Cellular Respiration and Redox Reactions
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Questions and Answers

What is the main function of chemotrophic energy metabolism in cells?

  • To catabolize nutrients and conserve ATP (correct)
  • To synthesize proteins from amino acids
  • To store nutrients for future use
  • To generate heat and prevent freezing

What does oxidation involve?

  • Loss of oxygen only
  • Gain of hydrogen atoms
  • Loss of electrons or hydrogen atoms, or gain of oxygen (correct)
  • Gain of oxygen only

Which molecule is identified as the oxidizing agent in the following reaction: NADH + R → RH + NAD+?

  • R
  • RH
  • NAD+ (correct)
  • NADH

What happens to the reducing agent during an oxidation-reduction reaction?

<p>It loses electrons and becomes oxidized (C)</p> Signup and view all the answers

Which statement best describes a reducing agent in cellular respiration?

<p>It loses electrons and becomes oxidized. (B)</p> Signup and view all the answers

Which of the following correctly describes reduction in a chemical reaction?

<p>Gain of electrons and gain of hydrogen atoms, or loss of oxygen (A)</p> Signup and view all the answers

Why can't oxidation occur without reduction?

<p>The oxidizing agent must gain electrons while the reducing agent loses them (A)</p> Signup and view all the answers

What is the main difference between chemolithotrophs and chemoorganotrophs?

<p>Chemolithotrophs gain energy from the oxidation of inorganic molecules. (A)</p> Signup and view all the answers

In the reaction involving methane, oxygen, carbon dioxide, and water, what roles do methane and oxygen play?

<p>Methane is the reducing agent, and oxygen is the oxidizing agent (D)</p> Signup and view all the answers

What type of cellular respiration occurs in the absence of oxygen?

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

What is the waste product formed during alcohol fermentation?

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

Which of the following defines the term 'exergonic' as related to cellular respiration?

<p>Releases energy. (B)</p> Signup and view all the answers

What occurs to the oxidizing agent after a reaction?

<p>It is reduced (B)</p> Signup and view all the answers

In energy flow within an ecosystem, how is energy primarily lost from the ecosystem?

<p>As heat. (B)</p> Signup and view all the answers

Which molecule is produced from pyruvate during lactic acid fermentation?

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

Which of the following best describes the process of cellular respiration?

<p>Oxidation of organic and inorganic molecules to release energy. (D)</p> Signup and view all the answers

Which type of fermentation is primarily associated with Baker’s yeast?

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

What role does NADH play in both lactic acid and alcohol fermentation?

<p>It donates electrons to form a byproduct. (C)</p> Signup and view all the answers

What is the role of phototrophs in an ecosystem?

<p>They convert solar energy into chemical energy. (B)</p> Signup and view all the answers

What is released as a byproduct during alcohol fermentation?

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

Which of the following is NOT a characteristic of chemotropism?

<p>They primarily utilize solar energy. (A)</p> Signup and view all the answers

What is the main purpose of cellular respiration?

<p>To release energy from food molecules to produce ATP (B)</p> Signup and view all the answers

Where does glycolysis occur within the cell?

<p>In the cytoplasm of both prokaryotic and eukaryotic cells (D)</p> Signup and view all the answers

What are the end products of glycolysis from one glucose molecule?

<p>Two pyruvate molecules and ATP (D)</p> Signup and view all the answers

What is the main product of the reaction catalyzed by the pyruvate dehydrogenase complex?

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

What occurs to pyruvate when oxygen is present?

<p>It is converted into acetyl-CoA and enters the citric acid cycle (C)</p> Signup and view all the answers

Which molecule is oxidized during the conversion of pyruvate to Acetyl CoA?

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

Which process occurs during anaerobic conditions?

<p>Oxidation of NADH back to NAD+ via fermentation (A)</p> Signup and view all the answers

Which enzyme is NOT involved in the glycolytic pathway?

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

In which part of the cell does the citric acid cycle occur?

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

During the electron transport chain, what is produced as a direct result of the proton gradient?

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

Which statement about ATP production is true during glycolysis?

<p>ATP is generated only from substrate-level phosphorylation (C)</p> Signup and view all the answers

What is the starting molecule of the citric acid cycle?

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

What is the function of NAD+ in glycolysis?

<p>To carry electrons and regenerate NADH (A)</p> Signup and view all the answers

Which process is primarily responsible for ATP synthesis in the electron transport chain?

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

How many molecules of CO2 are produced for every two molecules of pyruvate processed?

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

What role do NADH and FADH2 play in cellular respiration?

<p>They donate electrons to the electron transport chain. (A)</p> Signup and view all the answers

What is the main purpose of the oxidation of NADH and FADH2 in mitochondria?

<p>To establish a proton gradient (C)</p> Signup and view all the answers

What does chemiosmosis involve?

<p>The diffusion of ions across a membrane (B)</p> Signup and view all the answers

How many ATP molecules are generated from the oxidation of one molecule of NADH?

<p>3 ATP (C)</p> Signup and view all the answers

In what situation does fermentation primarily occur?

<p>When oxygen is limited or unavailable (A)</p> Signup and view all the answers

What is the final electron acceptor in aerobic cellular respiration?

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

During oxidative phosphorylation, how many ATP molecules are produced from two molecules of FADH2?

<p>4 ATP (A)</p> Signup and view all the answers

What occurs as a result of the proton gradient established by mitochondria?

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

Which process is NOT a characteristic of anaerobic cellular respiration?

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

Flashcards

Oxidation

The loss of electrons, hydrogen atoms, or gain of oxygen.

Reduction

The gain of electrons, hydrogen atoms, or loss of oxygen.

Redox Reaction

An oxidation-reduction reaction; simultaneous oxidation and reduction.

Oxidizing Agent

The reactant that gains electrons and gets reduced (causes oxidation of another substrate).

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Reducing Agent

The reactant that loses electrons and gets oxidized (causes reduction of another substrate).

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Chemotrophic Metabolism

The process of cells breaking down nutrients for energy and making ATP.

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NAD+

Nicotinamide adenine dinucleotide, an electron carrier in redox reactions.

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NADH

The reduced form of NAD+, carrying electrons.

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Fermentation

Metabolic process that generates ATP without oxygen, using organic molecules as electron acceptors.

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Alcoholic Fermentation

Fermentation pathway producing ethanol as a waste product. Pyruvate is converted to acetaldehyde, then to ethanol by NADH.

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Lactic Acid Fermentation

Fermentation pathway producing lactate as a waste product. Pyruvate receives electrons from NADH, forming lactate and regenerating NAD+.

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Saccharomyces cerevisiae

A type of yeast crucial for alcoholic fermentation, often used in bread making and brewing.

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What is the purpose of fermentation?

To generate ATP without oxygen in environments where oxygen is unavailable. It regenerates NAD+ for glycolysis to continue.

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Chemotroph

An organism that obtains energy by oxidizing chemical compounds, such as organic or inorganic molecules.

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Chemoorganotroph

A type of chemotroph that obtains energy from the oxidation of organic molecules.

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Chemolithotroph

A type of chemotroph that obtains energy from the oxidation of inorganic molecules.

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Cellular Respiration

A metabolic process that generates energy (ATP) through the oxidation of organic molecules in the presence or absence of oxygen.

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Aerobic Respiration

Cellular respiration that requires oxygen as the final electron acceptor.

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Anaerobic Respiration

Cellular respiration that does not require oxygen and utilizes other molecules as the final electron acceptor.

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ATP Production

The main goal of cellular respiration is to make ATP, the energy currency of cells.

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Glycolysis

The first stage of cellular respiration, breaking down glucose into pyruvate in the cytoplasm.

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Pyruvate Processing

The conversion of pyruvate into acetyl-CoA, which enters the citric acid cycle.

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Substrate-Level Phosphorylation

Direct transfer of phosphate group from a substrate to ADP, forming ATP.

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Proton Gradient

The difference in proton concentration across the mitochondrial membrane, with a higher concentration in the intermembrane space than in the matrix. This gradient is essential for ATP synthesis.

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Chemiosmosis

The movement of ions across a semi-permeable membrane, down their electrochemical gradient. In mitochondria, this refers to the movement of protons through ATP synthase, generating ATP.

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What does ATP synthase do?

ATP synthase is an enzyme that uses the proton gradient across the mitochondrial membrane to produce ATP. It acts like a molecular motor, harnessing the energy from proton movement to synthesize ATP.

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Oxidative Phosphorylation

The process of generating ATP from the oxidation of NADH and FADH2 in the electron transport chain. It involves the movement of electrons through a series of proteins, pumping protons across the mitochondrial membrane.

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How much ATP per NADH and FADH2?

Each molecule of NADH processed via oxidative phosphorylation yields 3 ATP molecules. Each FADH2 molecule generates 2 ATP molecules.

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Pyruvate Dehydrogenase

A multienzyme complex that catalyzes the conversion of pyruvate to Acetyl-CoA. It's crucial for linking glycolysis to the citric acid cycle.

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Acetyl-CoA

A molecule formed from pyruvate that carries two carbon atoms into the citric acid cycle. It's a key fuel source for cellular respiration.

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Citric Acid Cycle

A series of eight enzymatic reactions inside mitochondria that oxidizes Acetyl-CoA to CO2, generating ATP, NADH, and FADH2.

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Tricarboxylic Acid Cycle

Another name for the citric acid cycle, referring to the three carboxyl groups present in citrate, a key molecule in the cycle.

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Electron Transport Chain

A series of proteins in the mitochondrial membrane that carry electrons from NADH and FADH2, producing a proton gradient for ATP synthesis.

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What is the role of NADH and FADH2 in cellular respiration?

NADH and FADH2 are electron carriers that transfer electrons from earlier steps of cellular respiration to the electron transport chain, ultimately leading to ATP production.

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How is a proton gradient generated in mitochondria?

The electron transport chain pumps protons from the mitochondrial matrix to the intermembrane space, creating a concentration gradient that powers ATP synthesis.

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Study Notes

Chemotrophic Energy Metabolism - Cellular Respiration

  • Chemotrophic energy metabolism involves reactions where cells break down nutrients and store energy as ATP.
  • Some of the chemical energy is released during this breakdown that cells use to create energy from the food.
  • Catabolism (exergonic) is a crucial part of this process.

Oxidation

  • Oxidation is the loss of electrons, hydrogen atoms, or the gain of oxygen.
  • In the example Mg → Mg2+ + 2e-, Mg loses 2 electrons, hence oxidized.
  • NADH is reduced form of NAD, while NAD+ is the oxidized form.

Reduction

  • Reduction is the gain of electrons, hydrogen atoms, or loss of oxygen.
  • In the example Fe+3 → Fe+2, Fe+3 gains an electron, hence reduced.
  • NAD+ is oxidized form of NAD, while NADH is reduced form.

Oxidation-Reduction Reactions

  • Oxidation and reduction reactions are coupled, meaning one cannot happen without the other.
  • An oxidizing agent gains electrons and becomes reduced, while a reducing agent loses electrons and becomes oxidized.
  • The reaction is shown where 'R' is oxidized and NADH reduces to form 'RH'.

Cellular Respiration

  • Cellular respiration is the process where glucose plus oxygen is broken down to form carbon dioxide and water and releases energy.
  • The balanced chemical equation is C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy.

Chemotrophs

  • Chemotrophs obtain energy from the oxidation of chemicals.
  • Chemoorganotrophs derive energy from organic compounds (e.g., C-H compounds).
  • Chemolithotrophs derive energy from inorganic compounds (e.g., H compounds).
  • Inorganic molecules may contain carbon but are not bonded to hydrogen.

Energy Flow and Chemical Cycling in Ecosystems

  • Energy enters ecosystems as solar energy utilized by phototrophs (e.g., plants) for photosynthesis.
  • Energy exits the ecosystem as heat.

Cellular Respiration of Chemotrophs

  • Aerobic respiration occurs in the presence of oxygen.
  • Anaerobic respiration occurs in the absence of oxygen.

Glycolysis (Embden-Meyerhof-Parnas Pathway)

  • Glycolysis occurs in the cytoplasm.
  • A glucose molecule is broken down into two pyruvate molecules.
  • ATP is produced from ADP and inorganic phosphate.
  • NAD+ is reduced to form NADH, which yields electron carrying power.

Aerobic Respiration Overview

  • The process happens in the mitochondria.
  • Glycolysis, pyruvate oxidation, citric acid cycle, and electron transport chain/oxidative phosphorylation are involved.
  • Protons are pumped across membranes.
  • ATP is produced through chemiosmosis.

Substrate-Level Phosphorylation

  • ATP is produced by the direct transfer of a phosphate group from a phosphorylated substrate to ADP
  • This is different from Oxidative phosphorylation.

Fate of Pyruvate

  • The fate of pyruvate depends on the availability of oxygen.
  • In the presence of oxygen, pyruvate is oxidized into acetyl CoA, entering the citric acid cycle.
  • Without oxygen, pyruvate is reduced to regenerate NAD+ for glycolysis, which is known as fermentation.

Pyruvate Processing

  • Pyruvate processing occurs in the mitochondrial matrix of eukaryotes.
  • Pyruvate dehydrogenase is a multienzyme complex catalyzing the oxidation reaction of pyruvate to acetyl CoA and producing CO₂ and NADH.

Citric Acid Cycle

  • The Citric Acid Cycle (Krebs Cycle) starts when a 2-carbon acetyl group joins a 4-carbon oxaloacetate molecule to form citrate, a 6-carbon compound.
  • A series of eight reactions yield NADH, FADH₂, ATP, and releases carbon dioxide.
  • The cycle regenerates oxaloacetate to continue the cycle.

Electron Transport Chain and Oxidative Phosphorylation

  • The electron transport chain is a series of protein complexes.
  • NADH and FADH₂ transfer electrons through the chain.
  • Proton gradient is established across the inner mitochondrial membrane.
  • Chemiosmosis powers ATP synthesis.

Oxidative Phosphorylation

  • Oxidative phosphorylation is the process where ADP is phosphorylated to ATP (ATP synthase).
  • NADH and FADH₂ are used as electron donors.

Number of ATPs

  • Total ATP produced from glucose through aerobic respiration: 38

Fermentation

  • Fermentation is the process that occurs without oxygen.
  • It uses alternative electron acceptors to regenerate NAD+ without oxygen.
  • Two types are alcoholic fermentation (e.g., yeast) and lactic acid fermentation (e.g., muscle cells).

Alcoholic Fermentation

  • Pyruvate is converted into acetaldehyde, then ethanol (e.g., used in beer brewing).
  • Carbon dioxide is released.

Lactic Acid Fermentation

  • Pyruvate is converted into lactate (e.g., used in muscle cells).
  • No carbon dioxide is released.

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Chemotrophic Energy Metabolism - Cellular Respiration PDF

Description

This quiz explores the concepts of chemotrophic energy metabolism, including cellular respiration, oxidation, and reduction reactions. Understand the key processes involved in energy transfer and storage in biological systems through catabolic pathways. Test your knowledge on oxidation-reduction reactions and their crucial roles in cellular functions.

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