Biosynthetic pathways 2

• What does the pentose phosphate pathway generate?

  NADPH and 5-carbon sugars
• What is the primary function of NADPH in the pentose phosphate pathway?

  It acts as a biochemical reductant
• How does the pentose phosphate pathway relate to metabolism?

  It provides intermediates for nucleotide biosynthesis
• What are the two phases of the pentose phosphate pathway?

  • Oxidative phase: NADPH production
  • Cyclical phase: 5-carbon sugars produced
• What is the overall reaction of the oxidative phase of the pentose phosphate pathway?

  1 Glucose-6-P to ribulose-5-P, CO₂, and 2 NADPH
• Which enzyme catalyzes the first reaction of the oxidative phase?

  Glucose 6-phosphate dehydrogenase (G6PD)
• What is the role of NADPH in fatty acid synthesis?

  It supplies electrons and energy
• What is G6PD deficiency?

  An enzyme abnormality affecting NADPH production
• What are the epidemiological characteristics of G6PD deficiency?

  Most common enzyme abnormality globally
• How does G6PD deficiency lead to oxidative damage in erythrocytes?

  Reduced NADPH prevents glutathione regeneration
• What are Heinz bodies?

  Denatured proteins in erythrocytes due to oxidation
• What factors can precipitate hemolytic anemia in G6PD deficiency?

  Oxidant drugs and infections
• What is the primary source of amino acids in the body?

  Amino acids ingested in diet
• How are non-essential amino acids formed?

  By adding amino groups to α-keto acids
• What happens to amino acids during starvation?

  Muscle tissue is broken down for energy
• What is the urea cycle's role in amino acid metabolism?

  It disposes of excess nitrogen as urea
• What are glucogenic amino acids?

  Amino acids that yield TCA cycle intermediates
• What is the function of transaminases?

  They transfer amino groups between amino acids
• What is the significance of high levels of ALT and AST in plasma?

  Markers of liver damage
• What is the role of ornithine transcarbamoylase in the urea cycle?

  It incorporates nitrogen into urea
• How many ATP molecules are required to synthesize one molecule of urea?

  3 ATP molecules
• What is the primary source of nitrogen in the urea cycle?

  Free NH₄ and aspartate
• What are the two main pathways for nucleotide biosynthesis?

  De novo and salvage pathways
• What is the common intermediate in purine nucleotide synthesis?

  Inosine 5'-monophosphate (IMP)
• What is the role of folic acid in purine synthesis?

  It provides carbon atoms for the purine ring
• How do chemotherapy drugs affect nucleotide biosynthesis?

  They inhibit dTMP synthesis to prevent cell division
• What can excessive breakdown of purine bases lead to?

  Gout due to excess uric acid
• What are the key differences between purine and pyrimidine nucleotide metabolism?

  • Purines: Salvaged or degraded
  • Pyrimidines: Synthesized before attachment to ribose