Cellular Respiration Overview and Pathways
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What is the net reaction of glycolysis?

  • 2 CH3(C=O)COO- + 2 NADH + 4 ADP -> C6H12O6 + 2 CO2 + 2 ATP
  • C6H12O6 + 4 NAD+ + 2 ADP2- + 2 Pi -> 2 CH3(C=O)COO- + 4 H+ + 4 NADH + 2 ATP + 2 H2O
  • C6H12O6 + 2 NAD+ + 4 ADP2- + 2 Pi -> 2 CH3(C=O)COO- + 2 H+ + 4 NADH + 2 ATP + 2 H2O
  • C6H12O6 + 2 NAD+ + 2 ADP2- + 2 Pi -> 2 CH3(C=O)COO- + 2 H+ + 2 NADH + 4 ATP + 2 H2O (correct)

    • What is believed to be the rate-limiting step in glycolysis?

  • Conversion of phosphoenolpyruvate to pyruvate
  • Phosphorylation of glucose
  • Formation of fructose-1,6-bisphosphate
  • Catalysis by phosphofructokinase (correct)

    • What is produced alongside acetyl CoA during the breakdown of pyruvate?

  • FADH2 and glucose
  • CO2 and a hydrogen ion (correct)
  • NADH and water
  • ATP and a proton

    • In the citric acid cycle, how many molecules of CO2 are evolved per acetyl group oxidized?

    <p>Two CO2 molecules</p> Signup and view all the answers

    What is the total ATP yield from glycolysis and the citric acid cycle combined?

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

    What is the primary aim of cellular respiration?

    <p>To make ATP</p> Signup and view all the answers

    How much free energy is released when glucose is oxidized?

    <p>-685 kcal/mol</p> Signup and view all the answers

    Which pathway occurs in the cytosol of eukaryotic cells?

    <p>Glycolysis</p> Signup and view all the answers

    What is the net yield of ATP produced from glycolysis?

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

    During which phase of glycolysis is the fructose-1,6 bisphosphate created?

    <p>Energy investment</p> Signup and view all the answers

    What is produced as a result of the breakdown of each pyruvate molecule?

    <p>One acetyl group and one CO2</p> Signup and view all the answers

    Which molecule undergoes substrate-level phosphorylation during glycolysis?

    <p>ADP</p> Signup and view all the answers

    What type of respiration can glycolysis perform?

    <p>Both anaerobic and aerobic respiration</p> Signup and view all the answers

    What primarily regulates the rate of the citric acid cycle?

    <p>Availability of substrates and feedback inhibition</p> Signup and view all the answers

    Which enzymes are considered rate-limiting in the citric acid cycle?

    <p>Citrate synthase, Isocitrate dehydrogenase, a-ketoglutarate dehydrogenase</p> Signup and view all the answers

    What is produced during oxidative phosphorylation?

    <p>NADH, ATP, and water</p> Signup and view all the answers

    What process is utilized to synthesize ATP during chemiosmosis?

    <p>Proton gradient usage</p> Signup and view all the answers

    What is the net gain of ATP from glycolysis, the citric acid cycle, and oxidative phosphorylation combined?

    <p>34-38 ATP</p> Signup and view all the answers

    Where does the electron transport chain (ETC) primarily take place in eukaryotic cells?

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

    What is the role of oxygen in the electron transport chain?

    <p>It acts as the final electron acceptor</p> Signup and view all the answers

    During the movement of electrons through the ETC, what is directly generated?

    <p>Electrochemical gradients</p> Signup and view all the answers

    What is one characteristic of anaerobic respiration compared to aerobic respiration?

    <p>It utilizes substances other than O2 as final electron acceptors.</p> Signup and view all the answers

    How do muscle cells respond to the need for NAD+ under anaerobic conditions?

    <p>By reducing pyruvate into lactate.</p> Signup and view all the answers

    What is the main difference between anaerobic respiration and fermentation?

    <p>Fermentation does not involve net oxidation of organic molecules.</p> Signup and view all the answers

    What outcome does fermentation produce in yeast under anaerobic conditions?

    <p>Ethanol</p> Signup and view all the answers

    In anaerobic glycolysis, how much ATP is produced compared to aerobic respiration?

    <p>About 2 ATP.</p> Signup and view all the answers

    What is the main function of the proton gradient established by the electron transport chain?

    <p>To synthesize ATP</p> Signup and view all the answers

    Which of the following best describes the role of ATP synthase?

    <p>It synthesizes ATP from ADP and Pi</p> Signup and view all the answers

    How does the availability of substrates like NADH and O2 influence oxidative phosphorylation?

    <p>High ATP levels inhibit oxidative phosphorylation</p> Signup and view all the answers

    What is the maximum yield of ATP molecules produced from one glucose molecule during oxidative phosphorylation?

    <p>30 to 34 ATP molecules</p> Signup and view all the answers

    What happens to ATP synthesis when ADP levels are high?

    <p>ATP synthesis is stimulated</p> Signup and view all the answers

    What is the consequence of a relatively impermeable lipid bilayer of the inner mitochondrial membrane?

    <p>Protons must pass through ATP synthase to enter the matrix</p> Signup and view all the answers

    Which factor does NOT influence the regulation of oxidative phosphorylation?

    <p>Temperature of the cell</p> Signup and view all the answers

    Which of the following substances is primarily used in the oxidation process to create the H+ electrochemical gradient?

    <p>NADH</p> Signup and view all the answers

    Study Notes

    Cellular Respiration Overview

    • Living cells obtain energy from organic molecules and release waste products
    • The primary aim is to make ATP
    • Aerobic respiration requires oxygen: O2 consumed and CO2 released
    • When glucose is broken down via oxidation, a tremendous amount of free energy is released (-685kcal/mol)
    • Glucose metabolism equation: C6H12O6 + 6O2 → 6CO2 + 6H2O
    • Some energy from glucose breakdown is lost as heat, but much is used to make 3 energy intermediates: ATP, NADH, FADH2

    Four Metabolic Pathways of Cellular Respiration

    • Glycolysis: Glucose is broken down to two pyruvate molecules, producing 2 ATP and 2 NADH molecules.
    • Breakdown of Pyruvate: Occurs in the mitochondrial matrix in eukaryotes. Each pyruvate is broken down to an acetyl group and CO2, generating one NADH per pyruvate.
    • Citric Acid Cycle: Occurs in the mitochondrial matrix. Acetyl groups are incorporated into an organic molecule, later oxidized to liberate two CO2 molecules. Total yield: 4 CO2, 2 ATP, 6 NADH, 2 FADH2
    • Oxidative phosphorylation: Occurs in the cristae in eukaryotes. NADH and FADH2 contain high-energy electrons, which are harnessed to produce an H+ electrochemical gradient, ultimately generating 30-34 ATP molecules.

    Glycolysis

    • Can occur with or without oxygen.
    • Nearly identical in all living species.
    • Ten enzyme steps in three phases:
      • Energy investment: Steps 1 to 3, 2 ATP hydrolyzed (ATP to ADP) to create fructose-1,6 bisphosphate
      • Cleavage: Steps 4 to 5, 6 carbon molecules broken into two 3 carbon molecules of glyceraldehyde-3-phosphate
      • Energy liberation: Steps 6 to 10, Two glyceraldehyde-3-phosphate molecules are broken down into two pyruvate molecules, yielding 2 NADH and 4 ATP (net yield = 2 ATP).
    • The rate of glycolysis is regulated by the availability of substrates and feedback inhibition.
    • Phosphofructokinase catalyzes the third step (the rate-limiting step).
    • High ATP concentrations bind to phosphofructokinase, inhibiting the rate.

    Breakdown of Pyruvate

    • In eukaryotes, pyruvate is transported into the mitochondrial matrix.
    • Broken down by pyruvate dehydrogenase.
    • CO2 is removed from each pyruvate.
    • The remaining acetyl group is attached to CoA (coenzyme A) to make acetyl CoA.

    Citric Acid Cycle

    • A metabolic cycle where some molecules enter while others leave, and the series of organic molecules is regenerated in each cycle.
    • Acetyl is removed from Acetyl CoA and attached to oxaloacetate to form citrate (aka citric acid).
    • Each cycle releases: 2 CO2, 1 ATP, 3 NADH, and 1 FADH2.
    • Oxaloacetate is regenerated to start the cycle again.
    • The rate of the citric acid cycle is regulated by the availability of substrates and feedback inhibition.
    • Three steps are considered rate-limiting, catalyzed by: Citrate synthase, Isocitrate dehydrogenase, and a-ketoglutarate dehydrogenase.

    Oxidative Phosphorylation

    • First three stages of glucose metabolism yield 6 CO2, 4 ATP, 10 NADH, 2 FADH2.
    • High-energy electrons are removed from NADH and FADH2 to make ATP.
    • Requires oxygen, and the oxidative process involves an electron transport chain (ETC).
    • Phosphorylation occurs by ATP synthase.
    • The ETC consists of protein complexes and small organic molecules embedded in the inner mitochondrial membrane.
    • Electrons transfer in a linear manner in a series of redox reactions.
    • Electrons from NADH or FADH2 are transferred to components of the ETC, each having an increasingly higher electronegativity.
    • Oxygen is the final acceptor of electrons in the ETC, which is also called the respiratory chain.
    • Energy released during electron movement is used to pump protons (H+) across the mitochondrial membrane into the intermembrane space, forming a proton gradient.
    • The proton gradient provides the energy for synthesizing ATP.
    • ATP synthase is a rotary machine that allows protons to pass through the membrane, using the free energy difference to convert ADP to ATP.

    Connections Among Carbohydrate, Protein, and Fat Metabolism

    • Many molecules are used for energy: carbohydrates, proteins, and fats.
    • They enter glycolysis or the citric acid cycle at different points.
    • Utilizing the same pathways for breakdown increases efficiency.

    Anaerobic Respiration and Fermentation

    • Anaerobic Respiration: Occurs in the absence of oxygen. Uses a substance other than O2 as the final electron acceptor in the electron transport chain.
    • Fermentation: Produces ATP only via substrate-level phosphorylation.
    • Fermentation is the breakdown of organic molecules without net oxidation.
    • Many organisms can only use O2 as the final electron acceptor, so they need alternative ways to produce ATP under anaerobic conditions.

    Lactic Acid Fermentation

    • Muscle cells convert pyruvate into lactate to solve NADH buildup under anaerobic conditions.
    • Lactic acid fermentation produces much less ATP than oxidative phosphorylation.

    Alcohol Fermentation

    • Yeast use fermentation to produce ethanol, also solving NADH buildup.
    • Fermentation produces far less ATP than oxidative phosphorylation.

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    Cellular Respiration & Fermentation (Lesson 2)

    Description

    This quiz covers the essential concepts of cellular respiration, including the process of aerobic respiration and the various metabolic pathways involved in breaking down glucose. Explore glycolysis, the breakdown of pyruvate, and the citric acid cycle in detail to understand how cells generate energy. Test your knowledge on ATP production and the equations involved in these processes.

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