Metabolism - Respiration

4/7/13 Metabolism - Respiration & Photosynthesis

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Metabolism - Respiration & Photosynthesis

Due: 9:00am on Wednesday, March 20, 2013

Note: You will receive no credit for late submissions. To learn more, read your instructor's Grading Policy

Energy Flow in Plants -- Concept Map

Plants are best known for their ability to perform photosynthesis, the process by which light energy is converted to chemical energy in the form ofsugars. But plants don’t just make sugars; they use them, too. Like animals, plants must break sugars down to fuel cellular work. In this activity, youwill complete a concept map showing the interrelatedness of sugar production and sugar breakdown in a plant cell.

Part A - Photosynthesis and respiration in plants

Drag the labels from the left to their correct locations in the concept map on the right. Not all labels will be used.

Hint 1. What products are generated in chloroplasts?

Chloroplasts are the sites of photosynthesis.

Which two of the following molecules are products of chloroplasts?

ANSWER:

Hint 2. What products are generated in mitochondria?

Mitochondria house the metabolic pathways associated with cellular respiration.

Which two of the following molecules are products of mitochondria?

ANSWER:

ANSWER:

Biol 1002 - Spring 2013

Metabolism - Respiration & Photos... Resources

sugar

amino acid

oxygen gas

carbon dioxide

sugar

carbon dioxide

ATP

oxygen gas

Signed in as Nora Trejos Help Close

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Correct

A mutually dependent relationship exists between chloroplasts and mitochondria in the plant cell. Photosynthesis, which occurs inchloroplasts, generates the sugars and oxygen gas that are used in mitochondria for cellular respiration. Cellular respiration generates carbondioxide, which in turn is used as a carbon source for the synthesis of sugars during photosynthesis. Cellular respiration also generates ATPand water, which are used in various chemical reactions in the plant cell.

Activity: Overview of Photosynthesis

Click here to complete this activity.

Then answer the questions.



Part A

Which of these equations best summarizes photosynthesis?

ANSWER:

Correct

This is the equation that summarizes the reactions of photosynthesis.

Part B

Where does the Calvin cycle occur?

ANSWER:

Correct

The Calvin cycle occurs in the stroma.

Part C

The light reactions of photosynthesis use _____ and produce _____.

ANSWER:

Correct

NADPH is a reactant in the Calvin cycle.

Activity: Overview of Cellular Respiration

6 CO2 + 6 H2O → C6H12O6 + 6 O2

6 CO2 + 6 O2 → C6H12O6 + 6 H2O

H2O → 2 H+ + 1/2 O2 + 2e-

C6H12O6 + 6 O2 → 6 CO2 + 12 H2O

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy

D

B

C

E

A

NADPH ... NADP+

NADPH ... oxygen

carbon dioxide ... oxygen

carbon dioxide ... sugar

water ... NADPH





Part A

What process occurs in Box A?

ANSWER:

Correct

Glycolysis occurs in the cytosol.

Part B

What process occurs within Box B?

ANSWER:

the citric acid cycle

glycolysis

electron transport and oxidative phosphorylation

electron transport

oxidative phosphorylation

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Correct

The citric acid cycle transfers electrons to NADH and FADH2.

Part C

What molecule is indicated by the letter D?

ANSWER:

Correct

Oxygen is the final electron acceptor of cellular respiration.

Activity: Redox Reactions

Click here to view this animation.


Part A

the citric acid cycle

photophosphorylation

electron transport


glycolysis

water

pyruvate

oxygen

ATP

glucose





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

Hint 1.

Which is a property of atoms?

ANSWER:

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.

How does the electrical state of each atom change?

ANSWER:

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:

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?

Polarity.

Electronegativity.

Oxidation.

Reduction.

Proton and electron.

Anion and cation.

Ionic and covalent.

Polar and nonpolar.

There is equal sharing of the electrons between the oxygen atom and the two hydrogen atoms, and the net charge is zero.

Oxygen acts as the electron acceptor and is oxidized.

Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero.

The electron in each hydrogen atom is completely transferred to the oxygen atom, and each hydrogen atom has a net charge of +1.



Hint 1.

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

ANSWER:

Correct

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

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:

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:

Correct

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

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.

Redox.

Nonpolar covalent.

Polar covalent.

Ionic.

Hydrogen, nonpolar.

Oxygen, nonpolar.

Oxygen, polar.

Hydrogen, polar.



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?

Hint 1.

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

ANSWER:

Correct

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


Part A

In the combined processes of glycolysis and cellular respiration, what is consumed and what is produced?

Hint 1.

Consider what you consume and what your body eliminates.

ANSWER:

Correct

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

Cellular Respiration (2 of 5): Glycolysis (BioFlix tutorial)

In glycolysis, the first stage of cellular respiration, one molecule of glucose is oxidized to two molecules of pyruvate, with the production of ATP andNADH. As you watch the Glycolysis animation, pay attention to the reactions involved in the production of NADH. These reactions, called redox(oxidation-reduction) reactions, play a key role in cellular respiration. Also pay attention to the mechanism by which ATP is synthesized. Think abouthow ATP synthesis at this stage differs from ATP synthesis during oxidative phosphorylation, where most of the ATP in cellular respiration is made.

transforming the energy in glucose and related molecules in a chemical form that cells can use for work

catabolism of sugars and related compounds

producing complex molecules from chemical building blocks

breaking down ATP, so that ADP and P can be reused

the breakdown of glucose to carbon dioxide and water

Glucose is consumed, and carbon dioxide is produced.

ATP is consumed, and oxygen is produced.

Carbon dioxide is consumed, and water is produced.

Water is consumed, and ATP is produced.

Oxygen is consumed, and glucose is produced.



Part A - Redox (oxidation-reduction) reactions in glycolysis

In glycolysis, as in all the stages of cellular respiration, the transfer of electrons from electron donors to electron acceptors plays a critical role inthe overall conversion of the energy in foods to energy in ATP. These reactions involving electron transfers are known as oxidation-reduction, orredox, reactions.

Drag the words on the left to the appropriate blanks on the right to complete the sentences.

Hint 1. Redox reactions

Under normal circumstances, redox reactions always occur in pairs. In the first of the two reactions, the electron donor is oxidized (it loseselectrons). In the second reaction, the electron acceptor is reduced (it gains the electrons lost by the first compound). A generic redoxreaction showing the transfer of two electrons is illustrated here.

Note that compounds A and B each exist in two forms: One form is reduced (it carries the extra electrons) while the other form is oxidized(it does not carry the extra electrons). In the reaction shown here, the electron donor is the reduced form of compound A and the electronacceptor is the oxidized form of compound B.

Hint 2. The oxidation of carbon-containing compounds

In the net reaction of cellular respiration, glucose (C6H12O6) is completely oxidized to CO2.

In reality, glucose is not oxidized to CO2 in a single step, as suggested by the net reaction. Instead, there is a step-wise removal of 12 pairsof electrons from the carbon-containing intermediates of glucose catabolism (one pair at a time) until all of the carbons exist in the form ofCO2. Two of the 12 pairs of electrons are removed in the reactions of glycolysis.

Hint 3. What are the electron carriers in glycolysis?

In glycolysis and the other stages of cellular respiration, electrons removed from intermediates in glucose catabolism are not passeddirectly to O2. Instead, electron carriers shuttle the electrons from the oxidation of the carbon-containing compounds to the eventualreduction of O2 to water.



In glycolysis, which molecule picks up the electrons released by the oxidation of glucose?

Hint 1. Redox reactions involving NAD+ and NADH

Recall that compounds involved in redox reactions occur in pairs, an oxidized form and a reduced form. The most common pair of

electron carriers in cellular respiration is NAD+ (the oxidized form) and NADH (the reduced form).

ANSWER:

ANSWER:

Correct

In the net reaction for glycolysis, glucose (the electron donor) is oxidized to pyruvate. The electrons removed from glucose are transferred to

the electron acceptor, NAD+, creating NADH.

Part B - Energy from glycolysis

Among the products of glycolysis, which compounds contain energy that can be used by other biological reactions?

Hint 1. Energy in carbon-containing compounds

In the overall process of cellular respiration, glucose is oxidized to carbon dioxide and much of the energy generated by the breakdown ofglucose is used to make ATP. In glycolysis, however, glucose is only oxidized to pyruvate; no carbon dioxide is produced in this stage ofrespiration. In addition, only a small fraction (<10%) of the total ATP produced by cellular respiration is generated in glycolysis. Considerwhat this means in terms of the energy content of pyruvate and its oxidation in subsequent stages of cellular respiration.

Hint 2. ATP-- the energy currency of cells

ATP

NAD+

NADH

O2



The interconversion of ATP and ADP + Pi is a key step in the transfer of energy between reactions that release energy and those thatrequire an input of energy.

Most of the ATP produced in our cells comes from the oxidation of foods in cellular respiration. The reverse reaction, the hydrolysis of ATPto ADP and Pi, powers most of the energy-requiring reactions that take place in cells, such as active transport and muscle contraction.

Hint 3. What is the fate of NADH produced by glycolysis?

Is the NADH produced in glycolysis used in any other reactions of cellular respiration where ATP is produced?

ANSWER:

ANSWER:

Correct

ATP is the main product of cellular respiration that contains energy that can be used by other cellular processes. Some ATP is made inglycolysis. In addition, the NADH and pyruvate produced in glycolysis are used in subsequent steps of cellular respiration to make even moreATP.

Part C - ATP synthesis in glycolysis: substrate-level phosphorylation

The ATP that is generated in glycolysis is produced by substrate-level phosphorylation, a very different mechanism than the one used to produceATP during oxidative phosphorylation. Phosphorylation reactions involve the addition of a phosphate group to another molecule.

Sort the statements into the appropriate bin depending on whether or not they correctly describe some aspect of substrate-levelphosphorylation in glycolysis.

Hint 1. The reactions of glycolysis are catalyzed by soluble enzymes

All of the reactions of glycolysis are catalyzed by soluble enzymes located in the cytosol of the cell. None of the enzymes is associatedwith membranes.

Hint 2. Oxidative phosphorylation and ATP synthesis

In oxidative phosphorylation, the last stage of cellular respiration, energy released from the oxidation of NADH and FADH2 is used toproduce ATP from ADP and free inorganic phosphate (Pi) ions.

ANSWER:

Yes, NADH is an input to the citric acid cycle, where more ATP is produced.

Yes, NADH is an input to oxidative phosphorylation, where more ATP is produced.

Yes, NADH is an input to both the citric acid cycle and oxidative phosphorylation, where more ATP is produced.

No, NADH is used in oxidative phosphorylation, but no additional ATP is produced.

No, NADH is not used in any subsequent stages of cellular respiration.

ATP only

CO2 only

ATP and NADH only

NADH only

O2 only

pyruvate and ATP only

pyruvate, ATP, and NADH



Correct

In substrate-level phosphorylation, an enzyme transfers a phosphate group from one molecule (an intermediate in the breakdown of glucose topyruvate) to ADP to form ATP. This is very different from the mechanism of ATP synthesis that takes place in oxidative phosphorylation.

Activity: Glycolysis



Part A

How many NADH are produced by glycolysis?

ANSWER:

Correct

Two NADH molecules are produced by glycolysis.

1

2

5

4

3



Part B

In glycolysis, ATP molecules are produced by _____.

ANSWER:

Correct

A phosphate group is transferred from glyceraldehyde phosphate to ADP.

Part C

Which of these is NOT a product of glycolysis?

ANSWER:

Correct

FADH2 is a product of the citric acid cycle.

Part D

In glycolysis, what starts the process of glucose oxidation?

ANSWER:

Correct

Some ATP energy is used to start the process of glucose oxidation.

Part E

In glycolysis there is a net gain of _____ ATP.

ANSWER:

cellular respiration

photosynthesis


substrate-level phosphorylation


ATP

NADH

pyruvate

FADH2

ATP

FADH2

ADP

NADPH

hexokinase

1

3

5

2

4



Correct

It takes 2 ATP to produce 4 ATP.


Part A

Which of the following describes the process of glycolysis?

Hint 1.

Consider the net chemical reaction that is accomplished by glycolysis.

ANSWER:

Correct

Catabolism of glucose begins with glycolysis.

Chapter 9 Question 15

Part A

Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?

ANSWER:

Correct

Cellular Respiration (3 of 5): Acetyl CoA Formation and the Citric Acid Cycle (BioFlix tutorial)

Before beginning this tutorial, watch the animation showing the second and third stages of cellular respiration – acetyl CoA formation and the citric acidcycle (also known as the Krebs cycle). In these two stages, the pyruvate produced in glycolysis is completely oxidized to CO2, with the production ofNADH, FADH2, and some ATP. Consider carefully the unique cyclic sequence of reactions of the citric acid cycle and the many redox reactions thatoccur within it.

It converts one glucose molecule to two molecules of pyruvate and carbon dioxide.

Glycolysis produces 30 ATP from each molecule of glucose.

It requires ATP and NADH.

It represents the first stage in the chemical oxidation of glucose by a cell.

Glycolysis occurs in the mitochondria.

38%

10%

2%

100%

0%



Part A - Carbon atoms in acetyl CoA formation and the citric acid cycle

During acetyl CoA formation and the citric acid cycle, all of the carbon atoms that enter cellular respiration in the glucose molecule are released inthe form of CO2. Use this diagram to track the carbon-containing compounds that play a role in these two stages.

Drag the labels from the left (which represent numbers of carbon atoms) onto the diagram to identify the number of carbon atoms ineach intermediate in acetyl CoA formation and the citric acid cycle. Labels may be used more than once.

Hint 1. How many carbon atoms are in pyruvate and acetyl CoA?

In glycolysis, glucose (a six-carbon molecule) is broken down to form two molecules of pyruvate. Then, during acetyl CoA formation,pyruvate is converted to acetyl CoA through a series of reactions.

Which statement is true about the number of carbon atoms in the compounds involved in acetyl CoA formation?

ANSWER:

Hint 2. Carbon atoms in citrate, the first intermediate in the citric acid cycle

Citrate (citric acid), the first intermediate in the citric acid cycle, contains six carbon atoms.

ANSWER:

Both pyruvate and acetyl CoA are six-carbon molecules.

Pyruvate is a three-carbon molecule, while acetyl CoA is a two-carbon molecule. One molecule of CO2 is released.

Both pyruvate and acetyl CoA are two-carbon molecules.

Both pyruvate and acetyl CoA are three-carbon molecules.

Pyruvate is a six-carbon molecule, while acetyl CoA is a five-carbon molecule. One molecule of CO2 is released.



Correct

This diagram of the citric acid cycle shows the carbon skeletons of each intermediate. The net result of this complex series of reactions is thecomplete oxidation of the two carbon atoms in the acetyl group of acetyl CoA to two molecules of CO2.

Part B - Net redox reaction in acetyl CoA formation and the citric acid cycle

In the sequential reactions of acetyl CoA formation and the citric acid cycle, pyruvate (the output from glycolysis) is completely oxidized, and theelectrons produced from this oxidation are passed on to two types of electron acceptors.

Drag the labels on the left to show the net redox reaction in acetyl CoA formation and the citric acid cycle. Note that two types ofelectron carriers are involved.

Hint 1. Redox reactions

Under normal circumstances, redox reactions always occur in pairs. In the first of the two reactions, the electron donor is oxidized (it loses



electrons). In the second reaction, the electron acceptor is reduced (it gains the electrons lost by the first compound). A generic redox

reaction involving the transfer of two electrons is illustrated here.

Note that compounds A and B each exist in two forms: One form is reduced (it carries the extra electrons) while the other form is oxidized(it does not carry the extra electrons). In the reaction shown here, the electron donor is the reduced form of compound A and the electronacceptor is the oxidized form of compound B.

Hint 2. What are the electron carriers in acetyl CoA formation and the citric acid cycle?

In acetyl CoA formation and the citric acid cycle, as in glycolysis, electron carriers shuttle the electrons removed from carbon-containingintermediates to a later stage in cellular respiration. The most common pair of electron carriers in cellular respiration is NAD+ (the oxidizedform) and NADH (the reduced form):

In the citric acid cycle, however, another pair of electron carriers shuttles electrons in addition to NAD+/NADH.

What is the second pair of electron carriers in the citric acid cycle?

ANSWER:

Hint 3. Can you identify the electron donor and acceptor in a reaction?

One of the reactions in the citric acid cycle is the oxidation of the six-carbon molecule isocitrate to the five-carbon molecule alpha-ketoglutarate, with the release of one molecule of CO2.

In this reaction, the electron donor is __________ and the electron acceptor is __________.

ANSWER:

ANSWER:

ADP (the oxidized form) and ATP (the reduced form)

ATP (the oxidized form) and ADP (the reduced form)

O2 (the oxidized form) and H2O (the reduced form)

FAD (the oxidized form) and FADH2 (the reduced form)

FADH2 (the oxidized form) and FAD (the reduced form)

H2O (the oxidized form) and O2 (the reduced form)

isocitrate/alpha-ketoglutarate

alpha-ketoglutarate/NADH

NAD+/NADH

isocitrate/NAD+

NADH/NAD+



Correct

As in glycolysis, the electrons removed from carbon-containing intermediates during acetyl CoA formation and the citric acid cycle are passed

to the electron carrier NAD+, reducing it to NADH. The citric acid cycle also uses a second electron carrier, FAD (flavin adenine dinucleotide),the oxidized form, and FADH2, the reduced form.

Part C - 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—inacetate—to CO2 requires a complex, eight-step pathway—the citric acid cycle. Consider four possible explanations for why the last two carbons inacetate 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.

Hint 1. What is the fate of carbon atoms entering the citric acid cycle?

With each turn of the citric acid cycle, two carbon atoms from the acetyl group of acetyl CoA join with the four-carbon oxaloacetate (the lastintermediate in the citric acid cycle) to form citrate, a six-carbon acid.

In the remaining steps of the citric acid cycle, the six-carbon citrate is converted back to the four-carbon oxaloacetate.

What happens to the other two carbon atoms?

ANSWER:

Hint 2. How many carbon atoms are in the molecules from which CO2 is released in the citric acid cycle?

Two molecules of CO2 are produced for each molecule of acetyl CoA that enters the citric acid cycle. These two molecules of CO2 areremoved from specific carbon intermediates in the cycle. How many carbon atoms are present in the intermediates from which CO2 is

They are used to convert ADP and Pi to ATP.

They are used to convert NAD+ to NADH.

They are released as two CO2 molecules.

They are converted into pyruvate.

They increase the number of carbon atoms stored in the intermediates of the citric acid cycle.



removed?

How many carbon atoms are present in the intermediates from which CO2 is removed?

Hint 1. Reactions that release CO2 in the citric acid cycle

This diagram shows the carbon skeletons of the intermediates in the citric acid cycle. Locate the intermediates involved in reactionsin which CO2 is released to determine how many carbon atoms they contain.

ANSWER:

ANSWER:

Correct

Although it is possible to oxidize the two-carbon acetyl group of acetyl CoA to two molecules of CO2, it is much more difficult than adding theacetyl group to a four-carbon acid to form a six-carbon acid (citrate). Citrate can then be oxidized sequentially to release two molecules ofCO2.

2

3

4

5

6

2 or 6

4 or 5

5 or 6

More ATP is produced per CO2 released in cyclic processes than in linear processes.

It is easier to remove electrons and produce CO2 from compounds with three or more carbon atoms than from a two-carbon compoundsuch as acetyl CoA.

Redox reactions that simultaneously produce CO2 and NADH occur only in cyclic processes.

Cyclic processes, such as the citric acid cycle, require a different mechanism of ATP synthesis than linear processes, such asglycolysis.




Part A

Which statement about the citric acid cycle is correct?

Hint 1.

Think about how the citric acid cycle fits into the larger picture of cellular respiration.

ANSWER:

Correct

This is the correct description of the cyclic nature of this sequence of reactions.

Activity: Electron Transport



Part A

For each glucose that enters glycolysis, _____ acetyl CoA enter the citric acid cycle.

ANSWER:

Correct

Each glucose produces two pyruvates, each of which is converted into acetyl CoA.

Part B

For each glucose that enters glycolysis, _____ NADH + H+ are produced by the citric acid cycle.

ANSWER:

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.

The citric acid cycle produces most of the ATP that is subsequently used by the electron transport chain.

The citric acid cycle depends on the availability of NAD+, which is a product of glycolysis.

The oxidation of compounds by the citric acid cycle requires molecular oxygen.

0

1

4

2

5





Correct

3 NADH + H+ are produced per each acetyl CoA that enters the citric acid cycle.

Part C

In cellular respiration, most ATP molecules are produced by _____.

ANSWER:

Correct

This process utilizes energy released by electron transport.

Part D

The final electron acceptor of cellular respiration is _____.

ANSWER:

Correct

Oxygen is combined with electrons and hydrogen to form water.

Part E

During electron transport, energy from _____ is used to pump hydrogen ions into the _____.

ANSWER:

Correct

The energy released as electrons, which have been donated by NADH and FADH2, is passed along the electron transport chain and used topump hydrogen ions into the intermembrane space.

2

3 to 6

3

0

6

cellular respiration


photosynthesis



FADH2

NADH

CO2

oxygen

water

NADH ... mitochondrial matrix

NADH ... intermembrane space

NADH and FADH2 ... mitochondrial matrix

NADH and FADH2 ... intermembrane space

acetyl CoA ... intermembrane space



Part F

Structure A is _____.

ANSWER:

Correct

ATP synthase phosphorylates ADP.

Part G

The proximate (immediate) source of energy for oxidative phosphorylation is _____.

ANSWER:

Correct

Concentration gradients are a form of potential energy.

Activity: Fermentation



Part A

In muscle cells, fermentation produces _____.

sensory protein

an electron acceptor

an electron donor

ATP synthase

phospholipid


NADH and FADH2

ATP

kinetic energy that is released as hydrogen ions diffuse down their concentration gradient

ATP synthase





ANSWER:

Correct

These are the products of fermentation as it occurs in muscle cells.

Part B

In fermentation _____ is reduced and _____ is oxidized.

ANSWER:

Correct

The pyruvate from glycolysis is reduced to either lactate or ethanol, and NADH is oxidized to NAD+.

Activity: Chemiosmosis



Part A

Which term describes ATP production resulting from the capture of light energy by chlorophyll?

Hint 1.

Which ATP-producing process uses light energy?

ANSWER:

carbon dioxide, ethanol, and NAD+

pyruvate

carbon dioxide, ethanol, NADH, and ATP

lactate and NAD+

lactate, NADH, and ATP

pyruvate ... NADH

NAD+ ... pyruvate

lactate ... ethanol

NADH ... lactate

lactate ... NADH





Correct

The excitation of chlorophyll by light energy initiates a chain of events that leads to ATP production.

Part B

True or false? The chemiosmotic hypothesis states that the synthesis of ATP generates a proton gradient that leads to electron flow through anelectron transport chain.

Hint 1.

How are electron flow and ATP production linked in organisms?

ANSWER:

Correct

The chemiosmotic hypothesis states that the flow of electrons through an electron transport chain generates a proton gradient that leads tothe synthesis of ATP.

Part C

According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis?

Hint 1.

What is the chemiosmotic hypothesis?

ANSWER:

Correct

A proton gradient across chloroplast and mitochondrial membranes drives ATP synthesis by the enzyme ATP synthase.

Part D

Which of the following particles can pass through the ATP synthase channel?

Hint 1.

This particle directly drives the synthesis of ATP.

ANSWER:

Substrate-level phosphorylation

Dephosphorylation

Photophosphorylation

Oxidative phosphorylation

True

False

Temperature gradient

Proton gradient

Electrons

Osmotic gradient



Correct

The channels formed by ATP synthase are specific for protons.

Part E

True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplastmembrane.

Hint 1.

Consider the functions of the two main parts of the ATP synthase enzyme.

ANSWER:

Correct

The region of ATP synthase that catalyzes ATP production protrudes out of, but does not span, the chloroplast membrane; the region thatspans the membrane is an ion channel through which protons can pass.

Part F

Chloroplast membrane vesicles are equilibrated in a simple solution of pH 5. The solution is then adjusted to pH 8. Which of the followingconclusions can be drawn from these experimental conditions?

Hint 1.

Review the conditions that resulted in the production of ATP in the experiment described in the animation.

ANSWER:

Correct

This statement is true; although the proton gradient is present, ADP and inorganic phosphate are required to make ATP and were not added tothe reaction.

Activity: Photosynthesis

ADP

Protons

ATP

Inorganic phosphate

True

False

ATP will be produced because the proton gradient favors proton movement through the ATP synthase channels.

Protons will not diffuse toward the outside of the vesicles.

ATP will not be produced because there is no ADP and inorganic phosphate in the solution.

The change in the solution's pH results in a gradient across the chloroplast membranes such that there is a lower concentration ofprotons inside the vesicles and a higher concentration outside.





Part A

Which process produces oxygen?

Hint 1.

Where does oxygen come from?

ANSWER:

Correct

Oxygen is a by-product of the photosynthetic process.

Part B

Which set of reactions uses H2O and produces O2?

Hint 1.

What happens to the hydrogen atoms?

ANSWER:

Correct

The light-dependent reactions use H2O and produce O2.

Part C

What is the importance of the light-independent reactions in terms of carbon flow in the biosphere?

Hint 1.

In plants, if carbon dioxide goes in, what comes out?

ANSWER:

Photosynthesis

Cellular respiration

The light-dependent reactions

The light-independent reactions





Correct

CO2 is unusable until plants have "fixed" this carbon into sugar.

Part D

True or false? The light-dependent reactions of photosynthesis use water and produce oxygen.

Hint 1.

Think about how water is used during photosynthesis.

ANSWER:

Correct

The water molecules are split to replenish electrons in photosystem II, leaving behind protons, which are used to generate a proton gradient forthe formation of ATP, and oxygen, which is released as a by-product.

Part E

Which of the following molecules is the primary product of photosystem I?

Hint 1.

Remember that photosystem I follows photosystem II in the light-dependent reactions of photosynthesis.

ANSWER:

Correct

The NADPH produced by photosystem I is used to supply energy for the production of sugars during photosynthesis.

Part F

What is the biological significance of the light-independent reactions of photosynthesis?

Hint 1.

The light-independent reactions are also known as the Calvin cycle.

ANSWER:

The light-independent reactions turn sugar into ATP for energy.

The light-independent reactions turn CO2, a gas, into usable carbon in the form of sugars.

The light-independent reactions use CO2 to make ATP.

The light-independent reactions turn glucose, a sugar, into CO2 gas.

True

False

ATP

NADPH

Carbon dioxide

Oxygen



Correct

All organisms use the sugars produced by photosynthesis to generate energy.

Part G

Which of the following statements best describes the relationship between the light-dependent and light-independent reactions of photosynthesis?

Hint 1.

One set of reactions generates products that are used in the other set of reactions.

ANSWER:

Correct

Light energy drives the formation of ATP and NADPH during the light-dependent reactions; these energy molecules are then used during thelight-independent reactions to form sugars.

Part H

Which of the following reactions ensures that the Calvin cycle can make a continuous supply of glucose?

Hint 1.

Think about which molecule is not produced by other reactions of photosynthesis.

ANSWER:

Correct

The regeneration of RuBP ensures that the Calvin cycle can proceed indefinitely, since RuBP fixes carbon dioxide into an organic moleculethat is used to produce sugar.

Activity: The Calvin Cycle

They convert ATP to sugar.

They make oxygen.

They convert carbon dioxide to sugar.

They generate ATP and NADPH.

The light-dependent reactions pass electrons through an electron transport chain to the light-independent reactions.

The light-independent reactions release energy, and the light-dependent reactions require energy.

The light-dependent reactions produce ATP and NADPH, which are then used by the light-independent reactions.

The light-dependent reactions produce carbon dioxide, which is then used by the light-independent reactions.

Carbon fixation

Production of G3P

Regneration of RuBP

Production of 3-phosphoglycerate





Part A

Carbon fixation involves the addition of carbon dioxide to _____.

ANSWER:

Correct

In the Calvin cycle, carbon dioxide is added to RuBP.

Part B

After 3-PGA is phosphorylated, it is reduced by _____.

ANSWER:

Correct

NADPH supplies the electrons that reduce the phosphorylated 3-PGA.

Part C

How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?

ANSWER:

Correct

Six carbon dioxide molecules are required to produce two G3P molecules, which can be combined to make one glucose molecule.

NADPH

G3P

Rubisco

RuBP

3-PGA

NADPH

ATP

ADP

NADP+

CO2

4

10

6

2

8





Part D

In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules?

ANSWER:

Correct

Correct.


Part A

C4 plants occur more commonly in desert conditions because _____.

Hint 1.

Consider how C4 plants differ from other (C3) plants.

ANSWER:

Correct

To conserve water during hot, dry conditions, the stomata are fully or partially closed, preventing CO2 from reaching high concentrations.


Part A

Photorespiration lowers the efficiency of photosynthesis by

ANSWER:

Correct

3

4

5

2

1

they produce water as a product of their photosynthetic pathways

they produce carbon dioxide internally via photorespiration

they can fix carbon at the lower CO2 concentrations that develop when the stomata are closed

they store carbon by incorporating CO2 into organic acids that are later catabolized

the stomata open at night and close in the day

reducing the amount of 3-phosphoglycerate forme.

generating excess ATP.

denaturing rubisco.

consuming carbon dioxide.

producing ribulose bisphosphate.




Part A

Which process is most directly driven by light energy?

ANSWER:

Correct

Score Summary:

Your score on this assignment is 99.1%.You received 19.82 out of a possible total of 20 points.

carbon fixation in the stroma

removal of electrons from chlorophyll molecules

reduction of NADP+ molecules

ATP synthesis

creation of a pH gradient by pumping protons across the thylakoid membrane

Documents

Metabolism - Respiration