Exam 13: How Cells Obtain Energy From Food

Glycolysis and the citric acid cycle comprise two different sets of oxidation reactions.The reaction sequence for glycolysis is linear, whereas the reaction sequence for the citric acid cycle forms a circle.How does this difference in the arrangement of reactions influence the rate of these processes when an excess amount of a single intermediate is added?

Although ATP and NADH are both important activated carrier molecules, ATP hydrolysis provides the direct molecular energy for most biochemical reactions.Why do the mitochondria also need to generate high levels of NADH?

Which of the following processes do NOT take place in the mitochondria?

Steps 7 and 10 of glycolysis result in substrate-level phosphorylation.Which of the following best describes this process?

The simultaneous oxidation and phosphorylation of glyceraldehyde 3-phosphate forms a highly reactive covalent thioester bond between a cysteine side chain (reactive group ?SH) on the enzyme (glyceraldehyde 3-phosphate dehydrogenase) and the oxidized intermediate (see the arrow in Figure 13-23A).If the enzyme had a serine (reactive group ?OH) instead of a cysteine at this position, which could form only a much lower energy bond to the oxidized substrate (see the arrow in Figure 13-23B), how might this new enzyme act? (A) (B) Figure 13-23

The concentration of H⁺ ions inside the mitochondrial matrix is lower than it is in the cytosol or the mitochondrial intermembrane space.What would be the IMMEDIATE effect of a membrane-permeable compound that carries and releases protons into the mitochondrial matrix?

Name the catabolic process that use substrate-level phosphorylation, identify where it takes place and how it is connected to oxidative phosphorylation.

In step 2 of the citric acid cycle, the enzyme aconitase generates isocitrate from citrate.Which of the following statements about this reaction is TRUE?

In anaerobic conditions, skeletal muscle produces

Which of the following cells rely exclusively on glycolysis to supply them with ATP?

Pyruvate must move from the cytosol into the mitochondria, where it is oxidized to form CO₂ and acetyl CoA by the pyruvate dehydrogenase complex.How many different enzymes and what total number of polypeptides, respectively, are required to perform this oxidation process in the mitochondrion?

The final metabolite produced by glycolysis is

The advantage to the cell of the gradual oxidation of glucose during cellular respiration compared with its combustion to CO₂ and H₂O in a single step is that

Compare and contrast the catabolism of carbohydrates, proteins and fats.Specifically, highlight the similarities and differences in how they are broken down (extracellular, and intracellular) for conversion into acetyl-CoA, the entry point into the citric acid cycle.

The oxygen-dependent reactions required for cellular respiration were originally thought to occur in a linear pathway.By using a competitive inhibitor for one enzyme in the pathway, investigators discovered that these reactions occur in a cycle.What compound served as the inhibitor?

Anaerobically growing yeast further metabolizes the pyruvate produced by glycolysis to CO₂ and ethanol as part of a series of fermentation reactions. A.What other important reaction occurs during this fermentation step? B.Why is this reaction (that is, the answer to part A) essential for the anaerobically growing cell?

In step 4 of glycolysis, a six-carbon sugar (fructose 1,6-bisphosphate) is cleaved to produce two three-carbon molecules (dihydroxyacetone phosphate and glyceraldehyde 3-phosphate).Which enzyme catalyzes this reaction?

Glycolysis is an anaerobic process used to catabolize glucose.What does it mean for this process to be anaerobic?

Which of the following descriptions best matches the function of a mutase?