Chapter 9 Bio
If we track the flow of electrons from glucose to NADH or FADH2 as glucose is oxidized to CO2, how many electrons will have been transferred before the citric acid cycle begins?
4 Four pairs of electrons are transferred to 4 NADH molecules. 2 NADH are formed in glycolysis and another 2 NADH are formed in pyruvate processing.
Which of the following statements correctly identifies why fermentation alone won't keep cells alive.?
The oxidation of glucose via cellular respiration has the potential yield of 29 ATP while the oxidation of glucose via fermentation yields only 2 ATP. Cellular respiration is much more efficient at harvesting potential energy from glucose.
Which of these is NOT a product of the citric acid cycle?
acetyl CoA, Acetyl CoA enters the citric acid cycle.
What would be the effect of abundant ATP on the citric acid cycle?
ATP binds at the allosteric regulatory site of the enzyme that combines acetyl CoA and oxaloacetate and slows the citric acid cycle. ATP can function as an allosteric regulator of the citric acid cycle.
In glycolysis there is a net gain of _____ ATP.
It takes 2 ATP to produce 4 ATP.
True or false? The potential energy in an ATP molecule is derived mainly from its three phosphate groups.
True, The three phosphate groups in an ATP molecule carry negative charges that strongly repel each other and give ATP a large amount of potential energy.
True or false? The reactions that generate the largest amounts of ATP during cellular respiration take place in the mitochondria.
True, glycolysis takes place in the cytoplasm, whereas the Krebs cycle and the electron transport chain, which generate the largest amounts of ATP during cellular respiration, take place in the mitochondria.
Which of the following statements about the electron transport chain is true?
NADH and FADH2 donate their electrons to the chain, The electrons lose energy as they move down the chain, and this energy is used to create a proton gradient that drives the synthesis of ATP.
Which of these enters the citric acid cycle?
acetyl CoA
For the oxidation of pyruvate shown in Figure 9.9, which answer correctly identifies molecules involved in the positive (++) and negative (−-) control of this reaction?
++: NAD++;, CoA, and AMP; −-: Acetyl CoA, NADH, and ATP, Pyruvate oxidation is a critical step in cellular respiration so it is advantageous for it to be feedback-inhibited by large supplies of products, and stimulated by large supplies of reactants and low supplies of products (AMP indicates low supplies of ATP).
In glycolysis, what starts the process of glucose oxidation?
ATP, Some ATP energy is used to start the process of glucose oxidation.
Into which molecule are all the carbon atoms in glucose ultimately incorporated during cellular respiration?
Carbon dioxide, All of the carbon atoms in glucose are incorporated into carbon dioxide: Two molecules are formed as pyruvate is converted to acetyl CoA, and four molecules are formed during the Krebs cycle.
Which answer correctly associates a process in cellular respiration with (1) what goes in and (2) what comes out?
Citric acid cycle: (1) Acetyl CoA; (2) NADH, ATP, FADH2,, and CO2
Which stage of glucose metabolism produces the most ATP?
Electron transport and chemiosmosis, Electron transport and chemiosmosis (oxidative phosphorylation) can yield around 26 molecules of ATP.
Which of these is NOT a product of glycolysis?
FADH2, FADH2 is a product of the citric acid cycle.
Which process is not part of the cellular respiration pathway that produces large amounts of ATP in a cell?
Fermentation, Fermentation is an alternate pathway used when oxygen levels are low.
Which molecule is metabolized in a cell to produce energy for performing work?
Glucose
In the phosphofructokinase molecule shown in Figure 9.7, the active site has a higher affinity for ATP than the regulatory site does. Which answer best summarizes what the consequences would be if the regulatory site had a higher affinity for ATP than the active site did?
Glucose oxidation would be inhibited even if ATP were scarce in the cell., Because the regulatory site has a higher affinity for ATP, more enzyme molecules would be inhibited at low ATP concentrations.
Which step of the cellular respiration pathway can take place in the absence of oxygen?
Glycolysis, Glycolysis can take place in the absence of oxygen; its product, pyruvate, enters the cellular respiration pathway or undergoes fermentation depending on the availability of oxygen.
What purpose does fermentation serve?
It regenerates NAD+ from NADH to keep glycolysis going in the absence of oxygen. Fermentation is unlikely to occur when oxygen is available as the final electron acceptor at the end of the electron transport chain.
What would happen to the proton gradient and ATP production after a drug has poisoned the enzyme that combines acetyl CoA and oxaloacetate to form citrate?
Less NADH production would create to a weaker proton gradient and less ATP production.
How many NADH are produced by glycolysis?
Two NADH molecules are produced by glycolysis.
During pyruvate processing, two carbons from pyruvate combine with ____.
coenzyme A, One carbon of the three-carbon pyruvate becomes oxidized to CO2 and the remaining two carbons (acetate) combine with coenzyme A to form acetyl coenzyme A.
What process occurs in Box A?
glycolysis, Glycolysis occurs in the cytosol.
What is the correct sequence of steps in cellular respiration, starting with glucose?
glycolysis, pyruvate processing, citric acid cycle, electron transport, oxidative phosphorylation
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 formation: mitochondrial matrix citric acid cycle:mitochondrial matrix oxidative phosphorylation: inner mitochondrial membrane
Where does the citric acid cycle occur in eukaryotes?
in the matrix of mitochondria
In eukaryotes, the components of the electron transport chain are located in the ____.
inner mitochondrial membrane
In muscle cells, fermentation produces _____.
lactate and NAD+
Oxidative Phosphorylation 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, O2, ADP net output Water, NAD+, ATP not input or output Coenzyme A, Acetyl CoA, CO2, Pyruvate, glucose
Citric Acid Cycle 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 CO2, NADH, ATP, Coenzyme A not input or output Glucose, O2, pyruvate
Glycolysis From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of glycolysis.
net input glucose, ADP, NAD+ net output NADH, pyruvate, ATP not input or output acetyl coA, coenzyme A, O2, CO2
Acetyl CoA Formation 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 pryuvate, NAD+, coenzyme A net output CO2, NADH, acetyl CoA not input or output Glucose, ATP, O2, ADP
What molecule is indicated by the letter D?
oxygen, Oxygen is the final electron acceptor of cellular respiration.
In fermentation _____ is reduced and _____ is oxidized.
pyruvate ... NADH, The pyruvate from glycolysis is reduced to either lactate or ethanol, and NADH is oxidized to NAD+.
In the citric acid cycle, ATP molecules are produced by _____.
substrate-level phosphorylation, A phosphate group is transferred from GTP to ADP.
In glycolysis, ATP molecules are produced by _____.
substrate-level phosphorylation, A phosphate group is transferred from glyceraldehyde phosphate to ADP.
What process occurs within Box B?
the citric acid cycle, The citric acid cycle transfers electrons to NADH and FADH2.
What is the primary function of the reactions that follow glycolysis in a fermentation pathway?
to regenerate NAD+ from NADH, so glycolysis can continue
For each molecule of glucose processed during glycolysis, the net yield is ____.
two molecules of NADH, two of ATP, and two of pyruvate Glycolysis begins by using molecules of ATP, but the net yield is positive