What is the term for metabolic pathways that release stored energy by breaking down complex molecules?
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
Which of the following statements describes NAD+?
NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
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?
Why are carbohydrates and fats considered high energy foods?
They have a lot of electrons associated with hydrogen.
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 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?
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
During aerobic respiration, electrons travel downhill in which sequence?
food NADH electron transport chain oxygen
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)
In chemiosmotic phosphorylation, 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 the electrochemical gradient
Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells?
mitochondrial intermembrane space
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.
Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water?
oxidative phosphorylation (chemiosmosis)
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.
Chemiosmotic ATP synthesis (oxidative phosphorylation) occurs in
all respiring cells, both prokaryotic and eukaryotic, using either oxygen or other electron acceptors.
What is proton-motive force?
the force exerted on a proton by a transmembrane proton concentration gradient
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.
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?
The ATP made during fermentation is generated by which of the following?
In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of
ATP, CO2, and ethanol (ethyl alcohol).
In alcohol fermentation, NAD+ is regenerated from NADH by
reduction of acetaldehyde to ethanol (ethyl alcohol).
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.
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.
When skeletal muscle cells are oxygen-deprived, the heart still pumps. What must the heart muscle cells be able to do?
continue aerobic metabolism when skeletal muscle cannot
When skeletal muscle cells undergo anaerobic respiration, they become fatigued and painful. This is now known to be caused by
buildup of lactate.
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.
Even though plants carry on photosynthesis, plant cells still use their mitochondria for oxidation of pyruvate. When and where will this occur?
in all cels all the time
Where do the catabolic products of fatty acid breakdown enter into the citric acid cycle?
What carbon sources can yeast cells metabolize to make ATP from ADP under anaerobic conditions?
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
During intense exercise, as skeletal muscle cells go into anaerobiosis, the human body will increase its catabolism of
Yeast cells that have defective mitochondria incapable of respiration will be able to grow by catabolizing which of the following carbon sources for energy?
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.
Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." These little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. If the membranes are agitated further, however, the ability to synthesize ATP is lost.
After the further agitation of the membrane vesicles, what must be lost from the membrane?
ATP synthase, in whole or in part
The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the
H+ concentration across the membrane holding ATP synthase.
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is
When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?
The pH of the matrix increases.