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Questions and Answers
Synthesis of ______ also takes place in the liver.
Synthesis of ______ also takes place in the liver.
urea
The liver synthesizes bile acids and excretes bile into the ______.
The liver synthesizes bile acids and excretes bile into the ______.
intestinal tract
The liver plays a big ______ role, inactivating both endogenic and exogenic substances.
The liver plays a big ______ role, inactivating both endogenic and exogenic substances.
detoxification
The liver is a depot for iron, some other metals, and vitamins A, D, E, B12, and ______.
The liver is a depot for iron, some other metals, and vitamins A, D, E, B12, and ______.
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The liver releases glucose from glycogen stores to maintain blood ______ levels.
The liver releases glucose from glycogen stores to maintain blood ______ levels.
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Glycogenesis is activated in a well-fed, ______ state.
Glycogenesis is activated in a well-fed, ______ state.
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Glucose-6-phosphate can be converted to glycogen, pyruvate, or ______.
Glucose-6-phosphate can be converted to glycogen, pyruvate, or ______.
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Pyruvate is then converted to the ______ cycle.
Pyruvate is then converted to the ______ cycle.
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The liver synthesizes primary bile acids from ______.
The liver synthesizes primary bile acids from ______.
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Bile salts are formed when bile acids are ______.
Bile salts are formed when bile acids are ______.
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The ______ is where bile salts are stored.
The ______ is where bile salts are stored.
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The breakdown of bile salts by intestinal bacteria produces ______ bile acids.
The breakdown of bile salts by intestinal bacteria produces ______ bile acids.
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The process of reabsorbing bile acids from the intestine back to the liver is known as ______.
The process of reabsorbing bile acids from the intestine back to the liver is known as ______.
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The liver synthesizes 100% of ______, a key plasma protein.
The liver synthesizes 100% of ______, a key plasma protein.
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Xenobiotics are compounds that are ______ to the body.
Xenobiotics are compounds that are ______ to the body.
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Reactions of detoxification primarily take place in the ______.
Reactions of detoxification primarily take place in the ______.
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The liver receives blood from the ______ vein.
The liver receives blood from the ______ vein.
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The functional units of the liver are called ______.
The functional units of the liver are called ______.
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The liver produces ______ for excretion through the bile duct.
The liver produces ______ for excretion through the bile duct.
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The main function of the liver in detoxification is termed ______.
The main function of the liver in detoxification is termed ______.
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The ______ is responsible for supplying oxygen-rich blood to the liver.
The ______ is responsible for supplying oxygen-rich blood to the liver.
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The liver plays a critical role in ______ carbohydrates, lipids, and proteins.
The liver plays a critical role in ______ carbohydrates, lipids, and proteins.
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The liver synthesizes ______ proteins and lipoproteins necessary for various bodily functions.
The liver synthesizes ______ proteins and lipoproteins necessary for various bodily functions.
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Waste products from the liver are excreted into the ______ for elimination from the body.
Waste products from the liver are excreted into the ______ for elimination from the body.
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Phase 2 involves converting hydroxylated compounds to more polar metabolites by conjugation with __________.
Phase 2 involves converting hydroxylated compounds to more polar metabolites by conjugation with __________.
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Acetylsalicylic acid (aspirin) is hydrolyzed to __________.
Acetylsalicylic acid (aspirin) is hydrolyzed to __________.
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Norepinephrine is methylated to __________ in Phase 2.
Norepinephrine is methylated to __________ in Phase 2.
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The binding of a substrate to the heme group in cytochrome P450 leads to the transfer of an __________.
The binding of a substrate to the heme group in cytochrome P450 leads to the transfer of an __________.
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In cytochrome P450 reaction mechanism, the resting state begins with heme iron in the __________ form.
In cytochrome P450 reaction mechanism, the resting state begins with heme iron in the __________ form.
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The enzyme involved in the glucuronidation reaction is __________.
The enzyme involved in the glucuronidation reaction is __________.
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In Phase 1 reactions, an apolar substrate can undergo hydroxylation, epoxidation, and __________.
In Phase 1 reactions, an apolar substrate can undergo hydroxylation, epoxidation, and __________.
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During cytochrome P450's reaction steps, a hydroxyl ion is cleaved resulting in the formation of a reactive __________.
During cytochrome P450's reaction steps, a hydroxyl ion is cleaved resulting in the formation of a reactive __________.
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In phase 1, the major reaction involved is ______, catalyzed by enzymes known as monooxygenases.
In phase 1, the major reaction involved is ______, catalyzed by enzymes known as monooxygenases.
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The enzyme ______ is responsible for the hydrolysis reaction in phase 1.
The enzyme ______ is responsible for the hydrolysis reaction in phase 1.
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Epoxide hydrolase is involved in the ______ reaction.
Epoxide hydrolase is involved in the ______ reaction.
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Azo- and nitro-reduction occur largely in the ______ and microsomes.
Azo- and nitro-reduction occur largely in the ______ and microsomes.
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The enzyme ______ is responsible for carbonyl reduction.
The enzyme ______ is responsible for carbonyl reduction.
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Disulfide and sulfoxide reductions predominantly take place in the ______.
Disulfide and sulfoxide reductions predominantly take place in the ______.
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Alcohol dehydrogenase participates in the oxidation reaction and is found in the ______.
Alcohol dehydrogenase participates in the oxidation reaction and is found in the ______.
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Aldehyde dehydrogenase acts in the ______ and cytosol.
Aldehyde dehydrogenase acts in the ______ and cytosol.
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Xanthine oxidase is located in the ______ and is involved in purine metabolism.
Xanthine oxidase is located in the ______ and is involved in purine metabolism.
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Monoamine oxidase functions primarily in ______ and is important for neurotransmitter regulation.
Monoamine oxidase functions primarily in ______ and is important for neurotransmitter regulation.
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Cytochrome ______ enzymes are crucial for many phase 1 reactions.
Cytochrome ______ enzymes are crucial for many phase 1 reactions.
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In phase II reactions, glucuronide conjugation primarily occurs in ______.
In phase II reactions, glucuronide conjugation primarily occurs in ______.
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Sulfate conjugation is mainly carried out in the ______ and microsomes.
Sulfate conjugation is mainly carried out in the ______ and microsomes.
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Glutathione conjugation, a detoxification pathway, occurs in the ______.
Glutathione conjugation, a detoxification pathway, occurs in the ______.
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Phase 2 reactions convert hydroxylated compounds to various polar metabolites by conjugation with ______.
Phase 2 reactions convert hydroxylated compounds to various polar metabolites by conjugation with ______.
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In certain cases, phase 1 metabolic reactions convert xenobiotics to biologically active compounds known as ______.
In certain cases, phase 1 metabolic reactions convert xenobiotics to biologically active compounds known as ______.
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The sulfate donor in sulfation reactions is ______.
The sulfate donor in sulfation reactions is ______.
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Glutathione is commonly abbreviated to ______.
Glutathione is commonly abbreviated to ______.
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The SH group in glutathione indicates the ______ group of its cysteine.
The SH group in glutathione indicates the ______ group of its cysteine.
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The reactions of acetylation are catalyzed by ______ present in the cytosol.
The reactions of acetylation are catalyzed by ______ present in the cytosol.
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In glucuronidation, the glucuronyl donor is derived from ______.
In glucuronidation, the glucuronyl donor is derived from ______.
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Glutathione conjugation reactions are catalyzed by ______ S-transferases.
Glutathione conjugation reactions are catalyzed by ______ S-transferases.
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Study Notes
Biochemistry of Liver
- The liver is a crucial organ responsible for various metabolic processes, including carbohydrate, lipid, and protein metabolism.
- It plays a vital role in detoxification, breaking down harmful substances and converting them into less toxic forms.
Liver Structure
- The liver comprises lobules, which are functional units.
- Sinusoids: Specialized capillaries facilitating nutrient and waste exchange.
- Portal vein, Hepatic artery: Blood vessels delivering nutrients and oxygen.
- Bile duct, Bile canaliculi: Structures involved in bile secretion and transport.
- Central vein: Collecting vessel for blood exiting the lobule.
Liver Functions
- Metabolism: Biosynthesis (creation of substances), storage (holding), conversion, and degradation (breakdown) of nutrients. Specific roles involving carbohydrates, lipids, and proteins are further detailed below.
- Uptake: Absorption of substances from the gastrointestinal tract, pancreas, and spleen.
- Excretion: Removal of waste and bile through the bile duct.
- Detoxification: Inactivation of harmful substances (drugs, toxins).
- Biotransformation: Conversion of substances into more easily excretable forms.
Liver Metabolism: Breakdown
- Carbohydrate Metabolism: Key functions include glucose metabolism (storage as glycogen and release as glucose), galactose, fructose, mannose, pentose, lactate, glycerol, and glycogen metabolism.
- Lipid Metabolism: Lipogenesis (lipid production), fatty acid synthesis, ketone body formation, cholesterol synthesis.
- Amino Acid Metabolism: Conversion of amino acids to other substances and urea formation. Also involved in protein synthesis.
- Biotransformation: Involves steroid hormone, bile pigments, and drug metabolism.
Liver's Functions (Summary)
- The liver is involved in carbohydrate metabolism.
- It produces and secretes bile that aids in lipid digestion.
- The liver plays a critical role in detoxification.
- It stores iron, certain vitamins, and other minerals.
Role of the Liver in Carbohydrate Metabolism
- Glucose from the intestine enters the liver and undergoes phosphorylation.
- Key enzymes like hexokinase and glucokinase catalyze this process, forming glucose-6-phosphate.
- Glucose-6-phosphate is a crucial component in carbohydrate metabolism.
- Liver metabolism of glucose depends on body needs.
Fate of Glucose Molecule in the Cell
- Glycogenesis (glycogen synthesis): Occurs when glucose levels are high.
- Glycogenolysis (glycogen degradation): Occurs when glucose levels are low.
- Gluconeogenesis: Creation of glucose from non-carbohydrate precursors.
- Pentose phosphate pathway: Plays a role in lipid synthesis and nucleic acid synthesis.
Role of the Liver in Lipid Metabolism
- Lipogenesis is the primary process of fatty acid and lipid synthesis in the liver.
- The liver synthesizes cholesterol, a significant portion (80%) occurring intracellularly.
- Cholesterol synthesis is regulated by a negative feedback mechanism.
- The liver produces ketone bodies upon fatty acid oxidation and transports them to other tissues like the heart, muscles, kidneys, and brain.
Bile Acids and Bile Salts
- Bile acids are synthesized from cholesterol.
- Primary bile acids are conjugated (combined with glycine or taurine) to form bile salts.
- Bile salts aid in lipid digestion.
- They are involved in enterohepatic circulation, where they are reabsorbed and reused by the liver.
Role of the Liver in Protein Metabolism
- The liver carries out protein synthesis, among other functions.
- It plays a crucial role in degrading proteins and carbohydrates.
- It also helps transform amino acids to other substances and removes nitrogenous waste as urea.
- The liver is responsible for synthesizing various proteins, including plasma proteins and clotting factors.
Liver in Detoxification
- The liver is a primary organ for detoxification reactions.
- Large molecules like bilirubin are broken down by the liver and excreted in the bile.
- Smaller molecules are processed by the liver and excreted via the kidneys.
Xenobiotic Biotransformation
- The liver carries out specific reactions to convert xenobiotics (foreign substances) into more excretable forms.
- Phase 1 reactions involve hydroxylation, reduction, and oxidation.
- Phase 2 reactions involve conjugation (with other molecules).
Cytochrome P450
- Abundant in hepatocytes' endoplasmic reticulum (microsomes)
- The protein catalyzes the monooxygenation of oxygen atoms to substrates.
- Involved in the biotransformation of drugs and other xenobiotics.
Glucuronidation
- A major phase 2 reaction.
- Involves UDP glucuronic acid in conjugating substances.
- The products of glucuronidation are widely excreted.
Sulfation
- Some substances are sulfated in phase 2.
- The liver uses a special sulfate donor called PAPS.
Conjugation with Glutathione
- Glutathione is a tripeptide.
- The liver conjugates certain xenobiotics with glutathione, making them more easily excretable.
Acetylation
- The liver carries out acetylation of certain substances.
- Acetylation involves acetyl-CoA and acetyltransferases.
Methylation
- A detoxification process, where methyl groups are added to certain substances.
- Methyltransferases utilize S-adenosylmethionine (SAM) as a methyl donor.
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Description
Test your knowledge on the various functions and synthesis processes of the liver. This quiz covers bile acids, glucose regulation, and the liver's role in detoxifying substances. Perfect for students of biology or health sciences.
