Electron Transport Chain and Oxidative Phosphorylation
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Questions and Answers

What is the primary function of Complex 1 in the Electron Transport Chain?

  • Catalyze the reaction to form water from oxygen
  • Transfer electrons from FADH2 to UQ
  • Pump protons into the mitochondrial matrix
  • Transfer electrons from NADH to UQ (correct)

    • Which statement about Complex 2 is correct?

  • It transfers electrons from NADH to cytochrome c.
  • It pumps protons into the intermembrane space during electron transfer.
  • It catalyzes the transfer of electrons from FADH2 to UQ. (correct)
  • It is responsible for reducing oxygen to water.

    • What is the outcome of the electron transfer chain at Complex 4?

  • Electrons are transferred to FADH2.
  • Electrons are stored in reduced UQ.
  • Oxygen is reduced to form water. (correct)
  • UQH2 transfers electrons to NADH.

    • During the electron transfer in Complex 1, how many protons are pumped into the intermembrane space?

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

    Which of the following correctly describes the role of UQ in the electron transport chain?

    <p>It serves as a lipid-soluble electron carrier between complexes.</p> Signup and view all the answers

    What role do reactive oxygen species (ROS) play in macrophages and neutrophils?

    <p>They are used to destroy pathogens.</p> Signup and view all the answers

    Which enzyme is responsible for converting superoxide radicals into hydrogen peroxide?

    <p>Superoxide dismutase</p> Signup and view all the answers

    What is formed as a result of the reaction catalyzed by catalase?

    <p>Water and oxygen</p> Signup and view all the answers

    Which component of the glutathione-centered system is oxidized during the reduction of hydrogen peroxide?

    <p>Glutathione (GSH)</p> Signup and view all the answers

    What is the function of NADPH-oxidase in phagocytosis?

    <p>It generates reactive oxygen species.</p> Signup and view all the answers

    What is the primary function of sphingomyelin in the nervous system?

    <p>Insulates nerve cells and facilitates rapid transmission of impulses</p> Signup and view all the answers

    Which statement correctly describes glycolipids?

    <p>They act as receptors for viruses and facilitate cell-cell interactions.</p> Signup and view all the answers

    What characterizes gangliosides as a class of sphingolipids?

    <p>They contain oligosaccharide groups with sialic acid residues.</p> Signup and view all the answers

    Which enzyme is responsible for adding fatty acids to phosphoglycerides?

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

    What is Ceramide primarily composed of?

    <p>Sphingosine and a fatty acid</p> Signup and view all the answers

    What is the role of pancreatic lipase in lipid digestion?

    <p>It digests the ester bonds at C1 and C3 of dietary triacylglycerols.</p> Signup and view all the answers

    What is formed from the digestion of dietary phospholipids by pancreatic phospholipase A2?

    <p>Lysophosphatidate and a free fatty acid</p> Signup and view all the answers

    Which components are absorbed freely into intestinal cells during lipid absorption?

    <p>Mixed micelles, lysophosphatides, and cholesterol</p> Signup and view all the answers

    What changes occur to the sulfhydryl (SH) group in proteins during redox reactions?

    <p>It can become sulfenic, sulfinic, or sulfonic acid.</p> Signup and view all the answers

    What are chylomicrons primarily composed of?

    <p>Lipids, cholesterol, and protein</p> Signup and view all the answers

    What happens to free fatty acids inside intestinal cells?

    <p>They are converted to Acyl-CoA for further synthesis.</p> Signup and view all the answers

    Which intracellular compartment is characterized by more oxidized redox conditions?

    <p>Endoplasmic Reticulum</p> Signup and view all the answers

    What is a key step in triglyceride synthesis within intestinal cells?

    <p>Reassembly of two Acyl-CoA with monoacylglycerol</p> Signup and view all the answers

    What does the reaction O2- + NO- → ONOO- describe?

    <p>Formation of peroxynitrite from superoxide and nitric oxide.</p> Signup and view all the answers

    What initiates the radical chain reaction in lipid peroxidation?

    <p>Extraction of a hydrogen atom from an unsaturated fatty acid.</p> Signup and view all the answers

    Which type of fatty acids are absorbed directly into the blood?

    <p>Short-chain (C1-C5) and medium-chain (C6-C12) fatty acids</p> Signup and view all the answers

    What is a consequence of lipid peroxidation involving radical cleavage?

    <p>Generation of α,β-unsaturated aldehydes.</p> Signup and view all the answers

    What determines the classification of lipoproteins?

    <p>Their density</p> Signup and view all the answers

    What is superoxide (O2-) in the context of reactive oxygen species?

    <p>A radical formed during electron transport chain malfunction.</p> Signup and view all the answers

    What describes the primary role of nitric oxide (NO-) in the body?

    <p>It serves as a signaling molecule that regulates blood pressure.</p> Signup and view all the answers

    During electron transport, which complexes are associated with the leakage of electrons leading to reactive oxygen species formation?

    <p>Complex I and III</p> Signup and view all the answers

    Study Notes

    Electron Transport Chain

    • Electron transport chain (ETC) consists of four protein complexes located in the inner mitochondrial membrane.
    • Complex I (NADH Dehydrogenase Complex): Transfers electrons from NADH to coenzyme Q (UQ) and pumps four protons (H+) from the matrix into the intermembrane space.
    • Complex II (Succinate Dehydrogenase Complex): Transfers electrons from FADH2 to UQ without pumping protons.
    • Complex III (Cytochrome bc1 Complex): Transfers electrons from reduced UQ (UQH2) to cytochrome c, one electron at a time.
    • Complex IV (Cytochrome C Oxidase): Catalyzes the transfer of four electrons to oxygen, producing water (H2O).

    Oxidative Phosphorylation and ROS Formation

    • Reactive oxygen species (ROS) are formed during the electron transport chain due to electron leaks.
    • These leaks occur when electrons exit the ETC while being transferred by Complex I or Complex III.
    • The leaked electrons react with oxygen, generating superoxide radical (O2-), which can further convert to Hydrogen Peroxide (H2O2) and Hydroxyl Radical (OH).

    Reactive Nitrogen Species (RNS)

    • Reactive nitrogen species (RNS) include:
      • Nitric Oxide (NO-) which has a signaling function.
      • Nitrogen dioxide (NO2).
      • Peroxynitrite (ONOO-), which damages proteins and nucleic acids.
    • O2- reacts with NO- to form ONOO-.

    Radical Chain Reaction

    • Lipid peroxidation reactions can be initiated with the abstraction of a hydrogen atom from an unsaturated fatty acid.
    • Lipid radical reacts with O2 forming a peroxyl radical, which further reacts with another fatty acid, leading to a chain reaction.
    • Transition metals like Fe2+ can initiate further radical formation.
    • Lipid peroxidation can result in the formation of α,β-unsaturated aldehyde, which involves a radical cleavage reaction.

    Respiratory Burst

    • ROS are also produced during respiratory burst within macrophages and neutrophils.
    • During phagocytosis, these cells produce large quantities of ROS to kill pathogens.
    • NADPH oxidase on phagolysosome membranes converts O2 to O2-.
    • O2- reacts with molecules to generate various free radicals that destroy bacteria.

    Antioxidants

    • Living organisms have developed defense mechanisms to protect against oxidative stress, called antioxidants.
    • Enzyme systems:
      • Superoxide dismutase (SOD): Catalyzes the conversion of superoxide radical into H2O2 and O2.
      • Catalase: Degrades H2O2 into H2O and O2.
      • Glutathione-centered system: Uses GSH to reduce H2O2 and organic peroxides.
      • Thioredoxin-centered system.
    • Molecule systems:
      • α-Tocopherol (Vitamin E)
      • β-carotene (Vitamin A)
      • Ascorbic acid (Vitamin C)

    Lipid Digestion

    • Dietary fat is mainly composed of triacylglycerols (TG), along with phospholipids and cholesterol.
    • Lipid digestion and absorption occurs in the small intestine.
    • Bile salts emulsify dietary fat in the intestine, forming micelles.
    • Pancreas secretes lipase and phospholipase A2 (PLA2).
    • PLA2 digests the ester bond at C2 of the dietary phospholipids, releasing one free fatty acid and lysophosphatidate.
    • Pancreatic lipase digests the ester bonds at C1 and C3 of the dietary triacylglycerols, releasing two free fatty acids and a monoacylglycerol.

    Lipid Absorption

    • Free fatty acids (FFAs), monoacylglycerols, lysophosphatides, and cholesterol form mixed micelles and are absorbed freely into the intestinal cells.
    • Inside the cells, FFA are activated to form acyl-CoA.
    • Acyl-CoA is reassembled with monoacylglycerol to synthesize triacylglycerol.
    • Acyl-CoA is reassembled with lysophosphatides to synthesize phospholipids.
    • Newly synthesized triacylglycerols, phospholipids, cholesterol, and ApoProtein-B48 are packaged into nascent chylomicrons.

    Chylomicrons/Lipoproteins

    • Chylomicrons, also called lipoproteins, are composed of lipids, cholesterol, cholesterol esters, and proteins.
    • They are classified based on their density.

    Fatty Acid Activation by Coenzyme-A

    • Fatty acids are activated by Coenzyme-A to form acyl-CoA.

    Triglyceride Synthesis

    • Triglycerides are synthesized by combining two acyl-CoA with a monoacylglycerol.

    Phospholipid Synthesis

    • Phospholipids are synthesized by reassembling FFA with lysophosphatides inside intestinal cells.

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    Unit 3 Study Guide (Vazhaikkurichi Rajendran) PDF

    Description

    Explore the intricacies of the Electron Transport Chain (ETC) and its role in oxidative phosphorylation. Learn about the four protein complexes involved, their functions and the formation of reactive oxygen species (ROS) during the process. This quiz will test your understanding of mitochondrial energy production.

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