Question 1

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?

Accepted Answer

The answer of Glycolysis and the citric acid cycle comprise...

Question 2

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?

Accepted Answer

The answer of Although ATP and NADH are both important...

Question 3

Match between columns Premises: Amino acids can be transported into the mitochondria and converted into acetyl CoA.
Anaerobic respiration is not the same as fermentation, as only the former requires an electron-transport chain.
When subjected to anaerobic conditions, glycolysis in mammalian cells continues and causes a buildup of pyruvate in the cytosol.
The pyruvate dehydrogenase complex catalyzes three different, but linked, enzymatic reactions.
During glycolysis, glucose molecules are broken down to yield CO₂ and H₂O. The cleavage of fructose 1,6-bisphosphate yields two molecules of glyceraldehyde 3-phosphate.

Accepted Answer

The Answer of False and True is...

Question 4

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

Accepted Answer

A) citric acid cycle 
B) conversion of pyruvate to activated acetyl groups 
C) oxidation of fatty acids to acetyl CoA 
D) glycogen breakdown

Question 5

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

Accepted Answer

A) ATP is being hydrolyzed to phosphorylate the substrate. 
B) The energy derived from substrate oxidation is coupled to the conversion of ADP to ATP. 
C) Two successive phosphates are transferred, first to AMP, then to ADP, finally forming ATP. 
D) The substrate is hydrolyzed using ATP as an energy source.

Question 6

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

Accepted Answer

A) It would oxidize the substrate and phosphorylate it without releasing it. 
B) It would oxidize the substrate but not release it. 
C) It would phosphorylate the substrate on the 2 position instead of the 1 position. 
D) It would behave just like the normal enzyme.

Question 7

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?

Accepted Answer

A) inhibition of the electron-transport chain 
B) inhibition of ATP synthesis 
C) increased import of ADP into the matrix 
D) inhibition of the citric acid cycle

Question 8

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

Accepted Answer

The answer of Name the catabolic process that use substrate-level...

Question 9

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?

Accepted Answer

A) There is a substantial free-energy difference between the reactants and products of this reaction. 
B) The unbonded electrons from hydroxide ions provide energy for this reaction. 
C) The aconitase enzyme functions as a mutase in this reaction. 
D) The reaction sequence first generates one molecule of water and then consumes one molecule of water.

Question 10

In anaerobic conditions, skeletal muscle produces

Accepted Answer

A) lactate and CO2. 
B) ethanol and CO2. 
C) lactate only. 
D) ethanol only.

Question 11

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

Accepted Answer

A) anaerobically growing yeast 
B) aerobic bacteria 
C) skeletal muscle cells 
D) plant cells

Question 12

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?

Accepted Answer

A) 1; 60 
B) 3; 3 
C) 3; 26 
D) 3; 60

Question 13

The final metabolite produced by glycolysis is

Accepted Answer

A) acetyl CoA. 
B) pyruvate. 
C) 3-phosphoglycerate. 
D) glyceraldehyde 3-phosphate.

Question 14

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

Accepted Answer

A) more free energy is released for a given amount of glucose oxidized. 
B) no energy is lost as heat. 
C) energy can be extracted in usable amounts. 
D) more CO2 is produced for a given amount of glucose oxidized.

Question 15

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.

Accepted Answer

The answer of Compare and contrast the catabolism of carbohydrates,...

Question 16

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?

Accepted Answer

A) malonate 
B) malate 
C) fumarate 
D) succinate

Question 17

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?

Accepted Answer

The answer of Anaerobically growing yeast further metabolizes the pyruvate...

Question 18

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?

Accepted Answer

A) aldolase 
B) phosphoglucose isomerase 
C) enolase 
D) triose phosphate isomerase

Question 19

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

Accepted Answer

A) No oxygen is required. 
B) No oxidation occurs. 
C) It takes place in the lysosome. 
D) Glucose is broken down by the addition of electrons.

Question 20

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

Accepted Answer

A) an enzyme that catalyzes the rearrangement of bonds within a single molecule 
B) an enzyme that catalyzes a change in the position of a specific chemical group within a single molecule 
C) an enzyme that catalyzes the oxidation of a molecule by removing a hydride ion 
D) an enzyme that catalyzes the addition of phosphate groups to other molecules

Exam 13: How Cells Obtain Energy From Food