Chapter 10 Oxidative Respiration

Proton gradient

According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis?

NADPH

After 3-PGA is phosphorylated, it is reduced by _____.

shifts to a more electronegative atom.

An electron loses potential energy when it

correct statement

An enzyme is required in order for the reaction to occur.

carbon dioxide and water

Carbon dioxide and water are by-products of cellular respiration.

RuBP

Carbon fixation involves the addition of carbon dioxide to _____.

Glucose utilization would increase a lot. 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.

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?

Carbon dioxide

Into which molecule are all the carbon atoms in glucose ultimately incorporated during cellular respiration?

oxidative phosphorylation

It is possible to prepare vesicles from portions of the inner mitochondrial membrane. Which one of the following processes might still be carried on by this isolated inner membrane?

ATP levels would fall at first, decreasing the inhibition of PFK and increasing the rate of ATP production. 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.

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?

Oxygen

The final electron acceptor of electron transport chain that functions in aerobic oxidative phosphorylation is

Most of the free energy available from the oxidation of glucose remains in pyruvate, one of the products of glycolysis.

The free energy for the oxidation of glucose to CO2 and water is -686 kcal/mol and the free energy for the reduction of NAD+ to NADH is +53 kcal/mol. Why are only two molecules of NADH formed during glycolysis when it appears that as many as a dozen could be formed?

They convert carbon dioxide to sugar.

What is the biological significance of the light-independent reactions of photosynthesis?

The light-independent reactions turn CO2, a gas, into usable carbon in the form of sugars.

What is the importance of the light-independent reactions in terms of carbon flow in the biosphere?

Pyruvate

What is the oxidizing agent in the following reaction? Pyruvate + NADH + H+ -> Lactate + NAD+

Ionic The complete transfer of an electron from lithium to fluorine results in a stable compound in which both atoms have full outermost shells.

What kind of bond is formed when lithium and fluorine combine to form lithium fluoride?

reduced

When a compound accepts (gains) electrons, that compound becomes _________. Such a compound is often referred to as an electron acceptor.

oxidized

When a compound donates (loses) electrons, that compound becomes __________. Such a compound is often referred to as an electron donor.

reduced.

When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes

The pH of the matrix increases

When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?

The more electronegative atom is reduced, and energy is released

When electrons move closer to a more electronegative atom, what happens?

creation of a proton-motive force.

When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the

glycolysis, pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation, using an electron acceptor other than oxygen

Which catabolic processes may have been used by cells on ancient Earth before free oxygen became available?

Glycosis

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

Glucose

Which molecule is metabolized in a cell to produce energy "currency" in the form of ATP?

RuBP

Which molecule is regenerated in the regeneration phase of the Calvin cycle? Without regeneration of this molecule, the Calvin cycle would stop.

NADPH

Which of the following molecules is the primary product of photosystem I?

Each electron carrier alternates between being reduced and being oxidized.

Which of the following most accurately describes what is happening along the electron transport chain in the figure?

Protons

Which of the following particles can pass through the ATP synthase channel?

oxidative phosphorylation (chemiosmosis)

Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water?

NADH and FADH2 donate their electrons to the chain.

Which of the following statements about the electron transport chain is true?

The function of glycolysis is to begin catabolism by breaking glucose into two molecules of pyruvate, with a net yield of two ATP. Glycolysis is the first stage in cellular respiration and does not depend on the presence of oxygen.

Which of the following statements accurately describes the function of a metabolic pathway involved in cellular respiration?

The light-dependent reactions produce ATP and NADPH, which are then used by the light-independent reactions.

Which of the following statements best describes the relationship between the light-dependent and light-independent reactions of photosynthesis?

NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.

Which of the following statements describes NAD+?

The oxygen and hydrogen atoms in water have partial charges, but the molecule has a net charge of zero.

Which of the following statements is true of the bonds in a water molecule?

acetyl CoA

Which of these enters the citric acid cycle?

6 CO2 + 6 H2O → C6H12O6 + 6 O2

Which of these equations best summarizes photosynthesis?

FADH2 is a product of the citric acid cycle.

Which of these is NOT a product of glycolysis?

acetyl CoA

Which of these is NOT a product of the citric acid cycle?

ATP synthase phosphorylates ADP.

Which of these phosphorylates ADP to make ATP?

Fermentation

Which process is not part of the cellular respiration pathway that produces large amounts of ATP in a cell?

Photosynthesis

Which process produces oxygen?

The light-dependent reactions

Which set of reactions uses H2O and produces O2?

Electron transport and chemiosmosis

Which stage of glucose metabolism produces the most ATP?

Fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor. Electrons derived from the oxidation of FADH2 enter the electron transport chain at Complex II, farther down the chain than electrons from NADH (which enter at Complex I). This results in fewer H+ ions being pumped across the membrane for FADH2 compared to NADH, as this diagram shows. Thus, more ATP can be produced per NADH than FADH2.

Which statement best explains why more ATP is made per molecule of NADH than per molecule of FADH2?

Glycolysis

Which step of the cellular respiration pathway can take place in the absence of oxygen?

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.

Why is the citric acid cycle a cyclic pathway rather than a linear pathway?

The energy released as electrons are passed along the electron transport chain is used to pump protons into the thylakoid compartment.

_____ releases energy that is used to pump hydrogen ions from the stroma into the thylakoid compartment.

Photosystem II splits water into 1/2 O2, H+, and e- .

_____ splits water into 1/2 O2, H+, and e- .

NAD+

_______ is the compound that functions as the electron acceptor in glycolysis

correct statement

A bond must be broken between an organic molecule and phosphate before ATP can form.

has an increased chemical potential energy; it is primed to do cellular work.

A molecule that is phosphorylated

His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane.

A young animal has never had much energy. He is brought to a veterinarian for help and is sent to the animal hospital for some tests. There they discover his mitochondria can use only fatty acids and amino acids for respiration, and his cells produce more lactate than normal. Of the following, which is the best explanation of his condition?

all respiring cells, both prokaryotic and eukaryotic, using either oxygen or other electron acceptors.

Chemiosmotic ATP synthesis (oxidative phosphorylation) occurs in

The photosystems contain chlorophyll.

Chlorophyll can be found in _____

ATP will not be produced because there is no ADP and inorganic phosphate in the solution.

Chloroplast membrane vesicles are equilibrated in a simple solution of pH 5‎ . The solution is then adjusted to pH 8‎ . Which of the following conclusions can be drawn from these experimental conditions?

photosynthesis

Chloroplasts are the sites of photosynthesis.

molecular oxygen (O2)

During aerobic respiration, H2O is formed. Where does the oxygen atom for the formation of the water come from?

food → NADH → electron transport chain → oxygen

During aerobic respiration, electrons travel downhill in which sequence?

FADH2

During aerobic respiration, which of the following directly donates electrons to the electron transport chain at the lowest energy level?

retained in the two pyruvates.

During glycolysis, when each molecule of glucose is catabolized to two molecules of pyruvate, most of the potential energy contained in glucose is

Energized electrons from photosystem I are used to reduce NADP+.

Energized electrons from ____ are used to reduce NADP+.

mitochondrial intermembrane space

Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells?

Hydrogen, polar Hydrogen loses electrons to oxygen, which is more electronegative and thus pulls the electrons closer to itself in the water molecule.

Gaseous hydrogen burns in the presence of oxygen to form water: 2H2 + O2 → 2H2 O + energy Which molecule is oxidized and what kind of bond is formed?

glycolysis

Glycolysis occurs in the cytosol.

Two NADH molecules are produced by glycolysis

How many NADH are produced by glycolysis?

6

How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?

The individual's ATP production will not change significantly. Catabolism can harvest energy from fats in fatty tissue or from storage proteins or glycogen in the liver. As a result, glycolysis and cellular respiration continue to produce ATP during a fast. Read about the diversity of catabolism.

How will a healthy individual's ATP production change during an eight-hour fast?

Both electron transport and ATP synthesis would stop. Oxygen plays an essential role in cellular respiration because it is the final electron acceptor for the entire process. Without O2, mitochondria are unable to oxidize the NADH and FADH2 produced in the first three steps of cellular respiration, and thus cannot make any ATP via oxidative phosphorylation. In addition, without O2 the mitochondria cannot oxidize the NADH and FADH2 back to NAD+ and FAD, which are needed as inputs to the first three stages of cellular respiration.

How would anaerobic conditions (when no O2 is present) affect the rate of electron transport and ATP production during oxidative phosphorylation? (Note that you should not consider the effect on ATP synthesis in glycolysis or the citric acid cycle.)

The basic function of fermentation is the regeneration of NAD+, which allows continued ATP production by glycolysis. Fermentation occurs in the absence of oxygen and does not yield as much ATP. Read about fermentation.

Identify all correct statements about the basic function of fermentation.

The advantage of an electron transport chain is that a small amount of energy is released with the transfer of an electron between each pair of intermediates.

In cellular respiration, a series of molecules forming an electron transport chain alternately accepts and then donates electrons. What is the advantage of such an electron transport chain?

a proton gradient across a membrane.

In cellular respiration, the energy for most ATP synthesis is supplied by

pyruvate ... NADH

In fermentation _____ is reduced and _____ is oxidized.

2 (Takes 2 to produce 4)

In glycolysis there is a net gain of _____ ATP.

substrate-level phosphorylation A phosphate group is transferred from glyceraldehyde phosphate to ADP.

In glycolysis, ATP molecules are produced by _____.

glucose

In glycolysis, the carbon-containing compound that functions as the electron donor is _________

ATP

In glycolysis, what starts the process of glucose oxidation?

provide the energy that establishes the proton gradient

In mitochondria, exergonic redox reactions

to function as the final electron acceptor in the electron transport chain The only place that O2 participates in cellular respiration is at the end of the electron transport chain, as the final electron acceptor. Oxygen's high affinity for electrons ensures its success in this role. Its contributions to driving electron transport, forming a proton gradient, and synthesizing ATP are all indirect effects of its role as the terminal electron acceptor.

In mitochondrial electron transport, what is the direct role of O2?

lactate and NAD+

In muscle cells, fermentation produces _____.

3

In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules?

substrate-level phosphorylation

In the citric acid cycle, ATP molecules are produced by _____.

acetyl CoA, NADH, H+, and CO2.

In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid cycle. First, however, the pyruvate (1) loses a carbon, which is given off as a molecule of CO2, (2) is oxidized to form a two-carbon compound called acetate, and (3) is bonded to coenzyme A. These three steps result in the formation of

mitochondrion

Mitochondria are the sites of cellular respiration.

the citric acid cycle

Most CO2 from catabolism is released during

pyruvate

Once the electron donor in glycolysis gives up its electrons, it is oxidized to a compound called ________

correct statement

One of the substrates is a molecule derived from the breakdown of glucose.

oxygen

Oxygen is the final electron acceptor of cellular respiration.

glucose and oxygen

Photosynthesis produces glucose and releases oxygen into the atmosphere.

Cellular respiration and breathing differ in that cellular respiration is at the cellular level, whereas breathing is at the organismal level.

Select the correct statement about cellular respiration -Cellular respiration and breathing differ in that cellular respiration is at the cellular level, whereas breathing is at the organismal level. -Animals carry out cellular respiration whereas plants carry out photosynthesis. -Plants carry out cellular respiration only in organs such as roots that cannot carry out photosynthesis.

100%

Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?

the citric acid cycle

The citric acid cycle transfers electrons to NADH and FADH2.

the proton-motive force across the inner mitochondrial membrane.

The direct energy source that drives ATP synthesis during respiratory oxidative phosphorylation in eukaryotic cells is

incorrect statement

The enzymes involved in ATP synthesis must be attached to a membrane to produce ATP.

NADH, FADH2, and O2

The figure shows the electron transport chain. Which of the following is the combination of substances that is initially added to the chain?

H+ concentration across the membrane holding ATP synthase

The immediate energy source that drives ATP synthase during oxidative phosphorylation is the _____

water ... NADPH

The light reactions of photosynthesis use _____ and produce _____.

loses electrons and loses potential energy.

The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction

incorrect statement

The phosphate group added to ADP to make ATP comes from free inorganic phosphate ions.

NADH

The reduced form of the electron acceptor in glycolysis is _______

an endergonic reaction coupled to an exergonic process.

The synthesis of ATP by oxidative phosphorylation, using the energy released by movement of protons across the membrane down their electrochemical gradient, is an example of

False The chemiosmotic hypothesis states that the flow of electrons through an electron transport chain generates a proton gradient that leads to the synthesis of ATP.

True or false? The chemiosmotic hypothesis states that the synthesis of ATP generates a proton gradient that leads to electron flow through an electron transport chain.

True The water molecules are split to replenish electrons in photosystem II, leaving behind protons, which are used to generate a proton gradient for the formation of ATP, and oxygen, which is released as a by-product.

True or false? The light-dependent reactions of photosynthesis use water and produce oxygen.

True

True or false? The potential energy in an ATP molecule is derived mainly from its three phosphate groups.

True

True or false? The reactions that generate the largest amounts of ATP during cellular respiration take place in the mitochondria.

False The region of ATP synthase that catalyzes ATP production protrudes out of, but does not span, the chloroplast membrane; the region that spans the membrane is an ion channel through which protons can pass.

True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplast membrane.

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. 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+.

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?

The Calvin cycle occurs in the stroma.

Where does the Calvin cycle occur?

Photophosphorylation

Which term describes ATP production resulting from the capture of light energy by chlorophyll?

Electronegativity

Which term describes the degree to which an element attracts electrons?

Anion and cation

Which terms describe two atoms when they form a bond in which electrons are completely transferred from one atom to the other?

Electrons are being moved from atoms that have a lower affinity for electrons (such as C) to atoms with a higher affinity for electrons (such as O).

Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and water release free energy?

Red has a longer wavelength than green.

_____ has a longer wavelength than _____.