Chapter 9 Mastering Biology

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

fermentation

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

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

glucose

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

glucose

Yeast cells that have defective mitochondria incapable of respiration will be able to grow by catabolizing which of the following carbon sources for energy?

glucose

What molecules belong in space A and B?

glucose and oxygen

What process occurs in Box A?

glycolysis

Which of the following normally occurs regardless of whether or not oxygen (O2) is present?

glycolysis

Which of the following occurs in the cytosol of a eukaryotic cell?

glycolysis and fermentation

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

oxidized

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

oxidized

What variable responded to thyroid hormone level (the independent variable), and what are the units for this variable?

oxygen consumption rate of liver cells, in nmol O2/min • mg cells

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

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

What process occurs in structure H?

photosynthesis

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

pyruvate

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

pyruvate

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

Based on what you know about mitochondrial electron transport and heat production, predict which rats had the highest body temperature, and which had the lowest body temperature.

rats with elevated thyroid hormone had the highest body temperature; rats with low thyroid hormone had the lowest

Sort the following items according to whether they are reactants or products in the anaerobic reduction of pyruvate during lactic acid fermentation. Drag each item to the appropriate bin.

reactants: pyruvate, NADH Products: lactate, NAD+

In glycolysis, ATP molecules are produced by _____.

substrate-level phosphorylation

Do the results in the graph support the researchers' hypothesis?

Yes; cells that were exposed to elevated thyroid hormone levels showed increased oxygen consumption, indicating that the efficiency of the electron transport chain was reduced

Which of the following statements is not true of most cellular redox reactions?

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

Drag the labels on the left to show the net redox reaction in acetyl CoA formation and the citric acid cycle. Note that two types of electron carriers are involved.

a) CO2 (b) NADH (c) FAD (d)FADH2

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

carbon dioxide

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

glucose is consumed, and carbon dioxide is produced

What would happen to the cell's rate of glucose utilization?

glucose utilization would increase a lot

During aerobic respiration, electrons travel downhill in which sequence?

glucose → NADH → electron transport chain oxygen

What molecules belong in spaces E and F?

carbon dioxide and water

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 ATP

Which cell type(s) had the highest rate of oxygen consumption?

cells from rats with elevated thyroid hormone

Which cell type(s) had the lowest rate of oxygen consumption?

cells from rats with low thyroid hormone

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

glycolysis

For each glucose that enters glycolysis, _____ NADH + H+ are produced by the citric acid cycle.

6

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

30-32

_____ is the compound that functions as the electron acceptor in glycolysis.

NAD+

Starting with one molecule of glucose, the energy-containing products of glycolysis are _____.

2 NADH, 2 pyruvate, and 2 ATP

In cellular respiration, most ATP molecules are produced by _____.

oxidative phosphorylation

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

100%

If a cell is able to synthesize 30 ATP molecules for each molecule of glucose completely oxidized to carbon dioxide and water, approximately how many ATP molecules can the cell synthesize for each molecule of pyruvate oxidized to carbon dioxide and water?

12

For each glucose that enters glycolysis, _____ acetyl CoA enter the citric acid cycle.

2

How many NADH are produced by glycolysis?

2

In glycolysis there is a net gain of _____ ATP.

2

Assuming that the y-axis tick marks will be separated by 1.0 (0.0, 1.0, 2.0, and so on), what is the largest value that should appear on the y-axis?

9.0

Drag the labels from the left (which represent numbers of carbon atoms) onto the diagram to identify the number of carbon atoms in each intermediate in acetyl CoA formation and the citric acid cycle. Labels may be used more than once.

A) 2 C B) 6 C C) 6 C D) 5 C E) 4 C F) 4 C G) 4 C H) 4 C I) 4 C

In glycolysis, what starts the process of glucose oxidation?

ATP

Which statement correctly describes how this increased demand would lead to an increased rate of ATP production?

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

Structure A is _____.

ATP synthase

In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of _____.

ATP, CO2, and ethanol (ethyl alcohol)

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

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

FADH2

Which of these is NOT a product of glycolysis?

FADH2

Match each product of pyruvate metabolism with the condition under which it is produced. Drag each item to the appropriate bin.

Lactate: fermentation in human muscle Ethanol: fermentation in yeast and bacteria Acetyl CoA: aerobic oxidation

Which of the following statements about NAD+ is true?

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

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

The reduced form of the electron acceptor in glycolysis is _____.

NADH

Which electron carrier(s) function in the citric acid cycle?

NADH and FADH2

During electron transport, energy from _____ is used to pump hydrogen ions into the _____.

NADH and FADH2 ... intermembrane space

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

NADH and FADH2 donate their electrons to the chain

Sort the statements into the appropriate bin depending on whether or not they correctly describe some aspect 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.

Sort the labels into the correct bin according to the effect that gramicidin would have on each process.

Remains the same: proton pumping rate, electron transport rate, rate of oxygen uptake Decreases (or goes to zero): Rate of ATP synthesis, size of the proton gradient

Sort the statements into the appropriate bin depending on whether or not they correctly describe some aspect of substrate-level phosphorylation in glycolysis. 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.

Drag the labels on the left onto the diagram to identify the compounds that couple each stage. Labels may be used once, more than once, or not at all.

a. pyruvate b. NADH c. NAD+ d. NADH e. NAD+

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

accepting electrons at the end of the electron transport chain

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

The primary role of oxygen in cellular respiration is to _____.

act as an acceptor for electrons and hydrogen, forming water

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

all cells all the time

After the disruption, when electron transfer and ATP synthesis still occur, what must be present?

all of the electron transport proteins and ATP synthase

High levels of citric acid inhibit the enzyme phosphofructokinase, a key enzyme in glycolysis. Citric acid binds to the enzyme at a different location from the active site. This is an example of _____.

allosteric regulation

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

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

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 _____.

an endergonic reaction coupled to an exergonic reaction

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

anion and cation

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.)

both electron transport and ATP synthesis would stop

Which stage of glucose metabolism produces the most ATP?

electron transport and chemiosmosis

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

electronegativity

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

Carbohydrates and fats are considered high-energy foods because they _____.

have a lot of electrons associated with hydrogen

A young dog has never had much energy. He is brought to a veterinarian for help and she decides to conduct several diagnostic tests. She discovers that the dog's 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 the dog's condition?

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

Gaseous hydrogen burns in the presence of oxygen to form water: 2H2 + O2 -> 2H2O + energy Which molecule is oxidized and what kind of bond is formed?

hydrogen, polar

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

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

ionic

An organism is discovered that thrives in both the presence and absence of oxygen in the air. Curiously, the consumption of sugar increases as oxygen is removed from the organism's environment, even though the organism does not gain much weight. This organism _____.

is a facultative anaerobe

The electron transport chain _____.

is a series of redox reactions

Why is glycolysis considered to be one of the first metabolic pathways to have evolved?

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

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 for oxidative phosphorylation

Use your knowledge of the first three stages of cellular respiration to determine which explanation is correct.

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

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?

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

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

it was released as CO2 and H2O

The proximate (immediate) source of energy for oxidative phosphorylation is _____.

kinetic energy that is released as hydrogen ions diffuse down their concentration gradient

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

Assuming that the x-axis tick marks will be used to identify the thyroid hormone level of each type of rat, what bars should appear on the x-axis?

low, normal, elevated

Where are the proteins of the electron transport chain located?

mitochondrial inner membrane

What organelle is indicated by the letter C?

mitochondrion

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

molecular oxygen (O2)

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

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+

The final electron acceptor of cellular respiration is _____.

oxygen

What molecule is indicated by the letter D?

oxygen

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

reduced

When electrons move closer to a more electronegative atom, what happens? The more electronegative atom is _____.

reduced, and energy is released

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 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

What process occurs within Box B?

the citric acid cycle

Which statement about the citric acid cycle is correct?

the last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of the citric acid cycle

What variable did the researchers intentionally vary in the experiment, and what are the units for this variable?

thyroid hormone level of the rats chosen for the experiment, in relative units

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

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

Which of the following best describes the main purpose of the combined processes of glycolysis and cellular respiration?

transforming the energy in glucose and related molecules in a chemical form that cells can use for work

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 the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis?

two ATP

In glycolysis, for each molecule of glucose oxidized to pyruvate _____.

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

The electrons stripped from glucose in cellular respiration end up in which compound?

water