Cellular respiration and fermentation

All of the processes involved in cellular respiration produce ATP. Which of the following processes produces the most ATP?

Oxidative phosphorylation

Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?

Glycolysis Glycolysis is a metabolic pathway common to both fermentation and cellular respiration of a glucose molecule. Fermentation consists of glycolysis plus reactions that regenerate NAD+ by transferring electrons from NADH to pyruvate or derivatives of pyruvate. The NAD+ can then be reused to oxidize sugar by glycolysis, which nets two molecules of ATP by substrate-level phosphorylation.

The function of cellular respiration is to __________.

extract usable energy from glucose

Glucose is the primary fuel for cellular respiration. Which of the following molecules can also be used by cellular respiration to generate ATP?

Answer: All of the listed responses are correct. -All of the listed responses are correct. -Amino acids -Glycerol =Fatty acids -None of the listed responses is correct.

Which of the following pairs of pathways and their location in the cell is incorrectly matched?

Answer: Citric acid cycle: cytosol -Citric acid cycle: cytosol -Glycolysis: cytosol -Electron transport chain: mitochondrion -Oxidative phosphorylation: mitochondrion -All of the responses are correctly matched.

Which statement correctly describes the difference between alcohol fermentation and lactic acid fermentation?

Answer: Lactic acid fermentation produces lactate, and alcohol fermentation produces ethanol. -Lactic acid fermentation produces lactate, and alcohol fermentation produces ethanol. -Alcohol fermentation produces lactate, and lactic acid fermentation produces ethanol. -Only lactic acid fermentation produces NAD+ to facilitate the production of ATP in glycolysis. -Alcohol fermentation is an aerobic pathway, and lactic acid fermentation is an anaerobic pathway. -None of the listed responses is correct. * Fermentation consists of glycolysis plus reactions that regenerate NAD+ by transferring electrons from NADH to pyruvate or derivatives of pyruvate. The NAD+ can then be reused to oxidize sugar by glycolysis, which nets two molecules of ATP by substrate-level phosphorylation. There are many types of fermentation, and they differ in the end products formed from pyruvate. Two types commonly harnessed by humans for food and industrial production are alcohol fermentation and lactic acid fermentation. In alcohol fermentation, pyruvate is converted to ethanol (ethyl alcohol) in two steps. The first step releases carbon dioxide from the pyruvate, which is converted to the two-carbon compound acetaldehyde. In the second step, acetaldehyde is reduced by NADH to ethanol. This regenerates the supply of NAD+ needed for the continuation of glycolysis. During lactic acid fermentation, pyruvate is reduced directly by NADH to form lactate as an end product, with no release of CO2.

Which of the following is a correct description of the events of cellular respiration and the sequence of events in cellular respiration?

Answer: Oxidation of glucose to pyruvate; oxidation of pyruvate; oxidation of acetyl-coA; oxidative phosphorylation -Oxidation of glucose to pyruvate; oxidation of pyruvate; oxidation of acetyl-coA; oxidative phosphorylation -Oxidation of glucose to pyruvate; reduction of pyruvate; TCA cycle; oxidative phosphorylation -Glycolysis; reduction of pyruvate; TCA cycle; oxidative phosphorylation -Glycolysis; oxidative phosphorylation; TCA cycle; oxidation of pyruvate -Oxidation of pyruvate; TCA cycle; oxidation of glucose to pyruvate; oxidative phosphorylation

Which of the following metabolic pathways produce(s) the most ATP, per glucose molecule metabolized, during cellular respiration?

Answer: The electron transport chain and oxidative phosphorylation -The electron transport chain and oxidative phosphorylation -Glycolysis -Fermentation -Substrate-level phosphorylation -Citric acid cycle

A small amount of ATP is made in glycolysis by which of the following processes?

Answer: Transfer of a phosphate group from a fragment of glucose to ADP by substrate-level phosphorylation -Transfer of a phosphate group from a fragment of glucose to ADP by substrate-level phosphorylation -Harnessing energy from the sun -Transport of electrons through a series of carriers -Transfer of electrons and hydrogen atoms to NAD+ -Attachment of a free inorganic phosphate (Pi) group to ADP to make ATP

Muscle tissues make lactate from pyruvate to do which of the following?

Answer: regenerate NAD+ - regenerate NAD+ -speed up the rate of glycolysis -get rid of pyruvate produced by glycolysis -utilize the energy in pyruvate -produce additional CO2 * Human muscle cells make ATP by lactic acid fermentation when oxygen is scarce. This allows them to regenerate NAD+ so that glycolysis can continue. On the cellular level, our muscle cells behave as facultative anaerobes. In such cells, pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes. Under aerobic conditions, pyruvate can be converted to acetyl CoA, and oxidation continues in the citric acid cycle via aerobic respiration. Under anaerobic conditions, lactic acid fermentation occurs: Pyruvate is diverted from the citric acid cycle, serving instead as an electron acceptor to recycle NAD+. To make the same amount of ATP, a facultative anaerobe has to consume sugar at a much faster rate when fermenting than when respiring.

During aerobic respiration, molecular oxygen (O2) is used for which of the following purposes?

At the end of the electron transport chain to accept electrons and form H2O * In aerobic respiration, the final electron acceptor is oxygen but in anaerobic respiration, the final acceptor is another molecule that is electronegative (although invariably less so than oxygen). Passage of electrons from NADH to the electron transport chain not only regenerates the NAD+ required for glycolysis but pays an ATP bonus when the stepwise electron transport from this NADH to oxygen drives oxidative phosphorylation. An even bigger ATP payoff comes from the oxidation of pyruvate in the mitochondrion, which is unique to respiration. Without an electron transport chain, the energy still stored in pyruvate is unavailable to most cells.

Cells must regulate their metabolic pathways so that they do not waste resources. What is the most common mechanism that regulates cellular respiration in most cells?

Feedback inhibition of glycolysis *Basic principles of supply and demand regulate the metabolic economy. A cell does not waste energy making more of a particular substance than it needs. The most common mechanism for this regulation is feedback inhibition. If the cell is working hard and its ATP concentration begins to drop, respiration speeds up. When there is plenty of ATP to meet demand, respiration slows down, sparing valuable organic molecules for other functions. Control is based mainly on regulating the activity of enzymes at strategic points in the catabolic pathway. One important switch is phosphofructokinase, the enzyme that catalyzes step 3 of glycolysis. This is the first step that commits the substrate irreversibly to the glycolytic pathway. By controlling the rate of this step, the cell can speed up or slow down the entire catabolic process.

Fermentation by itself produces no ATP but keeps glycolysis going, which produces a small amount of ATP. How does fermentation do this?

Fermentation oxidizes NADH to NAD+, which facilitates the production of ATP in glycolysis.

In which process is glucose oxidized to form two molecules of pyruvate?

Glycolysis

Most of the ATP in cellular respiration is produced by the process of chemiosmosis. How does this process produce ATP?

H+ flows across the inner mitochondrial membrane through the enzyme ATP synthase.

What is the role of oxygen in the electron transport chain?

It is reduced to form water.

After completion of the citric acid cycle, most of the usable energy from the original glucose molecule is in the form of __________.

NADH

During the energy payoff phase of glycolysis, __________.

NADH and ATP are produced

In what molecule(s) is the majority of the chemical energy from pyruvate transferred during the citric acid cycle?

NADH and FADH2

In preparing pyruvate to enter the citric acid cycle, which of the following steps occurs?

Pyruvate is oxidized and decarboxylated, and the removed electrons are used to reduce an NAD+ to an NADH.

Most of the electrons removed from glucose by cellular respiration are used for which of the following processes?

Reducing NAD+ to NADH in glycolysis and the citric acid cycle AND producing a proton gradient for ATP synthesis in the mitochondria.

Most of the NADH that delivers electrons to the electron transport chain comes from which of the following processes?

The citric acid cycle

Which part of the catabolism of glucose by cellular respiration requires molecular oxygen (O2) and produces CO2?

The combination of the citric acid cycle and electron transport

The ATP synthase in a human cell obtains energy for synthesizing ATP directly from which of the following processes?

The flow of H+ across the inner mitochondrial membrane through the ATP synthase enzyme

The energy from the electrons in NADH and FADH2 fuel what process in the electron transport chain?

The pumping of H+ across the cristae of the mitochondrion

What is the total production of ATP, NADH, and FADH2 in the citric acid cycle from one molecule of glucose?

Two ATP, six NADH, and two FADH2

Fermentation is essentially glycolysis plus an extra step in which pyruvate is reduced to form lactate or alcohol and carbon dioxide. This last step __________.

enables the cell to recycle the reduced NADH to oxidized NAD+

During the energy investment phase of glycolysis, __________.

glucose is phosphorylated before it is split into two three-carbon molecules

In the overall process of glycolysis and cellular respiration, __________ is oxidized and __________ is reduced.

glucose; oxygen

A molecule becomes more oxidized when it __________.

loses an electron