Chapter 9: Mastering Biology
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.
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
How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of pyruvate?
two
In the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis?
two ATP
The electrons stripped from glucose in cellular respiration end up in which compound?
water
Which one of the following statements about the redox reactions of the electron transport chain is correct?
The redox reactions of the electron transport chain are directly coupled to the movement of protons across a membrane.
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 of the following normally occurs regardless of whether or not oxygen (O2) is present?
glycolysis
Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent?
glycolysis
A molecule that is phosphorylated
has an increased chemical potential energy; it is primed to do cellular work.
In fermentation _____ is reduced and _____ is oxidized.
pyruvate ... NADH
What is the oxidizing agent in the following reaction? Pyruvate + NADH + H+ → Lactate + NAD+
pyruvate
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.
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.
Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells?
mitochondrial intermembrane space
In the combined processes of glycolysis and cellular respiration, what is consumed and what is produced?
Glucose is consumed, and carbon dioxide is produced.
For each molecule of glucose that is metabolized by glycolysis and the citric acid cycle (see the figure), what is the total number of NADH + FADH2 molecules produced?
12
How many NADH are produced by glycolysis?
2
In glycolysis there is a net gain of _____ ATP.
2
Approximately how many molecules of ATP are produced from the complete oxidation of two molecules of glucose (C6H12O6) in aerobic cellular respiration?
60-64
In glycolysis, what starts the process of glucose oxidation?
ATP
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.
During cellular respiration, acetyl CoA accumulates in which location?
mitochondrial matrix
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.
Which term describes the degree to which an element attracts electrons?
Electronegativity.
Which of these is NOT a product of glycolysis?
FADH2
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.
The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the
H+ concentration across the membrane holding ATP synthase.
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.
What kind of bond is formed when lithium and fluorine combine to form lithium fluoride?
Ionic.
In the oxidation of pyruvate to acetyl CoA, one carbon atom is released as CO2. However, the oxidation of the remaining two carbon atoms—in acetate—to CO2 requires a complex, eight-step pathway—the citric acid cycle. Consider four possible explanations for why the last two carbons in acetate are converted to CO2 in a complex cyclic pathway rather than through a simple, linear reaction.
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.
Which of the following statements describes NAD+?
NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
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.
When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?
The pH of the matrix increases.
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.
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.
Why are carbohydrates and fats considered high energy foods?
They have a lot of electrons associated with hydrogen.
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 of these enters the citric acid cycle?
acetyl CoA
Which of these is NOT a product of the citric acid cycle?
acetyl CoA
What is the purpose of beta oxidation in respiration?
breakdown of fatty acids
What is the term for metabolic pathways that release stored energy by breaking down complex molecules?
catabolic pathways
Where does glycolysis take place in eukaryotic cells?
cytosol
Where is ATP synthase located in the mitochondrion?
inner membrane
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.
Where are the proteins of the electron transport chain located?
mitochondrial inner membrane
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
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.
Among the products of glycolysis, which compounds contain energy that can be used by other biological reactions?
pyruvate, ATP, and NADH NADH only ATP only O2 only CO2 only ATP and NADH only pyruvate and ATP only
In glycolysis, ATP molecules are produced by _____.
substrate-level phosphorylation
In the citric acid cycle, ATP molecules are produced by _____.
substrate-level phosphorylation
Most CO2 from catabolism is released during
the citric acid cycle.
What is proton-motive force?
the force provided by a transmembrane hydrogen ion gradient