Ch 9 of bio exam 3
During acetyl CoA formation and the citric acid cycle, all of the carbon atoms that enter cellular respiration in the glucose molecule are released in the form of CO2. Use this diagram to track the carbon-containing compounds that play a role in these two stages.
Start: acetyl CoA - 2 C; continue clockwise: 6 C, 6 C, 5 C, 4 C, 4 C, 4 C, 4 C, 4 C
The oxygen consumed during cellular respiration is directly involved in which of the following processes or events?
accepting electrons at the end of the electron transport chain.
Which of the following sequences describes the path by which electrons travel downhill energetically in aerobic respiration?
glucose→NADH→electron transport chain→oxygen
What process occurs in Box A? [A scheme of cellular respiration. At box A, which is located in the cytosol, glucose turns into pyruvate with release of ATP and electrons carried by NADH. Pyruvate from this stage is used in a cycle in box B, which is located in the mitochondrion. As a result, ATP, CO2, and electrons carried by NADH and FADH2 are released. The electrons carried by NADH and FADH2 from boxes A and B are used in box C (inside the mitochondrion) for transformation of a substance marked D (that comes from the cytosol) into a substance marked E (released to the cytosol) with release of ATP.]
glycolosis; which occurs in the cytosol
In acetyl CoA formation, the carbon-containing compound from glycolysis is oxidized to produce acetyl CoA. From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of acetyl CoA formation.
net Input: NAD⁺, coenzyme A, pyruvate net Output: NADH, acetyl CoA, CO₂ not input or output: O₂, ADP, glucose and ATP
Among the products of glycolysis, which compounds contain energy that can be used by other biological reactions?
pyruvate, ATP, and NADH
Which of the following statements about NAD+ is true?
NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
Following glycolysis and the citric acid cycle, but before the electron transport chain and oxidative phosphorylation, the carbon skeleton of glucose has been broken down to CO2 with some net gain of ATP. Most of the energy from the original glucose molecule at that point in the process, however, is stored in the form of which of the following molecules?
NADH
In the citric acid cycle (also known as the Krebs cycle), acetyl CoA is completely oxidized. From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of the citric acid cycle.
Net Input: Acetyl CoA, NAD⁺, ADP Net Output: Coenzyme A, CO₂, NADH, ATP Not Input or Output: Pyruvate, Glucose, O₂
In the last stage of cellular respiration, oxidative phosphorylation, all of the reduced electron carriers produced in the previous stages are oxidized by oxygen via the electron transport chain. The energy from this oxidation is stored in a form that is used by most other energy-requiring reactions in cells. From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of oxidative phosphorylation.
Net Input: NADH, ADP, O₂ Net Output: NAD⁺, ATP, CO₂ and Water Not Input or Output: Pyruvate, Glucose, Acetyl CoA, Coenzyme A and CO₂.
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 glycolysis, as in all the stages of cellular respiration, the transfer of electrons from electron donors to electron acceptors plays a critical role in the overall conversion of the energy in foods to energy in ATP. These reactions involving electron transfers are known as oxidation-reduction, or redox, reactions.
1. When a compound donates (loses) electrons, that compound becomes OXIDIZED*. Such a compound is often referred to as an electron donor. 2. When a compound accepts (gains) electrons, that compound becomes REDUCED*. Such a compound is often referred to as an electron acceptor. In glycolysis, the carbon-containing compound that functions as the electron donor is GLUCOSE*. 4. Once the electron donor in glycolysis gives up its electrons, it is oxidized to a compound called PYRUVATE*. 5. NAD+* is the compound that functions as the electron acceptor in glycolysis. 6. The reduced form of the electron acceptor in glycolysis is NADH*.
If glucose is the sole energy source, what fraction of the carbon dioxide exhaled by animals is generated only by the reactions involved in oxidation of pyruvate to acetyl CoA?
1/3
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.
In glycolysis, what starts the process of glucose oxidation?
ATP
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.
Which of the summary statements below describes the results of the following 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
NADH and FADH2 are both electron carriers that donate their electrons to the electron transport chain. The electrons ultimately reduce O2 to 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. 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.
Each of the four stages of cellular respiration occurs in a specific location inside or outside the mitochondria. These locations permit precise regulation and partitioning of cellular resources to optimize the utilization of cellular energy.
Glycolysis - Cytosol Acetyl CoA - Mitochondrial matrix Citric acid cycle - Mitochondrial matrix Oxidative phosphorylation - inner mitochondrial membrane
Which terms describe two atoms when they form a bond in which electrons are completely transferred from one atom to the other?
Ionic and covalent
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 best describes the primary role played by oxygen in cellular respiration?
It serves as the final acceptor for electrons from the electron transport chain.
How many NADH are produced by glycolysis?
Two NADH molecules are produced by glycolysis.
In chemiosmosis, 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 their electrochemical gradient
In the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis?
four ATP
Which of the following metabolic processes take place in the cytosol of a eukaryotic cell?
glycolysis and fermentation
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
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+ ions into which location in eukaryotic cells?
mitochondrial intermembrane space
From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of glycolysis.
net Input: ADP, NAD⁺, Glucose net Output: ATP, NADH and Pyruvate, not input or output: O₂, CO₂, coenzyme A and acetyl CoA
Which of the following statements describes a primary function of both alcohol fermentation and lactic acid fermentation?
oxidation of NADH to NAD+
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
What molecule is indicated by the letter D? [A scheme of cellular respiration. At box A, which is located in the cytosol, glucose turns into pyruvate with release of ATP and electrons carried by NADH. Pyruvate from this stage is used in a cycle in box B, which is located in the mitochondrion. As a result, ATP, CO2, and electrons carried by NADH and FADH2 are released. The electrons carried by NADH and FADH2 from boxes A and B are used in box C (inside the mitochondrion) for transformation of a substance marked D (that comes from the cytosol) into a substance marked E (released to the cytosol) with release of ATP.]
oxygen; the final electron acceptor of cellular respiration
In the sequential reactions of acetyl CoA formation and the citric acid cycle, pyruvate (the output from glycolysis) is completely oxidized, and the electrons produced from this oxidation are passed on to two types of electron acceptors.
pyruvate is oxidized to (a) CO2 NAD+ is reduced to (b) NADH (c) FAD is reduced to (d)FADH2
When the protein gramicidin is integrated into a membrane, an H+ channel forms and the membrane becomes very permeable to protons (H+ ions). If gramicidin is added to an actively respiring muscle cell, how would it affect the rates of electron transport, proton pumping, and ATP synthesis in oxidative phosphorylation? (Assume that gramicidin does not affect the production of NADH and FADH2 during the early stages of cellular respiration.)
remains the same: proton pumping rate, electron transport rate, rate of oxygen uptake. decreases or goes to zero: rate of ATP synthesis, size of protein gradient
In glycolysis, ATP molecules are produced by _____.
substrate-level phosphorylation
What occurs within Box B? [A scheme of cellular respiration. At box A, which is located in the cytosol, glucose turns into pyruvate with release of ATP and electrons carried by NADH. Pyruvate from this stage is used in a cycle in box B, which is located in the mitochondrion. As a result, ATP, CO2, and electrons carried by NADH and FADH2 are released. The electrons carried by NADH and FADH2 from boxes A and B are used in box C (inside the mitochondrion) for transformation of a substance marked D (that comes from the cytosol) into a substance marked E (released to the cytosol) with release of ATP.]
the citric acid cycle; transfers electrons to NADH and FADH_2
Which of the following events takes place in the electron transport chain?
the extraction of energy from high-energy electrons remaining from glycolysis and the citric acid cycle
What happens when electrons are passed from one atom to a more electronegative atom?
the more electronegative atom is reduced, and energy is released
In mitochondrial electron transport, what is the direct role of O2?
to function as the final electron acceptor in the electron transport chain
In glycolysis there is a net gain of _____ ATP.
two
In glycolysis, for each molecule of glucose oxidized to pyruvate, ________.
two molecules of ATP are used and four molecules of ATP are produced.
