolysis to shut down and activating the lactic acid fermentation pathway. - Oxidation of fatty acids to form acetyl CoA will be stimulated, which will stimulate gluconeogenesis to form glucose that the cell can store as an energy source. - Glycolysis and pyruvate oxidation will be stimulated, causing citrate to build up and activate fatty acid synthase. - Oxidation of fatty acids through the citric acid cycle will be stimulated until ATP builds up and inhibits citrate synthase, diverting fatty acids into storage molecules such as triglycerides. - Glycolysis will be stimulated and pyruvate oxidation will be inhibited as acetyl CoA builds up to high levels in the cell.

Oxidation of fatty acids through the citric acid cycle will be stimulated until ATP builds up and inhibits citrate synthase, diverting fatty acids into storage molecules such as triglycerides.

Certain types of cell shave very low levels of metabolic activity for long time periods, but then rapidly shift to grow and divide. To undergo this shift, these cells must activate anabolic pathways. Which is one way they are able to accomplish this? - Large molecules influence metabolic flux through competitive inhibition effects on enzymes. - Small molecules affect metabolic flux through allosteric effects on enzymes. - Anabolic enzymes inhibit catabolic enzymes. - Cells only synthesize anabolic enzymes and cease synthesizing catabolic enzymes - Cells begin directing all of their energy toward toward reactions with negative ΔGs.

Small molecules affect metabolic flux through allosteric effects on enzymes.

A biochemist generates an enzyme activity curve for an unknown enzyme. The curve is shown below. Which statement best explains the shape of this curve? - The enzyme has multiple active sites. As the substrate concentration increases, all sites must be equally bound for the reaction to proceed. - The enzyme has a single active site. As the enzyme binds substrate, the activity of the enzyme stalls until it can clear the active site. - The enzyme has a single active site. Substrate binding at this particular site occurs within a narrow pH range, termed the equivalence point. - The enzyme has multiple active sites. Substrate binding at each of the sites is dependent upon the temperature of the reaction. - The enzyme has multiple active sites. As the enzyme binds substrate at one site, its affinity for binding substrate at other active sites increases.

The enzyme has multiple active sites. As the enzyme binds substrate at one site, its affinity for binding substrate at other active sites increases.

Enzyme Y is a component of a metabolic pathway and is inhibited by a metabolite produced at the end of that particular metabolic pathway. Which statement would not be true regarding this enzyme? - This enzyme regulates the pathway through a feedback inhibition mechanism. - This enzyme may also be activated by metabolites of another pathway. - This enzyme is very likely involved in the first commitment step of the metabolic pathway mentioned in the question. - This enzyme uses competitive inhibition as a mechanism for its regulation by downstream metabolites in the pathway. - Levels of this enzyme may be regulated at the level of transcription of its gene.

This enzyme uses competitive inhibition as a mechanism for its regulation by downstream metabolites in the pathway.

Metabolic pathways can be controlled through the availability of enzymes and modulation of their catalytic activities. Enzyme availability can be regulated _____, while enzyme activity is commonly regulated via _____. - gene expression; allosteric activation and inhibition - allosteric activation and inhibition; covalent modification - proteolytic breakdown; gene expression - gene expression; covalent modification - covalent modification; proteolytic breakdown

gene expression; allosteric activation and inhibition