Exam 13: How Cells Obtain Energy From Food

The citric acid cycle is a critical sequence of reactions for energy production, which take place in the matrix of the mitochondria.The reaction cycle requires materials from the cytosol to be converted into acetyl CoA, which represents the starting point of a new cycle.Which of the following statements about acetyl CoA is TRUE?

It can be useful to analyze the steps of glycolysis with respect to the four basic types of enzymes required by this central catabolic pathway and to consider whether each enzyme produces or harvests the energy of an activated carrier.For each step of glycolysis (see Figure 13-60 or Panel 13-1), indicate which type of enzyme (of the four listed below and in Table 13-60) is required-or if none apply.Also, indicate whether an activated energy carrier is involved, and, if so, how. Step 1 __________ Step 2 __________ Step 3 __________ Step 4 __________ Step 5 __________ Step 6 __________ Step 7 __________ Step 8 __________ Step 9 __________ Step 10 __________ Enzyme types: kinase, isomerase, mutase, dehydrogenase

In step 4 of the citric acid cycle, the reduction of NAD⁺ to NADH is coupled to the generation of CO₂ and the formation of a high-energy thioester bond.Which molecule provides the sulfhydryl group necessary to form the thioester bond?

Which reaction does the enzyme phosphoglucose isomerase catalyze?

In the final step of the citric acid cycle, oxaloacetate is regenerated through the oxidation of malate and this is coupled with the production of which other molecule?

Where does oxidative phosphorylation take place and what materials are the reactants and the products in this process?

In the reaction cycle involved in the oxidation of pyruvate, what are the advantages of having three enzyme activities contained in a single large complex instead of having three smaller and physically independent enzymes?

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.Which product in the reaction pathway builds up when the inhibitor is added?

Glycolysis generates more stored energy than it expends.What is the net number of activated carrier molecules produced in this process (number and type of molecules produced minus the number of those molecules used as input)?

The oxidative reactions of cellular respiration were the focus of intense study in the 1930s.These reactions are represented in a linear pathway, as they were thought to occur.Each product is designated as a lettered compound (A through H) in Figure 13-16. A \longrightarrow B \longrightarrow C \longrightarrow D \longrightarrow E \longrightarrow F \longrightarrow G \longrightarrow H citrate isocitrate \alpha -ketoglutarate succinyl CoA succinate fumarate malate oxaloacetate Figure 13-16 A.What was the first observation that Krebs made when he added malonic acid to the minced muscle samples, and what was his conclusion about how and where it was acting in the reactions he was studying? B.What happens when the malonate block is introduced and subsequently compound A is added in excess? What is the result if compound G is added after the block, instead of A? How did Krebs attempt to reconcile these two results? C.What additional observation led Krebs to hypothesize that what was previously thought to be a linear sequence of reactions is actually a cyclic sequence of reactions? How did this idea further explain the earliest observations that the addition of any single compound in the pathway greatly increases oxygen uptake by the muscle tissue?