Lecture 10 Study Question
Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed directly by the reactions of glycolysis?
100%
What portion of the pathway shown in the figure below involves an endergonic reaction?
A
Which portion of the pathway shown in the figure below contains a phosphorylation reaction in which ATP is the phosphate source?
A
During the chemiosmosis phase of oxidative phosphorylation, potential energy stored during the electron transport phase is converted to energy stored in the form of
ATP
In a mitochondrion, if the matrix ATP concentration is high, and the intermembrane space proton concentration is too low to generate sufficient proton-motive force, then
ATP synthase will hydrolyze ATP and pump protons into the intermembrane space
Brown fat cells produce a protein called thermogenin in their mitochondrial inner membrane. Thermogenin is a channel for facilitated transport of protons across their membrane. What will occur in the brown fat cells when they produce thermogenin?
ATP synthesis will decrease, and heat generation will increase
Drugs known as uncouplers facilitate diffusion of protons across the membrane. When such a drug is added, what will happen to ATP synthesis and oxygen consumption, if the rates of glycolysis and the citric acid cycle stay the same?
ATP synthesis will decrease; oxygen consumption will stay the same
In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of
ATP, CO2, and ethanol (ethyl alcohol).
The oxygen consumed during cellular respiration is involved directly in which process or event?
Accepting electrons at the end of the electron transport chain
Why is less ATP produced by anaerobic respiration than by aerobic respiration?
Anaerobic respiration uses a final electron acceptor that is less electronegative than O2, which is used as the final electron acceptor in aerobic respiration.
Which step in the figure shown below is a redox reaction?
C
Which of the following statements describes the results of this reaction? C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
C6H12O6 is oxidized and O2 is reduced.
In the reaction shown below CH4 + 2 O2 → CO2 + energy + 2 H2O
CH4 is oxidized and O2 is reduced
During cellular respiration, what is the direction of energy flow?
Chemical bonds in food--to NADH--to a proton gradient--to chemical bonds in ATP
Which of the following most accurately describes what happens along the electron transport chain?
Each electron carrier alternates between being reduced and being oxidized
Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and water release free energy
Electrons are being moved from atoms that have a lower affinity for electrons (suchs as C) to atoms with a higher affinity for electrons (such as O)
When electrons move closer to a more electronegative atom, what happens?
Energy is released and the more electronegative atom is reduced
The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the
H+ concentration across the membrane holding ATP synthase
Why is glycolysis described as having an investment phase and a payoff phase?
It first uses two stored ATP and then forms four ATP, for a net increase of two ATP
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 phophorylation
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 her body?
It was released as CO2 and H2O
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. What is the main reason that only two molecules of NADH formed during glycolysis when it appears that as many as a dozen could be formed?
Most of the free energy available from the oxidation of glucose remains in pyruvate, one of the products of glycolysis
Which of the following statements describes NAD+?
NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
In addition to ATP, what are the end products of glycolysis?
NADH and pyruvate
Which of the following shows the molecules in the order of least to most electronegative?
NADH, e-, transport chain, O2
In the reaction shown below Na and Cl → Na+ and Cl-
Na is oxidized and Cl is reduced
In the reaction shown below Na and Cl → Na+ and Cl-
Na is the reducing agent and Cl is the oxidizing agent
Which of the following is an important difference between aerobic and anaerobic respiration
The electron transport chain used in aerobic respiration uses O2 as the final electron acceptor whereas the electron transport chain used in anaerobic respiration uses something other than O2 as the final electron acceptor.
What is proton-motive force?
The force exerted on a proton by a transmembrane proton concentration gradient
A mutation in yeast makes it unable to convert pyruvate to ethanol. How will this mutation affect these yeast cells?
The mutant yeast will be unable to grow anaerobically
Why are carbohydrates and fats considered high-energy foods?
They have a lot of electrons associated with hydrogen
If your muscles used alcohol fermentation instead of lactic acid fermentation, which of the following might occur?
You might become drunk during an intense workout
In the process known as "substrate-level phosphorylation",
a phosphate group is transferred from a substrate molecule to ADP
During the electron transport phase of oxidative phosphorylation, most of the energy that is captured for later use is in the form of
a proton gradient
In cellular respiration, the energy for most ATP synthesis is supplied by
a proton gradient across a membrane
Pyruvate is transported into mitochondria by
a symporter that transports pyruvate up its concentration gradient while transporting protons down their electrochemical gradient
Which of the following intermediary metabolites enters the citric acid cycle and is formed, in part, by the removal of a carbon (CO2) from one molecule of pyruvate?
acetyl CoA
The primary role of oxygen in cellular respiration is to
act as an acceptor for electrons and hydrogen, forming water
The transport of pyruvate into mitochondria depends on the proton-motive force across the inner mitochondrial membrane. How does the pyruvate enter the mitochondrion?
active transport
Which of the following occur in both aerobic and anaerobic respiration?
all of these answers are correct: an electron transport chain, glycolysis, citric acid cycle
Which of the following metabolic processes include glycolysis?
all of these answers are correct: fermentation, anaerobic respiration, aerobic respiration
When comparing electronegativities,
all of these answers are correct: oxygen is more electronegative than all of the components of the electron transport chain, oxygen is more electronegative than FADH2, oxygen is more electronegative than NADH
When an electron moves from
all of these statements are true: NADH to the first subunit of the electron transport chain, energy is released that can be used to do work, the second to the third subunit of the electron transport chain, energy is released that can be used to do work, the first to the second subunit of the electron transport chain, energy is released that can be used to do work
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
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
Most of the energy released during cellular respiration ends up
being lost as heat
Redox reactions
both "a" and "b" are correct: can result in a transfer of electrons, can result in a change in electron sharing in covalent bonds
When skeletal muscle cells continue to do work under conditions of insufficient oxygen (i.e. anaerobic exercise), they become fatigued and painful. This is now known to be caused by
buildup of lactate
What is the term for metabolic pathways that release stored energy by breaking down complex molecules?
catabolic pathways
Inside an active mitochondrion, most electrons follow which pathway?
citric acid cycle → NADH → electron transport chain → oxygen
Which of the protein complexes labeled with Roman numerals in the figure shown below will transfer electrons to O2?
complex IV
When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the direct result is the
creation of a proton-matrix force
Where does glycolysis take place in eukaryotic cells?
cytosol
In chemiosmotic phosphorylation, what is the most direct source of energy that is used to convert ADP + inorganic phosphate to ATP?
energy released from movement of protons through ATP synthase, down the electrochemical gradient
During aerobic respiration, electrons travel downhill in which sequence?
food to NADH to electron transport chain to oxygen
Which metabolic pathway is common to both cellular respiration and fermentation?
glycolysis
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
glycolysis
Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent?
glycolysis
Which of the following occurs in the cytosol of a eukaryotic cell?
glycolysis and fermentation
A molecule that is phosphorylated
has an increased chemical potential energy; it is primed to do cellular work
Even though plants carry on photosynthesis, plant cells still use their mitochondria for oxidation of pyruvate. When and where will this occur?
in all cells all the time
In prokaryotes, the respiratory electron transport chain is located
in the plasma membrane
Phosphofructokinase is an allosteric enzyme that catalyzes the conversion ofo fructose 6-phosphate to fructose 1, 6-biphosphate, an early step of glycolysis. In the presence of oxygen, an increase in the amount of ATP in a cell would be expected to
inhibit the enzyme and thus slow the rates of glycolysis and the citric acid cycle
Where is ATP synthase located in the mitochondrion?
inner membrane
The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction
loses electrons and loses energy
Where are the proteins of the electron transport chain located?
mitochondrial inner membrane
Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells?
mitochondrial intermembrane space
During cellular respiration, acetyl CoA accumulates in which location?
mitochondrial matrix
During aerobic respiration, H2O is formed. Where does the oxygen atom for the formation of the water come from?
molecular oxygen (O2)
The process known as "substrate-level phosphorylation"
occurs during both glycolysis and the citric acid cycle
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 aerobic metabolism, most of the ATP produced by the oxidation of glucose to carbon dioxide is produced by
oxidative phosphorylation
It is possible to prepare vesicles from portions of the inner mitochondrial membrane. Which one of the following processes could still be carried on by this isolated membrane?
oxidative phosphorylation
Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water?
oxidative phosphorylation (chemiosmosis)
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
The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is
oxygen
In mitochondria, exergonic redox reactions
provide the energy that establishes the proton gradient
What is the oxidizing agent in the following reaction? Pyruvate + NADH + H+ → Lactate + NAD+
pyruvate
When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes
reduced
To sustain high rates of glycolysis under anaerobic conditions, cells require
regeneration of NAD+
Curing glycolysis, when each molecule of glucose is catabolized to two molecules of pyruvate, most of the potential energy contained in glucose is
retained in the two pyruvates
An electron loses potential energy when it
shifts to a more electronegative atom
When an electron moves from one molecule to another molecule that is more electronegative than the first molecule
some of the potential energy that is given up by the electron is lost as heat
The ATP made during fermentation is generated by which of the following?
substrate-level phosphorylation
The ATP made during glycolysis is generated by
substrate-level phosphorylation
Which pathways generate reduced electron carriers?
the citric acid cycle and glycolysis
When an electron moves from one molecule to another molecule that is more electronegative
the electron loses potential energy
When electrons flow along the electron transport chain in mitochondria, which of the following changes occurs?
the pH of the matrix increases
The direct energy source that drives ATP synthesis during respiratory oxidative phosphorylation in eukaryotic cells is
the proton-motive force across the inner mitochondrial membrane
The purpose of fermentation reactions is
to regenerate NAD+ so glycolysis can continue
In vertebrate animals, brown fat tissue's color is due to abundant blood vessels and capillaries. White fat tissue, on the other hand, is specialized for fat storage and contains relatively few blood vessels or capillaries. Brown fat cells have a specialized protein that dissipates the proton-motive force across the mitochondrial membranes. Which of the following might be the function of the brown fat tissue?
to regulate temperature by converting most of the energy from NADH oxidation to heat
Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." These little vesicles that result an still transfer electrons from NADH to oxygen and synthesize ATP. There inside-out membrane vesicles
will become acidic inside the vesicles when NADH is added
