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What is the primary function of Complex 1 in the Electron Transport Chain?
Which statement about Complex 2 is correct?
What is the outcome of the electron transfer chain at Complex 4?
During the electron transfer in Complex 1, how many protons are pumped into the intermembrane space?
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Which of the following correctly describes the role of UQ in the electron transport chain?
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What role do reactive oxygen species (ROS) play in macrophages and neutrophils?
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Which enzyme is responsible for converting superoxide radicals into hydrogen peroxide?
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What is formed as a result of the reaction catalyzed by catalase?
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Which component of the glutathione-centered system is oxidized during the reduction of hydrogen peroxide?
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What is the function of NADPH-oxidase in phagocytosis?
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What is the primary function of sphingomyelin in the nervous system?
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Which statement correctly describes glycolipids?
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What characterizes gangliosides as a class of sphingolipids?
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Which enzyme is responsible for adding fatty acids to phosphoglycerides?
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What is Ceramide primarily composed of?
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What is the role of pancreatic lipase in lipid digestion?
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What is formed from the digestion of dietary phospholipids by pancreatic phospholipase A2?
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Which components are absorbed freely into intestinal cells during lipid absorption?
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What changes occur to the sulfhydryl (SH) group in proteins during redox reactions?
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What are chylomicrons primarily composed of?
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What happens to free fatty acids inside intestinal cells?
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Which intracellular compartment is characterized by more oxidized redox conditions?
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What is a key step in triglyceride synthesis within intestinal cells?
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What does the reaction O2- + NO- → ONOO- describe?
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What initiates the radical chain reaction in lipid peroxidation?
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Which type of fatty acids are absorbed directly into the blood?
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What is a consequence of lipid peroxidation involving radical cleavage?
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What determines the classification of lipoproteins?
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What is superoxide (O2-) in the context of reactive oxygen species?
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What describes the primary role of nitric oxide (NO-) in the body?
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During electron transport, which complexes are associated with the leakage of electrons leading to reactive oxygen species formation?
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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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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.