Chapter 9 Cellular Respiration And Fermentation Flashcards
_______ is a prosthetic group present in several components of the electron transport chain.
Fe-S
________ is a multi-protein complex within the electron transport chain.
Complex 3
_________ is the final electron acceptor of the electron transport chain.
O2 molecular oxygen
_________donates electrons to the electron transport chain.
NADH
_________ is a nonprotein organic electron carrier within the electron transport chain.
Q (ubiquinone)
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.
-FMN of Complex I – Q – Fe-S of Complex II – FADH2 – 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
-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 – Fe-S of Complex III – Q – Cyt a of Complex IV – Cyt c – 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
Approximately how much more free energy is supplied to the electron transport chain by NADH than by FADH2?
8 kcal/mol
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
- O2 – Fe-S of Complex I – NADH – Q – Fe-S of Complex III – Cyt c– Cyt a of Complex IV
- O2 – Cyt a of Complex IV – Cyt c – Fe-S of Complex III – Q – Fe-S of Complex I – NADH
- NADH – Cyt c – Fe-S of Complex I – Q – Fe-S of Complex III – Cyt a of Complex IV– O2
NADH – Fe-S of Complex I – 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.
- FADH2 would be the main electron donor to the electron transport chain instead of NADH.
- Electrons would start to flow in the opposite direction, converting water into O2 and H+.
- H2O would be made instead of O2 at the end of the chain.
- Cyt a 3 prosthetic groups would remain oxidized and Cyt a would have nowhere to donate electrons.
- FMN prosthetic groups would remain reduced and NADH would have nowhere to donate electrons.
FMN prosthetic groups would remain reduced and NADH would have nowhere to donate electrons.
When a compound donates (loses) electrons, that compound becomes ___________. Such a compound is often referred to as an electron donor.
Oxidized
When a compound accepts (gains) electrons, that compound becomes _________. Such a compound is often referred to as an electron acceptor.
Reduced
In glycolysis, the carbon-containing compound that functions as the electron donor is _________.
Glucose
Once the electron donor in glycolysis gives up its electrons, it is oxidized to a compound called _________.
Pyruvare
______ is the compound that functions as the electron acceptor in glycolysis.
NAD+
The reduced form of the electron acceptor in glycolysis is ______.
NADH
Among the products of glycolysis, which compounds contain energy that can be used by other biological reactions?
pyruvate, ATP, and NADH
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.
In mitochondrial electron transport, what is the direct role of O2O2?
to function as the final electron acceptor in the electron transport chain
How would anaerobic conditions (when no O2O2 is present) affect the rate of electron transport and ATPATP production during oxidative phosphorylation? (Note that you should not consider the effect on ATPATP synthesis in glycolysis or the citric acid cycle.)
Both electron transport and ATP synthesis would stop.
NADH and FADH2 are both electron carriers that donate their electrons to the electron transport chain. The electrons ultimately reduce O2to water in the final step of electron transport. However, the amount of ATP made by electrons from an NADH molecule is greater than the amount made by electrons from an FADH2 molecule.
Fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor.
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.
The rate of cellular respiration is regulated by its major product, ATP, via feedback inhibition. As the diagram shows, high levels of ATP inhibit phosphofructokinase (PFK), an early enzyme in glycolysis. As a result, the rate of cellular respiration, and thus ATP production, decreases. Feedback inhibition enables cells to adjust their rate of cellular respiration to match their demand for 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.
Under anaerobic conditions (a lack of oxygen), glycolysis continues in most cells despite the fact that oxidative phosphorylation stops, and its production of NAD+ (which is needed as an input to glycolysis) also stops. The diagram illustrates the process of fermentation, which is used by many cells in the absence of oxygen. In fermentation, the NADH produced by glycolysis is used to reduce the pyruvate produced by glycolysis to either lactate or ethanol. Fermentation results in a net production of 2 ATP per glucose molecule.
During strenuous exercise, anaerobic conditions can result if the cardiovascular system cannot supply oxygen fast enough to meet the demands of muscle cells. Assume that a muscle cell’s demand for ATP under anaerobic conditions remains the same as it was under aerobic conditions.
What would happen to the cell’s rate of glucose utilization?
Glucose utilization would increase a lot.
Based on oxygen consumption, when does the anaerobic portion of cellular respiration end and the aerobic portion begin?
The anaerobic portion of cellular respiration ends and the aerobic portion begins at approximately 1.25 milliseconds.
What happens to ATP production as oxygen levels change?
As oxygen levels decrease, ATP production decreases.
Why is some ATP produced even at very low oxygen levels?
Glycolysis produces some ATP, even in the absence of oxygen.
What is the optimal temperature for ATP production?
37 ∘ C
ATP production is highest at a pH of _____ because there are plenty of H+ ions in the intermembrane space to flow through ATP synthase.
5
ATP production is low at a pH of _____ even though this pH indicates a large number of H+ ions in the intermembrane space. ATP production is low because this pH level tends to denature the proteins involved.
3
ATP production is low at pH values above _____ because there are too few H+ ions in the intermembrane space to flow through ATP synthase.
7
Why does ATP production and oxygen consumption increase as the initial NADH concentration increases?
More NADH provides more electrons to the electron transport chain, which results in more H+ being available for chemiosmosis.
Considering this graph, under which condition is phosphofructokinase more active?
Phosphofructokinase is more active at low ATP
concentration.
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?
Phosphofructokinase is an allosteric enzyme that is inhibited by ATP and stimulated by AMP.
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.
Which term describes the degree to which an element attracts electrons?
Electronegativity.
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.
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.
What kind of bond is formed when lithium and fluorine combine to form lithium fluoride?
Ionic.
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.
How many NADH are produced by glycolysis?
2
In glycolysis, ATP molecules are produced by _____.
substrate-level phosphorylation
Which of these is NOT a product of glycolysis?
FADH2
NADH
ATP
In glycolysis, what starts the process of glucose oxidation?
ATP
In glycolysis there is a net gain of _____ ATP.
2
Which of these enters the citric acid cycle?
acetyl CoA
In the citric acid cycle, ATP molecules are produced by _____.
substrate-level phosphorylation
Which of these is NOT a product of the citric acid cycle?
acetyl CoA
Which molecule is metabolized in a cell to produce energy “currency” in the form of ATP?
Glucose
True or false? The potential energy in an ATP molecule is derived mainly from its three phosphate groups.
True
Which process is not part of the cellular respiration pathway that produces large amounts of ATP in a cell?
Fermentation
Which step of the cellular respiration pathway can take place in the absence of oxygen?
Glycolysis
Into which molecule are all the carbon atoms in glucose ultimately incorporated during cellular respiration?
Carbon dioxide
Which of the following statements about the electron transport chain is true?
NADH and FADH2 donate their electrons to the chain.
Which stage of glucose metabolism produces the most ATP?
Electron transport and chemiosmosis
True or false? The reactions that generate the largest amounts of ATP during cellular respiration take place in the mitochondria.
True
For each glucose that enters glycolysis, _____ acetyl CoA enter the citric acid cycle.
2
For each glucose that enters glycolysis, _____ NADH + H+ are produced by the citric acid cycle.
6
In cellular respiration, most ATP molecules are produced by _____.
oxidative phosphorylation
The final electron acceptor of aerobic cellular respiration is _____.
oxygen
During electron transport, energy from _____ is used to pump hydrogen ions into the _____.
NADH and FADH2 … intermembrane space
In muscle cells, fermentation produces _____.
lactate and NAD+
In fermentation _____ is reduced and _____ is oxidized.
pyruvate … NADH
Which of the following is the most important result of the process of cellular respiration in biological systems?
transforming the energy in glucose and related molecules into a chemical form that cells can use for work
In the process of cellular respiration, what is consumed and what is produced?
glucose is consumed and carbon dioxide is produced
In which reactions of cellular respiration does substrate-level phosphorylation occur?
in both glycolysis and the citric acid cycle
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
glycolysis
Which of the summary statements below best describes the results of the following reaction?
C6H12O6 + 6O2 →
6CO2 + 6H2O + Energy
O2 is oxidized and H2O is reduced.
Which of the following statements best describes what happens to a molecule of NAD+ (nicotinamide adenine dinucleotide) when it gains a hydrogen atom?
NAD+ becomes reduced.
Which of the following statements describing the process of glycolysis is correct?
It represents the first stage in the chemical oxidation of glucose by a cell.
Glycolysis results in the net production of which of the following sets of molecules per glucose molecule?
2 NADH, 2 pyruvate, and 2 ATP
Which of the following statements 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.
Inhibition of which of the following metabolic pathways would result in a decrease of CO2 production compared to fully functional cellular respiration?
oxidation of pyruvate to acetyl CoA and the citric acid cycle
The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is
O2
.
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 events takes place in the electron transport chain?
the harnessing of energy from redox reactions to generate a proton gradient
Which of the following processes is driven by chemiosmosis?
oxidative phosphorylation
Which of the following sequences describes the path by which electrons move from high-energy to lower-energy molecules in aerobic respiration?
glucose →
NADH →
electron transport chain →
oxygen
Which of the following statements about the chemiosmotic synthesis of ATP is correct?
The chemiosmotic synthesis of ATP requires that electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane.
In the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis?
two ATP
Which of the following metabolic processes normally occurs in yeast cells regardless of oxygen (O2) availability?
glycolysis
Which of the following metabolic processes take place in the cytosol of a eukaryotic cell?
glycolysis and fermentation
In the absence of oxygen, yeast cells can obtain energy by fermentation, which results in the net production of which of the following sets of molecules?
ATP, NADH, and ethanol
