Nucleotide Synthesis and Metabolism
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What is the best-known example of a heme?

  • Heme proteins
  • Methylene bridges
  • Pyrrole rings
  • Iron porphyrin (correct)

    • What are the precursors of HEME biosynthesis?

  • Metal ions (Fe2+), (Fe3+)
  • N-containing rings
  • Porphyrin
  • Porphyrins (correct)

    • Where are heme proteins rapidly synthesized and degraded to keep up with losses?

  • Liver
  • Red blood cells (correct)
  • Bone marrow
  • Spleen

    • Which enzyme produces the secondary messenger cAMP?

    <p>Adenylyl Cyclase</p> Signup and view all the answers

    What happens to cAMP in the cell?

    <p>It is broken down by Phosphodiesterase</p> Signup and view all the answers

    Which type of receptor is coupled with a G protein?

    <p>GPCR (G Protein-Coupled Receptor)</p> Signup and view all the answers

    What is the role of Phospholipase C in the second messenger system?

    <p>Produces IP3 plus DAG</p> Signup and view all the answers

    In the cAMP pathway, what does Protein Kinase A do?

    <p>$PKA$ adds phosphates to specific proteins</p> Signup and view all the answers

    6

    <p>All G proteins are active when bound to GTP and inactive when bound to GDP.</p> Signup and view all the answers

    What happens when a G protein activates the enzyme in the second-messenger system?

    <p>The second-messenger molecules increase.</p> Signup and view all the answers

    In the cAMP pathway, what is the significance of Phosphodiesterase?

    <p>It breaks down cAMP.</p> Signup and view all the answers

    Where does heme biosynthesis occur?

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

    Which enzymes are sensitive to lead inhibition, leading to protoporphyrin and ALA accumulation in urine?

    <p>Ferrochelatase and ALA dehydratase</p> Signup and view all the answers

    What is the result of deficiency in hydroxymethylbilane synthase?

    <p>Accumulation of porphobilinogen and δ-aminolaevulinic acid in the urine</p> Signup and view all the answers

    Which type of porphyria is characterized by a deficiency in ferrochelatase?

    <p>Erythropoietic protoporphyria</p> Signup and view all the answers

    Which enzyme deficiency leads to the accumulation of uroporphyrinogen I and coproporphyrinogen I in the urine?

    <p>Uroporphyrinogen III synthase</p> Signup and view all the answers

    What is the composition of hemoglobin's heme?

    <p>Porphyrin ring and iron (Fe2+)</p> Signup and view all the answers

    'Hemoglobin's quaternary structure changes from a taut (deoxy) to a relaxed (oxy) conformation when oxygen binds.' What factors shift the hemoglobin oxygen binding curve to the right?

    <p>Decreased pH, increased CO2, increased 2,3-BPG</p> Signup and view all the answers

    Which hormone stimulates the synthesis and release of Cortisol?

    <p>Corticotropin Releasing Hormone (CRH)</p> Signup and view all the answers

    Which hormone causes vasoconstriction, platelet aggregation, uterine contraction, and glucocorticoid release?

    <p>Angiotensin II</p> Signup and view all the answers

    Which hormone is released by the adrenal medulla and stimulates a variety of tissue and organ responses including glycogenolysis, increases in heart rate, and relaxation of bronchial smooth muscle?

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

    Which hormone is secreted by the Parafollicular Cells of the thyroid and lowers blood calcium levels?

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

    Which hormone stimulates follicle maturation and ovulation in women, and testosterone synthesis and spermatogenesis in men?

    <p>Luteinizing Hormone (LH)</p> Signup and view all the answers

    What is the main function of Gαi in hormonal signaling pathways?

    <p>Inhibits the production of cAMP from ATP</p> Signup and view all the answers

    Which type of hormones bind to cell membrane receptors and activate intracellular kinases?

    <p>Lipophobic/hydrophilic hormones</p> Signup and view all the answers

    What type of receptors are linked to a second-messenger-generating enzyme via membrane proteins called G proteins?

    <p>G protein–coupled receptors (GPCRs)</p> Signup and view all the answers

    What is the role of G protein–coupled receptors (GPCRs) in cellular signaling?

    <p>Link receptors to a second-messenger-generating enzyme via membrane proteins called G proteins</p> Signup and view all the answers

    Which type of hormone receptor binds to intracellular receptors and activates genes?

    <p>Lipophilic/hydrophobic hormones</p> Signup and view all the answers

    Which hormone is responsible for promoting diuresis and sodium excretion?

    <p>Atrial Natriuretic Hormone (ANH)</p> Signup and view all the answers

    Which type of hormones can bind to cell membrane or intracellular receptors?

    <p>All of the above</p> Signup and view all the answers

    What is the primary cause of overproduction of uric acid?

    <p>Increased purine availability</p> Signup and view all the answers

    Which hormone uses a cAMP-dependent pathway to function?

    <p>Anti-Diuretic Hormone (ADH)</p> Signup and view all the answers

    What causes severe combined immunodeficiency (SCID) due to inhibited DNA synthesis and cell proliferation?

    <p>Adenosine deaminase (ADA) deficiency</p> Signup and view all the answers

    What role does the endocrine system play in maintaining homeostasis?

    <p>Regulating blood glucose levels</p> Signup and view all the answers

    What is the primary cause of gout?

    <p>Underexcretion of uric acid</p> Signup and view all the answers

    What causes sickle cell trait?

    <p>Heterozygous form (one mutated gene)</p> Signup and view all the answers

    What is the characteristic of β-thalassemia?

    <p>Decreased synthesis of β globin chains</p> Signup and view all the answers

    What is the consequence of sickled RBCs getting trapped in small capillaries?

    <p>Hemolytic anemia</p> Signup and view all the answers

    What is the result of HGPRT deficiency?

    <p>$\text{Lesch-Nyhan Syndrome}$</p> Signup and view all the answers

    What causes posthepatic jaundice?

    <p>Bile duct obstruction or gallstones</p> Signup and view all the answers

    What is the consequence of hyperbilirubinemia?

    <p>Skin and eye yellowing due to deposition of bilirubin in the blood</p> Signup and view all the answers

    What are the precipitating factors for sickle cell disease?

    <p>Low oxygen levels, high pCO2, low pH, and high HbS concentration</p> Signup and view all the answers

    What happens in homozygous form of sickle cell anemia?

    <p>Results in sickle cell anemia</p> Signup and view all the answers

    What is the imbalance in thalassemia?

    <p>Imbalance in the synthesis of one of the two globin chains leading to anemia</p> Signup and view all the answers

    How is bilirubin excreted from the body?

    <p>Conjugated in the liver and excreted in bile</p> Signup and view all the answers

    Which water-soluble vitamin is involved in reactions of energy production as a coenzyme for pyruvate dehydrogenase and for a TCA cycle enzyme?

    <p>Thiamine (B1)</p> Signup and view all the answers

    Which fat-soluble vitamin is associated with the normal lipid absorption mechanisms, including emulsification by bile, normal mucosal cells, and transport in chylomicrons?

    <p>Vitamin K</p> Signup and view all the answers

    Which water-soluble vitamin is required by enzymes involved in amino acid metabolism, such as transaminases?

    <p>Pyridoxine (Vitamin B6)</p> Signup and view all the answers

    Which fat-soluble vitamin is stored in the body in the liver and adipose tissue?

    <p>Vitamin D</p> Signup and view all the answers

    Which water-soluble vitamin is a constituent of the coenzymes FAD and FMN, functioning as electron carriers for oxidoreductases?

    <p>Riboflavin (B2)</p> Signup and view all the answers

    Which fat-soluble vitamin functions as a hormone and is associated with lipids of the diet?

    <p>Vitamin A</p> Signup and view all the answers

    Which water-soluble vitamin is a constituent of the coenzymes NAD+ and NADP+, functioning as electron carriers for oxidoreductases?

    <p>Niacin (Nicotinic Acid) (B3)</p> Signup and view all the answers

    Which fat-soluble vitamin functions as an antioxidant and requires normal lipid absorption mechanisms for absorption?

    <p>Vitamin E</p> Signup and view all the answers

    Which deficiency results in a disease marked by dermatitis, dementia, and diarrhea?

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

    What is the characteristic symptom of Vitamin A deficiency?

    <p>Night blindness</p> Signup and view all the answers

    Which condition is linked to Vitamin C deficiency?

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

    What does severe thiamine deficiency result in?

    <p>Eye muscle weakness, poor muscular coordination, and memory loss</p> Signup and view all the answers

    What is the main consequence of Vitamin B12 deficiency?

    <p>Megaloblastic anemia and neurological damage</p> Signup and view all the answers

    What does excess upper body fat indicate?

    <p>A higher risk of metabolic diseases</p> Signup and view all the answers

    What is the normal range for Body Mass Index (BMI)?

    <p>18.5-25 kg/m2</p> Signup and view all the answers

    What is the characteristic symptom of Vitamin K deficiency?

    <p>Bleeding disorders like hemorrhagic disease of the newborn</p> Signup and view all the answers

    What are the consequences of folate deficiency?

    <p>Impaired DNA synthesis and cell division leading to megaloblastic anemia and neural tube defects</p> Signup and view all the answers

    Which vitamin is a coenzyme in the hydroxylation of proline and lysine residues in collagen production?

    <p>Vitamin C</p> Signup and view all the answers

    Which vitamin is required for the post-translational modification of coagulation factors II, VII, IX, and X?

    <p>Vitamin K</p> Signup and view all the answers

    Which vitamin functions as an antioxidant in the blood and in membranes, protecting membrane phospholipids from attack by reactive oxygen species?

    <p>Vitamin E</p> Signup and view all the answers

    Which vitamin is involved in the conversion of homocysteine to methionine?

    <p>Vitamin B12</p> Signup and view all the answers

    What is the active form of Vitamin D responsible for enhancing the absorption of calcium and phosphorus from the small intestines?

    <p>1,25-dihydroxycholecalciferol (calcitriol)</p> Signup and view all the answers

    What is a consequence of Vitamin C deficiency?

    <p>All of the above</p> Signup and view all the answers

    Which vitamin is required for nucleotide synthesis and synthesis of methionine from homocysteine?

    <p>Vitamin B9 (Folic Acid)</p> Signup and view all the answers

    In what form are animal sources absorbed and incorporated into chylomicrons?

    <p>Retinol and retinyl esters</p> Signup and view all the answers

    Study Notes

    • Sickle cell anemia is an autosomal recessive disease, caused by mutations in the beta-globin gene producing sickle hemoglobin (HbS)

    • Homozygous form (both mutated genes) results in sickle cell anemia, while heterozygous form (one mutated gene) is sickle cell trait

    • Sickle cell disease affects approximately 10% of African Americans

    • Hemolytic anemia and recurrent pain result from sickled RBCs getting trapped in small capillaries

    • Precipitating factors include low oxygen levels, high pCO2, low pH, and high HbS concentration

    • Thalassemia is an imbalance in the synthesis of one of the two globin chains, leading to anemia

    • β-thalassemia is characterized by decreased synthesis of β globin chains, and homozygous form is known as Cooley's anemia

    • Hemoglobin turnover and heme degradation lead to the production of bilirubin

    • Bilirubin is conjugated in the liver and excreted in bile, giving stool its brown color

    • Hyperbilirubinemia can result from massive hemolysis, damage to liver cells, or inefficiency in conjugation activity

    • Jaundice is a manifestation of skin and eye yellowing due to deposition of bilirubin in the blood

    • Prehepatic jaundice can be caused by hemolysis, autoimmune diseases, or abnormal hemoglobin

    • Intrahepatic jaundice can be caused by infection, drugs, or neonatal conditions

    • Posthepatic jaundice can be caused by bile duct obstruction or gallstones

    • Nucleotide synthesis occurs through a series of reactions involving amino acids, phosphoribosylpyrophosphate (PRPP), tetrahydrofolate (FH4), and purine and pyrimidine nucleotides.

    • HGPRT deficiency, which affects the purine salvage pathway, can lead to Lesch-Nyhan Syndrome, characterized by neurologic abnormalities and self-mutilation.

    • Gout is a condition characterized by hyperuricemia, recurrent attacks of joint inflammation, and uric acid crystal deposition in cartilage, joints, and kidneys.

    • Gout can be genetic or secondary to other diseases.

    • Underexcretion of uric acid is the primary cause of gout.

    • Thiamine deficiency: severe deficiency leads to beriberi, a disease with neurological disorders, cardiovascular issues, and muscle weakness

    • Inhibition of glutamate production and GABA in the TCA cycle due to thiamine deficiency

    • Severe thiamine deficiency results in Wernicke-Korsakoff syndrome, characterized by eye muscle weakness, poor muscular coordination, and memory loss, commonly seen in chronic alcoholism

    • Niacin deficiency results in pellagra, a disease marked by dermatitis, dementia, and diarrhea (the three Ds)

    • Niacin deficiency also linked to an unbalanced amino acid ratio with insufficient tryptophan

    • Folate deficiency impairs DNA synthesis and cell division, leading to megaloblastic anemia and neural tube defects

    • Vitamin B12 deficiency, or pernicious anemia, is caused by an autoimmune destruction of stomach cells responsible for producing intrinsic factor, leading to symptoms including megaloblastic anemia and neurological damage

    • Vitamin C deficiency results in a variety of health issues, most notably scurvy, characterized by weakness, anemia, and joint pain

    • Vitamin A deficiency results in night blindness and a decreased ability to regenerate rhodopsin, leading to potentially permanent blindness

    • Vitamin K deficiency is linked to bleeding disorders, such as hemorrhagic disease of the newborn and is often treated with vitamin K antagonists like warfarin

    • Excess calories, obesity, and a genetic component contribute to the development of type II diabetes

    • Hepatic insulin resistance and pancreatic dysfunction are caused by fatty liver and a fatty pancreas

    • Metabolic syndrome is characterized by a cluster of conditions including insulin resistance, hypertension, and abnormal blood lipid levels.

    • Body Mass Index (BMI) is a measure of body weight relative to height, with a normal range being 18.5-25 kg/m2

    • The distribution of body fat, specifically excess visceral and abdominal subcutaneous fat, is associated with increased health risks in obesity.

    • Excess upper body fat is linked to a higher risk of metabolic diseases and is often used as a clinical marker.

    • A waist-to-hip ratio greater than 0.8 for women and greater than 1.0 for men indicates an increased health risk associated with obesity.

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    Description

    Test your knowledge on nucleotide synthesis, metabolism, and related pathways. Explore the causes of overproduction of uric acid and the role of enzymes like adenosine deaminase.

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