Ch 9 Cellular Respiration and Fermentation
The role of O2 in electron transport 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
In substrate-level phosphorylation in glycolysis, an enzyme is required in order for the reaction to occur.
true
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
How many NADH are produced by glycolysis?
2
In glycolysis there is a net gain of _____ ATP.
2
Fermentation
A catabolic process that makes a limited amount of ATP from glucose (or other organic molecules) without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid.
Citric Acid Cycle
A chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing acetyl CoA (derived from pyruvate) to carbon dioxide; occurs within the mitochondrion in eukaryotic cells and in the cytosol of prokaryotes; the second stage of cellular respiration
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.
Beta Oxidation
A metabolic sequence that breaks fatty acids down to two-carbon fragments that enter the citric acid cycle as acetyl CoA.
Electron Transport Chain
A sequence of electron carrier molecules (membrane proteins) that shuttle electrons down a series of redox reactions that release energy used to make ATP.
Glycolysis
A series of reactions that ultimately splits glucose into pyruvate. Glycolysis occurs in almost all living cells, serving as the starting point for fermentation or cellular respiration..
In glycolysis, what starts the process of glucose oxidation?
ATP
Cellular respiration and a cell's demand for ATP 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. Simple diagram showing glycolosis, the citric acid cycle, and oxidative phophorylation. High levels of ATP produced by these processes inhibits phosphofructokinase, an early enzyme in glycolosis. 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
Acetyl CoA
Acetyl coenzyme A; the entry compound for the citric acid cycle in cellular respiration, formed from a two-carbon fragment of pyruvate attached to a coenzyme.
Chemiosmosis
An energy-coupling mechanism that uses energy stored in the from of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Under aerobic conditions, most ATP synthesis in cells occurs by chemiosmosis.
Cytochrome
An iron-containing protein that is a component of electron transport chains in the mitochondria and chloroplasts of eukaryotic cells and the plasma membranes of prokaryotic cells.
Obligate Anaerobe
An organism that carries out only fermentation or anaerobic respiration. Such organisms cannot use oxygen and in fact may be poisoned by it.
Facultative Anaerobe
An organism that make ATP by aerobic respiration if oxygen is present but that switches to anaerobic respiration or fermentation if oxygen is not present
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.
The effects of anaerobic conditions 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
Into which molecule are all the carbon atoms in glucose ultimately incorporated during cellular respiration?
Carbon dioxide
Select the correct statement about cellular respiration. Cellular respiration and breathing differ in that cellular respiration is at the cellular level, whereas breathing is at the organismal level. Animals carry out cellular respiration whereas plants carry out photosynthesis. Plants carry out cellular respiration only in organs such as roots that cannot carry out photosynthesis.
Cellular respiration and breathing differ in that cellular respiration is at the cellular level, whereas breathing is at the organismal level.
Which stage of glucose metabolism produces the most ATP?
Electron transport and chemiosmosis
Which term describes the degree to which an element attracts electrons?
Electronegativity.
Which of these is NOT a product of glycolysis?
FADH2
Which process is not part of the cellular respiration pathway that produces large amounts of ATP in a cell? Glycolysis Fermentation Krebs cycle Electron transport chain
Fermentation
Comparing the amount of ATP synthesis from NADH and 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
Which molecule is metabolized in a cell to produce energy for performing work?
Glucose
In the combined processes of glycolysis and cellular respiration, what is consumed and what is produced?
Glucose is consumed, and carbon dioxide is produced.
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. Diagram showing the process of fermentation 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.
Which step of the cellular respiration pathway can take place in the absence of oxygen?
Glycolysis
Cellular locations of the four stages of cellular respiration 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
Alcohol Fermentation
Glycolysis followed by the reduction of pyruvate to ethyl alcohol, regenerating NAD and releasing Carbon Dioxide
Lactic Acid Fermentation
Glycolysis followed by the reduction of pyruvate to lactate, regenerating NAD with no release of carbon dioxide.
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.
Anaerobic conditions and acetyl CoA formation Under anaerobic conditions (a lack of oxygen), the conversion of pyruvate to acetyl CoA stops. Which of these statements is the correct explanation for this observation?
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.
What kind of bond is formed when lithium and fluorine combine to form lithium fluoride?
Ionic
Why is the citric acid cycle a cyclic pathway rather than a linear pathway? 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. Use your knowledge of the first three stages of cellular respiration to determine which explanation is correct.
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.
Products of pyruvate metabolism Match each product of pyruvate metabolism with the condition under which it is produced.
Lactate: Fermentation in human muscle ethanol: Fermentation in yeast and bacteria Acetyl CoA: Aerobic Oxidation
____________ is the compound that functions as the electron acceptor in glycolysis.
NAD+
The reduced form of the electron acceptor in glycolysis is
NADH
Which of the following statements about the electron transport chain is true? Which of the following statements about the electron transport chain is true? The electron transport chain is the first step in cellular respiration. NADH and FADH2 donate their electrons to the chain. Electrons gain energy as they move down the chain. Water is the last electron acceptor.
NADH and FADH2 donate their electrons to the chain.
From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of glycolysis. Drag each compound to the appropriate bin. If the compound is not involved in glycolysis, drag it to the "not input or output" bin.
Net Input: ADP, NAD⁺, Glucose Net Output: ATP, NADH and Pyruvate, not input or output: O₂, CO₂, coenzyme A and acetyl CoA
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.
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
NAD
Nicotinamide Adenine Dinucleotide, a coenzyme that cycles easily between oxidized (NAD) and reduced (NADH) states, thus acting as an electron carrier.
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.
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?
PFK is an allosteric enzyme that is inhibited by ATP and stimulated by AMP
Phosphofructokinase (PFK) is an enzyme that acts on fructose 6-phosphate at an early step in glucose breakdown. Regulation of this enzyme controls whether the sugar will continue on in the glycolytic pathway. Part A Based on the graph, is PFK more active at low or high ATP concentration?
PFK is more active at low ATP concentration.
Once the electron donor in glycolysis gives up its electrons, it is oxidized to a compound called ___________ .
Pyruvate
Reactants and products of lactic acid fermentation Sort the following items according to whether they are reactants or products in the anaerobic reduction of pyruvate during lactic acid fermentation.
Reactants: NADH & Pyruvate Products: NAD+ & Lactate
In cellular respiration, a series of molecules forming an electron transport chain alternately accepts and then donates electrons. What is the advantage of such an electron transport chain?
The advantage of an electron transport chain is that a small amount of energy is released with the transfer of an electron between each pair of intermediates.
Identify all correct statements about the basic function of fermentation. Select all that apply. The basic function of fermentation is the production of ethyl alcohol or lactic acid. The basic function of fermentation is the regeneration of NAD+, which allows continued ATP production by glycolysis. The basic function of fermentation is the production of additional ATP by further oxidation of the products of glycolysis.
The basic function of fermentation is the regeneration of NAD+, which allows continued ATP production by glycolysis
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.
Cellular respiration
The catabolic pathways of aerobic and anaerobic respiration, which break down organic molecules and use electron transport chain for the production of ATP
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.
Oxidizing Agent
The electron acceptor in a redox reaction
Reducing Agent
The electron donor in a redox reaction
Substrate-level phosphorylation
The enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism
Which of the following statements accurately describes the function of a metabolic pathway involved in cellular respiration?
The function of glycolysis is to begin catabolism by breaking glucose into two molecules of pyruvate, with a net yield of two ATP.
How will a healthy individual's ATP production change during an eight-hour fast?
The individual's ATP production will not change significantly.
Which statement about the citric acid cycle is correct? The oxidation of compounds by the citric acid cycle requires molecular oxygen. The citric acid cycle produces most of the ATP that is subsequently used by the electron transport chain. The last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of the citric acid cycle. The citric acid cycle depends on the availability of NAD+, which is a product of glycolysis. The citric acid cycle oxidizes glucose to carbon dioxide.
The last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of 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.
Proton-motive force
The potential energy stored in the form of a proton electrochemical gradient, generated by the pumping of hydrogen ions (H) across a biological membrane during chemiosmosis
Oxidative Phosphorylation
The production of ATP using energy derived from the redox reactions of an electron transport chain; the third major stage of cellular respiration
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.
True or false? The potential energy in an ATP molecule is derived mainly from its three phosphate groups.
True
True or false? The reactions that generate the largest amounts of ATP during cellular respiration take place in the mitochondria.
True
substrate-level phosphorylation in glycolysis, a bond must be broken between an organic molecule and phosphate before ATP can form.
True
substrate-level phosphorylation in glycolysis, one of the substrates is a molecule derived from the breakdown of glucose.
True
aerobic respiration
a catabolic pathway for organic molecules, using oxygen (O) as the final electron acceptor in an electron transport chain and ultimately producing ATP. This is the most efficient catabolic pathway and is carried out in most eukaryotic cells and many prokaryotic organisms
Redox Reaction
a chemical reaction involving the complete or partial transfer of one or more electrons from one reactant to another; short for reduction - oxidation reaction
ATP synthases
a complex of several membrane proteins that functions in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion (proton) concentration gradient to make ATP. ATP synthases are found in the inner mitochondrial membrane of eukaryotic cells and in the plasma membranes of prokaryotes.
Which of these enters the citric acid cycle?
acetyl CoA
Which of these is NOT a product of the citric acid cycle? Which of these is NOT a product of the citric acid cycle? CO2 FADH2 acetyl CoA ATP NADH + H+
acetyl CoA
substrate-level phosphorylation in glycolysis, the phosphate group added to ADP to make ATP comes from free inorganic phosphate ions.
fAlse
substrate-level phosphorylation in glycolysis, the enzymes involved in ATP synthesis must be attached to a membrane to produce ATP.
false
In glycolysis, the carbon-containing compound that functions as the electron donor is ______________
glucose
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
glycolysis
In muscle cells, fermentation produces _____.
lactate and NAD+
When a compound donates (loses) electrons, that compound becomes ____________ . Such a compound is often referred to as an electron donor.
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.
What is the oxidizing agent in the following reaction? Pyruvate + NADH + H+ → Lactate + NAD+
pyruvate
In fermentation _____ is reduced and _____ is oxidized.
pyruvate ... NADH
Energy from glycolysis Among the products of glycolysis, which compounds contain energy that can be used by other biological reactions?
pyruvate, ATP, and NADH
When a compound accepts (gains) electrons, that compound becomes ____________. Such a compound is often referred to as an electron acceptor.
reduced
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.) Sort the labels into the correct bin according to the effect that gramicidin would have on each process.
remains the same: proton pumping rate, electron transport rate, rate of oxygen uptake decreases(or goes to zero):rate of ATP synthesis, size of the proton gradient
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.
Reduction
the complete or partial addition of electrons to a substance involved in a redox reaction.
Oxidation
the complete or partial loss of electrons from a substance involved in a redox reaction.