Mastering Bio: Chapter 9
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.
Which best describes the primary role played by oxygen in cellular respiration?
It serves as the final acceptor for electrons from the electron transport chain.
A person on a strict diet and exercise regimen lost 7 kg (about 15 pounds) of body fat in just two weeks. What is the most likely way that the lost fat left the body?
It was released as CO2 and H2O.
____________ is the compound that functions as the electron acceptor in glycolysis.
NAD+
products
NAD+ and lactate
Which of the following statements about NAD+ is true?
NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
______ donates electrons to the electron transport chain.
NADH
the reduced form of the electron acceptor in glycolysis is _______
NADH
What is the correct order of electron transport compounds from least electronegative to most electronegative?
NADH -- Fe-S of Complex I -- Q -- Fe-S of Complex III -- Cyt c-- Cyt a of Complex IV -- O2
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.
True or false? The reactions that generate the largest amounts of ATP during cellular respiration take place in the mitochondria.
True
Which of these enters the citric acid cycle?
acetyl CoA
Which of these is NOT a product of the citric acid cycle?
acetyl CoA
Which one of the following is formed by the removal of a carbon (as CO2) from a molecule of pyruvate?
acetyl CoA
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 which process?
coupling of an endergonic reaction to an exergonic reaction
Glycolysis
cytosol
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
fermentation is yeast and bacteria
ethanol
In glycolysis, the carbon-containing compound that functions as the electron donor is ____________
glucose
Where are the proteins of the electron transport chain located?
mitochondrial inner membrane
Acetyl CoA formation
mitochondrial matrix
citric acid cycle
mitochondrial matrix
What process occurs in structure H?
photosynthesis
Which process generates a proton-motive force in mitochondria?
pumping of hydrogen ions from the mitochondrial matrix across the inner membrane and into the intermembrane space
Once the electron donor in glycolysis gives up its electrons, it is oxidized to a compound called ___________
pyruvate
In fermentation _____ is reduced and _____ is oxidized.
pyruvate ... NADH
reactants
pyruvate and NADH
in glycolysis, which compounds contain energy that can be used by other biological reactions
pyruvate, ATP, and NADH
When a compound accepts (gains) electrons, that compound becomes _____________. Such a compound is often referred to as an electron acceptor.
reduced
When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes _____.
reduced
When the protein gramicidin is integrated into a membrane, an H+ channel forms and the membrane becomes very permeable to protons (H+ ions). If gramicidin is added to an actively respiring muscle cell, how would it affect the rates of electron transport, proton pumping, and ATP synthesis in oxidative phosphorylation?
remains the same: proton pumping rate, electron transport rate, rate of oxygen uptake decreases (or goes to zero): size of the proton gradient, rate of ATP synthesis
In glycolysis, ATP molecules are produced by _____.
substrate-level phosphorylation
What process occurs within Box B?
the citric acid cycle
True or false? The potential energy in an ATP molecule is derived mainly from its three phosphate groups.
True
If glucose is the sole energy source, what fraction of the carbon dioxide exhaled by animals is generated only by the reactions involved in oxidation of pyruvate to acetyl CoA?
1/3
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
Starting with one molecule of glucose, glycolysis results in the net production of which of the following sets of energy-containing products?
2 NADH, 2 pyruvate, and 2 ATP
For each glucose that enters glycolysis, _____ NADH + H+ are produced by the citric acid cycle.
6
Approximately how much more free energy is supplied to the electron transport chain by NADH than by FADH2?
8 kcal/mol
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.
In glycolysis, what starts the process of glucose oxidation?
ATP
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?
ATP levels would fall at first, decreasing the inhibition of PFK and increasing the rate of ATP production.
Structure A is _____.
ATP synthase
aerobic oxidation
Acetyl CoA
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.
_______ is a prosthetic group present in several components of the electron transport chain.
Fe-S
Which of the summary statements below 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?
Carbon dioxide
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.
cellular respiration
Cellular respiration and breathing differ in that cellular respiration is at the cellular level, whereas breathing is at the organismal level.
___________ is a multi-protein complex within the electron transport chain.
Complex III
Which process is not part of the cellular respiration pathway that produces large amounts of ATP in a cell?
Fermentation
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
During aerobic respiration, which of the following molecules directly donates electrons to the electron transport chain at the lowest energy level?
FADH2
Which of these is NOT a product of glycolysis?
FADH2
Of the following lists of electron transport compounds, which one lists them in order from the one containing electrons with the highest free energy to the one containing electrons with the lowest free energy? Note that not all electron transport compounds in the electron transport chain are listed. FADH2 -- FMN of Complex I -- Fe-S of Complex II -- Fe-S of Complex III -- Q -- Cyt a of Complex IV -- Cyt c -- O2 FMN of Complex I -- Q -- Fe-S of Complex II -- FADH2 -- Fe-S of Complex III -- Cyt c -- Cyt a of Complex IV -- O2 O2 -- Cyt a of Complex IV -- Cyt c -- Fe-S of Complex III -- Q -- Fe-S of Complex II -- FMN of Complex I -- FADH2 FADH2 -- FMN of Complex I -- Fe-S of Complex II -- Q -- Fe-S of Complex III -- Cyt c -- Cyt a of Complex IV -- O2
FADH2 -- FMN of Complex I -- Fe-S of Complex II -- Q -- Fe-S of Complex III -- Cyt c -- Cyt a of Complex IV -- O2
If a mitochondrion ran out of molecular oxygen (O2), predict which of the following situations would occur in its electron transport chain.
FMN prosthetic groups would remain reduced and NADH would have nowhere to donate electrons.
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.
Which molecule is metabolized in a cell to produce energy "currency" in the form of ATP?
Glucose
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.
Which step of the cellular respiration pathway can take place in the absence of oxygen?
Glycolysis
Under anaerobic conditions (a lack of oxygen), the conversion of pyruvate to acetyl CoA stops.
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.
In the citric acid cycle, ATP molecules are produced by _____.
In the citric acid cycle, ATP molecules are produced by _____.
What kind of bond is formed when lithium and fluorine combine to form lithium fluoride?
Ionic
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.
Which of the following statements describes what happens to a molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction?
It loses electrons and loses potential energy.
________ is the final electron acceptor of the electron transport chain.
O2 (molecular oxygen)
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.
What molecule is indicated by the letter D?
Oxygen
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.
Given what you know about glycolysis and regulation of metabolism by PFK, what is the likely mechanism by which PFK activity differs depending on ATP concentration?
PFK is an allosteric enzyme that is inhibited by ATP and stimulated by AMP.
Based on the graph, is PFK more active at low or high ATP concentration?
PFK is more active at low ATP concentration.
_________ is a nonprotein organic electron carrier within the electron transport chain.
Q (ubiquinone)
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 accurately describes the function of a metabolic pathway involved in cellular respiration?
The function of glycolysis is to begin catabolism by breaking glucose into two molecules of pyruvate, with a net yield of two ATP.
How will a healthy individual's ATP production change during an eight-hour fast?
The individual's ATP production will not change significantly.
What happens when electrons are passed from one atom to a more electronegative atom?
The more electronegative atom is reduced, and energy is released.
Why are carbohydrates and fats frequently considered high-energy foods?
They contain many electrons associated with hydrogen atoms.
What molecules belong in spaces E and F?
carbon dioxide and water
what molecules belong in space A and B?
glucose and oxygen
Which of the following sequences describes the path by which electrons travel downhill energetically in aerobic respiration?
glucose → NADH → electron transport chain → oxygen
What process occurs in Box A?
glycolysis
In which reactions of cellular respiration and fermentation does substrate-level phosphorylation occur?
in both glycolysis and the citric acid cycle
Oxidate Phosphorylation
inner mitochondrial membrane
The proximate (immediate) source of energy for oxidative phosphorylation is _____.
kinetic energy that is released as hydrogen ions diffuse down their concentration gradient
fermentation in human muscle
lactate
In muscle cells, fermentation produces _____.
lactate and NAD+
What organelle is indicated by the letter C?
mitochondrion
Water is one of the end products of aerobic respiration. What is the source of the oxygen atom used in formation of the water?
molecular oxygen (O2)
In the citric acid cycle (also known as the Krebs cycle), acetyl CoA is completely oxidized. From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of the citric acid cycle.
net input: ADP, NAD+, Acetyl CoA net output: NADH, CO2, Coenzyme A, ATP not input or output: Glucose, O2, Pyruvate
From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of glycolysis.
net input: Glucose, ADP, NAD net output: Pyruvate, NADH, ATP not input or output: CO2, O2, Coenzyme A , Acetyl CoA
In the last stage of cellular respiration, oxidative phosphorylation, all of the reduced electron carriers produced in the previous stages are oxidized by oxygen via the electron transport chain. The energy from this oxidation is stored in a form that is used by most other energy-requiring reactions in cells. From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of oxidative phosphorylation.
net input: O2, NADH, ADP, net output: H2O,ATP,NAD+ not input or output: Glucose, CO2, Acetyl CoA, Pyruvate, Coenzyme A
Which describes a primary function of both alcohol fermentation and lactic acid fermentation?
oxidation of NADH to NAD+
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
In cellular respiration, most ATP molecules are produced by _____.
oxidative phosphorylation
When a compound donates (loses) electrons, that compound becomes ___________. Such a compound is often referred to as an electron donor.
oxidized
The final electron acceptor of cellular respiration is _____.
oxygen
basic function of fermentation
the regeneration of NAD+, which allows continued ATP production by glycolysis.
In mitochondrial electron transport, what is the direct role of O2?
to function as the final electron acceptor in the electron transport chain
what is the main purpose of the combined processes of glycolysis and cellular respiration?
transforming the energy in glucose and related molecules into a chemical form that cells can use for work
In glycolysis, for each molecule of glucose oxidized to pyruvate, ________.
two molecules of ATP are used, and four molecules of ATP are produced
