Cellular Respiration: Harvesting Energy

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Questions and Answers

What is the primary purpose of cellular respiration?

  • To synthesize glucose from carbon dioxide and water.
  • To facilitate the release of carbon dioxide and oxygen.
  • To transfer energy from organic molecules to ATP. (correct)
  • To store energy in complex organic molecules.

Which of the following correctly lists the metabolic stages of cellular respiration?

  • Hydrolysis, Glycolysis, Citric Acid Cycle
  • Fermentation, Citric Acid Cycle, Glycolysis
  • Glycolysis, Citric Acid Cycle, Oxidative Phosphorylation (correct)
  • Glycolysis, Fermentation, Electron Transport Chain

During which stage of cellular respiration is glucose primarily broken down?

  • Citric Acid Cycle
  • Oxidative Phosphorylation
  • Glycolysis (correct)
  • Electron Transport Chain

What is generated as a direct result of the oxidation of organic molecules during cellular respiration?

<p>NADH (C)</p> Signup and view all the answers

In the context of redox reactions during cellular respiration, which of the following is true?

<p>Oxidizing agents donate electrons during the process. (A)</p> Signup and view all the answers

Which of the following occurs in the cytosol during the process of cellular respiration?

<p>Glycolysis (D)</p> Signup and view all the answers

What is the net energy yield (in ATP) from one molecule of glucose during glycolysis?

<p>2 ATP (A)</p> Signup and view all the answers

Which product of the Citric Acid Cycle is immediately used for cellular respiration?

<p>NADH (B)</p> Signup and view all the answers

What type of biological reaction do the processes of oxidation and reduction represent?

<p>Redox reactions (C)</p> Signup and view all the answers

Which of the following statements about cellular respiration is false?

<p>It requires oxygen for the glycolysis stage. (B)</p> Signup and view all the answers

What role do cytochromes play in the electron transport chain?

<p>They transfer electrons from NADH and FADH2 to oxygen. (A)</p> Signup and view all the answers

How many protons are required to synthesize one ATP through ATP synthase?

<p>3 to 4 H+ (B)</p> Signup and view all the answers

What is the primary source of energy for the proton gradient established in the inner mitochondrial membrane?

<p>The exergonic flow of electrons through the electron transport chain (B)</p> Signup and view all the answers

What is the final electron acceptor in the electron transport chain?

<p>O2 (A)</p> Signup and view all the answers

What product is formed when ATP is synthesized by ATP synthase?

<p>ATP and water (C)</p> Signup and view all the answers

What is the overall equation for cellular respiration in terms of glucose conversion?

<p>C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 36 ATP (A)</p> Signup and view all the answers

What mechanism does ATP synthase use to generate ATP?

<p>It uses the proton motive force established by the gradient. (A)</p> Signup and view all the answers

What happens to protons after they flow through ATP synthase?

<p>They combine with electrons and oxygen to form water. (A)</p> Signup and view all the answers

What best describes the flow of energy during cellular respiration?

<p>Glucose → NADH → Electron Transport Chain → ATP (A)</p> Signup and view all the answers

What is the significance of the proton motive force in cellular respiration?

<p>It is essential for the production of ATP. (A)</p> Signup and view all the answers

What phase of glycolysis involves the consumption of ATP?

<p>Energy investment phase (D)</p> Signup and view all the answers

What type of phosphorylation is responsible for the production of ATP during glycolysis?

<p>Substrate-level phosphorylation (C)</p> Signup and view all the answers

What is produced from the conversion of 2 pyruvate during the Citric Acid Cycle?

<p>3 CO2, 4 NADH, 1 ATP, and 1 FADH2 (C)</p> Signup and view all the answers

During oxidative phosphorylation, where do the electron transport chains reside?

<p>Inner mitochondrial membrane (D)</p> Signup and view all the answers

What role does NAD+ play in the production of NADH during glycolysis?

<p>It accepts electrons and protons. (C)</p> Signup and view all the answers

Which enzyme complex is responsible for converting pyruvate to acetyl CoA?

<p>Pyruvate Dehydrogenase Complex (C)</p> Signup and view all the answers

What is the main purpose of the electron transport chain in cellular respiration?

<p>To generate a proton gradient for ATP synthesis. (D)</p> Signup and view all the answers

During the energy payoff phase of glycolysis, which of these is NOT produced?

<p>FADH2 (B)</p> Signup and view all the answers

In the absence of oxygen, how will NADH regenerate NAD+?

<p>By undergoing fermentation. (C)</p> Signup and view all the answers

Which product is a direct result of the dehydrogenase enzyme's action during glycolysis?

<p>NADH (B)</p> Signup and view all the answers

Flashcards

Cellular Respiration

The process cells use to convert energy stored in organic molecules into usable energy (ATP).

Oxidation

The loss of electrons during a chemical reaction.

Reduction

The gain of electrons during a chemical reaction; always paired with oxidation.

Redox Reactions

Chemical reactions involving the transfer of electrons between atoms or molecules.

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Glycolysis

The first stage of cellular respiration, breaking down glucose into pyruvate without oxygen.

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ATP

Adenosine triphosphate; the primary energy currency of the cell.

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Glucose

A simple sugar and common energy source in living things.

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Citric Acid Cycle

A series of reactions in cellular respiration that produces NADH and ATP, and carbon dioxide.

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Oxidative Phosphorylation

The final stage of cellular respiration, generating ATP via electron transport chain and chemiosmosis.

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Energy Storage in Organic compounds

Organic molecules like carbohydrates, fats, and proteins are rich in energy stored in their chemical bonds.

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Electron Transport Chain

A series of protein complexes that transfer electrons from NADH or FADH2 to O2, creating a proton gradient.

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Glycolysis

The 10-step process that breaks down glucose into pyruvate, producing ATP and NADH.

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Proton Gradient

A difference in proton concentration across a membrane, storing energy.

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ATP Synthase

An enzyme that uses the proton gradient to synthesize ATP from ADP and Pi.

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Substrate-level phosphorylation

The production of ATP in glycolysis by transferring a phosphate group directly to ADP from a substrate molecule.

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Proton Motive Force

The electrochemical gradient of protons across the inner mitochondrial membrane.

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NADH

Electron carrier produced during glycolysis and the citric acid cycle, holding high-energy electrons.

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NADH/FADH2

Electron carriers that donate electrons to the electron transport chain.

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Citric Acid Cycle

A series of 8 steps that fully oxidizes acetyl-CoA, producing CO2, NADH, FADH2, and ATP.

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Pyruvate

Three-carbon molecule produced from the breakdown of glucose in glycolysis, which can be converted to acetyl-CoA.

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Cytochromes

Proteins in the electron transport chain with iron atoms that transfer electrons.

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Acetyl CoA

A molecule that carries the acetyl group from pyruvate to the citric acid cycle.

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Inner Mitochondrial Membrane

The location of the electron transport chain and ATP synthase.

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Oxidative Phosphorylation

The process that generates most ATP through the electron transport chain, powered by NADH and FADH2.

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Cellular Respiration

The process of breaking down glucose to produce ATP.

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ATP Production (Net)

Glucose generates 36 ATP molecules.

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Electron Transport Chain

A series of proteins in the inner mitochondrial membrane that transfers electrons and creates a proton gradient.

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ATP

Adenosine triphosphate, the main energy currency of the cell.

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Mitochondrial Matrix

The inner compartment of the mitochondrion, where ATP synthase is located.

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Aerobic Respiration

The process of cellular respiration using oxygen to produce ATP, involving glycolysis, citric acid cycle, and oxidative phosphorylation.

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Study Notes

Cellular Respiration: Harvesting Chemical Energy

  • Organic compounds store energy in their atomic arrangements.
  • Catabolic pathways break down complex organic molecules (high energy) into simpler waste products (lower energy).
  • Energy is transferred from nutrient molecules to energy-rich molecules used by cells for work.
  • Cellular respiration breaks down organic compounds in the presence of oxygen to produce carbon dioxide, water, and usable energy (ATP).
  • Organic compounds broken down include carbohydrates (e.g., glucose), fats, and proteins.
  • Chemical reaction for glucose breakdown: C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + Energy (ATP + Heat)
  • AG = -686 kcal/mol of glucose

Where does Cellular Respiration Occur?

  • Cellular respiration is the controlled stepwise oxidation of organic molecules in cells.
  • Enzymes catalyze oxidation in small steps, transferring energy to carrier molecules (often ATP and NADH).

What is Oxidation?

  • Catabolism involves electron relocation, releasing stored energy used for ATP synthesis.
  • Relocating electrons involves transferring one or more electrons from one reactant to another.
  • These electron transfers are oxidation-reduction (Redox) reactions
  • Oxidations and reductions always occur together.

Cellular Respiration Stages

  • Cellular respiration of glucose has three metabolic stages:
    • Glycolysis
    • Citric Acid Cycle (Krebs Cycle, TCA Cycle)
    • Oxidative Phosphorylation (Electron Transport and Chemiosmosis)

Glycolysis

  • Occurs in the cytosol.
  • Does not require oxygen.
  • Breaks down glucose into pyruvate.
  • Produces 2 ATP, 2 NADH molecules.
  • 10 enzymatic steps.

Citric Acid Cycle

  • Occurs in the mitochondrial matrix.
  • Pyruvate converted to acetyl-CoA.
  • Produces 2 ATP, 6 NADH, 2 FADH₂ through a series of oxidation-reduction reactions.
  • Each cycle releases 3 CO2.

Oxidative Phosphorylation

  • Occurs in the inner mitochondrial membrane.
  • Electron transport chain (ETC) transfers electrons from NADH and FADH₂ to oxygen.
  • Generates a proton gradient used by ATP synthase to produce ATP (chemiosmosis).
  • Maximum ATP production per glucose is 30-32 ATP.

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