1 Biology Energy Processing www.njctl.org 2 Vocabulary Click on - - PowerPoint PPT Presentation

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Biology Energy Processing

www.njctl.org

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Vocabulary

glycolysis aerobic anabolic pathway anaerobic Calvin Cycle chlorophyll cellular respiration

FADH2

fermentation lactic acid fermentation metabolism

ATP

NADH citric acid cycle electron transport chain Krebs cycle electron acceptor facultative anaerobe Acetyl Co­A ATP synthase NADPH catabolic pathway ethanol fermentation cyclic energy transport light dependent reactions light independent reactions Click on each word below to go to the definition.

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Vocabulary

p y r u v a t e

• xidation

reduction pyruvate decarboxylation phosphorylation

• xidative phosphorylation
• bligate anaerobe
• bligate aerobe

photosynthesis photosystem I photosystem II noncyclic energy transport t h y l a k

• i

d

Click on each word below to go to the definition.

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Energy Processing Unit Topics

· Metabolism & ATP · Cellular Respiration

Click on the topic to go to that section

· Fermentation

· Photosynthesis

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Chapter 8

Metabolism & ATP

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Table of

Contents

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Metabolism is the totality of an organism’s chemical reactions. Metabolism is a property of all life.

Metabolic Pathways

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A metabolic pathway begins with a specific molecule and

ends with a product Each step is catalyzed by a specific enzyme Without enzymes, metabolic pathways would proceed very

slowly.

Metabolic Pathways

enzyme 1

enzyme 2 enzyme 3

A

B C D

Starting Molecule Product

Reaction 1 Reaction 3 Reaction 2

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There are two types of metabolic pathways: Catabolic pathways Anabolic pathways

Metabolic Pathways

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Catabolic pathways break down molecules from the environment. Living things use the energy derived from breaking the bonds in these molecules to build structures and drive cell processes.

Catabolic Pathways

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Reactants Energy Products Progress of the reaction Free energy Amount of free energy released (ΔG<0)

Exergonic Reaction

Catabolic pathways are exergonic reactions; the change in Gibbs free energy is negative. Thus, they release energy and occur spontaneously

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Anabolic pathways synthesize complex organic molecules and power cell processes using the energy derived from catabolic pathways.

Anabolic Pathways

Examples: building bones building muscle building starch powering active transport Click here for a pneumonic device

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Reactants Energy Products Progress of the reaction Amount of free energy required (ΔG > 0) Free energy

Endergonic Reaction

Anabolic pathways are endergonic reactions; the change in Gibbs free energy is positive. Thus, they require an input of energy and do not occur spontaneously

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A process will occur spontaneously if the result is a reduction of the Gibbs Free Energy (G) of the system. G takes into account the resulting change in the energy of a system and the change in its entropy. If the effect of a reaction is to reduce G, the process will proceed spontaneously. If ∆G is negative, the reaction will occur spontaneously. If ∆G is zero or positive, it will not occur spontaneously.

Spontaneous Processes

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Free Energy and Metabolism

Biological systems often need an endergonic reaction to

• ccur, but on it's own, it won't proceed spontaneously.

To be able to occur, the endergonic reaction is coupled to a reaction that is exergonic, so that together, they are exergonic.

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NH2 Glu Non­spontaneous reaction: ∆G is positive ∆G = +3.4 kcal/mol NH3 Glu Glutamic acid Ammonia + ATP + H2O ADP Spontaneous Reaction: ∆G is negative + Pi ∆G = ­7.3 kcal/mol ∆G = –3.9 kcal/mol together, reactions are spontaneous

Adding Coupled Reactions

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1 A spontaneous reaction _____.

A

• ccurs only when an enzyme or other catalyst is present

B

cannot occur outside of a living cell

C

releases free energy when proceeding in the forward direction

D

is common in anabolic pathways

E

leads to a decrease in the entropy of the universe

Answer

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2 Anabolic pathways are ___________ and catabolic pathways are ______________.

A

spontaneous, non­spontaneous

B

endergonic, exergonic

C

exergonic, endergonic

D

endothermic, endergonic

Answer

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3 Which of the following correctly states the relationship between anabolic and catabolic pathways?

A

Degradation of organic molecules by anabolic pathways provides the energy to drive catabolic pathways.

B

Energy derived from catabolic pathways is used to drive the breakdown of organic molecules in anabolic pathways.

C

Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.

Answer

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A cell does three main kinds of work:

• Mechanical (motion)
• Transport (crossing a barrier)
• Chemical (changing a molecule)

To do work, cells manage energy resources by energy coupling, using an exergonic reaction to drive an endergonic one

Cell Energy

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ATP

Cells can store the energy from catabolic pathways in a molecule called ATP (adenosine triphosphate). ATP can be broken down later to fuel anabolic reactions.

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ATP (adenosine triphosphate) includes three phosphate groups (PO4­3). Each Phosphate group has an ionic charge of ­3e. In this model of ATP, each PO4­3 is circled in blue.

ATP

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ATP

The phosphate groups repel each

• ther, since they each have a

negative charge. Therefore it requires Work to add the second phosphate group; to go from AMP (monophosphate) to ADP (diphosphate). To add the third group, to go from ADP to ATP (triphosphate), requires even more work since it is repelled by both of the other phosphate groups.

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ATP

This is like the work in compressing a spring. The energy from the work needed to bring each phosphate group to the molecule is stored in that phosphate bond. When the bond is broken to go

from ATP to ADP, significant energy is released. Going from ADP to AMP releases less energy, since there is less total charge in ADP than ATP.

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The bonds between the phosphate groups of ATP’s tail can be broken by hydrolysis. Energy is released from ATP when the terminal phosphate bond is broken. The released energy is equal to the work that was done to form the bond. That work overcame the electrostatic repulsion between the last phosphate group and the initial ADP molecule. The result is a chemical change to a state of lower free

energy.

ATP

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In the living systems, the energy from the exergonic reaction

• f ATP hydrolysis can be used to drive an endergonic

reaction. Overall, the coupled reactions are exergonic.

ATP

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ATP Performs Work

ATP drives endergonic reactions by phosphorylation, transferring a phosphate group to some other molecule, such as a reactant. The recipient molecule is now "phosphorylated". The three types of cellular work are powered by the hydrolysis of ATP.

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NH2 Glu P

i

P i P i Pi

Glu NH3

P P

P

ATP ADP

Motor protein Mechanical work: ATP phosphorylates motor proteins Protein moved Membrane protein Solute Transport work: ATP phosphorylates transport proteins Solute transported Chemical work: ATP phosphorylates key reactants Reactants: Glutamic acid and ammonia Product (glutamine) made

+ + +

ATP Performs

Work

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The Regeneration of ATP

ATP is a renewable resource that is regenerated by addition

• f a phosphate group to ADP

The energy to phosphorylate ADP comes from catabolic reactions in the cell The chemical potential energy temporarily stored in ATP drives most cellular work Each cell is converting millions of ATP to ADP and back again every second.

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Pi Energy for cellular work (endergonic, energy consuming processes) Energy from catabolism (exergonic, energy yielding processes) + ATP ADP

The Regeneration of ATP

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4 In general, the hydrolysis of ATP drives cellular work by _____.

A releasing free energy that can be coupled to other reactions B releasing heat C acting as a catalyst D lowering the free energy of the reaction

Answer

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5 What best characterizes the role of ATP in cellular metabolism?

A

The release of free energy during the hydrolysis of ATP heats the surrounding environment.

B

The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate.

C

It is catabolized to carbon dioxide and water.

D

The ΔG associated with its hydrolysis is positive.

Answer

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6 Which of the following is not an example of the cellular work accomplished with the free energy derived from the hydrolysis of ATP?

A

Mechanical work, such as the movement of the cell

B

Transport work, such as the active transport of an ion into a cell.

C

Chemical work, such as the synthesis of new proteins.

D

The production of heat, which raises the temperature of the cell.

Answer

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Cellular Respiration

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Table of

Contents

35

Equilibrium and Metabolism

Reactions in a closed system eventually reach equilibrium and then stop. Life is not in equilibrium Life is an open system, experiencing a constant flow of materials and energy. Life cannot survive without connection to the environment.

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The Production of ATP Catabolic Pathways

Cellular respiration is a catabolic pathway that consumes

• rganic molecules and yields ATP.

Carbohydrates, fats, and proteins can all fuel cellular respiration. We'll look first at the simplest case, the breakdown of the sugar ­ glucose. But before doing that we have to learn about two molecules that are essential to respiration.

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NAD+ + 2H+ + 2e­ + Energy NADH + H+

NAD+ and FAD

The molecules NAD+ and FAD are used to store, and later release, energy during respiration; they are key to respiration. Each molecule has two forms, each form stores a different amount of energy. So moving between those two forms either stores chemical potential energy or releases it. Here are the reactions: FAD + 2H+ + 2e­ + Energy FADH2 The double arrows indicate that each reaction is reversible, they can proceed in either direction. When the reaction goes to the right, energy is stored. When it goes to the left, energy is released

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NAD+ and FAD

The amount of energy that is useable when the reaction goes to the left, depends on the availability of electron acceptors. Without a molecule, such as O2, to accept the excess electrons the energy stored in NADH and FADH2 cannot be used to make ATP. NAD+ + 2H+ + 2e­ + Energy NADH + H+ FAD + 2H+ + 2e­ + Energy FADH2

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Electron Acceptors

Oxygen is the best electron acceptor because it generates the greatest free energy change (∆G) and produces the most energy. In the absence of oxygen, other molecules, such as nitrate, sulfate, and carbon dioxide can be used as electron acceptors. If O2 is present,

• 1 NADH stores enough energy to create about 3 ATPs
• 1 FADH

2 stores enough energy to make about 2 ATPs

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7 NADH is converted to NAD+. During this process,

A energy is released B energy is stored C no energy is stored or released

Answer

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8 FADH2 is converted to FAD. During this process,

A energy is stored B energy is released C no energy is stored or released

Answer

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Reduction and Oxidation

When we go from left to right we are adding electrons to a

• molecule. That is called reducing the molecule, or the process of

reduction. Going from right to left, we are taking electrons from a molecule. That is called oxidizing the molecule, or the process of oxidation. NAD+ + 2H+ + 2e­ + Energy NADH + H+ FAD + 2H+ + 2e­ + Energy FADH2

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The reason for the term oxidation is that this is the effect that

• xygen usually has: it takes electrons from a molecule, oxidizing

the molecule The rusting of iron is an example of oxidation: oxygen is taking electrons from the metal, oxidizing it.

Oxidation

4 Fe + 3 O2 → 2 Fe2O3

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Reduction and Oxidation

LEO says GER

Losing

Electrons is Oxidation Gaining Electrons is Reduction

Since it doesn't seem right that adding electrons is called "reduction"; here's a way to remember these two terms.

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9 Which of the following cannot act as an electron acceptor?

A sulfate B oxygen C ammonia D nitrate

Answer

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10 The loss of an electron is __________ and the gain of an

electron is ____________.

A oxidation, reduction B reduction, oxidation C catalysis, phosphorylation D phosphoroylation, catalysis

Answer

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11 NADH is the reduced form of NAD+.

True False

Answer

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Types of Cellular Respiration

Cells follow different paths of cellular respiration depending on the presence or absence of oxygen. Cells can be classified into 3 categories based on their response to oxygen.

• Obligate Anaerobes ­ which cannot survive in the presence of
• xygen
• Obligate Aerobes ­ which require oxygen
• Facultative Anaerobes ­ which can survive in the presence or

absence of oxygen.

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The Stages of Respiration

Cellular respiration consists of four stages:

• Glycolysis
• Pyruvate Decarboxylation
• The Citric Acid Cycle (Krebs Cycle)
• Oxidative Phosphorylation

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The net result is: a net of 2 ATPs are formed along with 2 NADHs and the 2 pryuvates. Glycolysis means the splitting of glucose Some ATP is needed to start the process (Ea)

C6H12O6

(Glucose)

Gycolysis

2 ATP 4 ATP

2 NADH

2 C3H4O3 (Pyruvate)

2 NAD+

Glycolysis

Glycolysis is the first stage of cellular respiration. It involves the breakdown of glucose, a 6 carbon sugar, into 2 molecules of pyruvate, a 3 carbon sugar. Glycolysis means the splitting of glucose The net result is: a net of 2 ATPs are formed along with 2 NADHs and the 2 pryuvates. Some ATP is needed to start the process

(Ea)

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12 Until 2.5 billon years ago there was no oxygen in the Earth's atmosphere. Which of the following was also not present?

A facultative anaerobes B obligate anaerobes C obligate aerobes D bacteria

Answer

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13 How much activation energy is required to start glycolysis?

A 0 ATP B 1 ATP C 2 ATP D 4 ATP

Answer

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14 The net products of glycolysis are:

A 2 pyruvate B 2 NADH and 2 pyruvate C 2 ATP, 2 NADH, and 2 pyruvate D 4 ATP, 2 NADH, and 2 pyruvate

Answer

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Pyruvate Decarboxylation (PD)

The Citric Acid Cycle can only process 2­carbon molecules, and pyruvate is a 3­carbon molecule: C3H4O3

PDC 2 NADH 2 NAD+

2 C3H4O3 (Pyruvate)

2 CO2 2 Acetyl Co­A

PD is an enzyme catalyzed reaction that takes the 2 pyruvate molecules and converts them to 2 Acetyl Co­ A molecules: these are 2­carbon molecules. Energy is stored during PD by the converting 2 NAD+ to 2 NADH and the extra pyruvate carbons are expelled as CO2.

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The Citric Acid Cycle

This shows one cycle, which is due to one Acetyl Co­A molecule. To account for one glucose molecule, two cycles are needed. Let's tally up the

• utput for one cycle

to confirm our results.

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1 ATP

3 NADH 1 FADH2

The Citric Acid Cycle

1 ATP

3 NADH 1 FADH2

2 ATP

6 NADH 2 FADH2

But 1 glucose molecule, yields 2 Acetyl Co­A molecules, (therefore, 2 turns of the cycle) yielding : This is one turn of the cycle, due to 1 Acetyl Co­

• A. Note the production
• f:

Click here for a video of the Citric Acid Cycle

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The citric acid cycle is sometimes called the Krebs cycle. The cycle breaks down one Acetyl­CoA for each turn, generating 1 ATP, 3 NADH, 2 CO2 and 1 FADH2 per Acetyl­CoA. Since 2 Acetyl­CoA molecules were created from each glucose, the Citric Acid Cycle creates 2 ATP; 6 NADH; 4CO

2, and 2 FADH2 for

each glucose molecule.

The Citric Acid Cycle

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15 Glycolysis produces ____ ATP. Pyruvate Decarboxylation produces ____ ATP. The Citric Acid Cycle produces _____ ATP.

A 1, 1, 2 B 4, 0, 2 C 4, 0, 4 D 2, 0, 2

Answer

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16 During pyruvate decarboxylation, 3­carbon pyruvate is converted to 2­carbon Acetyl­CoA. What happens to the excess carbons atoms in this process?

A They are expelled in molecules of CH4 B They are expelled in molecules of CO2 C They are covalently bonded to NADH D They are recycled to reform glucose

Answer

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17 In total, the first 3 stages of cellular respiration produce how many molecules of carbon dioxide?

A 1 B 2 C 3 D 6

Answer

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So far we've done a lot of work to just get a net gain of 4 ATPs. But we have stored a lot of potential energy in the form of NADH and FADH2. The big energy payoff is in oxidative phosphorylation, where we convert the energy stored in those molecules to ATP.

Oxidative Phosphorylation (OP)

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Stage NADH FADH2 ATP Glycolysis 2 2 PD 2 CAC 6 2 2 Total 10 2 4

Oxidative Phosphorylation (OP)

We're now going to convert all the NADH and FADH2 into ATP, so the energy can be stored throughout the cell. Here's what we start this cycle with. When O2 is present, we get about 3 ATPs per NADH and 2 ATPs per FADH2. So how many ATPs would we have at the end of this next stage?

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Oxidative phosphorylation is powered by the electron transport

• chain. One way to think of the ETC is as a proton pump.

The ETC transports electrons, through chemical reactions, out and then back through a plasma membrane. The net effect is to pump protons from the inside to the outside of a plasma membrane, creating a proton gradient which is used to power

• xidative phosphorylation.

Electron Transport Chain (ETC)

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Electron Transport Chain (ETC)

The

electron path is shown in black.

The proton path in red.

The ETC generates no ATP, but enables Oxidative Phosphorylation, which accounts for most of the ATP produced.

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Anaerobic ETC

For the first 2 billion years of life on Earth, anaerobic (no O

2)

respiration was the only means of obtaining energy from food. These organisms used the electron acceptors, NO

3 ­, SO4 2­, or

CO2 to pull the electrons through the ETC. These molecules would accept the electrons at the end of the chain forming N

2,

H2S, and CH

4 respectively.

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Aerobic ETC

Click here for a video of the ETC

But then, the Oxygen Revolution occurred about 2.5 BYA, flooding the planet with oxygen. In aerobic respiration, the final electron acceptor of the electron transport chain is O2; forming water (H2O). Oxygen strongly attracts electrons in order to fill its outer shell. This stronger pull makes much more energy available to life, enabling the more complex food chains we see today.

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18 Which of the following is created during the electron transport chain in human cells? I ATP II NADH III proton gradient IV H2O

A I, II, III, IV B I, II only

C III only D III, IV only

Answer

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19 Obligate aerobes use which of the following as their final electron acceptor?

A CO2 B NO3­ C O2 D SO42­

Answer

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Oxidative Phosphorylation (OP)

The ETC creates a positive electrostatic potential outside the plasma membrane and a negative potential inside. The excess protons outside, are strongly attracted to the inside, but are blocked by the membrane. One path is open to the protons, but they must do work to use it. ATP Synthase is essentially a motor, constructed of proteins. The protons must travel through that motor in order to return to the cell, creating an electric current that powers the motor. As the motor turns, it adds a phosphate group to ADP, creating

• ATP. Electrical energy is transformed to chemical energy.

Click here for a video of ATP Synthase

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Oxidative Phosphorylation The Hydroelectric Analogy

The Hoover Dam is a massive structure that holds back the potential energy of 9 trillion gallons of water

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Like oxidative phosphorylation, it creates a gradient then exploits the stored energy by allowing water to pass through a small pipeline, transforming it to kinetic

energy.

Oxidative Phosphorylation The Hydroelectric Analogy

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Massive turbines are spun, causing the kinetic energy to be turned into mechanical energy which is utilized to make electrical energy.

Oxidative Phosphorylation The Hydroelectric Analogy

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We calculated earlier that we would expect to get 38 ATP molecules by the time we'd converted all the NADH

and FADH2 to ATP. The actual yield is between 36 ­ 38 ATP molecules per

glucose molecule. The reason for the small variance is that in some cases energy is needed to transport the NADH molecules to the site of the ETC.

Aerobic Respiration

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20 ATP synthase...

A synthesizes ATP B is an enzyme C is a protein complex D all of the above

Answer

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21 Energy released by the electron transport chain is used to pump H+ ions into which location?

A Outside the membrane B Inside the membrane

Answer

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22 What is the maximum number of ATP produced from a breakdown of a glucose molecule?

A 4 B 18 C 36 D 38

Answer

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The Versatility of Catabolism

Catabolic pathways funnel electrons from many kinds of

• rganic molecules into cellular respiration.

· Glycolysis accepts a wide range of carbohydrates · Proteins must be digested to amino acids; amino groups can feed

glycolysis or the citric acid cycle

· Fats are digested to glycerol which is used in glycolysis. An

• xidized gram of fat produces more than twice as much ATP as

an oxidized gram of carbohydrate

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The Versatility of Catabolism

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Fermentation

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Contents

80

When no electron acceptors are available, obligate anaerobes and facultative anaerobes can still break down glucose to release energy through a process called fermentation.

Fermentation

Fermentation begins just as cellular respiration does, with glycolysis.

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Fermentation

Glycolysis results in 2 pyruvate molecules and 2 NADH2

• molecules. Without an electron

acceptor, the energy stored in these molecules can't be used. The net energy gain is just 2 ATPs. (Remember 2 were invested and 4 were produced, netting 2) C6H12O6 (Glucose)

Gycolysis

2 ATP 4 ATP 2 NADH 2 C3H4O3 (Pyruvate) 2 NAD+

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However, the Pyruvate still needs to be cleared from the cell, and the NADH converted back to NAD+ to begin another cycle. The process of doing this is called fermentation. No additional energy is released during this process.

Fermentation

C6H12O6 (Glucose)

Gycolysis

2 ATP 4 ATP 2 NADH 2 C3H4O3 (Pyruvate) 2 NAD+

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Fermentation 2 NADH 2 NAD+ 2 C3H4O3 (Pyruvate) CO2 & 2 Ethanol 2 Lactic Acid Lactic Acid Fermentation Ethanol Fermentation OR

Types of Fermentation

There are two types of fermentation:

• Lactic acid fermentation
• Ethanol fermentation

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CO2 & Ethanol. The pyruvates and NADHs are fermented into 2 NAD+ and either Lactic Acid or 1 glucose molecule had yielded 2 ATPs, 2 Pyruvates and 2

• NADHs. That is the input to the

fermentation stage of anaerobic respiration.

Fermentation 2 NADH 2 NAD+

2 C3H4O3 (Pyruvate)

CO2 & 2 Ethanol

2 Lactic Acid

Lactic Acid Fermentation Ethanol Fermentation

OR

1 glucose molecule had yielded 2 ATPs, 2 Pyruvates and 2

• NADHs. That is the input to the

fermentation stage of anaerobic respiration.

Fermentation

Fermentation breaks down the products of glycolysis so that glycolysis can be repeated with another glucose molecule. The pyruvates and NADHs are fermented into 2 NAD+ and either Lactic Acid or CO2 & Ethanol.

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Fermentation

The result of the combined steps of glycolysis and fermentation is:

• The input is 1 Glucose + 2 ATP molecules
• The output is 4 ATP molecules (for a net gain of 2 ATP's)

In addition,

• Lactic Acid fermentation results in lactic acid
• Ethanol fermentation results in ethanol and CO2

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The big difference is that for each glucose molecule: aerobic cellular respiration yields 36 to 38 ATPs fermentation yields only 2 ATPs

Cellular Respiration vs. Fermentation

87

• Some anaerobic bacteria rely soley on fermentation, such as

lactobacillus, which is used to make cheese and yogurt.

• The alcohol in wine, beer, etc. results from yeast (a facultative

anaerobe) undergoing ethanol fermentation.

• Bread rises due to the release of CO2 bubbles by fermenting

yeast.

• Your muscles burn after a strenuous workout because they can't

get enough O2, so they perform lactic acid fermentation. Lactic acid results in soreness.

Examples of Fermentation

88

23 When a cell has completed glycolysis and lactic acid fermentation, the final products are: I Lactic acid II Ethanol III Carbon dioxide IV NADH V ATP

A

I, II, III, IV, V

B I, II, III, V

C

I, IV, V

D

I, V

Answer

89

24 Bread rises due to the production of _______ during fermentation.

A ethanol B carbon dioxide C lactic acid D pyruvate

Answer

90

25 Muscles produce lactic acid during strenuous exercise. Therefore, muscles are an example of what kind of cell?

A facultative anaerobe B facultative aerobe C obligate anaerobe D obligate aerobe

Answer

91

Photosynthesis

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Table of

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92

Respiration gets energy from glucose and stores it as ATP. But what is the source of glucose? And, where did the oxygen that flooded Earth 2.5 BYA come from?

Photosynthesis

93

Here's the balanced chemical equation for aerobic respiration: And here's the balanced chemical equation for photosynthesis:

C6H12O6 + 6O

2 6CO 2 + 6H 2O + ATP

6CO

2 + 6H 2O + Light Energy C 6H12O6 + 6O 2

Aerobic Respiration vs. Photosynthesis

94

Aerobic respiration uses oxygen (O2) and glucose (C6H12O6) to create carbon dioxide (CO2) and water (H2O)...and release energy. Photosynthesis is the exact opposite, it takes carbon dioxide (CO2) and water (H2O) plus energy to make glucose (C6H12O6) and oxygen (O2)

Aerobic Respiration vs. Photosynthesis

C6H12O6 + 6O

2 6CO 2 + 6H 2O + ATP

6CO

2 + 6H 2O + Light Energy C 6H12O6 + 6O 2

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Photosynthesis and Respiration

Summing these two equations reveals that the ATP used by cells is derived from light energy, from the sun. That is the source of energy for most life on Earth.

C6H12O6 + 6O2 6CO2 + 6H2O + ATP (Energy) 6CO2 + 6H2O + Light Energy C6H12O6 + 6O2

Light Energy ATP (Energy)

96

Except for a small number of bacteria that live on chemical reactions in challenging environments, the energy for all life on Earth comes from these processes...from the energy of sunlight. Even though not every organism undergoes photosythesis, the products that plants produce are used in reactions that consumers use. In this way, you can say that . . .

You are solar powered! Light Energy ATP (Energy)

Photosynthesis and Respiration

97

26What are the reactants of cellular respiration?

A

Oxygen and Water

B

Glucose and Carbon Dioxide

C

Glucose and Water

D

Glucose and Oxygen

Answer

98

27What are the products of photosynthesis?

A

Glucose and Oxygen

B

Oxygen and Water

C

Glucose and Carbon Dioxide

D

Carbon Dioxide and Water

Answer

99

28What are the reactants of photosynthesis?

A

Carbon Dioxide and Water

B

Oxygen and Water

C

Glucose and Oxygen

D

Glucose and Carbon Dioxide

Answer

100

29Photosynthesis ____________ energy, whereas cellular respiration __________ energy.

A

consumes, produces

B

produces, consumes

C

produces, produces

D

consumes, consumes

Answer

101

What is the source of glucose? Where did the oxygen that flooded Earth 2.5 BYA come from?

Our Original Questions

102

The products of photosynthesis are:

• oxygen (O2)
• glucose (C6H12O6)

Photosynthesis produces the glucose that feeds respiration, and eventually, all of us. Photosynthesis also produces the oxygen that filled the atmosphere and made complex life, as we know it possible.

Photosynthesis

103

Photosynthesis and the addition of oxygen to Earth's atmosphere, began about 2.5 BYA, and was having a major impact by 2.0 BYA. This is called the Oxygen Catastrophe because it spelled the extinction of a vast number of obligate anaerobes. Some survive today, but only in locations where they are not exposed to the atmosphere.

The Oxygen Catastrophe

104

This simple equation sums up the result of photosynthesis: its reactants and products. However, the processes that make photosynthesis possible are not very simple. Just like the four stages of respiration result in a simple equation, the process itself is complicated. Similarly, the process of photosynthesis is complicated. And in some ways similar to the steps of respiration, but backwards.

Photosynthesis

6CO

2 + 6H 2O + Light Energy C 6H12O6 + 6O 2

105

30 In the comparison of aerobic respiration to

photosynthesis, which statement is true?

A

• xygen is a waste product in photosynthesis but

not in respiration

B

glucose is produced in respiration but not in photosynthesis

C

carbon dioxide is formed in photosynthesis but not in respiration

D

water is formed in photosynthesis but not in respiration

Answer

106

During respiration the molecules NAD+and FAD are used to store energy. Photosynthesis uses the molecule NADP+, which is a lot like NAD+, to store energy, and convert it between its two stages. The reduced form of NADP+ is NADPH.

NADPH

107

Photosynthesis also depends on chlorophyll, a molecule that absorbs red and violet­blue light and uses it to energize electrons to a higher energy level.

Chlorophyll

Chlorophyll gives plants their green color.

108

Chlorophyll is housed in thylakoids, membrane­bound structures within photosynthetic cells.

Thylakoids

109

31 NAD+ is to NADP+ as NADH is to ______.

A NADP2+ B NADP C NADPH D NADPH2

Answer

110

32 Which of the following is found stored in the thylakoid?

A ATP B chlorophyll C NADH D NADPH

Answer

111

There are two types of photosynthesis:

Cyclic Energy Transport Non­Cyclic Energy Transport

Two Types of Photosynthesis

112

Cyclic Energy Transport was probably the first type of photosynthesis to originate. It does not create glucose, it just converts solar energy to ATP.

Cyclic Energy Transport

113 e­ e­

Photosystem I Electron Transport Chain ADP + P i ATP

ATP Synthase

Energy of molecules

chlorophyll

e­ e­

photon This process is "cyclic" because the final electrons return to chlorophyll after ATP is generated.

Cyclic Energy Transport

Cyclic Energy Transport uses Photosystem I, a protein complex embedded in the thylakoid membrane to convert light energy to ATP.

114

33 Noncyclic energy transport arose before cyclic energy transport.

True False

Answer

115

34 Which of the following statements about cyclic energy transport is true?

A Cyclic energy transport requires water. B Glucose is produced by cyclic energy transport. C Cyclic energy transport reduces NADP+ D Light energy is converted to chemical energy during

cyclic energy transport.

Answer

116

There are two major stages to Noncyclic Energy Transport:

Light Dependent Reactions Light Independent Reactions (Calvin Cycle)

Noncyclic Energy Transport

117

Light Dependent Reactions occur in membrane bound structures called thylakoids. It's necessary to have a membrane surface separating the inside from the outside on an enclosed volume, thylakoids provide that. The inside is called the lumen; the outside is called the stroma.

Light Dependent Reactions

118

Light Dependent Reactions

2 H2O + 2 NADP+ + 3 ADP + 3 Pi O2 + 2NADPH + 3 ATP The Light Dependent Reactions use light energy and water to form ATP, NADPH, and oxygen gas. This process requires 2 photosystems, Photosystem II and Photosystem I. They occur in this order (they were named in the

• rder in which they were discovered).

119

Thylakoid

This shows the membrane, separating the stroma from the lumen, the two photosystems and the enzymes, ATP Synthase and NADP Reductase. The light reactions will use Photosystem II and Photosystem I to create an excess of protons in the stroma, and a deficit in the lumen. The only way protons can get back to the lumen, is through ATP Synthase, to produce ATP.

120

Photosystem II

First, Photosystem II absorbs light and energizes electrons, splitting a water molecule in the process. Those are used to pump protons across the membrane, creating an electrical potential difference which is used to create ATP.

e­ e­

Photosystem II Electron Transport Chain ADP + P i ATP

ATP Synthase

chlorophyll e­ e­

photon to Photosystem I H2O O2+2H+ Energy of molecules

121

Photosystem I

chlorophyll

e­ e­ e­

Photosystem I

e­

from Photosystem II

NADP Reductase

NADP+ NADPH photon

Energy of molecules

Then, Photosystem I absorbs more light and re­energizes those

• electrons. They are used to store energy by using NADP Reductase

to reduce NADP+ to NADPH (adding electrons to NADP+, instead of returning them to chlorophyll as in cyclic energy transport).

122

35 The inside of the thylakoid is called the ______ and the

• utside is called the ______.

A

lumen, stroma B stroma, lumen

Answer

123

36 Light dependent reaction produce ____ ATP and ____ NADPH for each O2 produced.

A 1, 1 B 2, 3 C 3, 2 D 2, 4

Answer

124

37 Water is split, releasing O2, in which protein complex?

A photosystem I B photosystem II C ATP synthase D NADP reductase

Answer

125

Light Independent Reactions

The ATP and NADPH created during the light dependent reactions proceed to the Light Independent Reaction. The light independent reactions are also know as the Calvin Cycle or Dark Reactions. These reactions can occur in light or dark, thus dark reactions is not an accurate name. The Calvin Cycle uses the ATP and NADPH to convert CO2 into Glucose (C6H12O6) in a multi step process.

126

Light Independent Reactions

In 3 turns of the cycle we use 9 ATP and 6 NADPH and 3 CO2 to make a 3­carbon sugar

127

Light Independent Reactions

To make one 6­carbon glucose molecule: 18 ATP and

12 NADPH

and 6 CO2 are required.

128

The Carbon Cycle

The Calvin Cycle is also called Carbon Fixing.

This means that carbon, a gas in the atmosphere, in the

form of CO2, is turned into a solid as a glucose. When glucose is used in respiration, that carbon is then released back into the atmosphere. This process of fixing and releasing carbon is called the Carbon Cycle. Carbon is not being created or destroyed, but cycles through the environment.

129

The Light Reactions produce equal amounts of ATP and NADPH, but the Calvin Cycle use more ATP (18) than NADPH (12) to make a glucose molecule. To have enough ATP, photosynthetic organisms use Cyclic Energy Transport to create the needed ATP.

Cyclic vs. Noncyclic Energy Transport

130

38 Carbon dioxide is fixed in the form of glucose in

A Krebs cycle B light­dependent reactions C Calvin cycle D cyclic energy transport

Answer

131

39 During what stage of photosynthesis are ATP and NADPH coverted to ADP + P

i and NADP+?

A light dependent reactions B light independent reactions C photosystem I D photosystem II

Answer

132

40 Which of the following statements about photosynthesis is true?

A

The light dependent reactions can only occur in the light, the light independent reactions can only occur in the dark.

B Cyclic energy transport is more efficient at

producing glucose than noncyclic energy transport.

C The light dependent reactions produce ATP which is

used to power the Calvin cycle.

D Cyclic energy transport occurs only in bacteria.

Answer

133

41 The Calvin cycle is an anabolic pathway.

True False

Answer

True

134

Global Climate Change

The carbon cycle plays a key role in Global Climate Change. Photosynthesis releases oxygen into the air, but also takes CO2 out of the air. CO2 is a greenhouse gas, it absorbs infrared light that would

• therwise carry heat away from Earth, into space; cooling

Earth.

135

Global Climate Change

If it were not for CO2, and other greenhouse gases, Earth would be far colder, perhaps too cold to support life as we know it. Greenhouse gases are essential for life. However, the amount of greenhouse gases in Earth's atmosphere is critical to maintaining a constant average temperature for the planet.

136

Global Climate Change

A great deal of carbon was trapped under the surface of Earth by life forms that died over many millions of years; effectively taking that carbon out of the carbon cycle. That reduced the CO2 in the atmosphere, reducing the temperature of Earth by allowing more heat to leave, leading to

• ur current temperature.

137

Global Climate Change

The hydrocarbons we use for energy (oil and natural gas) were formed from the breakdown of that long­dead plant and animal life. As we burn those fuels, we are releasing CO2 back into the atmosphere, increasing the greenhouse gases in the atmosphere.

138

Global Climate Change

As a result, more heat is being trapped in our atmosphere; the balance of energy brought to Earth by solar energy, and released from Earth in infrared radiation is being changed. This is causing Earth's average temperature to rise. The effect of this temperature rise is not that the temperature goes up in all places or in all years necessarily. But it is projected that there will be massive changes in climate in the future, with accompanying changes in sea level, crops, plant and animal life, etc.

139

42 Greenhouses gases are dangerous and should be reduced as much as possible.

True False

Answer

False

140

43 Carbon was used from the carbon cycle, reducing CO2 in the air, as __________

A the amount of life on Earth decreased

B as animals died and were buried under earth

C fermentation began D All of the above

E None of the above

Answer

141

44 A very warm winter in New Jersey this year would indicate that global climate change is occurring.

True False

Answer

False

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