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The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction
loses electrons and loses potential energy.
When electrons move closer to a more electronegative atom, what happens?
The more electronegative atom is reduced, and energy is released.
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 (such as C) to atoms with a higher affinity for electrons (such as O).
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.
When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes
When a molecule of NAD⁺ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes
Where does glycolysis take place in eukaryotic cells?
The ATP made during glycolysis is generated by
The oxygen consumed during cellular respiration is involved directly in which process or event?
accepting electrons at the end of the electron transport chain
Which process in eukaryotic cells will proceed normally whether oxygen (O₂) is present or absent?
An electron loses potential energy when it
shifts to a more electronegative atom.
Why are carbohydrates and fats considered high energy foods?
They have a lot of electrons associated with hydrogen.
Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?
During 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.
In addition to ATP, what are the end products of glycolysis?
NADH and pyruvate
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. Why are 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.
Starting with one molecule of glucose, the energy-containing products of glycolysis are
2 NADH, 2 pyruvate, and 2 ATP.
In glycolysis, for each molecule of glucose oxidized to pyruvate
two molecules of ATP are used and four molecules of ATP are produced.
A molecule that is phosphorylated
has an increased chemical potential energy; it is primed to do cellular work.
Which kind of metabolic poison would most directly interfere with glycolysis?
an agent that closely mimics the structure of glucose but is not metabolized
Why is glycolysis described as having an investment phase and a payoff phase?
It uses stored ATP and then forms a net increase in ATP.
The transport of pyruvate into mitochondria depends on the proton-motive force across the inner mitochondrial membrane. How does pyruvate enter the mitochondrion?
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?
During cellular respiration, acetyl CoA accumulates in which location?
How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of pyruvate?
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
A young animal has never had much energy. He is brought to a veterinarian for help and is sent to the animal hospital for some tests. There they discover his 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 his condition?
His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane.
During aerobic respiration, electrons travel downhill in which sequence?
food → NADH → electron transport chain → oxygen
Where are the proteins of the electron transport chain located?
mitochondrial inner membrane
In cellular respiration, the energy for most ATP synthesis is supplied by
a proton gradient across a membrane.
During aerobic respiration, which of the following directly donates electrons to the electron transport chain at the lowest energy level?
The primary role of oxygen in cellular respiration is to
act as an acceptor for electrons and hydrogen, forming water.
Inside an active mitochondrion, most electrons follow which pathway?
citric acid cycle → NADH → electron transport chain → oxygen
During aerobic respiration, H₂O is formed. Where does the oxygen atom for the formation of the water come from?
molecular oxygen (O₂)
Energy released by the electron transport chain is used to pump H⁺ into which location in eukaryotic cells?
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.
When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the
creation of a proton-motive force.
Where is ATP synthase located in the mitochondrion?
How many oxygen molecules (O₂) are required each time a molecule of glucose (C₆H₁₂O₆) is completely oxidized to carbon dioxide and water via aerobic respiration,?
Which of the following produces the most ATP when glucose (C₆H₁₂O₆) is completely oxidized to carbon dioxide (CO₂) and water?
oxidative phosphorylation (chemiosmosis)
Approximately how many molecules of ATP are produced from the complete oxidation of two molecules of glucose (C₆H₁₂O₆) in aerobic cellular respiration?
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.
If a cell is able to synthesize 30 ATP molecules for each molecule of glucose completely oxidized by carbon dioxide and water, how many ATP molecules can the cell synthesize for each molecule of pyruvate oxidized to carbon dioxide and water?
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.
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.
Which catabolic processes may have been used by cells on ancient Earth before free oxygen became available?
glycolysis, pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation, using an electron acceptor other than oxygen
Which of the following normally occurs regardless of whether or not oxygen (O₂) is present?
Which of the following occurs in the cytosol of a eukaryotic cell?
glycolysis and fermentation
Which metabolic pathway is common to both cellular respiration and fermentation?
When an individual is exercising heavily and when the muscle becomes oxygen-deprived, muscle cells convert pyruvate to lactate. What happens to the lactate in skeletal muscle cells?
It is taken to the liver and converted back to pyruvate
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 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
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.
acetyl CoA, NADH, H⁺, and CO₂.
Most CO₂ from catabolism is released during
the citric acid cycle.
When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?
The pH of the matrix increases.
What is the oxidizing agent in the following reaction?
Pyruvate + NADH + H⁺ → Lactate + NAD⁺
The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is
In mitochondria, exergonic redox reactions
provide the energy that establishes the proton gradient.
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
the immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the
H⁺ concentration across the membrane holding ATP synthase.
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