Biochemistry: Anabolic Pathways and Gluconeogenesis
127 Questions
4 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary role of NADPH in the body?

  • Biosynthetic reactions (correct)
  • Energy production through oxidative phosphorylation
  • Interconversion of sugar molecules
  • Oxygen transport in blood

    • Which metabolite acts as a competitive inhibitor of glucose-6-phosphate dehydrogenase?

  • 6-Phosphogluconolactone
  • NADH
  • Insulin
  • Glucose-6-P (correct)

    • In what physiological state does insulin increase the activity of the pentose phosphate pathway?

  • During exercise
  • Under stress
  • In a well-fed state (correct)
  • In a fasted state

    • Which of the following sugars can be interconverted in the non-oxidative reactions of the pentose phosphate pathway?

    <p>7-carbon sugars</p> Signup and view all the answers

    How do NADPH and NADH differ in terms of their usage in the body?

    <p>NADPH is primarily for biosynthesis, NADH for energy production</p> Signup and view all the answers

    What is a key requirement for anabolic pathways?

    <p>Production of energy</p> Signup and view all the answers

    Which molecule serves as a primary reducing power in anabolic reactions?

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

    What is the primary substrate for gluconeogenesis primarily derived from triglycerides?

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

    Which of the following tissues specifically requires glucose as its preferred energy source?

    <p>Red blood cells</p> Signup and view all the answers

    Which of the following statements best describes gluconeogenesis?

    <p>It requires special routes to bypass irreversible steps.</p> Signup and view all the answers

    Which of the following substances is a major precursor for gluconeogenesis?

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

    Which components play a crucial role in linking complex molecules in anabolic pathways?

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

    What is the consequence of glycogen depletion in certain tissues?

    <p>Need for glucose from alternative sources</p> Signup and view all the answers

    What is the primary effect of many anti-cancer drugs on DNA replication?

    <p>They prevent dTMP synthesis.</p> Signup and view all the answers

    Which condition can result from excessive breakdown of purine bases?

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

    What deficit results from a genetic deficiency in adenosine deaminase?

    <p>Severe immunodeficiency</p> Signup and view all the answers

    Which amino acid is considered essential?

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

    What process do aminotransferases primarily facilitate?

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

    Which of the following pathways involves generating non-essential amino acids from ketoacids?

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

    Which compound is produced when glutamate reacts with ATP and NH3?

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

    Which neurotransmitter is derived from amino acids?

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

    What source is primarily used for synthesizing asparagine?

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

    Which amino acid is synthesized largely from glucose metabolic intermediates?

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

    What is one of the primary biosynthetic uses of NADPH?

    <p>Lipid synthesis</p> Signup and view all the answers

    Which hormone is synthesized using NADPH?

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

    Which process is affected by feedback inhibition involving AMP?

    <p>Purine biosynthesis</p> Signup and view all the answers

    What is the role of PRPP in nucleotide metabolism?

    <p>Donates ribose-5-phosphate</p> Signup and view all the answers

    What is the common intermediate in the pyrimidine biosynthesis pathway?

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

    Which enzyme is inhibited by UTP in pyrimidine biosynthesis?

    <p>Carbamoyl phosphate synthetase II</p> Signup and view all the answers

    What is the cofactor required for thymidylate synthase activity?

    <p>Folic acid</p> Signup and view all the answers

    What is the initial substrate for purine biosynthesis in the pentose phosphate pathway?

    <p>Ribose-5-phosphate</p> Signup and view all the answers

    Which of the following is NOT a process where NADPH is utilized?

    <p>Oxidative phosphorylation</p> Signup and view all the answers

    Which atom sources are involved in pyrimidine ring synthesis?

    <p>Glutamine and CO2</p> Signup and view all the answers

    What is the role of pyruvate carboxylase in gluconeogenesis?

    <p>Converts pyruvate to oxaloacetate</p> Signup and view all the answers

    Which enzyme is responsible for converting fructose 1,6-bisphosphate to fructose-6-phosphate?

    <p>Fructose-1,6-bisphosphatase</p> Signup and view all the answers

    What is the primary product of the oxidative phase of the pentose phosphate pathway?

    <p>Ribulose-5-phosphate and NADPH</p> Signup and view all the answers

    In which organelles do gluconeogenic reactions primarily occur?

    <p>Mitochondrion and cytosol</p> Signup and view all the answers

    Which of the following inhibits fructose-1,6-bisphosphatase?

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

    What does glucose-6-phosphatase do in the gluconeogenic process?

    <p>Releases glucose from glucose-6-phosphate</p> Signup and view all the answers

    What is produced alongside CO2 during the oxidative phase of the pentose phosphate pathway?

    <p>NADPH and ribulose-5-phosphate</p> Signup and view all the answers

    Which two reactions are irreversible in the pentose phosphate pathway's oxidative phase?

    <p>Conversion of glucose-6-phosphate to 6-phosphogluconate</p> Signup and view all the answers

    What is essential for the gluconeogenic step of converting oxaloacetate to phosphoenolpyruvate?

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

    Which hormone increases the rate of gluconeogenesis by decreasing levels of fructose 2,6-bisphosphate?

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

    What is the primary function of gluconeogenesis in the body?

    <p>To convert non-carbohydrate precursors to glucose</p> Signup and view all the answers

    Which substrates can be utilized for gluconeogenesis?

    <p>Lactate, glycerol, and glucogenic amino acids</p> Signup and view all the answers

    Which process is specifically required to overcome the irreversible steps of glycolysis during gluconeogenesis?

    <p>Special bypass pathways</p> Signup and view all the answers

    Which high-energy molecule plays an essential role in providing reducing power for anabolic pathways?

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

    What is the significance of the pentose phosphate pathway in metabolism?

    <p>It produces NADPH and ribose-5-phosphate for biosynthesis</p> Signup and view all the answers

    In gluconeogenesis, which intermediate is derived from lactate?

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

    What primarily regulates the rate of reactions in the pentose phosphate pathway?

    <p>Supply of glucose-6-phosphate</p> Signup and view all the answers

    What is the role of ATP in anabolic pathways?

    <p>It supplies energy via high energy phosphate bonds</p> Signup and view all the answers

    How does NADPH function in relation to the glucose-6-phosphate dehydrogenase reaction?

    <p>It functions as a competitive inhibitor</p> Signup and view all the answers

    During fasting, what primarily happens to glycogen stores in tissues that require glucose?

    <p>They are depleted and need replenishment from glucose precursors</p> Signup and view all the answers

    What is the main difference between NADPH and NADH in terms of their metabolic roles?

    <p>NADPH primarily functions in biosynthetic reactions, while NADH is used for energy yielding reactions.</p> Signup and view all the answers

    Which molecule is specifically produced for DNA and RNA synthesis in the pentose phosphate pathway?

    <p>Ribose-5-phosphate</p> Signup and view all the answers

    What effect does insulin have on the pentose phosphate pathway?

    <p>It increases glucose-6-phosphate dehydrogenase activity.</p> Signup and view all the answers

    What condition arises from excessive purine breakdown?

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

    Which amino acid is classified as non-essential?

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

    What is one of the primary functions of adenosine deaminase?

    <p>To degrade AMP</p> Signup and view all the answers

    Which enzyme catalyzes the reaction that produces asparagine from aspartate?

    <p>Asparagine synthase</p> Signup and view all the answers

    What is the role of transaminases in amino acid metabolism?

    <p>To transfer amide groups</p> Signup and view all the answers

    Which drug class acts by inhibiting dTMP synthesis to halt cell division?

    <p>Chemotherapy agents</p> Signup and view all the answers

    Which metabolic intermediate is primarily used to synthesize alanine?

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

    Which of the following amines is NOT derived from amino acids?

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

    Which mechanism is primarily used to generate non-essential amino acids from ketoacids?

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

    What is the precursor for synthesizing glutamine?

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

    What role does pyruvate carboxylase play in gluconeogenesis?

    <p>Converts pyruvate to oxaloacetate</p> Signup and view all the answers

    Which tissue types are primarily responsible for performing gluconeogenesis?

    <p>Liver and kidney</p> Signup and view all the answers

    What is the consequence of the irreversible step catalyzed by phosphofructokinase in glycolysis?

    <p>This step allows the pathway to be effectively regulated</p> Signup and view all the answers

    Which enzyme catalyzes the conversion of oxaloacetate to phosphoenolpyruvate in gluconeogenesis?

    <p>PEP carboxykinase</p> Signup and view all the answers

    Which component is required for the conversion of glucose-6-phosphate to glucose in gluconeogenesis?

    <p>Glucose-6-phosphatase</p> Signup and view all the answers

    What does the oxidative phase of the pentose phosphate pathway mainly produce?

    <p>NADPH and ribulose-5-phosphate</p> Signup and view all the answers

    How is the enzyme fructose-1,6-bisphosphatase regulated?

    <p>Inhibited by fructose 2,6-bisphosphate</p> Signup and view all the answers

    What is the main purpose of the pentose phosphate pathway?

    <p>Produce NADPH for anabolic reactions</p> Signup and view all the answers

    Which of the following is a biosynthetic use of NADPH?

    <p>Sphingomyelin synthesis</p> Signup and view all the answers

    Which enzyme is activated by PRPP in purine biosynthesis?

    <p>PRPP amidotransferase</p> Signup and view all the answers

    What type of reactions primarily take place during the cyclical phase of the pentose phosphate pathway?

    <p>Reversible reactions</p> Signup and view all the answers

    What regulates the activity of ribonucleotide reductase?

    <p>AMP and GMP</p> Signup and view all the answers

    Which of the following enzymes is involved in the oxidative phase of the pentose phosphate pathway?

    <p>Glucose 6-phosphate dehydrogenase</p> Signup and view all the answers

    What is a common intermediate in nucleotide biosynthesis?

    <p>Orotidine 5'-monophosphate</p> Signup and view all the answers

    Which statement is true regarding the sources of atoms in purine ring structure synthesis?

    <p>From folic acid and ribose-5-phosphate</p> Signup and view all the answers

    Which molecule is produced during the oxidative phase of the pentose phosphate pathway?

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

    What is the role of CO2 in pyrimidine biosynthesis?

    <p>Incorporated into the pyrimidine ring</p> Signup and view all the answers

    Which enzyme is inhibited by UTP during pyrimidine biosynthesis?

    <p>Carbamoyl phosphate synthetase II</p> Signup and view all the answers

    In purine biosynthesis, which molecule serves as a precursor for ribonucleotide synthesis?

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

    What is the main role of NADPH in cellular metabolism?

    <p>Acting as a reducing agent for anabolic reactions</p> Signup and view all the answers

    Which compound is a significant substrate for the regulation of glucose-6-phosphate dehydrogenase activity?

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

    How does insulin influence the pentose phosphate pathway during the fed state?

    <p>By inducing glucose-6-phosphate levels</p> Signup and view all the answers

    What differentiates the metabolic roles of NADPH and NADH?

    <p>NADPH is primarily involved in biosynthetic reactions while NADH is used in energy yielding reactions</p> Signup and view all the answers

    What is a result of increased glucose-6-phosphate levels in the pentose phosphate pathway?

    <p>Enhanced activity of pentose phosphate pathway enzymes</p> Signup and view all the answers

    What role does glycerol play in gluconeogenesis?

    <p>It is transformed into dihydroxyacetone phosphate via glycerol kinase.</p> Signup and view all the answers

    Which of the following tissues predominantly relies on glucose as a primary energy source?

    <p>Red blood cells</p> Signup and view all the answers

    What is a significant limitation of gluconeogenesis in the context of irreversible steps in glycolysis?

    <p>Specific irreversible enzymes cannot be bypassed.</p> Signup and view all the answers

    Which of the following substrates is a major precursor for gluconeogenesis derived from amino acids?

    <p>Glucogenic amino acids</p> Signup and view all the answers

    In the context of energy sources for anabolism, how does NADPH differ from ATP?

    <p>NADPH provides reducing power, whereas ATP provides the energy needed for reactions.</p> Signup and view all the answers

    What mechanism allows the continuation of gluconeogenesis after glycogen reserves are depleted?

    <p>Use of lactate and glucogenic amino acids as precursors.</p> Signup and view all the answers

    What is the relationship between the pentose phosphate pathway and metabolism?

    <p>It produces NADPH and ribose-5-phosphate for biosynthetic reactions.</p> Signup and view all the answers

    Which of the following accurately describes the steps of anabolism?

    <p>Forms complex molecules and links them, requiring energy.</p> Signup and view all the answers

    Which of the following enzymes is responsible for converting pyruvate into oxaloacetate during gluconeogenesis?

    <p>Pyruvate carboxylase</p> Signup and view all the answers

    What is the primary energy requirement for the gluconeogenic step converting oxaloacetate to phosphoenolpyruvate?

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

    In which cellular location does glucose-6-phosphatase operate during gluconeogenesis?

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

    Which molecule inhibits fructose-1,6-bisphosphatase, thereby affecting gluconeogenesis?

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

    What type of reaction is catalyzed by glucose-6-phosphate dehydrogenase in the oxidative phase of the pentose phosphate pathway?

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

    Which of the following substrates is directly required by PEP carboxykinase during gluconeogenesis?

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

    Which pathway primarily produces NADPH in the body?

    <p>Pentose phosphate pathway</p> Signup and view all the answers

    What is the effect of glucagon on fructose-2,6-bisphosphate levels in the context of gluconeogenesis?

    <p>Decreases levels</p> Signup and view all the answers

    Which of the following reactions is not part of gluconeogenesis?

    <p>Phosphoenolpyruvate to pyruvate conversion</p> Signup and view all the answers

    What does the cyclical phase of the pentose phosphate pathway primarily produce?

    <p>5-carbon sugars</p> Signup and view all the answers

    Which of the following biosynthetic processes does NADPH NOT play a role in?

    <p>Glucose breakdown</p> Signup and view all the answers

    What is a common intermediate in pyrimidine biosynthesis?

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

    Which compound serves as an inhibitor for PRPP amidotransferase in purine biosynthesis?

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

    In pyrimidine biosynthesis, which enzyme requires ATP as an activator?

    <p>Carbamoyl phosphate synthetase</p> Signup and view all the answers

    What is the primary function of ribonucleotide reductase in nucleotide metabolism?

    <p>To reduce ribonucleotides to deoxyribonucleotides</p> Signup and view all the answers

    What is the primary consequence of inhibiting dTMP synthesis in anti-cancer treatments?

    <p>Inhibition of DNA replication</p> Signup and view all the answers

    Which of the following statements about purine ring structure is TRUE?

    <p>It requires a combination of ribose and ATP for activation.</p> Signup and view all the answers

    Which metabolite is involved in the feedback inhibition of pyrimidine biosynthesis?

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

    What leads to inflammation and severe pain in the joints as a result of excessive purine breakdown?

    <p>Uric acid crystallization</p> Signup and view all the answers

    Which non-essential amino acid can be synthesized from α-ketoglutarate?

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

    What role does folic acid play in nucleotide synthesis?

    <p>It provides carbon atoms for nucleotide ring structures.</p> Signup and view all the answers

    In nucleotide degradation, which of the following processes occurs first?

    <p>Conversion of nucleotides to nucleosides</p> Signup and view all the answers

    What is the primary role of glutamine synthetase in amino acid metabolism?

    <p>Transport of ammonia in a non-toxic form</p> Signup and view all the answers

    Which of the following amino acids is both essential and can be synthesized from dietary sources?

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

    Which enzyme facilitates the transamination process for generating non-essential amino acids?

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

    Which compound is an essential amino acid derived from glucose?

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

    What is the purpose of feedback inhibition in metabolic pathways?

    <p>To regulate pathway flux</p> Signup and view all the answers

    Which neurotransmitter is produced as a derivative of amino acids?

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

    In the context of purine biosynthesis, what is the significance of common intermediates like IMP?

    <p>They serve as key regulatory points in nucleotide synthesis.</p> Signup and view all the answers

    Study Notes

    Anabolic Pathways

    • Anabolic pathways build complex molecules from simpler ones.
    • These processes require energy and use electrons in reduction reactions.
    • ATP provides high energy phosphate bonds.
    • NADH provides reducing power and electrons.
    • NADPH provides reducing power and electrons.

    Gluconeogenesis

    • Some tissues require glucose as their preferred energy source: Red blood cells, Brain, testes, lens of the eye.
    • Glycogen stores last for only 10-18 hours. Afterward, glucose must be made from other precursors.
    • Main precursors of gluconeogenesis are: Lactate, Glycerol, Glucogenic amino acids.
    • Several glycolytic steps are irreversible, requiring special routes for gluconeogenesis.

    Gluconeogenesis: Substrates

    • Glycerol: Derived from triglyceride backbones.
      • Converted to dihydroxyacetone phosphate, a glycolytic intermediate.
    • Lactate: Derived from anaerobic glycolysis.
      • Converted to pyruvate by lactate dehydrogenase.
    • Amino Acids:
      • Converted to TCA intermediates and oxaloacetate through TCA cycle reactions.
      • Also converted to glycolytic intermediates.

    Gluconeogenesis: Specific Steps

    • Carboxylation of Pyruvate:
      • Glycolytic step: Pyruvate kinase converts phosphoenolpyruvate (PEP) to pyruvate.
      • Gluconeogenic step: Pyruvate carboxylase converts pyruvate to oxaloacetate. Occurs in the mitochondria, requiring ATP.
      • PEP carboxykinase converts oxaloacetate to PEP. Occurs in the mitochondria and cytosol, requiring GTP.
    • Dephosphorylation of Fructose-1,6-bisphosphate:
      • Glycolytic step: Phosphofructokinase converts fructose-6-phosphate to fructose-1,6-bisphosphate.
      • Gluconeogenic step: Fructose 1,6 bisphosphatase reverses this step.
      • Control: Inhibited by AMP and fructose 2,6-bisphosphate. Glucagon decreases F-2,6-BP levels, increasing gluconeogenesis.
    • Dephosphorylation of Glucose-6-phosphate:
      • Glycolytic step: Hexokinase converts glucose to glucose-6-phosphate.
      • Gluconeogenic step: Glucose-6-phosphatase releases phosphate, occurring in the Endoplasmic Reticulum.
      • Requires glucose-6-phosphate translocase for transport into the ER.
      • Only occurs in the liver and kidney, which are the only gluconeogenic tissues.

    Pentose Phosphate Pathway

    • Generates NADPH and 5-carbon sugars for biosynthesis.
    • Occurring in the cytoplasm, it generates significant portion of the body's NADPH.
    • Two phases:
      • Oxidative phase: NADPH is produced.
      • Cyclical phase: 5-carbon sugars are made.

    Regulation of the Pentose Phosphate Pathway

    • Regulated at the Glucose-6-phosphate dehydrogenase step.
    • NADPH, the product, acts as a competitive inhibitor to regulate the pathway.
    • Insulin increases G6PD gene expression, boosting pathway activity during well-fed periods.

    NADPH vs NADH

    • NADPH: Used mainly in biosynthetic reactions.
    • NADH: Used mainly in energy yielding reactions (oxidative phosphorylation).
    • They are not metabolically interchangeable.

    Uses of NADPH

    • Biosynthesis:
      • Lipid synthesis
      • Cholesterol synthesis
      • Steroid hormone synthesis
      • Sphingomyelin synthesis
      • Fatty acid synthesis
      • Certain phospholipids
    • Protective:
      • Combats oxidative stress.
      • Regenerates reduced glutathione (GSH).

    Nucleotide Biosynthesis and Degradation

    • Purine Biosynthesis (A, G):
      • Inosine 5’-monophosphate (IMP) is the common intermediate.
      • Regulated by feedback inhibition and precursor activation.
    • Pyrimidine Biosynthesis (C, T, U):
      • Uridine monophosphate (UMP) is the common intermediate.
      • Regulated by feedback inhibition and precursor activation.
    • Nucleotide Degradation:
      • Pyrimidines: Degraded to simple carbon skeletons.
      • Purines: Either reused (salvaged) or degraded to uric acid, which is excreted.

    Clinical Aspects

    • Many anti-cancer drugs inhibit nucleotide synthesis. This prevents cell division and DNA replication.
    • Excessive purine breakdown leads to Gout, caused by uric acid crystal formation.
    • Adenosine deaminase deficiency leads to severe immunodeficiency.

    Biosynthesis of Amino Acids

    • Essential amino acids: Cannot be synthesized by the body.
    • Non-essential amino acids: Synthesized de novo, including alanine, aspartate, cysteine, glutamate, glutamine, glycine, proline, serine, tyrosine.
    • Transamination: Amide groups are moved between carbon backbones.
    • Amidation: Addition of an amide group, mediated by glutamine synthetase and asparagine synthetase.

    Synthesis of Non-Essential Amino Acids

    • Alanine from pyruvate.
    • Aspartate from oxaloacetate.
    • Glutamate from α-ketoglutarate.
    • Asparagine from aspartate.
    • Glutamine from glutamate.
    • Proline from glutamate.
    • Serine from 3-phosphoglycerate.
    • Glycine from serine.

    Biosynthesis of Physiologically Active Amines

    • GABA, histamine, serotonin, epinephrine, norepinephrine, and dopamine are amino acid derivatives.

    Anabolic Pathways

    • Anabolic pathways require energy and electron donors for reduction reactions.

    Gluconeogenesis

    • Gluconeogenesis is the process of synthesizing glucose from non-carbohydrate precursors.
    • It is essential for maintaining blood glucose levels during fasting or starvation.
    • Some tissues, such as red blood cells, the brain, testes, and the lens of the eye, rely primarily on glucose for energy.
    • Gluconeogenesis mainly utilizes lactate, glycerol, and glucogenic amino acids.
    • Glycolysis is irreversible in some steps, so gluconeogenesis utilizes unique routes to bypass these steps.

    Gluconeogenesis Substrates

    • Glycerol: derived from triglyceride backbones, converted to dihydroxyacetone phosphate, then to glyceraldehyde-3-phosphate (a glycolytic intermediate).
    • Lactate: generated during anaerobic glycolysis, converted to pyruvate by lactate dehydrogenase.
    • Amino Acids: converted to TCA intermediates, then to oxaloacetate via TCA cycle reactions, or directly to glycolytic intermediates.

    Gluconeogenesis Reactions

    • Pyruvate Carboxylase: converts pyruvate to oxaloacetate, requiring ATP and occurring in mitochondria.
    • PEP Carboxykinase: converts oxaloacetate to phosphoenolpyruvate, requiring GTP and active in both mitochondria and cytosol.
    • Fructose 1,6-bisphosphatase: reverses the irreversible glycolytic step catalyzed by phosphofructokinase.
    • Gluconeogenic Pathway: involves the dephosphorylation of glucose-6-phosphate by glucose-6-phosphatase, which is located in the endoplasmic reticulum.
    • Only Liver and Kidney: are gluconeogenic tissues as they are the only tissues that can release glucose to the bloodstream.

    Pentose Phosphate Pathway (PPP)

    • Generates NADPH and 5-carbon sugars for biosynthetic processes.
    • More anabolic than catabolic, occurring in the cytoplasm.
    • Produces a significant proportion of the body's NADPH.
    • Divided into two phases: an oxidative phase where NADPH is produced and a cyclical phase where 5-carbon sugars are synthesized.

    NADPH vs NADH

    • NADPH: used primarily in biosynthetic reactions.
    • NADH: used predominantly in energy-yielding reactions (oxidative phosphorylation).
    • Not Interchangeable: NADPH and NADH are not metabolically interchangeable due to the presence or absence of a phosphate group.

    Uses of NADPH

    • Biosynthetic Reactions: lipid synthesis, including cholesterol, steroid hormones, sphingomyelin, fatty acids, and specific phospholipids.
    • Protective Role: combats oxidative stress and regenerates reduced glutathione (GSH)

    Nucleotide Biosynthesis and Degradation

    Purine Biosynthesis

    • Source of Atoms: from the pentose phosphate pathway.
    • Activation: via PRPP synthetase, activated by inorganic phosphate (Pi) and inhibited by purine nucleotides (AMP, GMP).
    • PRPP Amidotransferase: activated by PRPP and inhibited by AMP, GMP, and IMP.
    • Ribonucleotide Reductase: reduces ribonucleotides to deoxyribonucleotides.
    • Inosine 5'-monophosphate (IMP): common intermediate in the synthesis of adenine and guanine nucleotides.

    Pyrimidine Biosynthesis

    • Source of Atoms: from glutamine and carbon dioxide.
    • Activation: by ATP and PRPP.
    • Carbamoyl Phosphate Synthetase II: inhibited by UTP.
    • Orotidine 5'-monophosphate (OMP): common intermediate in the synthesis of cytosine, thymine, and uracil nucleotides.

    Nucleotide Degradation

    • Pyrimidines: broken down to simple carbon skeletons (β-alanine or β-aminoisobutyrate) and further degraded.
    • Purines: either reused (salvaged) or degraded: purine bases yield xanthine, which is then converted to uric acid for excretion.

    Clinical Aspects

    • Anti-Cancer Drugs: target nucleotide biosynthesis, particularly the synthesis of dTMP to disrupt DNA replication and cell growth.
    • Gout: excessive degradation of purines leading to uric acid accumulation, causing painful inflammation in joints and kidneys.
    • Adenosine Deaminase Deficiency: genetic deficiency leads to severe immunodeficiency due to impaired AMP degradation.

    Biosynthesis of Amino Acids

    • Essential Amino Acids: must be obtained from the diet as the body cannot synthesize them.
    • Non-Essential Amino Acids: can be synthesized by the body from other metabolic intermediates.

    Transamination

    • Aminotransferases: enzymes that catalyze the transfer of amino groups between different carbon backbones.
    • Reversible reactions: allow the synthesis of non-essential amino acids from ketoacids.

    Amidation

    • Glutamine Synthetase: converts glutamate to glutamine, utilizing ATP and ammonia. Important in ammonia detoxification and transport.
    • Asparagine Synthetase: converts aspartate to asparagine, requiring ATP and glutamine.

    Synthesis of Non-Essential Amino Acids

    • Alanine: synthesized from pyruvate via transamination.
    • Aspartate: synthesized from oxaloacetate via transamination.
    • Glutamate: synthesized from α-ketoglutarate via transamination or glutamate dehydrogenase.
    • Asparagine: synthesized from aspartate by asparagine synthetase.
    • Glutamine: synthesized from glutamate by glutamine synthetase.
    • Proline: synthesized from glutamate via cyclization.
    • Serine: synthesized from 3-phosphoglycerate through a series of reactions.
    • Glycine: synthesized from serine by serine hydroxymethyltransferase.

    Biosynthesis of Physiologically Active Amines

    • Derivatives of Amino Acids: GABA, histamine, serotonin, epinephrine, norepinephrine, and dopamine are all derived from amino acids.

    Anabolic Pathways

    • Anabolic pathways are the processes of building complex molecules from simpler ones, requiring energy.
    • Energy sources include ATP, NADH, and NADPH.

    Gluconeogenesis

    • Allows the body to synthesize glucose from non-carbohydrate sources when glycogen stores are depleted.
    • Main precursors are lactate, glycerol, and glucogenic amino acids.
    • Some steps of glycolysis are irreversible, requiring specific bypass routes in gluconeogenesis.
    • Gluconeogenesis is mainly carried out in the liver and kidneys.
    • Tissues like RBC, brain, testes, and the lens of the eye rely heavily on glucose for energy.
    • Gluconeogenesis is regulated by factors like AMP and fructose 2,6-bisphosphate.
    • Glucagon stimulates gluconeogenesis, while insulin inhibits it.

    Pentose Phosphate Pathway (PPP)

    • Generates NADPH and 5-carbon sugars for anabolic processes.
    • Occurs in the cytoplasm.
    • Has two phases: the oxidative phase produces NADPH, and the cyclical phase synthesizes 5-carbon sugars.
    • Ribose-5-phosphate, produced by PPP, is essential for DNA and RNA synthesis.

    NADPH vs NADH

    • NADPH: Used in biosynthetic reactions like lipid synthesis and protection against oxidative stress.
    • NADH: Used in energy-yielding reactions like oxidative phosphorylation.

    Nucleotide Biosynthesis

    • Purine biosynthesis (A, G): Derived from folic acid, ATP, and the pentose phosphate pathway.
    • Pyrimidine biosynthesis (C, T, U): Uses glutamine, CO2, and ATP, and involves the synthesis of the pyrimidine ring before attachment to ribose-5-phosphate.
    • Common intermediates in both purine and pyrimidine synthesis: IMP for purines and UMP for pyrimidines.

    Nucleotide Degradation

    • Pyrimidines: Degraded to simple carbon skeletons.
    • Purines: Can be reused or degraded, with excessive breakdown leading to uric acid accumulation.

    Clinical Aspects

    • Chemotherapy: Many anti-cancer drugs target nucleotide biosynthesis, inhibiting dTMP synthesis and DNA replication.
    • Gout: Caused by excessive uric acid accumulation, which can crystalize and cause joint and kidney inflammation.
    • Adenosine deaminase deficiency: Genetic deficiency in purine degradation, leading to severe immunodeficiency.

    Amino Acid Biosynthesis

    • Amino acids are classified as essential (obtained from diet) and non-essential (synthesized by the body).
    • Non-essential amino acids can be synthesized through transamination of ketoacids.
    • Glutamine synthetase plays a crucial role in ammonia transport.

    Synthesis of Non-Essential Amino Acids

    • Alanine: Synthesized from pyruvate by transamination.
    • Aspartate: Synthesized from oxaloacetate by transamination.
    • Glutamate: Synthesized from α-ketoglutarate by transamination and glutamate dehydrogenase.
    • Glutamine: Synthesized from glutamate by glutamine synthase.
    • Proline: Synthesized from glutamate by cyclization.
    • Serine: Synthesized from 3-phosphoglycerate through a series of reactions.
    • Glycine: Synthesized from serine by serine hydroxymethyl transferase

    Biosynthesis of Physiologically Active Amines

    • Many physiologically active amines, including GABA, histamine, serotonin, epinephrine, norepinephrine, and dopamine, are derived from amino acids.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Biosynthetic Pathways FFP1 2022-2023 PDF

    Description

    This quiz covers key concepts related to anabolic pathways and gluconeogenesis. It explores how complex molecules are formed from simpler ones and the role of various substrates in glucose production. Test your understanding of energy requirements, irreversible steps, and substrates involved in gluconeogenesis.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser