Chapter 9 BIOL 1107

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

100%

how many NADH are produced by glycolosis?

2

in glycolysis there is a net gain of ___ ATP

2

In the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis? four ATP none, because all of the available energy remains in either lactate or ethanol none, because in the absence of oxygen, no ATP can be made two ATP up to 30 ATP

2 ATP

starting with one molecule of glucose, the energy-containing products of glycolysis are___

2 NADH, 2 pyruvate, and 2 ATP

Which stage of glucose metabolism produces the most ATP? 1. Glycolysis 2. Electron transport and chemiosmosis 3. Fermentation of pyruvate to lactate 4. Krebs cycle

2. Electron transport and chemiosmosis

Starting with citrate, which of the following combinations of products would result from three acetyl CoA molecules entering the citric acid cycle (see the accompanying figure)?

3 ATP, 6 CO2, 9 NADH, and 3 FADH2

approx. how many molecules of ATP are produced from the complete oxidation of one molecule of glucose (C6H12O6) in aerobic cellular respiration?

30-32

For each mole of glucose (C6H12O6) oxidized by cellular respiration, how many moles of CO2 are released in the citric acid cycle (see the accompanying figure)?

4

in glycolysis, what starts the process of glucose oxidation

ATP

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.) It takes more energy to make ATP from ADP and Pi using FADH2 than using NADH. FADH2 is made only in the citric acid cycle while NADH is made in glycolysis, acetyl CoA formation, and the citric acid cycle. There is more NADH than FADH2 made for every glucose that enters cellular respiration. The H+ gradient made from electron transport using NADH is located in a different part of the mitochondrion than the H+ gradient made using FADH2. Fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor.

Both electron transport and ATP synthesis would stop.

which of the listed statements describes the results of the following reaction. C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy

C6H12O6 is oxidized and O2 is reduced.

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

CO2

Which of these is NOT a product of glycolysis? FADH2 ATP pyruvate NADH

FADH2

NADH and FADH2 are both electron carriers that donate their electrons to the electron transport chain. The electrons ultimately reduce O2 to water in the final step of electron transport. However, the amount of ATP made by electrons from an NADH molecule is greater than the amount made by electrons from an FADH2 molecule. Which statement best explains why more ATP is made per molecule of NADH than per molecule of FADH2?

Fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor.

the immediate energy source that drives ATP syntheses by ATP synthase during oxidative phosphorylation is the

H+ concentration across the membrane holding ATP synthase

Which of the following statements about NAD+ is true? NAD+ has more chemical energy than NADH. NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle. NAD+ can donate electrons for use in oxidative phosphorylation. In the absence of NAD+, glycolysis can still function.

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

Following glycolysis and the citric acid cycle, but before the electron transport chain and oxidative phosphorylation, the carbon skeleton of glucose has been broken down to CO2 with some net gain of ATP. Most of the energy from the original glucose molecule at that point in the process, however, is in the form of _____.

NADH

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

NADH and FADH2 donate their electrons to the chain.

If pyruvate oxidation is blocked, what will happen to the levels of oxaloacetate and citric acid in the citric acid cycle shown in the accompanying figure?

Oxaloacetate will accumulate and citric acid will decrease.

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?

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.

Which of the following statements is not true of most cellular redox reactions? The electron acceptor is reduced. Changes in potential energy can be released as heat. The reactant that is oxidized loses electrons. A hydrogen atom is transferred to the atom that loses an electron.

a hydrogen atom is transferred to the atom that loses an electron

The oxygen consumed during cellular respiration is involved directly in which process or event?

accepting electrons at the end of the ETC

Which of these enters the citric acid cycle? G3P acetyl CoA pyruvate glucose NADH + H+

acetyl CoA

Which of these is NOT a product of the citric acid cycle? ATP FADH2 NADH + H+ acetyl CoA CO2

acetyl CoA

Which one of the following is formed by the removal of a carbon (as CO2) from a molecule of pyruvate?

acetyl CoA

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. The three listed steps result in the formation of _____.

acetyl CoA, NADH, and CO2

even though plants cells photosynthesize, they still use their mitochondria for oxidation of pyruvate. This will occur in ____.

all cells all the time

which kind of metabolic poison would most directly interfere with glycolysis?

an agent that closely mimics the structure of glucose, but is not metabolized

Which terms describe two atoms when they form a bond in which electrons are completely transferred from one atom to the other? Proton and electron. Polar and nonpolar. Anion and cation. Ionic and covalent.

anion and cation

A cell has enough available ATP to meet its needs for about 30 seconds. What is likely to happen when an athlete exhausts his or her ATP supply?

catabolic processes are activated that generate more APT

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. Plants carry out cellular respiration only in organs such as roots that cannot carry out photosynthesis. Animals carry out cellular respiration whereas plants carry out photosynthesis.

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

New biosensors, applied like a temporary tattoo to the skin, can alert serious athletes that they are about to "hit the wall" and find it difficult to continue exercising. These biosensors monitor lactate, a form of lactic acid, released in sweat during strenuous exercise. Which of the statements below is the best explanation of why athletes would need to monitor lactate levels? During aerobic respiration, muscles cells produce too much lactate which causes a rise in the pH of the muscle cells, thus athletes must consume increased amounts of sports drinks, high in electrolytes, to buffer the pH. During anaerobic respiration, muscle cells receive too little oxygen and begin to convert lactate to pyruvate (pyruvic acid), thus athletes experience cramping and fatigue. During anaerobic respiration, lactate levels increase when muscles cells need more energy, however muscles cells eventually fatigue, thus athletes should modify their activities to increase aerobic respiration. During aerobic respiration, muscle cells cannot produce enough lactate to fuel muscle cell contractions and muscles begin to cramp, thus athletic performance suffers.

during anaerobic respiration, lactate levels increase when muscles cells need more energy, however muscles cells eventually fatigue, thus athletes should modify their activities to increase aerobic respiration

Which term describes the degree to which an element attracts electrons? Polarity. Electronegativity. Oxidation. Reduction.

electronegativty

In chemiosmosis, what is the most direct source of energy that is used to convert ADP +Pi to ATP?

energy released from movement of protons through ATP synthase, down their electrochemical gradient

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

fermentation

Which molecule is metabolized in a cell to produce energy for performing work?

glucose

during aerobic respiration, electrons travel downhill in which sequence?

glucose --> NADH --> ETC --> O2

in the combined processes of glycolysis and cellular respiration, what is consumed and what is produced?

glucose is consumed, and CO2 is produced

Which step of the cellular respiration pathway can take place in the absence of oxygen? Glycolysis Fermentation Electron transport chain Krebs cycle

glycolysis

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

glycolysis

which of the following normally occurs regardless of whether or not O2 is present citric acid cycle fermentation oxidative phosphorylation (chemiosmosis) glycolysis

glycolysis

which of the following occurs in the cytosol of a eukaryotic cell? glycolysis and fermentation oxidation of pyruvate to acetyl CoA citric acid cycle fermentation and chemiosmosis

glycolysis and fermintation

the chemiosmotic hypothesis is an important concept in our understanding of cellular metabolism in general because it explains ___.

how ATP is synthesized by a proton motive force

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?

hydrogen, polar

substrate level phosphorylation occurs

in both glycolysis and the citric acid cycle

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? 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 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. Oxygen is required to convert glucose to pyruvate in glycolysis. Without oxygen, no pyruvate can be made

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

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

ionic

the electron transport chain ____

is a series of redox reactions

why is glycolysis considered to one of the first metabolic pathways to have evolved

it does not involve organelles or specialized structure, does not require oxygen, and is present in most organisms

A glucose molecule is completely broken down to carbon dioxide and water in glycolysis and the citric acid cycle, but together these two processes yield only a few molecules of ATP. What happened to most of the energy that the cell obtains from the oxidation of glucose?

it is stored in NADH and FADH2

Which of the following describes the process of glycolysis? Glycolysis occurs in the mitochondria. It converts one glucose molecule to two molecules of pyruvate and carbon dioxide. Glycolysis produces 30 ATP from each molecule of glucose. It represents the first stage in the chemical oxidation of glucose by a cell. It requires ATP and NADH.

it represents the first stage in the chemical oxidation of glucose by a cell

you have a friend who lost 7kg (15lbs) of fat on a regimen of strict diet and exercise. How did the fat leave his body?

it was release as CO2 and H2O

In muscle cells, fermentation produces _____

lactate and NAD+

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

loses electrons and loses potential energy

where are the proteins of the ETC located

mitochondrial inner matrix

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

mitochondrial intermembrane space

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

molecular oxygen (O2)

Carbon dioxide (CO2) is released during which of the following stages of cellular respiration?

oxidation of pyruvate to acetyl CoA and the citric acid cycle

one function of both alcohol fermentation and lactic acid fermentation is to

oxidize NADH to NAD+

When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes _____.

oxidized

Which of the following statements is true of the bonds in a water molecule? There is equal sharing of the electrons between the oxygen atom and the two hydrogen atoms, and the net charge is zero. The electron in each hydrogen atom is completely transferred to the oxygen atom, and each hydrogen atom has a net charge of +1. Oxygen acts as the electron acceptor and is oxidized. Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero.

oxygen holds electrons more tightly than hydrogen does, and the net charge is zero

In fermentation _____ is reduced and _____ is oxidized.

pyruvate ... NADH

Among the products of glycolysis, which compounds contain energy that can be used by other biological reactions?

pyruvate, ATP, and NADH

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

reduced

in glycolysis, ATP molecules are produced by

substrate- level phosphorylation

in the citric acid cycle, ATP molecules are produced by ___

substrate-level phosphorylation

Identify all correct statements about basic function of fermentation

the basic function of fermentation is the regeneration of NAD+, which allows continued ATP production by glycolysis

In most cells, not all of the carbon compounds that participate in glycolysis and the citric acid cycle are converted to carbon dioxide by cellular respiration. What happens to the carbon in these compounds that does not end up as CO2?

the carbon compounds are removed from these processes to serve as building blocks for other complex molecules

Which of the following statements about the chemiosmotic synthesis of ATP is correct? 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.

the chemiosmotic synthesis of ATP requires that the electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane

Most of the CO2 from the catabolism of glucose is released during _____.

the citric acid cycle

Which of the following events takes place in the electron transport chain? the extraction of energy from high-energy electrons remaining from glycolysis and the citric acid cycle the breakdown of glucose into two pyruvate molecules the breakdown of an acetyl group to carbon dioxide substrate-level phosphorylation

the extraction of energy from high-energy electrons remaining from glycolysis and the citric acid cycle

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

the individual's ATP will not change significantly

Which one of the following statements about the redox reactions of the electron transport chain is correct? The oxidation of NADH is directly coupled to the reduction of oxygen to water. 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 with the synthesis of ATP. The redox reactions of the electron transport chain are directly coupled to the movement of protons across a membrane.

the redox reactions of the electron transport chain are directly coupled to the movement of protons across a membrane

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

to function as the final electron acceptor in the electron transport chain

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.

true

in glycolysis, for each molecule of glucose oxidized to pyruvate ___

two molecules of ATP are used and four molecules of ATP are produced