AP Bio Chapter 9: Cellular Respiration

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Questions and Answers

Explain the difference between fermentation and cellular respiration.

Fermentation is the partial degradation of sugars or other organic fuel without oxygen while cellular respiration uses oxygen.

Give the formula (with names) for the catabolic degradation of glucose by cellular respiration.

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + Energy (ATP + Heat) or Glucose + Oxygen → Carbon Dioxide + Water + Energy (ATP + Heat)

What is the difference between oxidation and reduction?

Oxidation is the loss of electrons from one substance and reduction is the gain of electrons to another substance.

Which component is oxidized and which component is reduced in the reaction Xe⁻ + Y → X + Ye⁻?

Xe⁻ is oxidized and Y is reduced. Signup and view all the answers

When compounds lose electrons, they __ energy; when compounds gain electrons, they _ energy.

gain; lose Signup and view all the answers

What electron carrier is hydrogen transferred to first?

NAD⁺ Signup and view all the answers

What are coenzymes?

An organic molecule serving as a cofactor. EX: Most vitamins function as coenzymes in metabolic reactions. Signup and view all the answers

Describe what happens when NAD⁺ is reduced. What enzyme is involved?

NAD⁺ receives two negatively charged electrons and one positively charged electron which neutralizes its charge and is reduced to NADH. Dehydrogenase is the enzyme involved. Signup and view all the answers

What is the function of the electron transport chain in cellular respiration?

Breaks the fall of electrons. Signup and view all the answers

Where are electron transport chains found in eukaryotic cells?

Inner mitochondrial membrane. Signup and view all the answers

Where are electron transport chains found in prokaryotic cells?

Plasma membrane. Signup and view all the answers

What strongly electronegative atom is the final electron acceptor?

Oxygen Signup and view all the answers

What are the three steps of the conversion process in the citric acid cycle?

1.) Pyruvate's carboxyl group is removed & given off as a molecule of CO₂. 2.) The remaining two-carbon fragment is oxidized, forming acetate. Extracted electrons are transferred to NAD⁺ storing energy in the form of NADH. 3.) CoA is attached by its sulfur atom to the acetate forming acetyl CoA. Signup and view all the answers

How many NADHs are formed in the citric acid cycle?

3 Signup and view all the answers

How many times does the citric acid cycle occur for each molecule of glucose?

2 Signup and view all the answers

How many ATPs are formed in the citric acid cycle?

2 Signup and view all the answers

How many FADH₂ have been formed in the citric acid cycle?

2 Signup and view all the answers

How many total carbons are lost as pyruvate is oxidized in the citric acid cycle?

4 Signup and view all the answers

The oxidation of pyruvate accounts for two additional reduced __________ molecules and two molecules of CO₂.

NADH Signup and view all the answers

Explain what has happened to each of the 6 carbons found in the original glucose molecule.

For each pyruvate molecule formed from the original glucose molecule, the pyruvate is broken down to three CO₂ molecules, including the molecule of CO₂ released during the conversion of pyruvate to acetyl CoA. Signup and view all the answers

Why is oxygen the ultimate electron acceptor?

Oxygen has high electronegativity which pulls electrons toward it. Signup and view all the answers

Oxygen stabilizes the electrons by combining with two hydrogen ions to form what compound?

water Signup and view all the answers

The two electron carrier molecules that feed electrons into the electron transport system are ______ and .

NADH; FADH₂ Signup and view all the answers

Explain how ATP synthase uses the flow of hydrogen ions to produce ATP.

H+ ions flow down their gradient and enter binding sites within a rotor, changing the shape of each subunit so that the rotor spins within the membrane, before leaving the rotor and passing through a second half channel into the mitochondrial matrix. The spinning of the rotor causes an internal rod to spin, activating catalytic sites in the knob that produce ATP. Signup and view all the answers

What is the role of the electron transport chain in forming the H⁺ gradient across the inner mitochondrial membrane?

The chain is an energy converter that uses the exergonic flow of electrons from NADH to FADH₂ to pump H⁺ across the membranes from the mitochondrial matrix to the intermembrane space. The H⁺ has a tendency to move back across the membrane, diffusing down its gradient. And the ATP synthases are the only sites that provide a route through the membrane for H⁺. Signup and view all the answers

Two key terms are chemiosmosis and proton-motive force. Relate both of these terms to the process of oxidative phosphorylation.

In oxidative phosphorylation, chemiosmosis uses energy stored in the form of H⁺ and proton-motive force is an H⁺ gradient. Signup and view all the answers

Each NADH can form a maximum of ATP molecules. Each FADH, which donates electrons that activate only two proton pumps, makes ATP molecules.

3; 2 Signup and view all the answers

Why is the total count 36 or 38 ATP molecules rather than a specific number?

→Ratio of NAD⁺ to ATP is not a whole number → ATP yield varies depending on type of shuttle used to transport → Use of proton-motive force generated by the redox reactions of respiration to drive other work. Signup and view all the answers

Fermentation allows for production of ATP without using either or any .

oxygen; electron transport chain Signup and view all the answers

What is the electron acceptor in fermentation?

Organic molecules (pyruvate or acetaldehyde) Signup and view all the answers

Explain the process of alcohol fermentation starting with glucose and yielding ethanol, and describe how NAD⁺ is recycled.

CO₂ releases from the pyruvate & is converted to acetaldehyde. Acetaldehyde is reduced by NADH to ethanol which regenerates the supply of NAD⁺ needed for glycolysis to continue. Signup and view all the answers

Explain the process of lactic acid fermentation starting with glucose and yielding lactate, and describe how NAD⁺ is recycled.

Pyruvate is reduced by NADH to form lactate with no release of CO₂. Signup and view all the answers

Why is pyruvate a key juncture in metabolism?

Signup and view all the answers

What three organic macromolecules are often utilized to make ATP by cellular respiration?

1.) proteins 2.) carbohydrates 3.) fats Signup and view all the answers

Explain the difference in energy usage between the catabolic reactions of cellular respiration and anabolic pathways of biosynthesis.

Catabolic: energy is generated; anabolic: energy is consumed. Signup and view all the answers

Explain how AMP stimulates cellular respiration while citrate and ATP inhibit it.

As ATP is used up, AMP accumulates which signals more ATP to be made. The more ATP there is, the slower glycolysis is. Signup and view all the answers

Explain how phosphofructokinase acts as a control point in cellular respiration.

Phosphofructokinase is the pacemaker of cellular respiration. Signup and view all the answers

Is NAD⁺ oxidized or reduced? Lower or higher potential energy? Is NADH oxidized or reduced? Lower or higher potential energy?

NAD⁺ is oxidized; lower potential energy. NADH is reduced; higher potential energy. Signup and view all the answers

Explain how the electron transport chain is utilized in oxidative phosphorylation.

The electron transport chain accepts electrons from the breakdown products of the first two stages of cellular respiration and passes the electrons from one molecule to the next. Signup and view all the answers

What is the meaning of glycolysis? What occurs in this step of cellular respiration?

Glycolysis means sugar splitting. During glycolysis chemical energy is harvested by oxidizing glucose to pyruvate. Signup and view all the answers

The starting point of glycolysis is the six-carbon sugar _, and the ending products are two ____-carbon molecules of pyruvate.

glucose; organic Signup and view all the answers

What two stages can glycolysis be divided into?

Energy investment phase and energy payoff. Signup and view all the answers

In the energy investment phase, which two steps use ATP? In the energy payoff phase, which two steps produce ATP and which step forms NADH?

3 & 1; 7 & 10; 6 Signup and view all the answers

Notice that glycolysis occurs in the __________ of the cell. Is oxygen required?

cytosol; no Signup and view all the answers

Each member of the electron transport chain is lower in free ______ than the preceding member of the chain, but higher in _. The molecule at zero free energy, which is _________, is lowest of all the molecules in free energy and highest in electronegativity.

energy; NADH; oxygen Signup and view all the answers

Study Notes

Fermentation vs Cellular Respiration

Fermentation partially degrades organic fuels without oxygen.
Cellular respiration fully degrades glucose using oxygen.

Cellular Respiration Process

Formula: Glucose + Oxygen → Carbon Dioxide + Water + Energy (ATP + Heat).
Involves redox reactions: oxidation (loss of electrons) and reduction (gain of electrons).

Oxidation and Reduction

Oxidation: loss of electrons from one substance, while reduction involves gain to another.
Example reaction: Xe⁻ is oxidized while Y is reduced.

Electron Carriers

First electron carrier for hydrogen is NAD⁺.
NAD⁺ is reduced to NADH when it gains electrons, aided by dehydrogenase enzymes.
FADH₂ also participates in electron transport.

Citric Acid Cycle (Krebs Cycle)

Occurs after glycolysis, involving pyruvate conversion and oxidation.
Outputs: 3 NADH, 1 FADH₂, 1 ATP, and 2 CO₂ per cycle.
Cycle runs twice per glucose, totaling 6 NADH and 2 FADH₂.

Electron Transport Chain

Located in the inner mitochondrial membrane in eukaryotes; prokaryotes use their plasma membrane.
Oxygen is the final electron acceptor due to its high electronegativity.
Creates a proton gradient; ATP synthase utilizes this to produce ATP.

ATP Production

NADH can yield up to 3 ATP, whereas FADH₂ yields up to 2 ATP.
Total ATP yield varies due to inefficiencies and shuttle mechanisms, estimated at 36-38 ATP.

Fermentation Processes

Involves organic molecules as electron acceptors.
Alcohol fermentation produces ethanol and recycles NAD⁺ from NADH.
Lactic acid fermentation forms lactate without CO₂ release.

Energy Utilization

Catabolic pathways generate energy; anabolic pathways consume energy.
AMP stimulates respiration, while ATP and citrate inhibit it.

Glycolysis Overview

Means "sugar splitting"; glucose is converted to pyruvate.
Divided into energy investment (ATP is consumed) and energy payoff phases (ATP and NADH generated).
Occurs in cellular cytosol; does not require oxygen.

Key Terms and Concepts

Phosphofructokinase acts as a control point in glycolysis; it is an allosteric enzyme.
Each electron transport chain member has lower free energy than the previous; oxygen is the terminal electron acceptor.
Pyruvate oxidation represents a critical juncture for metabolic pathways, producing NADH and CO₂.

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Test your knowledge on the key concepts of cellular respiration and fermentation in AP Biology Chapter 9. This quiz covers differences, processes, and formulas relating to energy production in cells. Perfect for reviewing essential topics for your upcoming exam!

AP Bio Chapter 9: Cellular Respiration

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Podcast

Questions and Answers

Explain the difference between fermentation and cellular respiration.

Give the formula (with names) for the catabolic degradation of glucose by cellular respiration.

What is the difference between oxidation and reduction?

Which component is oxidized and which component is reduced in the reaction Xe⁻ + Y → X + Ye⁻?

When compounds lose electrons, they ________________ energy; when compounds gain electrons, they _______________ energy.

What electron carrier is hydrogen transferred to first?

What are coenzymes?

Describe what happens when NAD⁺ is reduced. What enzyme is involved?

What is the function of the electron transport chain in cellular respiration?

Where are electron transport chains found in eukaryotic cells?

Where are electron transport chains found in prokaryotic cells?

What strongly electronegative atom is the final electron acceptor?

What are the three steps of the conversion process in the citric acid cycle?

How many NADHs are formed in the citric acid cycle?

How many times does the citric acid cycle occur for each molecule of glucose?

How many ATPs are formed in the citric acid cycle?

How many FADH₂ have been formed in the citric acid cycle?

How many total carbons are lost as pyruvate is oxidized in the citric acid cycle?

The oxidation of pyruvate accounts for two additional reduced __________ molecules and two molecules of CO₂.

Explain what has happened to each of the 6 carbons found in the original glucose molecule.

Why is oxygen the ultimate electron acceptor?

Oxygen stabilizes the electrons by combining with two hydrogen ions to form what compound?

The two electron carrier molecules that feed electrons into the electron transport system are __________________ and ____________.

Explain how ATP synthase uses the flow of hydrogen ions to produce ATP.

What is the role of the electron transport chain in forming the H⁺ gradient across the inner mitochondrial membrane?

Two key terms are chemiosmosis and proton-motive force. Relate both of these terms to the process of oxidative phosphorylation.

Each NADH can form a maximum of ______________ ATP molecules. Each FADH, which donates electrons that activate only two proton pumps, makes ______________ ATP molecules.

Why is the total count 36 or 38 ATP molecules rather than a specific number?

Fermentation allows for production of ATP without using either ____________ or any ____________.

What is the electron acceptor in fermentation?

Explain the process of alcohol fermentation starting with glucose and yielding ethanol, and describe how NAD⁺ is recycled.

Explain the process of lactic acid fermentation starting with glucose and yielding lactate, and describe how NAD⁺ is recycled.

Why is pyruvate a key juncture in metabolism?

What three organic macromolecules are often utilized to make ATP by cellular respiration?

Explain the difference in energy usage between the catabolic reactions of cellular respiration and anabolic pathways of biosynthesis.

Explain how AMP stimulates cellular respiration while citrate and ATP inhibit it.

Explain how phosphofructokinase acts as a control point in cellular respiration.

Is NAD⁺ oxidized or reduced? Lower or higher potential energy? Is NADH oxidized or reduced? Lower or higher potential energy?

Explain how the electron transport chain is utilized in oxidative phosphorylation.

What is the meaning of glycolysis? What occurs in this step of cellular respiration?

The starting point of glycolysis is the six-carbon sugar ___________, and the ending products are two ______________-carbon molecules of pyruvate.

What two stages can glycolysis be divided into?

In the energy investment phase, which two steps use ATP? In the energy payoff phase, which two steps produce ATP and which step forms NADH?

Notice that glycolysis occurs in the __________ of the cell. Is oxygen required?

Each member of the electron transport chain is lower in free __________ than the preceding member of the chain, but higher in _________. The molecule at zero free energy, which is _____________, is lowest of all the molecules in free energy and highest in electronegativity.

Study Notes

Fermentation vs Cellular Respiration

Cellular Respiration Process

Oxidation and Reduction

Electron Carriers

Citric Acid Cycle (Krebs Cycle)

Electron Transport Chain

ATP Production

Fermentation Processes

Energy Utilization

Glycolysis Overview

Key Terms and Concepts

Studying That Suits You

Description

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When compounds lose electrons, they __ energy; when compounds gain electrons, they _ energy.

The two electron carrier molecules that feed electrons into the electron transport system are ______ and .

Each NADH can form a maximum of ATP molecules. Each FADH, which donates electrons that activate only two proton pumps, makes ATP molecules.

Fermentation allows for production of ATP without using either or any .

The starting point of glycolysis is the six-carbon sugar _, and the ending products are two ____-carbon molecules of pyruvate.

Each member of the electron transport chain is lower in free ______ than the preceding member of the chain, but higher in _. The molecule at zero free energy, which is _________, is lowest of all the molecules in free energy and highest in electronegativity.