Mastering Chapter 9 PDF

Preview

Summary

Mastering Biology Ch.9...

Description

10/26/2020

Chapter 9

Chapter 9 Due: 11:59pm on Friday, October 30, 2020 You will receive no credit for items you complete after the assignment is due. Grading Policy

Cellular Respiration (5 of 5): Summary (BioFlix tutorial)

Before beginning this tutorial, watch the Cellular Respiration animation. You can review relevant parts of the animation at any point in the tutorial.

Part A - The coupled stages of cellular respiration The four stages of cellular respiration do not function independently. Instead, they are coupled together because one or more outputs from one stage functions as an input to another stage. The coupling works in both directions, as indicated by the arrows in the diagram below. In this activity, you will identify the compounds that couple the stages of cellular respiration. Drag the labels on the left onto the diagram to identify the compounds that couple each stage. Labels may be used once, more than once, or not at all.

Hint 1. Can you identify a compound that couples two processes? Coupling is extremely important in the regulation of metabolic pathways, such as cellular respiration. Two processes are coupled when an output from one process is an input to the other process. In that way, one process depends on the other to supply the reactant it needs. What compound couples glycolysis to acetyl CoA formation? ANSWER:

NADH pyruvate ADP + Pi ATP NAD+ glucose

Hint 2. Inputs and outputs of the stages of cellular respiration The following table summarizes the inputs and outputs of the stages of cellular respiration. Note that FAD and FADH2 are not included in this table. Glycolysis

Acetyl CoA Formation and the Citric Acid Cycle

Oxidative Phosphorylation

Inputs

Outputs

Inputs

Outputs

Inputs

Outputs

glucose

pyruvate

pyruvate

CO2

O2

water

NAD+

NADH

NAD+

NADH

NADH

NAD+

ADP + Pi

ATP

ADP + Pi

ATP

ADP + Pi

ATP

ANSWER:

https://session.masteringbiology.com/myct/assignmentPrintView?assignmentID=9462423

1/37

10/26/2020

Chapter 9 Reset

Help

Correct The main coupling among the stages of cellular respiration is accomplished by NAD+ and NADH. In the first three stages, NAD+ accepts electrons from the oxidation of glucose, pyruvate, and acetyl CoA. The NADH produced in these redox reactions then gets oxidized during oxidative phosphorylation, regenerating the NAD+ needed for the earlier stages.

Part B - 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?

Hint 1. What compound couples oxidative phosphorylation (the stage directly affected by the lack of oxygen) to acetyl CoA formation? Acetyl CoA formation is regulated by being coupled to oxidative phosphorylation. A compound produced (an output) in oxidative phosphorylation serves as a substrate (an input) in a reaction in acetyl CoA formation. If oxidative phosphorylation does not provide that compound, acetyl CoA formation will stop. What compound couples oxidative phosphorylation to acetyl CoA formation? ANSWER:

ADP + Pi ATP NADH NAD+ O2

ANSWER:

https://session.masteringbiology.com/myct/assignmentPrintView?assignmentID=9462423

2/37

10/26/2020

Chapter 9 Oxygen is required to convert glucose to pyruvate in glycolysis. Without oxygen, no pyruvate can be made. 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. ATP is needed to convert pyruvate to acetyl CoA. Without oxygen, no ATP can be made in oxidative phosphorylation. Oxygen is an input to acetyl CoA formation.

Correct NAD+ couples oxidative phosphorylation to acetyl CoA formation. The NAD+ needed to oxidize pyruvate to acetyl CoA is produced during electron transport. Without O2, electron transport stops, and the oxidation of pyruvate to acetyl CoA also stops because of the lack of NAD+.

Part C - 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.

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?

Hint 1. How to think about this problem These steps will help you think this problem through in a logical manner. 1. First, make sure you understand how ATP levels regulate PFK and the rate of cellular respiration. (See Hint 2 if you need more help.) 2. Next, consider how the balance between ATP synthesis (supply) and ATP use (demand) determines the ATP level in the cell. If the demand changes relative to the supply, how would the level of ATP in the cell change initially? (See Hint 3 if you need more help.) 3. Finally, use your prediction of how ATP levels would change to determine whether the rate of cellular respiration would then increase or decrease. Hint 2. Regulation of enzyme activity by ATP In the case of phosphofructokinase (PFK), ATP acts as an allosteric regulator. Increasing ATP levels inhibit the activity of the enzyme, slowing down glycolysis and cellular respiration. Decreasing ATP levels reverse the inhibition imposed by high ATP levels, speeding up glycolysis and cellular respiration. Hint 3. How do supply and demand initially affect cellular ATP levels? You are resting comfortably listening to music when an angry dog suddenly enters your room. What happens to the amount of ATP in your muscle cells in that first second, as you leap out of the room, slamming the door behind you? ANSWER:

The cellular ATP level increases. The cellular ATP level remains about the same. The cellular ATP level decreases.

https://session.masteringbiology.com/myct/assignmentPrintView?assignmentID=9462423

3/37

10/26/2020

Chapter 9

ANSWER:

ATP levels would fall at first, increasing the inhibition of PFK and increasing the rate of ATP production. ATP levels would fall at first, decreasing the inhibition of PFK and increasing the rate of ATP production. ATP levels would rise at first, increasing the inhibition of PFK and increasing the rate of ATP production. ATP levels would rise at first, decreasing the inhibition of PFK and increasing the rate of ATP production.

Correct An increased demand for ATP by a cell will cause an initial decrease in the level of cellular ATP. Lower ATP decreases the inhibition of the PFK enzyme, thus increasing the rate of glycolysis, cellular respiration, and ATP production. It is the initial decrease in ATP levels that leads to an increase in ATP production.

Part D - Fermentation - ATP production in the absence of oxygen 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?

Hint 1. How to think about this problem In Part C of this tutorial, you learned how supply and demand for cellular ATP regulates cellular respiration via a key enzyme in glycolysis. Using this knowledge, follow these steps to think this problem through in a logical manner. 1. First, remember that the cell’s demand for ATP under anaerobic conditions remains the same as it was under aerobic conditions. Consider what happens to the supply of ATP under anaerobic conditions. 2. Next, consider how an imbalance between the demand and supply of ATP will affect the ATP level in the cell. 3. Then, think about how the change in ATP level will affect phosphofructokinase (PFK) activity and the rate of glycolysis. 4. Next, determine how the rate of glycolysis will affect the cell’s utilization of glucose. 5. Finally, think about how much ATP is made under anaerobic conditions (fermentation only) compared to aerobic conditions (all of cellular respiration). See Hint 2 if you need more help. Hint 2. How much ATP is made during fermentation compared to during aerobic respiration? Under aerobic conditions, cellular respiration produces about 30 molecules of ATP per glucose molecule. How does the amount of ATP produced by fermentation compare to the amount produced by aerobic respiration? ANSWER:

https://session.masteringbiology.com/myct/assignmentPrintView?assignmentID=9462423

4/37

10/26/2020

Chapter 9 Fermentation produces about the same amount of ATP as aerobic respiration. Fermentation produces about 90% of the amount of ATP produced by aerobic respiration. Fermentation produces about 50% of the amount of ATP produced by aerobic respiration. Fermentation produces less than 10% of the amount of ATP produced by aerobic respiration.

ANSWER:

Glucose utilization would increase a lot. Glucose utilization would increase a little. Glucose utilization would remain the same. Glucose utilization would decrease a little. Glucose utilization would decrease a lot.

Correct ATP made during fermentation comes from glycolysis, which produces a net of only 2 ATP per glucose molecule. In contrast, aerobic cellular respiration produces about 30 ATP per glucose molecule. To meet the same ATP demand under anaerobic conditions as under aerobic conditions, a cell’s rate of glycolysis and glucose utilization must increase about 15-fold.

Activity: Overview of Cellular Respiration

Click here to complete this activity. Then answer the questions.

Part A What process occurs in Box A?

ANSWER:

https://session.masteringbiology.com/myct/assignmentPrintView?assignmentID=9462423

5/37

10/26/2020

Chapter 9 oxidative phosphorylation the citric acid cycle electron transport glycolysis electron transport and oxidative phosphorylation

Correct Glycolysis occurs in the cytosol.

Part B What process occurs within Box B?

ANSWER:

glycolysis electron transport photophosphorylation the citric acid cycle oxidative phosphorylation

Correct The citric acid cycle transfers electrons to NADH and FADH2.

Part C What molecule is indicated by the letter D?

https://session.masteringbiology.com/myct/assignmentPrintView?assignmentID=9462423

6/37

10/26/2020

Chapter 9

ANSWER:

water oxygen glucose pyruvate ATP

Correct Oxygen is the final electron acceptor of cellular respiration.

Activity: Redox Reactions

Click here to view this animation. Then answer the questions.

Part A Which term describes the degree to which an element attracts electrons?

Hint 1. Which is a property of atoms?

ANSWER:

Electronegativity. Polarity. Reduction. Oxidation.

Correct Electronegativity is the tendency of an atom to attract electrons toward itself.

Part B Which terms describe two atoms when they form a bond in which electrons are completely transferred from one atom to the other?

Hint 1.

https://session.masteringbiology.com/myct/assignmentPrintView?assignmentID=9462423

7/37

10/26/2020

Chapter 9

How does the electrical state of each atom change?

ANSWER:

Anion and cation. Polar and nonpolar. Ionic and covalent. Proton and electron.

Correct Each atom will carry a charge from the transfer of electrons.

Part C Which of the following statements is true of the bonds in a water molecule?

Hint 1. Consider the atomic properties of oxygen and hydrogen.

ANSWER:

Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero. Oxygen acts as the electron acceptor and is oxidized. The electron in each hydrogen atom is completely transferred to the oxygen atom, and each hydrogen atom has a net charge of +1. There is equal sharing of the electrons between the oxygen atom and the two hydrogen atoms, and the net charge is zero.

Correct The oxygen and hydrogen atoms in water have partial charges, but the molecule has a net charge of zero.

Part D Which of the following statements is not true of most cellular redox reactions?

Hint 1. What happens to the electrons and bonds during a redox reaction?

ANSWER:

The reactant that is oxidized loses electrons. A hydrogen atom is transferred to the atom that loses an electron. Changes in potential energy can be released as heat. The electron acceptor is reduced.

Correct A hydrogen atom (proton, or H+) is often transferred to the atom that gains an electron.

https://session.masteringbiology.com/myct/assignmentPrintView?assignmentID=9462423

8/37

10/26/2020

Chapter 9

Part E What kind of bond is formed when lithium and fluorine combine to form lithium fluoride?

Hint 1. Consider the electrons in the outermost shell of each atom.

ANSWER:

Ionic. Redox. Nonpolar covalent. Polar covalent.

Correct The complete transfer of an electron from lithium to fluorine results in a stable compound in which both atoms have full outermost shells.

Part F 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?

Hint 1. How are the electrons transferred?

ANSWER:

Hydrogen, polar. Hydrogen, nonpolar. Oxygen, polar. Oxygen, nonpolar.

Correct Hydrogen loses electrons to oxygen, which is more electronegative and thus pulls the electrons closer to itself in the water molecule.

Chapter 9 Question 6

Part A When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes _____. ANSWER:

https://session.masteringbiology.com/myct/assignmentPrintView?assignmentID=9462423

9/37

10/26/2020

Chapter 9 redoxed oxidized dehydrogenated reduced

Correct

Chapter 9 Question 7

Part A Which of the following statements about NAD+ is true? ANSWER:

NAD+ can donate electrons for use in oxidative phosphorylation. NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle. In the absence of NAD+, glycolysis can still function. NAD+ has more chemical energy than NADH.

Correct

Chapter 9 Question 10

Part A A cell has enough available ATP to meet its needs for about 30 seconds. What is likely to happen when an athlete exhausts his or her ATP supply? ANSWER:

Catabolic processes are activated that generate more ATP. ATP is transported into the cell from the circulatory system. He or she has to sit down and rest. Other cells take over, and the muscle cells that have used up their ATP cease to function.

Correct

Chapter 9 Pre-Test Question 1 Part A Which of the following best describes the main purpose of the combined processes of glycolysis and cellular respiration? See Concept 9.1 (Page 165)

Hint 1.

https://session.masteringbiology.com/myct/assignmentPrintView?assignmentID=9462423

10/37

10/26/2020

Chapter 9

Think about the products of these processes that are essential to cellular function.

ANSWER:

breaking down ATP, so that ADP and P can be reused transforming the energy in glucose and related molecules into a chemical form that cells can use for work producing complex molecules from chemical building blocks catabolism of sugars and related compounds the breakdown of glucose to carbon dioxide and water

Correct The energy made available during cellular respiration is coupled to a production of ATP, the basic energy currency that cells use for work.

Chapter 9 Pre-Test Question 2 Part A In the combined processes of glycolysis and cellular respiration, what is consumed and what is produced? See Concept 9.1 (Page 165)

Hint 1. Consider what you consume and what your body eliminates.

ANSWER:

Oxygen is consumed, and glucose is produced. Glucose is consumed, and carbon dioxide is produced. Carbon dioxide is consumed, and water is produced. Water is consumed, and ATP is produced. ATP is consumed, and oxygen is produced.

Correct The carbon in glucose is oxidized to carbon dioxide during cellular respiration.

Chapter 9 Question 1

Part A In which reactions of cellular respiration and fermentation does substrate-level phosphorylation occur? ANSWER:

only in the electron transport chain only in the citric acid cycle only in glycolysis in both glycolysis and the citric acid cycle

https://session.masteringbiology.com/myct/assignmentPrintView?assignmentID=9462423

11/37

10/26/2020

Chapter 9

Correct

Chapter 9 Question 3

Part A What happens when electrons are passed from one atom to a more electronegative atom? ANSWER:

The more electronegative atom is oxidized, and energy is released. The more electronegative atom is reduced, and energy is released. The more electronegative atom is reduced, and energy is consumed. The more electronegative atom is oxidized, and energy is consumed.

Correct

Chapter 9 Question 5

Part A What happens to a glucose molecule when it loses a hydrogen atom as the result of an oxidation-reduction reaction? ANSWER:

The glucose molecule is hydrolyzed. The glucose molecule is an oxidizing agent. The glucose molecule is reduced. The glucose molecule is oxidized.

Correct

Chapter 9 Question 8

Part A The oxygen consumed during cellular respiration is directly involved in which of the following processes or events? ANSWER:

accepting electrons at the end of the electron transport chain the citric acid cycle the oxidation of pyruvate to acetyl CoA glycolysis

https://session.masteringbiology.com/myct/assignmentPrintView?assignmentID=9462423

12/37

10/26/2020

Chapter 9

Correct

Chapter 9 Question 9

Part A Why are carbohydrates and fats ...