Cellular Respiration Overview
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Questions and Answers

What is the primary function of glycolysis in cellular respiration?

  • To produce oxygen as a byproduct for other cellular processes.
  • To convert pyruvate into carbon dioxide and water.
  • To break down glucose into pyruvate and generate ATP and NADH. (correct)
  • To synthesize glucose from pyruvate.

Which of the following statements accurately describes the location of glycolysis in both prokaryotic and eukaryotic cells?

  • It occurs in the mitochondria.
  • It occurs in the cytoplasm. (correct)
  • It takes place in the nucleus.
  • It takes place on the endoplasmic reticulum.

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

  • 2 ATP molecules (correct)
  • 3 ATP molecules
  • 1 ATP molecule
  • 4 ATP molecules

What is the role of ATP in the energy-requiring phase of glycolysis?

<p>ATP is converted to ADP to provide phosphate groups to glucose. (D)</p> Signup and view all the answers

What is the net gain of NADH molecules resulting from the breakdown of one glucose molecule during glycolysis?

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

What is the six-carbon sugar formed after the first step of glycolysis with the enzyme hexokinase?

<p>Glucose-6-phosphate (D)</p> Signup and view all the answers

Which enzyme is responsible for the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate?

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

What is the primary function of the electron transport chain?

<p>Create a proton gradient across the inner mitochondrial membrane. (C)</p> Signup and view all the answers

Which of the following is a characteristic of glycolysis?

<p>It is an anaerobic process. (A)</p> Signup and view all the answers

Which molecules initially donate electrons to the electron transport chain?

<p>NADH and $FADH_2$ (A)</p> Signup and view all the answers

What process directly utilizes the proton gradient established by the electron transport chain?

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

Where is the electron transport chain located in the mitochondria?

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

In the electron transport chain, what happens to the energy of electrons as they pass from one molecule to another?

<p>It is used to pump protons across the membrane. (A)</p> Signup and view all the answers

Which of the following is a characteristic of the mitochondrial outer membrane?

<p>It has large pores that allow the passage of ions and molecules, even small proteins. (D)</p> Signup and view all the answers

What type of reaction occurs when electrons are passed down the transport chain?

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

What is the combined process of the electron transport chain and chemiosmosis called?

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

The inner mitochondrial membrane is characterized by which of the following?

<p>It is folded into cristae which allows for a larger surface area for cellular metabolism. (C)</p> Signup and view all the answers

Where does the conversion of pyruvic acid to Acetyl-CoA occur?

<p>In the mitochondrial matrix. (C)</p> Signup and view all the answers

When NADH transfers its electrons to the electron transport chain, what is it converted to?

<p>$NAD^+$ (C)</p> Signup and view all the answers

Which of the following is a direct outcome of the Krebs cycle?

<p>The breakdown of acetyl-CoA into carbon dioxide and water. (B)</p> Signup and view all the answers

What is the product of the final electron acceptor from the electron transport chain that happens in the inner membrane?

<p>Water ($H_2O$) (A)</p> Signup and view all the answers

How many net ATP molecules are generated during glycolysis?

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

Which of the following molecules are produced during the conversion of pyruvic acid to Acetyl-CoA?

<p>$CO_2$, NADH and $H^+$ (A)</p> Signup and view all the answers

What is the primary function of the mitochondrial cristae?

<p>To increase the surface area for cellular respiration. (C)</p> Signup and view all the answers

Which enzyme catalyzes the conversion of fructose-1,6-bisphosphate into dihydroxyacetone-phosphate and glyceraldehyde-3-phosphate?

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

In glycolysis, how many net ATP molecules are produced per glucose molecule during the energy-releasing phase?

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

What is the role of the enzyme isomerase in glycolysis?

<p>To convert a 3 carbon molecule into a different 3 carbon molecule. (D)</p> Signup and view all the answers

The dehydration reaction catalyzed by enolase in glycolysis results in the formation of which molecule?

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

During which step of glycolysis is NADH produced?

<p>Oxidation of glyceraldehyde-3-phosphate. (C)</p> Signup and view all the answers

What is the primary function of phosphofructokinase in glycolysis?

<p>To speed up or slow down glycolysis in response to the cell's needs. (D)</p> Signup and view all the answers

Which of the following is the final product of glycolysis?

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

Which enzyme catalyzes the substrate-level phosphorylation in the last step of glycolysis?

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

What is the net ATP produced directly during the citric acid cycle for each molecule of glucose?

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

How many NADH molecules are produced from a single molecule of glucose during pyruvate oxidation?

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

Which stage of cellular respiration can proceed anaerobically?

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

What are the main end products of glycolysis?

<p>Pyruvate, ATP, NADH (D)</p> Signup and view all the answers

Which molecule is responsible for carrying hydrogen atoms to the electron transport chain?

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

What is the total theoretical maximum yield of ATP from one molecule of glucose undergoing complete cellular respiration based on the information provided?

<p>30-32 (B)</p> Signup and view all the answers

In which cellular location does the citric acid cycle occur?

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

How many molecules of FADH2 are directly produced from one molecule of glucose during the citric acid cycle?

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

What is the primary role of pyruvate in fermentation?

<p>To act as an electron acceptor, recycling NAD+. (C)</p> Signup and view all the answers

Which of the following molecules can act as terminal electron acceptors during anaerobic respiration?

<p>Sulfate, nitrate, or sulfur. (D)</p> Signup and view all the answers

In lactic acid fermentation, what molecule is produced from pyruvate?

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

Why is anaerobic respiration less efficient than aerobic respiration?

<p>The terminal electron acceptors in anaerobic respiration have a lower reduction potential. (B)</p> Signup and view all the answers

What is denitrification?

<p>A process that uses nitrate as the terminal electron acceptor. (C)</p> Signup and view all the answers

Which process is linked to the production of hydrogen sulfide (H2S) during anaerobic respiration?

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

What is the primary electron donor and acceptor for acetogenesis?

<p>Hydrogen (H2) as donor and carbon dioxide (CO2) as acceptor. (D)</p> Signup and view all the answers

What is the impact of anaerobic respiration on ATP production compared to aerobic respiration?

<p>Anaerobic respiration produces significantly less ATP. (A)</p> Signup and view all the answers

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Flashcards

What is Glycolysis?

The first stage of cellular respiration, where glucose is broken down into pyruvate. This process occurs in the cytoplasm of cells and does not require oxygen.

Glycolysis

Glycolysis is the metabolic pathway that converts glucose into pyruvate, a key process for energy production.

Where does glycolysis occur?

Glycolysis occurs in the cytoplasm of the cell, where it breaks down glucose into pyruvate.

What is the energy input and output of glycolysis?

Glycolysis requires two ATP molecules to initiate the process. However, it produces four ATP molecules and two NADH molecules, resulting in a net gain of two ATP molecules.

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Is glycolysis aerobic or anaerobic?

Glycolysis is an anaerobic process, meaning it does not require oxygen to happen.

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How many steps are involved in glycolysis?

The process of glycolysis involves a sequence of ten steps, each catalyzed by a specific enzyme.

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What is the main product of glycolysis?

In glycolysis, a six-carbon glucose molecule is broken down into two three-carbon pyruvate molecules.

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What is the purpose of the preparatory phase in glycolysis?

In the preparatory phase of glycolysis, two ATP molecules are used to add phosphate groups to glucose, making it unstable to split into two three-carbon molecules.

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Mitochondrial Cristae

The inner membrane of the mitochondria is folded into cristae, which significantly increases the surface area for cellular metabolism. This folding allows for more efficient production of ATP, the primary energy currency of cells.

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Mitochondrial Matrix

The inner membrane encloses the mitochondrial matrix, a space filled with enzymes and other molecules essential for cellular respiration. Key processes like the Krebs cycle and oxidative phosphorylation occur within this matrix.

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Selective Permeability of the Inner Membrane

The inner membrane of the mitochondria allows selective passage of molecules, much like a gatekeeper controlling what enters and exits a castle. It plays a crucial role in maintaining the concentration gradients necessary for ATP production.

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Conversion of Pyruvate to Acetyl-CoA

Pyruvate, a three-carbon molecule, is converted into Acetyl-CoA, a two-carbon molecule, in a process that releases carbon dioxide and produces NADH. This occurs in the mitochondrial matrix and is the transition step between glycolysis and the Krebs cycle.

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Krebs Cycle

The Krebs cycle, also known as the citric acid cycle, is a series of enzyme-catalyzed reactions that break down Acetyl-CoA into carbon dioxide, producing ATP, FADH2, and NADH. It occurs in the mitochondrial matrix.

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Electron Transport Chain

A series of protein complexes embedded in the inner membrane that transfers electrons from NADH and FADH2 to oxygen, generating a proton gradient used to produce ATP. This process is coupled with the movement of protons across the membrane and is the main source of ATP production in cellular respiration.

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Oxidative Phosphorylation

The process of producing ATP using the energy released from the electron transport chain. It occurs in the inner membrane of the mitochondria and is the final step of cellular respiration.

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Phosphofructokinase

The enzyme that catalyzes the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate, a key regulatory step in glycolysis.

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Energy-requiring phase

The first phase of glycolysis, where two ATP molecules are invested to activate the glucose molecule.

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Energy-releasing phase

The second phase of glycolysis, where four ATP molecules and two NADH molecules are produced.

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Pyruvate

A three-carbon molecule that is the end product of glycolysis.

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Glucose

A six-carbon sugar molecule that is broken down into two three-carbon molecules during glycolysis.

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Isomerization

The conversion of dihydroxyacetone-phosphate into its isomer, glyceraldehyde-3-phosphate.

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NADH

A molecule that carries electrons in cellular respiration, specifically during glycolysis.

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Lactic Acid Fermentation

In anaerobic respiration, pyruvate is converted to lactate, regenerating NAD+ for continued glycolysis.

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Alcohol Fermentation

In anaerobic respiration, pyruvate is broken down into CO2 and ethanol, regenerating NAD+ for glycolysis.

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Anaerobic Respiration

Anaerobic respiration involves using molecules other than oxygen as the final electron acceptor in the electron transport chain.

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Denitrification

The use of nitrate (NO3-) as the terminal electron acceptor in anaerobic respiration.

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Sulfate Reduction

Sulfate (SO2−4) acts as the final electron acceptor in anaerobic respiration, generating hydrogen sulfide (H2S) as a product.

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Acetogenesis

The process in microbial metabolism where hydrogen (H2) is used to produce acetate as an electron donor and carbon dioxide (CO2) as an electron acceptor.

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Ferric Iron Reduction

A type of anaerobic respiration used by both autotrophic and heterotrophic species, using ferric iron (Fe3+) as the final electron acceptor.

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Energy Yield in Anaerobic Respiration

Anaerobic respiration generates less energy than aerobic respiration because the alternative electron acceptors have lower reduction potential than oxygen.

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What is NADH?

A molecule involved in cellular respiration. It gets reduced (gain electrons) during glycolysis, storing chemical energy from glucose.

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Chemiosmosis

Chemiosmosis is a process that uses the proton gradient created by the electron transport chain to generate ATP. Protons flow down their concentration gradient through ATP synthase, driving the phosphorylation of ADP into ATP.

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What is pyruvate oxidation?

The process that links glycolysis to the citric acid cycle by converting pyruvate to acetyl CoA. It occurs within the mitochondria.

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Electron Carriers (NADH and FADH2)

NADH and FADH2 are electron carriers that deliver electrons to the electron transport chain, originating from earlier stages of cellular respiration.

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What is the Citric Acid Cycle?

A series of reactions that takes place in the mitochondrial matrix, generating ATP and reducing electron carriers NADH and FADH2.

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Proton Pumping

As electrons are passed down the electron transport chain, energy is released. This energy is used to pump protons across the inner mitochondrial membrane, creating a proton gradient.

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What is oxidative phosphorylation?

The final stage of cellular respiration where ATP is produced from the high-energy electrons carried by NADH and FADH2. It involves a chain of protein complexes located in the inner mitochondrial membrane.

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Proton Gradient

The proton gradient is a difference in proton concentration across the inner mitochondrial membrane. There's a higher concentration of protons in the intermembrane space than in the mitochondrial matrix.

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What are electron carriers?

These molecules, NADH and FADH2, are reduced forms of electron carriers that donate electrons to the electron transport chain, driving the production of ATP.

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What is aerobic respiration?

The process of converting glucose into energy in the presence of oxygen.

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ATP Synthase

The movement of protons down their concentration gradient through ATP synthase generates ATP, the energy currency of the cell.

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Phosphorylation

The process of converting ADP to ATP using the energy from the electron transport chain and the proton gradient is called phosphorylation.

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What is anaerobic respiration?

The process of generating energy in the absence of oxygen.

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Study Notes

Cellular Respiration

  • Cellular respiration is a process that releases energy from food molecules (glucose).
  • The equation for cellular respiration is: Glucose + oxygen → carbon dioxide + water + energy (ATP)
  • Cellular respiration takes place in mitochondria, which are often called the cell's power plants.

Obtaining Energy from Food

  • Autotrophs, such as plants, produce their own food through photosynthesis.
  • Heterotrophs depend on autotrophs for food.
  • Cellular respiration provides energy to organisms.

Mitochondria

  • Mitochondria are the sites of cellular respiration.
  • Mitochondria are oval-shaped organelles found in most eukaryotic cells.
  • They are essential for extracting energy from sugars, fats, and other fuels to create ATP (adenosine triphosphate).
  • The mitochondria have two membranes:
    • The outer membrane is selectively permeable and surrounds the mitochondria.
    • The inner membrane has folds called cristae, increasing the surface area for cellular metabolism.

Three Major Stages of Cellular Respiration

  • Glycolysis: Occurs in the cytoplasm; glucose is broken down into two pyruvate molecules, producing 2 ATP and 2 NADH.
  • Pyruvate Oxidation: Converts pyruvate into Acetyl-CoA; produces CO2 and NADH.
  • Krebs Cycle (Citric Acid Cycle): Acetyl-CoA is completely broken down into CO2, generating ATP, NADH, and FADH2.
  • Electron Transport Chain and Oxidative Phosphorylation: Electrons from NADH and FADH2 are passed down a chain, generating a proton gradient that drives ATP synthesis. This process results in a significant amount of ATP.
  • Note: The theoretical yield of ATP from one glucose molecule can vary slightly depending on how the electrons from NADH are transported into the mitochondria, but the most common values are between 30-38 ATP molecules.

Fermentation

  • Fermentation is a process that occurs when oxygen is unavailable.
  • It regenerates NAD+ for glycolysis to continue.
  • Two types of fermentation are:
    • Alcohol fermentation: Pyruvate is converted to ethanol and CO2. Used in alcoholic beverage production.
    • Lactic acid fermentation: Pyruvate is converted to lactic acid. Important in muscle cells during vigorous activity, and used in the production of dairy products.

Role of Oxygen in Respiration

  • Oxygen is the final electron acceptor in the electron transport chain.
  • This process produces water and a large amount of ATP.
  • Without oxygen, aerobic cellular respiration cannot occur.

Advantages and Disadvantages of Aerobic and Anaerobic Respiration

  • Aerobic respiration provides a large amount of ATP, whereas anaerobic respiration produces less.
  • Aerobic respiration is more efficient, whereas anaerobic respiration is faster.

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Description

This quiz covers the fundamental concepts of cellular respiration, including the process of energy extraction from food molecules such as glucose. Learn about the role of mitochondria in this vital energy-producing process and differentiate between autotrophs and heterotrophs. Perfect for students studying biology.

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