Cellular Respiration: Krebs Cycle and Glycolysis
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Questions and Answers

In what specific location within the cell does the Krebs cycle take place?

  • The mitochondrial matrix (correct)
  • The intermembrane space of the mitochondria
  • The cytoplasm
  • The inner mitochondrial membrane

What is the primary role of NADH and FADH2 molecules produced by the Krebs cycle?

  • To directly phosphorylate ADP into ATP
  • To serve as enzymes that catalyze metabolic reactions
  • To act as substrates in the Krebs Cycle reactions
  • To donate electrons to the electron transport chain (correct)

What byproduct of pyruvate breakdown is released during the Krebs cycle?

  • Oxygen
  • Lactic acid
  • Water
  • Carbon dioxide (correct)

How is the majority of ATP generated during aerobic respiration?

<p>By the movement of H+ ions through ATP synthase during chemiosmosis (B)</p> Signup and view all the answers

What is the final destination of the electrons from NADH and FADH2 that enter the electron transport chain?

<p>They are used to establish a H+ gradient, which powers ATP synthesis (B)</p> Signup and view all the answers

What is the net ATP gain from glycolysis?

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

In which cellular location does the Krebs cycle take place?

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

What is the primary role of NADH in cellular respiration?

<p>To carry high-energy electrons to the ETC (C)</p> Signup and view all the answers

Which process uses the energy of an H+ gradient to synthesize ATP?

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

Substrate-level phosphorylation is characterized by which of these?

<p>It involves an enzyme transferring a phosphate group. (C)</p> Signup and view all the answers

What is the end product of glycolysis?

<p>Pyruvic acid, ATP, and NADH (C)</p> Signup and view all the answers

How many ATP molecules are initially invested in the process of glycolysis?

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

What percentage of the total chemical energy available in a glucose molecule remains unused after glycolysis?

<p>90% (C)</p> Signup and view all the answers

What is the primary purpose of fermentation in cells?

<p>To regenerate NAD+ for glycolysis. (C)</p> Signup and view all the answers

Which molecule is produced during lactic acid fermentation?

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

Where does glycolysis occur in the cell?

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

What is one of the end products of alcoholic fermentation?

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

Under what condition does lactic acid build up in muscles?

<p>During intense exercise when oxygen is limited (B)</p> Signup and view all the answers

Substrate-level phosphorylation is a method of producing ATP. What is required for substrate-level phosphorylation?

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

Which of following processes would NOT occur in an anaerobic respiration pathway?

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

How many net ATP molecules are produced per glucose molecule during fermentation?

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

Where does the electron transport chain occur?

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

What is the net gain of ATP molecules during glycolysis?

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

Which molecule is the final product of glycolysis and proceeds to the Krebs cycle?

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

What is the primary function of NADH and FADH2 in cellular respiration?

<p>Act as electron carriers (C)</p> Signup and view all the answers

In which part of the mitochondria does the Krebs cycle take place?

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

What is the role of ATP synthase in the electron transport chain?

<p>To convert H+ gradient into ATP (C)</p> Signup and view all the answers

Besides ATP what is another product of glycolysis, that then moves to the Electron transport chain?

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

What is a byproduct of pyruvate breakdown in the Krebs cycle?

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

During strenuous exercise, why does lactic acid build up in muscles?

<p>Because oxygen cannot be delivered quickly enough (D)</p> Signup and view all the answers

Which of the following correctly describes the relationship between cellular respiration and fermentation?

<p>Fermentation is an anaerobic alternative mechanism for cells to create ATP when aerobic respiration is limited (A)</p> Signup and view all the answers

What is the end product of alcoholic fermentation in addition to carbon dioxide?

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

Where in the cell does lactic acid fermentation take place?

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

What is the primary role of oxygen in the electron transport chain (ETC)?

<p>To act as the final electron acceptor, forming water (B)</p> Signup and view all the answers

What is the net ATP production per glucose molecule through cellular respiration?

<p>38 ATP (A)</p> Signup and view all the answers

What is the function of the electron shuttle in cellular respiration?

<p>To move NADH electrons from glycolysis into the mitochondria (A)</p> Signup and view all the answers

Which of the following best describes fermentation?

<p>An anaerobic process that produces small amounts of ATP and regenerates NAD+ (B)</p> Signup and view all the answers

What is the consequence of running out of NAD+ during glycolysis?

<p>Glycolysis will stop because electron carriers are full (C)</p> Signup and view all the answers

What is the function of converting NADH to NAD+ during fermentation?

<p>To ensure that glycolysis can continue by replenishing electron carriers (B)</p> Signup and view all the answers

How do cells transfer high-energy electrons from NADH and FADH2 to ultimately produce water?

<p>Through a series of protein transfers in the electron transport chain (D)</p> Signup and view all the answers

What happens to pyruvic acid during fermentation?

<p>It is used to regenerate NAD+ by accepting electrons (C)</p> Signup and view all the answers

Flashcards

Chemiosmosis

A process that uses the energy stored in the concentration gradients of H+ ions across membranes to synthesize ATP.

ATP synthase

An enzyme that synthesizes ATP using the energy stored in concentration gradients of H+ ions across membranes.

Substrate-level phosphorylation

The process of transferring a phosphate group from a substrate molecule to ADP, resulting in ATP production.

NADH

A molecule that carries electrons during cellular respiration. It is reduced when it picks up electrons and oxidized when it releases electrons.

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Electron transport chain

A series of protein complexes embedded in the inner mitochondrial membrane that accept high-energy electrons from NADH and use them to pump protons across the membrane, creating a proton gradient.

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Glycolysis

The breakdown of glucose into two molecules of pyruvic acid.

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Krebs cycle

A cycle of reactions that occurs in the mitochondria, where pyruvic acid is further broken down, generating ATP, NADH, and FADH2.

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Oxidative phosphorylation

The process that occurs in the mitochondria, where the energy stored in the electron carriers NADH and FADH2 is used to generate ATP through chemiosmosis.

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What is the Krebs Cycle?

Krebs Cycle is a series of reactions that occur within the mitochondria's matrix. This cycle is responsible for completely breaking down glucose to extract energy in the form of NADH and FADH2, which are electron carriers. This process releases CO2 as a byproduct.

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What is the ETC?

Electron Transport Chain (ETC) is a series of protein complexes embedded within the inner mitochondrial membrane. It utilizes the energy from electrons carried by NADH and FADH2 to pump protons (H+) across the membrane, creating a concentration gradient, and this gradient powers the formation of ATP.

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What is Chemiosmosis?

Chemiosmosis is the process by which the ETC's proton gradient is used to generate ATP. As protons flow back through ATP synthase, the enzyme uses their potential energy to combine ADP and a phosphate group, creating ATP.

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How does the Krebs cycle create ATP?

The Krebs Cycle uses substrate-level phosphorylation to produce two ATP molecules per glucose molecule. But the majority of ATP is generated by the ETC and Chemiosmosis, through oxidative phosphorylation.

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What happens to pyruvate in the Krebs Cycle?

During the Krebs Cycle, pyruvate is broken down into carbon dioxide (CO2) which is then exhaled. This process releases energy stored in the chemical bonds of pyruvate.

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Alcoholic Fermentation

The process where pyruvic acid is converted to ethyl alcohol and carbon dioxide, regenerating NAD+ to sustain glycolysis.

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Lactic Acid Fermentation

The process where pyruvic acid is converted to lactic acid, regenerating NAD+ to sustain glycolysis.

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Lactic Acid Buildup

The buildup of lactic acid in muscles during strenuous exercise due to anaerobic conditions.

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Anaerobic Respiration

The process of energy production in the absence of oxygen, involving glycolysis and fermentation. It generates a much smaller amount of ATP compared to aerobic respiration.

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Aerobic Respiration

The process of energy production in the presence of oxygen, involving glycolysis, the Krebs cycle, and the electron transport chain. It generates a large amount of ATP.

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Photosynthesis

The process by which plants and some bacteria convert light energy into chemical energy in the form of glucose.

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Cellular Respiration

The process by which cells break down glucose to release energy in the form of ATP.

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Electron Transport Chain (ETC)

The movement of electrons down a chain of protein complexes, releasing energy that is used to pump protons across a membrane, creating a proton gradient for ATP synthesis.

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Oxygen in Cellular Respiration

The final electron acceptor in the electron transport chain, combining with electrons and protons to form water.

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Fermentation

An anaerobic process that occurs when oxygen is absent, allowing glycolysis to continue by converting NADH back to NAD+.

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Mitochondria

The main site of aerobic respiration in eukaryotic cells, where the Krebs cycle and electron transport chain occur. They contain their own DNA and ribosomes.

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Electron carrier

A molecule that can accept or donate electrons, playing a role in redox reactions. NADH and FADH2 are examples.

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Study Notes

Cellular Respiration

  • Cellular respiration is the aerobic process of harvesting energy from glucose to produce ATP.
  • Nearly all cells in the body break down sugars to create ATP for energy.
  • Glucose + Oxygen → Carbon Dioxide + Water + ATP (Energy)
  • 38 ATP molecules are produced per glucose molecule.
  • Cellular Respiration is a redox reaction; glucose is oxidized to carbon dioxide and oxygen is reduced to water.

What is ATP?

  • ATP is adenosine triphosphate.
  • It's the currency of biological energy.
  • Energy is stored in the high-energy phosphate bonds.
  • When ATP is hydrolyzed (broken down), it releases energy for cellular work.
  • When ATP is created, energy is stored.

How can we generate ATP?

  • Two methods: Chemiosmosis and substrate-level phosphorylation.
  • Chemiosmosis: ATP synthase uses the energy in the H+ ion concentration gradient across membranes to create ATP. This happens in the membranes.
  • Substrate-level phosphorylation: An enzyme transfers a phosphate group from a substrate to ADP to make ATP. This happens outside of membranes.

Stages of Cellular Respiration

  • Glycolysis: Occurs in the cytoplasm of the cell and breaks down glucose into two molecules of pyruvic acid. A net gain of 2 ATP is created per glucose molecule. NADH is also produced.
  • Krebs Cycle (Citric Acid Cycle): Occurs in the mitochondrial matrix. Pyruvic acid is oxidized further releasing COâ‚‚, NADH, and FADHâ‚‚. Several ATP molecules are made.
  • Electron Transport Chain (ETC): Occurs in the inner mitochondrial membrane. Electron carriers (NADH and FADHâ‚‚) release their electrons. Energy is released and used to pump H+ ions across the membrane creating a gradient. ATP synthase uses this gradient to produce a large amount of ATP. Oxygen is the final electron acceptor.

Fermentation

  • Fermentation is an anaerobic process that occurs when oxygen is unavailable.
  • It allows glycolysis to continue by regenerating NAD+ by transferring electrons to pyruvic acid.
  • Fermentation produces small amounts of ATP (2 per glucose).
  • Two types: Alcoholic Fermentation and Lactic Acid Fermentation

Alcoholic Fermentation

  • Pyruvic acid is converted into carbon dioxide and ethanol.
  • This process regenerates NAD+ for glycolysis to continue.

Lactic Acid Fermentation

  • Pyruvic acid is converted into lactic acid.
  • This regenerates NAD+ for glycolysis and produces lactic acid as a byproduct (leading to muscle pain).

Aerobic vs. Anaerobic Respiration

  • Aerobic respiration requires oxygen, and anaerobic does not.
  • Aerobic respiration is much more efficient, producing many more ATP molecules per glucose.
  • Anaerobic respiration only occurs in the cytoplasm, and aerobic also occurs in the mitochondria.

Mitochondria: Site of Aerobic Respiration

  • Mitochondria are the site of aerobic cellular respiration in eukaryotic cells. They are the "powerhouses" producing the majority of ATP needed for cellular work.
  • The major components are the outer membrane, inner membrane, matrix, and cristae.

Photosynthesis vs. Cellular Respiration

  • Photosynthesis and Cellular Respiration work together in the carbon cycle.
  • Photosynthesis takes carbon dioxide from the atmosphere and creates glucose.
  • Cellular respiration takes glucose and releases carbon dioxide into the atmosphere.

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Cell Respiration Honors 2025 Student Version PDF

Description

Test your knowledge on the Krebs cycle and glycolysis with this quiz. Explore the specific locations within the cell, the roles of NADH and FADH2, and the processes involved in ATP generation. Delve into cellular respiration and its key components to understand how energy is produced within cells.

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