Cellular Respiration Overview
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Questions and Answers

What is the primary role of glycolysis in cellular respiration?

  • It prepares pyruvate for the citric acid cycle. (correct)
  • It generates ATP directly through oxidative phosphorylation.
  • It is the main site for electron transport.
  • It converts glucose into carbon dioxide and water.

Which process is responsible for generating the majority of ATP during cellular respiration?

  • Glycolysis
  • Substrate level phosphorylation
  • Oxidative phosphorylation (correct)
  • Citric acid cycle

Where does the citric acid cycle occur in eukaryotic cells?

  • In the cytosol
  • In the plasma membrane
  • In the ribosomes
  • In the mitochondria (correct)

What does the energy investment phase of glycolysis involve?

<p>Utilization of ATP to prepare glucose for breakdown. (C)</p> Signup and view all the answers

What is the outcome of one complete oxidation of one molecule of glucose during cellular respiration?

<p>38 ATP produced and oxygen consumed. (A)</p> Signup and view all the answers

What role does NAD+ play in glycolysis?

<p>It is reduced to form NADH during the process. (A)</p> Signup and view all the answers

Which statement accurately describes oxidative phosphorylation?

<p>It involves electron transport and chemiosmosis. (D)</p> Signup and view all the answers

What is the function of substrate-level phosphorylation?

<p>It directly generates ATP by transferring a phosphate group from a substrate to ADP. (D)</p> Signup and view all the answers

What occurs when an electron moves towards a more electronegative element?

<p>It loses potential energy. (B)</p> Signup and view all the answers

What is the primary function of NAD+ in cellular respiration?

<p>Transporting electrons and protons. (D)</p> Signup and view all the answers

Which step is crucial for the oxidation of glucose during cellular respiration?

<p>Removing hydrogens from glucose. (B)</p> Signup and view all the answers

How does the electron transport chain function within eukaryotic cells?

<p>By utilizing proteins in the inner membrane. (D)</p> Signup and view all the answers

What is a result of moving electrons from NADH to oxygen?

<p>Energy is released to create more ATP. (B)</p> Signup and view all the answers

What role do enzymes play during the digestion of sugars?

<p>They lower the activation energy for digestion. (C)</p> Signup and view all the answers

Which compounds are preferred for energy due to their structure?

<p>Compounds with many hydrogen atoms. (D)</p> Signup and view all the answers

What comparison illustrates the controlled release of energy from organic molecules?

<p>Combining hydrogen and oxygen with a spark. (A)</p> Signup and view all the answers

What role do the folds called cristae play in the electron transport chain?

<p>They increase surface area for reactions. (B)</p> Signup and view all the answers

Which molecule acts as a mobile electron carrier in the electron transport chain?

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

What does the electron transport chain primarily generate as a result of the redox reactions?

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

What is the primary function of ATP synthase in the mitochondria?

<p>Producing ATP from ADP and inorganic phosphates. (A)</p> Signup and view all the answers

At which protein complex does FADH2 donate its electrons in the electron transport chain?

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

What is the result of oxygen atoms accepting electrons in the electron transport chain?

<p>Formation of water. (D)</p> Signup and view all the answers

What is the process by which ATP is produced using the proton gradient in mitochondria called?

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

How does the rotor portion of ATP synthase function in ATP synthesis?

<p>By spinning from the attachment of protons. (A)</p> Signup and view all the answers

What is the net gain of ATP from glycolysis?

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

Where does the conversion of pyruvate to acetyl CoA occur?

<p>In the mitochondria for eukaryotic cells (D)</p> Signup and view all the answers

What is produced during the transition from pyruvate to acetyl CoA?

<p>1 NADH and 1 CO2 (B)</p> Signup and view all the answers

How many carbon atoms enter the citric acid cycle from one acetyl group?

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

What is produced for each acetyl group during the citric acid cycle?

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

What role does FAD play in the citric acid cycle?

<p>It carries protons and electrons to the ETC. (D)</p> Signup and view all the answers

What process couples electron transport to ATP synthesis during oxidative phosphorylation?

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

How is most ATP generated during cellular respiration after glycolysis?

<p>By oxidative phosphorylation in the electron transport chain (D)</p> Signup and view all the answers

What is the primary role of the proton motive force in mitochondria?

<p>To drive ATP synthesis via ATP synthase (A)</p> Signup and view all the answers

How many ATP are typically produced from one molecule of NADH?

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

Why does FADH2 yield less ATP compared to NADH?

<p>FADH2 donates electrons later in the ETC (D)</p> Signup and view all the answers

What is a possible result of the redox reactions in the electron transport chain (ETC)?

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

How many protons (H+) are typically expelled from the mitochondrial matrix for every NADH molecule?

<p>10 H+ (D)</p> Signup and view all the answers

What is the ATP yield from substrate-level phosphorylation per glucose molecule?

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

What impacts the amount of ATP produced from NADH obtained in the cytosol?

<p>The transport molecule it interacts with (C)</p> Signup and view all the answers

Which statement describes the relationship between proton ejection and ATP synthesis?

<p>Protons must re-enter the mitochondrial matrix to produce ATP (B)</p> Signup and view all the answers

What is the primary purpose of fermentation?

<p>To generate ATP and recycle NAD+ (B)</p> Signup and view all the answers

In alcoholic fermentation, which compound is produced from acetaldehyde?

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

What distinguishes lactic acid fermentation from alcoholic fermentation?

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

What is the final electron acceptor in fermentation?

<p>Acetaldehyde or an organic molecule (D)</p> Signup and view all the answers

Which type of organisms exclusively rely on fermentation for energy?

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

Which metabolic pathway is common to all living organisms and does not require oxygen?

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

How can proteins be utilized in cellular respiration when they are in excess?

<p>Converted into amino acids and then intermediates of glycolysis (B)</p> Signup and view all the answers

What is the main drawback of fermentation compared to aerobic respiration?

<p>Fermentation produces less energy from glucose (B)</p> Signup and view all the answers

Flashcards

Electronegativity and Energy

More electronegative elements require more energy to remove electrons from them, as electrons lose potential energy when moving towards them. This is similar to a ball losing potential energy as it moves downhill.

Oxidation of Glucose

Glucose combines with oxygen during cellular respiration, producing carbon dioxide, water, and releasing energy. Glucose loses electrons (oxidized), and oxygen gains electrons (reduced).

Stepwise Energy Release

Breaking down glucose in multiple steps through reactions is used to slowly release energy and produce ATP. Each step involves removing electrons.

NAD+ as Electron Carrier

NAD+ is an electron transporter that picks up electrons and hydrogen ions (protons) from glucose during cellular respiration. It acts as a temporary energy storage.

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NADH Energy Release

The energy released when electrons from NADH are passed to oxygen is significant and used for ATP synthesis.

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Electron Transport Chain

Proteins in the inner membrane of eukaryotic cells or the plasma membrane of prokaryotes that facilitate the movement of electrons from glucose to oxygen through a series of reactions.

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Enzymes in Cellular Respiration

Enzymes such as dehydrogenases speed up chemical reactions involved in glucose breakdown & facilitate the release of hydrogen atoms—which are protons plus electrons—to allow energy production.

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Dehydrogenases

Enzymes that remove hydrogen atoms from glucose molecules. Crucial for releasing energy by passing electrons to other molecules.

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Cellular Respiration Stages

Glycolysis, citric acid cycle, and oxidative phosphorylation are the three main stages of cellular respiration.

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Glycolysis Location

Glycolysis is the first stage of cellular respiration and occurs in the cytosol (cell fluid).

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Oxidative Phosphorylation

Oxidative phosphorylation is the final stage of cellular respiration, producing most ATP. It involves electron transport chain (ETC) and chemiosmosis.

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Substrate-level Phosphorylation

A metabolic pathway where a phosphate group is directly transferred from a substrate to ADP, forming ATP.

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Electron Transport Chain (ETC)

A series of protein complexes in the inner mitochondrial membrane where electrons are passed down, releasing energy to create a proton gradient.

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Citric Acid Cycle Location

The second stage of cellular respiration takes place in the mitochondrial matrix.

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Pyruvate

A 3-carbon molecule produced from glucose breakdown during glycolysis, serving as the input for the citric acid cycle.

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ATP (Adenosine Triphosphate)

The primary energy currency of the cell, used in various cellular processes. It stores 7.3 kcal/mol of energy.

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Glycolysis Net Gain

Glycolysis produces 2 ATP and 2 NADH molecules.

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Glycolysis Oxygen?

Glycolysis can occur with or without oxygen, but oxygen is required later in respiration for further reactions.

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Pyruvate to Acetyl CoA

Pyruvate is converted into Acetyl CoA in the mitochondria in 3 reactions, releasing CO2 and creating NADH.

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Krebs Cycle Function

The Krebs Cycle oxidizes organic molecules, producing ATP, NADH, and FADH2.

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Krebs Cycle Products

Krebs Cycle produces 3 NADH, 1 FADH2 and 1 ATP per acetyl CoA.

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Oxidative Phosphorylation

Oxidative phosphorylation uses electron transport chain to make ATP by chemiosmosis; NADH & FADH2 give e-

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Substrate-Level Phosphorylation

Direct transfer of phosphate groups to ADP to create ATP in Glycolysis and Krebs Cycle.

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Energy Yield per Glucose

Glycolysis and Krebs cycle produce only 4 ATP per glucose molecule; most energy comes from electron transport.

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Electron Transport Chain (ETC)

A series of protein complexes embedded in the inner mitochondrial membrane that transfer electrons from NADH and FADH2 to oxygen, releasing energy used to create a proton gradient.

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Cristae (Mitochondria)

Folds in the inner mitochondrial membrane that increase surface area, allowing more ETC protein complexes to be present, thus enhancing ATP production.

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Ubiquinone (Q)

A small, hydrophobic molecule in the ETC that shuttles electrons between protein complexes, acting as an electron carrier.

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Cytochromes

Proteins in the ETC with heme prosthetic groups, that contain iron and facilitate the transfer of electrons along the chain.

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Chemiosmosis

The process where the energy stored in the proton gradient across the inner mitochondrial membrane is used to synthesize ATP.

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ATP Synthase

An enzyme that uses the energy of the proton gradient to synthesize ATP from ADP and inorganic phosphate.

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Proton Gradient

A difference in proton (H+) concentration across a membrane, storing potential energy.

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Protein Complex 1

A protein complex in the ETC that takes electrons from NADH, passing them along the chain.

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Proton Motive Force

The force created by a concentration gradient of hydrogen ions (H+) across a membrane, used to generate ATP.

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ATP Synthase

An enzyme that uses the energy from the proton motive force to synthesize ATP from ADP and phosphate.

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Oxidative Phosphorylation ATP Yield

The process of creating 32-34 ATP molecules from NADH and FADH2 during the electron transport chain.

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NADH to ATP Ratio

Approximately 3 ATP molecules are produced for every NADH molecule oxidized.

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FADH2 to ATP Ratio

Approximately 2 ATP molecules are produced for every FADH2 molecule oxidized.

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Substrate-Level Phosphorylation

Direct transfer of phosphate group to ADP to form ATP during cellular respiration.

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Electron Transport Chain (ETC)

Series of protein complexes in the inner mitochondrial membrane where electrons are transferred to oxygen, creating a proton gradient for ATP synthesis.

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Proton Motive Force & Prokaryotes

In prokaryotes, the proton motive force is used for tasks such as moving flagella or transporting molecules across the membrane.

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Fermentation Types

Different methods of regenerating NAD+ for glycolysis, bypassing the electron transport chain. These include alcoholic and lactic acid fermentations.

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Alcoholic Fermentation

Converts pyruvate to ethanol, releasing carbon dioxide in the process. It regenerates NAD+.

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Lactic Acid Fermentation

Reduces pyruvate to lactate, regenerating NAD+. Used by muscles in oxygen-low conditions.

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Fermentation vs. Aerobic Respiration

Both start similarly, but differ in how NADH is recycled. Aerobic uses oxygen as the final electron acceptor. Fermentation uses an organic molecule.

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Obligate Anaerobe

Organism that survives only without oxygen, relying on fermentation for energy.

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Facultative Anaerobe

Organism that can use either fermentation or aerobic respiration, depending on the presence of oxygen.

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Glycolysis and Early Earth

Glycolysis is crucial for energy production and is present in all living organisms. It doesn't need oxygen.

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Catabolism of Diverse Molecules

Carbohydrates, proteins, and fats can all be broken down to provide energy for cellular processes by entering glycolysis or the citric acid cycle.

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Study Notes

Cellular Respiration

  • Living cells require energy from external sources, converting it into usable forms like ATP. This energy cycle involves recycling chemical elements, such as in photosynthesis.
  • Catabolic pathways break down complex organic molecules, releasing energy stored in their chemical bonds.
  • Organic molecules possess potential energy due to electron arrangements, fueling exergonic reactions.
  • Fermentation is an inefficient process that degrades sugars without oxygen. Aerobic respiration is more efficient, using oxygen as a reactant.
  • Aerobic respiration combines organic fuels (like glucose) with oxygen to produce ATP, releasing CO2 and water as byproducts. This is an exergonic reaction (with a large, negative ΔG). Though spontaneous, it does not drive other processes directly.
  • Redox reactions transfer electrons between molecules. Oxidation is the loss of electrons, and reduction is their gain. The molecule losing electrons acts as the reducing agent; the one gaining them as the oxidizing agent.

Redox Reactions

  • Redox reactions are crucial for electron transfer in cells.
  • During oxidation, molecules lose electrons, while during reduction, they gain electrons.
  • Oxidizing and reducing agents are involved in these reactions.
  • Electrons moving towards a more electronegative element lose potential energy.

Cellular Respiration Stages

  • Cellular respiration involves three main stages: glycolysis, the citric acid cycle, and oxidative phosphorylation.
  • Glycolysis occurs in the cytosol, breaking down glucose into pyruvate. It produces a net gain of 2 ATP and 2 NADH.
  • Pyruvate is then converted to acetyl CoA before entering the citric acid cycle in the mitochondrial matrix.
  • The citric acid cycle further oxidizes acetyl CoA, generating more NADH, FADH2, and ATP.
  • Oxidative phosphorylation, consisting of the electron transport chain and chemiosmosis, generates the majority of ATP. It uses electron carriers (NADH, and FADH2) to pump protons out of the matrix and develop a proton-motive force. The H+ flow through ATP synthase creates ATP.
  • The process of oxidative phosphorylation (ETC + Chemiosmosis) creates most of the ATP.

Fermentation

  • Fermentation is a metabolic pathway that regenerates NAD+ from NADH, allowing glycolysis to continue in the absence of oxygen.
  • Lactic acid fermentation converts pyruvate to lactate.
  • Alcoholic fermentation converts pyruvate to ethanol and CO2.

Energy Yield

  • Cellular respiration yields approximately 32-38 ATP molecules per glucose molecule.
  • Oxidative phosphorylation is the most efficient step.

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Description

This quiz covers the fundamental concepts of cellular respiration, including energy conversion processes, catabolic pathways, and the differences between aerobic respiration and fermentation. It explores the roles of organic molecules, redox reactions, and the overall efficiency of energy production in living cells.

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