Biology Mastering chapter 7

A molecule that is phosphorylated has increased chemical potential energy that may be used to do cellular work. has been reduced as a result of a redox reaction involving the loss of an inorganic phosphate. has been oxidized as a result of a redox reaction involving the gain of an inorganic phosphate. has a decreased chemical energy and is less likely to provide energy for cellular work.

a

Approximately how many molecules of ATP are produced from the complete oxidation of two molecules of glucose (C6H12O6) in aerobic cellular respiration? 2 4 15 60-64 30-32

D

Part complete Which of the following occur(s) in mitochondria? fermentation and chemiosmosis glycolysis and oxidation of pyruvate to acetyl CoA glycolysis and fermentation fermentation and oxidative phosphorylation oxidation of pyruvate to acetyl CoA and the citric acid cycle

E

True or false? The reactions that generate the largest amounts of ATP during cellular respiration take place in the mitochondria. View Available Hint(s) True False

T Glycolysis takes place in the cytoplasm, whereas the Krebs cycle and the electron transport chain, which generate the largest amounts of ATP during cellular respiration, take place in the mitochondria.

True or false? The potential energy in an ATP molecule is derived mainly from its three phosphate groups. View Available Hint(s) True False

T: The three phosphate groups in an ATP molecule carry negative charges that strongly repel each other and give ATP a large amount of potential energy.

Which process is not part of the cellular respiration pathway that produces large amounts of ATP in a cell? View Available Hint(s) Glycolysis Electron transport chain Krebs cycle Fermentation

fermentation

Which molecule is metabolized in a cell to produce energy "currency" in the form of ATP? View Available Hint(s) Carbon dioxide ADP Glucose Phosphate

glucose- used to produce high energy ATP

Carbon dioxide (CO2) is released during which of the following stages of cellular respiration? glycolysis and the citric acid cycle oxidation of pyruvate to acetyl CoA and the citric acid cycle glycolysis and the oxidation of pyruvate to acetyl CoA the citric acid cycle and oxidative phosphorylation

B

During glycolysis, when each molecule of glucose is catabolized to two molecules of pyruvate, most of the potential energy contained in glucose is released as heat. retained in the two pyruvates. transferred to ADP, forming ATP. stored in the NADH produced.

B

In the oxidation of pyruvate to acetyl CoA, one carbon atom is released as CO2. However, the oxidation of the remaining two carbon atoms—in acetate—to CO2 requires a complex, eight-step pathway—the citric acid cycle. Consider four possible explanations for why the last two carbons in acetate are converted to CO2 in a complex cyclic pathway rather than through a simple, linear reaction. Use your knowledge of the first three stages of cellular respiration to determine which explanation is correct. View Available Hint(s) -More ATP is produced per CO2 released in cyclic processes than in linear processes. -It is easier to remove electrons and produce CO2 from compounds with three or more carbon atoms than from a two-carbon compound such as acetyl CoA. -Redox reactions that simultaneously produce CO2 and NADH occur only in cyclic processes. -Cyclic processes, such as the citric acid cycle, require a different mechanism of ATP synthesis than linear processes, such as glycolysis.

B

Which of the following indicates a primary path by which electrons travel downhill energetically during aerobic respiration? glucose → glycolysis → citric acid cycle → NADH → ATP glucose → NADH → electron transport chain → oxygen glucose → pyruvate → acetyl CoA → ATP → oxygen glucose → citric acid cycle → ATP → NAD+ glucose → glycolysis → electron transport chain → NADH → ATP

B

Among the products of glycolysis, which compounds contain energy that can be used by other biological reactions? View Available Hint(s) O2 only pyruvate, ATP, and NADH ATP and NADH only ATP only NADH only pyruvate and ATP only CO2 only

B ATP is the main product of cellular respiration that contains energy that can be used by other cellular processes. Some ATP is made in glycolysis. In addition, the NADH and pyruvate produced in glycolysis are used in subsequent steps of cellular respiration to make even more ATP.

In liver cells, the inner mitochondrial membranes are about five times the area of the outer mitochondrial membranes. What purpose must this serve? It increases the surface area for oxidative phosphorylation. It increases the surface area for the citric acid cycle. It increases the surface area for glycolysis. It increases the surface area for substrate-level phosphorylation.

A

Redox (oxidation-reduction) reactions in glycolysis 1. When a compound donates (loses) electrons, that compound becomes ________. Such a compound is often referred to as an electron donor. 2. When a compound accepts (gains) electrons, that compound becomes ________. Such a compound is often referred to as an electron acceptor. 3. In glycolysis, the carbon-containing compound that functions as the electron donor is _________. 4. Once the electron donor in glycolysis gives up its electrons, it is oxidized to a compound called ___________. 5. ________ is the compound that functions as the electron acceptor in glycolysis. 6. The reduced form of the electron acceptor in glycolysis is ___________.

1. When a compound donates (loses) electrons, that compound becomes oxidized. Such a compound is often referred to as an electron donor. 2. When a compound accepts (gains) electrons, that compound becomes reduced. Such a compound is often referred to as an electron acceptor. 3. In glycolysis, the carbon-containing compound that functions as the electron donor is glucose. 4. Once the electron donor in glycolysis gives up its electrons, it is oxidized to a compound called pyruvate. 5. NAD+ is the compound that functions as the electron acceptor in glycolysis. 6. The reduced form of the electron acceptor in glycolysis isNADH.

The direct energy source that drives ATP synthesis during respiratory oxidative phosphorylation in eukaryotic cells is the proton-motive force across the inner mitochondrial membrane. the thermodynamically favorable flow of electrons from NADH to the mitochondrial electron transport carriers. the thermodynamically favorable transfer of phosphate from glycolysis and the citric acid cycle intermediate molecules of ADP. the final transfer of electrons to oxygen. oxidation of glucose to CO2 and water.

A

Why are carbohydrates and fats considered high-energy foods? They have a large number of electrons associated with hydrogen. They are easily reduced. They have few nitrogen atoms. They have a lot of carbon atoms bound together by single covalent bonds. They have a lot of oxygen atoms.

A

Under anaerobic conditions (a lack of oxygen), glycolysis continues in most cells despite the fact that oxidative phosphorylation stops, and its production of NAD+ (which is needed as an input to glycolysis) also stops. The diagram illustrates the process of fermentation, which is used by many cells in the absence of oxygen. In fermentation, the NADH produced by glycolysis is used to reduce the pyruvate produced by glycolysis to either lactate or ethanol. Fermentation results in a net production of 2 ATP per glucose molecule. Diagram showing the process of fermentation. Two pyruvate molecules are formed from one glucose molecule during glycolysis releasing energy enough to turn 2 ADP and 2 inorganic phosphates into 2 ATP.,2 NAD plus being reduced to 2 NADH as well. 2 pyruvate molecules are reduced by 2 NADH and 2 H plus to yield 2 lactate molecules and 2 NAD plus. This NAD plus is used in glycolysis, whereas NADH released after the glycolysis is used to turn pyruvate into lactate. During strenuous exercise, anaerobic conditions can result if the cardiovascular system cannot supply oxygen fast enough to meet the demands of muscle cells. Assume that a muscle cell's demand for ATP under anaerobic conditions remains the same as it was under aerobic conditions. What would happen to the cell's rate of glucose utilization? View Available Hint(s) Glucose utilization would increase a lot. Glucose utilization would increase a little. Glucose utilization would remain the same. Glucose utilization would decrease a little. Glucose utilization would decrease a lot.

A ATP made during fermentation comes from glycolysis, which produces a net of only 2 ATP per glucose molecule. In contrast, aerobic cellular respiration produces about 30 ATP per glucose molecule. To meet the same ATP demand under anaerobic conditions as under aerobic conditions, a cell's rate of glycolysis and glucose utilization must increase about 15-fold.

Under anaerobic conditions (a lack of oxygen), the conversion of pyruvate to acetyl CoA stops. Which of these statements is the correct explanation for this observation? View Available Hint(s) In the absence of oxygen, electron transport stops. NADH is no longer converted to NAD+, which is needed for the first three stages of cellular respiration. Oxygen is required to convert glucose to pyruvate in glycolysis. Without oxygen, no pyruvate can be made. Oxygen is an input to acetyl CoA formation. ATP is needed to convert pyruvate to acetyl CoA. Without oxygen, no ATP can be made in oxidative phosphorylation.

A NAD+ couples oxidative phosphorylation to acetyl CoA formation. The NAD+ needed to oxidize pyruvate to acetyl CoA is produced during electron transport. Without O2, electron transport stops, and the oxidation of pyruvate to acetyl CoA also stops because of the lack of NAD+.

Which of the following best describes the main purpose of the combined processes of glycolysis and cellular respiration? View Available Hint(s) transforming the energy in glucose and related molecules in a chemical form that cells can use for work catabolism of sugars and related compounds the breakdown of glucose to carbon dioxide and water breaking down ATP so that ADP and P can be reused producing complex molecules from chemical building blocks

A: The energy made available during cellular respiration is coupled to the production of ATP, the basic energy currency that cells use for work.

Which stage of glucose metabolism produces the most ATP? View Available Hint(s) Fermentation of pyruvate to lactate Electron transport and chemiosmosis Glycolysis Krebs cycle

B Electron transport and chemiosmosis (oxidative phosphorylation) can yield around 26 molecules of ATP.

What is the proton-motive force? the force that moves hydrogen to NAD+ the force required to remove an electron from hydrogen the force provided by a transmembrane hydrogen ion gradient the force that moves hydrogen into the intermembrane space the force that moves hydrogen into the mitochondrion

C

When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the NAD+ molecule becomes hydrolyzed. redoxed. reduced. dehydrogenated. oxidized.

C

Where in mitochondria is the enzyme ATP synthase localized? outer membrane electron transport chain inner membrane mitochondrial matrix

C

Which of the following statements about the chemiosmotic synthesis of ATP is correct? View Available Hint(s) The energy for production of ATP from ADP comes directly from a gradient of electrons across the inner mitochondrial membrane. Oxygen participates directly in the reaction that makes ATP from ADP and P. The chemiosmotic synthesis of ATP requires that the electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane. The chemiosmotic synthesis of ATP occurs only in eukaryotic cells because it occurs in mitochondria. Chemiosmotic ATP synthesis requires oxygen.

C Chemiosmosis uses the energy of a proton gradient to make ATP; the proton gradient is formed by coupling the energy produced by electron transport with movement of protons across the membrane.

Part complete Which of the following statements about the electron transport chain is true? View Available Hint(s) The electron transport chain is the first step in cellular respiration. Water is the last electron acceptor. NADH and FADH2 donate their electrons to the chain. Electrons gain energy as they move down the chain.

C: The electrons lose energy as they move down the chain, and this energy is used to create a proton gradient that drives the synthesis of ATP.

Into which molecule are all the carbon atoms in glucose ultimately incorporated during cellular respiration? View Available Hint(s) ATP Carbon dioxide Water NADH

CO2: All of the carbon atoms in glucose are incorporated into carbon dioxide: Two molecules are formed as pyruvate is converted to acetyl CoA, and four molecules are formed during the Krebs cycle.

Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells? outer mitochondrial membrane inner mitochondrial membrane cytosol mitochondrial intermembrane space mitochondrial matrix

D

Glycolysis results in a net production of which of the following from each molecule of glucose? 4 NADH, 2 pyruvate, and 4 ATP 6 CO2, 2 NADH, 2 pyruvate, and 2 ATP 6 CO2, 2 pyruvate, and 30 ATP 2 NADH, 2 pyruvate, and 2 ATP 2 NAD+, 2 pyruvate, and 2 ATP

D

One primary function of both alcohol fermentation and lactic acid fermentation is to reduce FADH2 to FAD+. reduce FAD+ to FADH2. reduce NAD+ to NADH. oxidize NADH to NAD+.

D

The primary role of oxygen in cellular respiration is to serve as an acceptor for released carbon, forming CO2. combine with acetyl CoA, forming pyruvate. donate high energy electrons to the electron transport chain. serve as an acceptor for electrons and hydrogen, forming water.

D

Why is glycolysis considered to be one of the first metabolic pathways to have evolved? It produces much less ATP than does oxidative phosphorylation. It is found in prokaryotic cells but not in eukaryotic cells. It relies on chemiosmosis, which is a metabolic mechanism present only in prokaryotic cells. It does not involve organelles or specialized structures, does not require oxygen, and is present in most organisms.

D

The complete oxidation of glucose in aerobic respiration occurs through which of the following sequence of metabolic reactions? - glucose → citric acid cycle → glycolysis → pyruvate oxidation → electron transport chain -glucose → pyruvate oxidation → citric acid cycle → glycolysis → electron transport chain -glucose → pyruvate oxidation → glycolysis → electron transport chain → citric acid cycle - glucose → glycolysis → citric acid cycle → pyruvate oxidation → electron transport chain - glucose → glycolysis → pyruvate oxidation → citric acid cycle → electron transport chain

E

Which metabolic pathway is common to both cellular respiration and fermentation? the citric acid cycle the oxidation of pyruvate to acetyl CoA oxidative phosphorylation chemiosmosis glycolysis

E

Which of the following occur(s) in the cytosol of a eukaryotic cell? fermentation and chemiosmosis oxidation of pyruvate to acetyl CoA citric acid cycle oxidative phosphorylation glycolysis and fermentation

E

Which one of the following statements about the redox reactions of the electron transport chain is correct? View Available Hint(s) The oxidation of NADH is directly coupled to the reduction of oxygen to water. The redox reactions of the electron transport chain are directly coupled with the synthesis of ATP. The electron transport chain takes electrons from water and gives them to oxygen. NADH gains electrons in the initial reaction of the electron transport chain. The redox reactions of the electron transport chain are directly coupled to the movement of protons across a membrane.

E The reduction and oxidation of electron carriers in the electron transport chain provide the energy to move protons across a membrane against the chemical gradient of protons.

During aerobic respiration, which of the following directly donates electrons to the electron transport chain at the highest energy level? FADH2 FAD ATP NAD+ NADH

F

Which step of the cellular respiration pathway can take place in the absence of oxygen? View Available Hint(s) Electron transport chain Krebs cycle Fermentation Glycolysis

Glycolysis can take place in the absence of oxygen; its product, pyruvate, enters the cellular respiration pathway or undergoes fermentation depending on the availability of oxygen.

glucose oxygen pyruvate ATP water which one enters purple box

O2

-The enzymes involved in ATP synthesis must be attached to a membrane to produce ATP. -One of the substrates is a molecule derived from the breakdown of glucose.The phosphate group added to -ADP to make ATP comes from free inorganic phosphate ions. -An enzyme is required in order for the reaction to occur. -A bond must be broken between an organic molecule and phosphate before ATP can form. True/ false of substrate-level phosphorylation in glycolysis

correct statements One of the substrates is a molecule derived from the breakdown of glucose. An enzyme is required in order for the reaction to occur. A bond must be broken between an organic molecule and phosphate before ATP can form. incorrect statements The enzymes involved in ATP synthesis must be attached to a membrane to produce ATP. The phosphate group added to ADP to make ATP comes from free inorganic phosphate ions. In substrate-level phosphorylation, an enzyme transfers a phosphate group from one molecule (an intermediate in the breakdown of glucose to pyruvate) to ADP to form ATP. This is very different from the mechanism of ATP synthesis that takes place in oxidative phosphorylation.

The rate of cellular respiration is regulated by its major product, ATP, via feedback inhibition. As the diagram shows, high levels of ATP inhibit phosphofructokinase (PFK), an early enzyme in glycolysis. As a result, the rate of cellular respiration, and thus ATP production, decreases. Feedback inhibition enables cells to adjust their rate of cellular respiration to match their demand for ATP. Simple diagram showing glycolosis, the citric acid cycle, and oxidative phophorylation. High levels of ATP produced by these processes inhibits phosphofructokinase, an early enzyme in glycolosis. Suppose that a cell's demand for ATP suddenly exceeds its supply of ATP from cellular respiration. Which statement correctly describes how this increased demand would lead to an increased rate of ATP production? View Available Hint(s) ATP levels would rise at first, increasing the inhibition of PFK and increasing the rate of ATP production. ATP levels would fall at first, increasing the inhibition of PFK and increasing the rate of ATP production. ATP levels would rise at first, decreasing the inhibition of PFK and increasing the rate of ATP production. ATP levels would fall at first, decreasing the inhibition of PFK and increasing the rate of ATP production.

d An increased demand for ATP by a cell will cause an initial decrease in the level of cellular ATP. Lower ATP decreases the inhibition of the PFK enzyme, thus increasing the rate of glycolysis, cellular respiration, and ATP production. It is the initial decrease in ATP levels that leads to an increase in ATP production.