Chapter 6: Cellular Respiration

In which of the following is the first molecule becoming reduced to the second molecule?

Pyruvate -> lactate (at the same time NADH is oxidized to NAD+)

Using the ATP generated during cellular respiration, the intermediates of glycolysis and the citric acid cycle can be siphoned off and used _____.

to power the biosynthesis of amino acids, fats, and sugars

A.V. Hill did his lactic acid experiments on frog muscles. This means that Hill was working under the premise that frog muscle __________.

undergoes the same lactic acid fermentation as human muscle cells; If frog muscle did not naturally undergo lactic acid fermentation, it would not have been a good choice for studying the effects of lactic acid on muscle.

Which of the following is a true distinction between cellular respiration and fermentation?

NADH is oxidized by passing electrons to the electron transport chain in respiration only.

Immediately after completion of the citric acid cycle, most of the usable energy from the original glucose molecule is in the form of _____.

NADH; Each NADH yields ATP once the electrons are delivered to the electron transport chain.

During fermentation, __________ that was produced during glycolysis is converted back to __________.

NADH; NAD+

Which statement describes the citric acid cycle?

This process produces some ATP and carbon dioxide in the mitochondrion.

Which statement describes glycolysis?

This process splits glucose in half making 2 pyruvate, produces 2 ATPs, and 2 NADHs for each glucose.

During aerobic respiration, molecular oxygen (O2) is used __________.

at the end of the electron transport chain to accept electrons and form H2O; O2 is the final electron acceptor.

Recent data suggests that heat-generatiing brown fat is most active in __________.

babies

In biological systems, an important enzyme involved in the regulation of redox reactions is

dehydrogenase

During cellular respiration, NADH

delivers its electron load to the first electron carrier molecule.

During redox reactions,

electrons are lost from one substance and added to another substance.

Which one of the following is the source of the energy that pumps hydrogen ions across the inner mitochondrial membrane?

electrons; Energy from the flow of electrons along the electron transport chain is used to pump hydrogen ions across the inner mitochondrial membrane.

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

enables the cell to recycle NAD+; Normally, the reduced NADH delivers its electrons to the electron transport chain, enabling NAD+ to be recycled to glycolysis.

Oxidative phosphorylation could not occur without glycolysis and the citric acid cycle, because _____.

these two stages supply the electrons needed for the electron transport chain

Oxidative phosphorylation could not occur without glycolysis and the citric acid cycle, because __________.

these two stages supply the electrons needed for the electron transport chain.

How many NADH are produced by glycolysis?

2

In glycolysis there is a net gain of _____ ATP.

2

During glycolysis, a molecule of glucose is partially oxidized. What is the net gain of ATP and NADH for each glucose molecule?

2 ATP and 2 NADH

Which one of the following best describes the electron transport chain?

Electrons pass from one carrier to another, releasing a little energy at each step. ... NADH and FADH2 deliver electrons from the breakdown products of glycolysis and the citric acid cycle to the electron transport chain, which passes these electrons from one molecule to another, releasing a small amount of energy at each step.

A biochemist wanted to study how various substances were used in cellular respiration. In one experiment, she allowed a mouse to breathe air containing O2 "labeled" by a particular isotope. In the mouse, the labeled oxygen first showed up in

H2O

What is the purpose of embedding the electron transport chain in the membrane of a cell?

The membrane is impermeable to H+.

Which of these enters the citric acid cycle?

acetyl CoA

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

acetyl CoA

In the electron transport chain, the final electron acceptor is

an oxygen atom.

The major (but not sole) energy accomplishment of the citric acid cycle is the __________.

formation of NADH and FADH2; Each turn of the citric acid cycle releases carbon dioxide, forms 1 ATP, and passes electrons to 3 NAD+ and 1 FAD.

Cellular respiration completely breaks down a glucose molecule through glycolysis and the citric acid cycle. However, these two processes yield only a few ATPs. The majority of the energy the cell derives from glucose is _____.

found in NADH and FADH2

Which of the following processes takes place in the cytosol of a eukaryotic cell?

glycolysis

Select the correct sequence of steps as energy is extracted from glucose during cellular respiration.

glycolysis → acetyl CoA → citric acid cycle → electron transport chain

What is the correct sequence of steps as energy is extracted from glucose during cellular respiration.

glycolysis → acetyl CoA → citric acid cycle → electron transport chain

Of the metabolic pathways listed below, the only pathway found in almost all organisms is __________.

glycolysis; Ancient prokaryotes probably used glycolysis to make ATP long before oxygen was present in Earth's atmosphere.

During respiration in a eukaryotic cell, reactions of glycolysis occur __________.

in the cytosol; Glycolysis occurs in the cytosol.

A molecule that functions as the electron donor in a redox reaction __________.

loses electrons and becomes oxidized.

Fat is the most efficient molecule for long-term energy storage even compared to carbohydrates because _____.

with their numerous hydrogen atoms, fats provide an abundant source of high-energy electrons

Lungs are to breathing as _____ are to cellular respiration.

mitochondria

In what organelle would you find acetyl CoA formation, the citric acid cycle, and the electron transport chain?

mitochondrion

A molecule is oxidized when it __________.

loses an electron

When did the level of oxygen in Earth's atmosphere become high enough to sustain aerobic respiration?

2.7 billion years ago

What is the correct general equation for cellular respiration?

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP energy

Respiration ________, and cellular respiration ________.

is gas exchange . . . produces ATP

Some human cells are restricted to aerobic respiration to recycle NADH and FADH2. If these cells are deprived of oxygen, then _____.

oxidative phosphorylation would come to a halt because there wouldn't be any oxygen to "pull" the electrons down the transport chain

One of the key differences between slow- and fast-twitch muscles is whether they require _____ when making ATP for energy.

oxygen

Bacteria are responsible for the _____.

taste of sourdough bread

Bacteria are responsible for the _____.

taste of sourdough bread breakdown of food in a cow's stomach eyes in Swis cheese

A drug is tested in the laboratory and is found to create holes in both mitochondrial membranes. Scientists suspect that the drug will be harmful to human cells because it will inhibit

the citric acid cycle and oxidative phosphorylation.

Most of the NADH that delivers electrons to the electron transport chain comes from _____.

the citric acid cycle; Both NADH and FADH2 are produced during the citric acid cycle.

Which part of the breakdown of glucose requires molecular oxygen (O2)?

the electron transport chain; The electron transport chain accepts electrons from the breakdown products of glycolysis and the citric acid cycle, and it passes these electrons from one molecule to another until they are passed (along with two hydrogen ions) to oxygen to form water.

Sunlight is essential for the varied life on Earth. Sunlight provides energy to photosynthetic organisms by providing _____.

the energy necessary to power the rearrangement of chemical bonds

Lactobacillus sanfrancisco is responsible for which of the following?

the flavor of sourdough bread

The ATP synthase in a human cell gets energy for making ATP directly from __________.

the flow of H+ through a membrane; As electrons move along the transport chain, hydrogen ions are pumped across the inner mitochondrial membrane.

Most of the ATP produced in cellular respiration comes from __________.

the flow of electrons across the inner mitochondrial membrane

During respiration in a eukaryotic cell, reactions of the citric acid cycle occur in __________.

the fluid within the mitochondrion; The citric acid cycle, which takes place in mitochondria, completes the degradation of glucose.

Some friends are trying to make wine in their basement. They've added yeast to a sweet grape juice mixture and have allowed the yeast to grow. After several days they find that sugar levels in the grape juice have dropped, but there's no alcohol in the mixture. The most likely explanation is that

the mixture needs less oxygen, because yeast only produce alcohol in the absence of oxygen.

Which of the following is the most immediate source of energy for making the most of the ATP in your cells?

the movement of H+ across a membrane down its concentration gradient

A child is born with a rare disease in which mitochondria are missing from skeletal muscle cells. However, the muscles still function. Physicians find that

the muscles contain large amounts of lactate following even mild physical exercise.

Humans use about ________ of their daily calories to maintain brain cells and power other life-sustaining activities.

75%

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

A compound called coenzyme A binds to acetic acid.; Coenzyme A binds to acetic acid before entering the citric acid cycle.

An average adult human requires 2,200 kcal of energy per day. Suppose your diet provides an average of 2,300 kcal per day. How many hours per week would you have to walk to burn it off?

100 kcal per day is 700 kcal per week. Walking 3 mph would require 700/245= 2.8 hours

In the citric acid cycle, the energy production per glucose molecule is __________.

2 ATP, 6 NADH, 2 FADH2; Then the NADH and FADH2 go through the electron transport chain.

How much ATP can a cell make from one glucose molecule in the presence of carbon monoxide?

2 ATP; That is what you could obtain in the absence of carbon monoxide and an abundance of oxygen.

The label on the box of breakfast cereal lists one serving as containing "200 kcalories" per serving. How many calories are in one serving?

200,000

Which of the following statements regarding photosynthesis and cellular respiration is true? A) Photosynthesis occurs in chloroplasts, and cellular respiration occurs in mitochondria. B) Photosynthesis occurs in mitochondria and in chloroplasts. C) Cellular respiration occurs in mitochondria and in chloroplasts. D) Photosynthesis occurs in mitochondria, and cellular respiration occurs in chloroplasts.

A) Photosynthesis occurs in chloroplasts, and cellular respiration occurs in mitochondria.

In glycolysis, what starts the process of glucose breakdown?

ATP

Explain how your body can convert excess carbohydrates in the diet to fats. Can excess carbohydrates be converted to protein? What else must be supplied?

As carbohydrates are broken down in glycolysis and the oxidation of pyruvate, glycerol can be made from G3P and fatty acids can be made from acetyl CoA. Amino groups, containing N atoms, must be supplied to various intermediated of glycolysis and the citric acid cycle to produce amino acids.

In the first stage of cellular respiration, two molecules of pyruvate are produced. In the remaining stages, a number of products are produced, including _____. These stages occur in the _____.

CO2 ... mitochondria

Compare and describe the roles of CO2 and H2O in cellular respiration and photosynthesis.

CO2 and H2O are the products of respiration; they are the reactants in photosynthesis. In respiration glucose is oxidized to CO2 as electrons are passed through an electron transfer chain from glucose to O2, producing H2O. In photosynthesis, H2O is the source of electrons, which are energized by light, temporarily stored in NADPH, and used to reduce CO2 to carbohydrate.

When pyruvic acid is converted to acetyl CoA __________.

CO2 and NADH are formed; Pyruvic acid loses a carbon dioxide molecule, which diffuses out of the cell. The remaining two-carbon fragment is oxidized while NAD+ is reduced to NADH.

Which one of the following serves primarily as a hydrogen-atom-carrier molecule in cells?

NAD; Like FAD, NAD+ accepts hydrogen ions that have been stripped from glucose and delivers them to the electron transport chain.

Which of these is NOT a product of glycolysis?

FADH2

Which of the three stages of cellular respiration if considered the most ancient?

Glycolysis because it occurs in all living cells and does;t require oxygen or membrane closed organelles.

Compare and contrast fermentation as it occurs in your muscle cells and in yeast cells.

In lactic fermentation in muscle cells, pyruvate is reduced by NADH to form lactate, and NAD+ is recycled. In alcohol fermentation for yeast, pyruvate is broken down to CO2 and ethanol as NADH is oxidized to NAD+ Both types of fermentation allow glycolysis to continue to produce 2 ATP per glucose by recycling NAD+

We inhale O2 and we exhale CO2. Carbon dioxide is produced __________.

In the reaction that creates acetyl CoA (coenzyme A) from pyruvate

A scientist wants to study the enzymes of the citric acid cycle in eukaryotic cells. What part of the cell would she use as a source of these enzymes?

Mitochondrial matrix

Given the relatively modest number of calories burned by anything but the most vigorous activities, why can people consume over 2,000 kilocalories a day, yet maintain a healthy body weight?

Most of the energy consumed in food is spent maintaining the body's functions, so only a fraction of food energy needs to be burned in exercise.

Your body makes NAD+ and FAD from two B vitamins, niacin and riboflavin. The recommended dietary allowance for niacin is 20 mg and for riboflavin, 1.7 mg. These amounts are thousands of times less than the amount of glucose your body needs each day to fuel its energy needs. Why is the daily requirement for these vitamins so small?

NAD+ and FAD are coenzymes that are not used up during the oxidation of glucose. NAD+ and FAD are recycled when NADH and FADH2 pass the electrons that they are carrying to the electron transport chain. We need a small additional supply to replace those that are damaged.

The electron transport chain is, in essence, a series of redox reactions that conclude cellular respiration. During these redox reactions, _____.

NAD+ is reduced, which then oxidizes an electron acceptor in the electron transport chain

In glycolysis in the absence of oxygen, cells need a way to regenerate which compound?

NAD+; The NAD+ needs to be regenerated, which is why ethyl alcohol or lactic acid is formed.

ATP synthase enzymes are found in the prokaryotic plasma membrane and in the inner membrane of a mitochondrion. What does this suggest about the evolutionary relationship of eukaryotic organelle to prokaryotes?

The presence of ATP synthase enzymes in prokaryotic plasma membranes and the inner membrane of mitochondria provides support for the theory of endosymbiosis that mitochondria evolved from an engulfed prokaryote that used aerobic respiration

Why is the citric acid cycle called a cycle?

The two-carbon acetic acid binds to a four-carbon molecule that is restored at the end of the cycle to be used again in the citric acid cycle.; The cycling referred to is that of the resynthesis of the four-carbon compound.

What is the fate of the electrons that are stripped from glucose during cellular respiration?

They are used to form water.

How do cells capture the energy released by cellular respiration?

They produce ATP.

The poison cyanide binds to an electron carrier within the electron transport chain and blocks the movement of electrons. When this happens glycolysis and the citric acid cycle soon grind to a halt as well. Why do you think these other two stages of cellular respiration stop?

They run out of NAD+ and FAD NAD+ and FAD are recycled by electron transport are in limited supply in a cell

Which statement describes the electron transport chain?

This process uses energy captured from electrons flowing to oxygen to produce most of the ATPs in cellular respiration.

The functioning of an electron transport chain is analogous to

a Slinky toy going down a flight of stairs.

Most of the electrons released from glucose by cell respiration __________.

are bound to NAD+ to be sent through electron transport; Most of the electrons released from the glucose are picked up by NAD+ and sent through the electron transport chain.

Some microorganisms that live around hydrothermal vents in the deep ocean use inorganic energy sources and compounds to produce their own food. Therefore, these organisms are considered to be _____.

autotrophs; Autotrophs are organisms that produce their own food.

By-products of cellular respiration include

carbon dioxide and water.

In an experiment, mice were fed glucose (C6H12O6) containing a small amount of radioactive oxygen. The mice were closely monitored, and in a few minutes radioactive oxygen atoms showed up in _____.

carbon dioxide; The oxidation of glucose involves the release of CO2.

In respiration, which one of the following is done during the electron transport chain phase?

carry electrons; As its name states, the electron transport chain transports electrons.

Cyanide differs from dinitrophenol in that

cyanide is an electron transport blocker, while dinitrophenol makes the membrane of the mitochondrion leaky to H+ ions.

The function of cellular respiration is to __________.

extract usable energy from glucose; The most prevalent and efficient energy-yielding pathway is cellular respiration, in which oxygen is consumed as a reactant, along with the organic fuel (frequently glucose).

Each turn of the critic acid cycle generates one ATP and __________ additional energy-rich molecules: __________.

four; 3 NADH and 1 FADH2

In glycolysis, __________ is oxidized and __________ is reduced.

glucose ... NAD+

In cellular respiration, _____ is oxidized and _____ is reduced.

glucose ... oxygen; In cellular respiration, electrons and hydrogen are removed from glucose and added to oxygen.

Which of the following options lists the stages in cellular respiration in the correct order?

glycolysis, the citric acid cycle, and oxidative phosphorylation

What is the name of the process in which glucose is converted to pyruvic acid?

glycolysis; Glycolysis, or the splitting of sugar, splits a 6-carbon glucose into two 3-carbon pyruvic acid molecules.

A chemist has discovered a drug that blocks an enzyme that catalyzes some of the reactions of glycolysis. He wants to use the drug to kill bacteria in people with infections. However, he cannot do this because __________.

human cells also perform glycolysis; the drug might also poison them; The chemist's drug could have a devastating effect on human cells.

During cellular respiration, the energy in glucose

is carried by electrons.

When a car engine burns gasoline, the results of the reaction are similar to when cells burn glucose. Both reactions release carbon dioxide and water. In cells, the chemical energy in food is converted to ATP and heat. In a moving car, the chemical energy in gasoline is converted to _____.

kinetic energy and heat

In muscle cells, fermentation produces _____.

lactate and NAD+

Sports physiologists at an Olympic training center wanted to monitor athletes to determine at what point their muscles were functioning anaerobically. They could do this by checking for a buildup of _____.

lactic acid;In humans, muscle cells switch to lactic acid fermentation after becoming anaerobic.

In cellular respiration, glucose _____ electrons, whereas _____ electrons.

loses ... oxygen gains

In cellular respiration, glucose __________ electrons, whereas __________ electrons.

loses ... oxygen gains

A molecule that functions as the electron donor in a redox reaction _____.

loses electrons and loses energy

Primarily, cellular respiration serves to _____.

make ATP to power the cell's activities

If humans did not breathe in O2, we would not __________.

make enough ATP to meet our energy requirements; The electron transport chain accepts electrons from the breakdown products of glycolysis and the citric acid cycle, and it passes these electrons from one molecule to another until they are passed (along with two hydrogen ions) to oxygen to form water.

The electron transport chain is a series of electron carrier molecules. In eukaryotes, where can this structure be found?

mitochondria

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

substrate-level phosphorylation

Some human cells, such as nerve cells, are restricted to aerobic respiration to recycle NADH and FADH2. If these cells are deprived of oxygen, then __________.

oxidative phosphorylation would come to a halt because there wouldn't be any oxygen to "pull" the electrons down the transport chain.

During the reaction C6H12O6 + 6 O2 → 6 CO2 + 6 H2O, _________.

oxygen becomes reduced

The energy given up by electrons as they move through the electron transport chain is used to __________.

pump H+ through a membrane; Many of the electron transport molecules in the mitochondrion pump hydrogen ions across the inner mitochondrial membrane when they pass an electron along the chain.

In oxidative phosphorylation, electrons are passed from one electron carrier to another. The energy released is used to __________.

pump protons (H+) across the mitochondrial membrane

In fermentation _____ is reduced and _____ is oxidized.

pyruvate ... NADH

A muscle cell deprived of molecular oxygen will convert glucose to lactic acid to _____.

recycle NADH through fermentation

An electron carrier acts as an energy-storage molecule when it is _____ (for example, _____)

reduced ... NADH; The most versatile electron acceptor in cellular respiration is NAD+, which gains electrons and is thereby reduced to NADH.

Glycolysis is the only stage of cellular respiration that __________.

requires ATP to make ATP

In glycolysis, ATP molecules are produced by _____.

substrate-level phosphorylation

A kilocalorie is defined as

the quantity of heat needed to raise the temperature of 1 kg of water by 1°C.

When a poison such as rotenone blocks the electron transport chain, glycolysis and the citric acid cycle soon grind to a halt as well, because __________.

they run out of NAD+ and FAD; Oxygen moves freely across cell membranes. It does not reach toxic concentrations unless an oxygen-enriched gas is being breathed.