Biochemistry Quiz on Amino Acids and Glutathione

Glycine Amino Acid Metabolism

• Glycine is a neutral, aliphatic, glucogenic, and non-essential amino acid.

Glycine Synthesis

• Glycine can be synthesized from:
  • Threonine
  • Serine
  • Glyoxylic acid via transaminase
  • Ammonia and CO2 via glycinesynthase
  • Choline through the choline cycle

Glycine Catabolism

• Glycine is catabolized to produce CO2 and NH3 by glycine cleavage enzyme
• Glycine can be converted to glyoxylic acid through oxidative deamination or transamination
• Glyoxylic acid can then undergo oxidative decarboxylation to produce formic acid
• Glycine is also a gluconeogenic amino acid and can be converted to pyruvate. Pyruvate can then be converted to glucose

Glycine Detoxification

• Glycine participates in the detoxification of certain substances by conjugation
• Benzoic acid, a food preservative, is converted to hippuric acid during this process

Glycine Anabolic Fates

• Glycine is used in protein synthesis, including collagen synthesis
• It's involved in purine and porphyrin (precursor of hemoglobin) synthesis
• Glycine is also involved in bile salt synthesis

Glutathione Synthesis

• Glutathione exists in two forms:
  • Reduced form (G-SH): contains a free sulfhydryl group
  • Oxidized form (G-S-S-G): contains a disulfide bond
• Glutathione functions include:
  • Amino acid absorption
  • Coenzyme for several enzymes
  • Detoxification reactions in the liver
  • Hydrogen donor in redox reactions
  • Inactivating insulin
  • Protecting cell membranes from damage (e.g., preventing RBC hemolysis and protecting pancreatic beta cells)

Creatine Synthesis

• Creatine is present in both blood and muscle
• In blood, it's only free creatine. In muscle, it's present as both free creatine and creatine phosphate (also called phosphagen).
• Creatine is synthesized from arginine and glycine via two reactions:
  • Transamidation in the kidneys
  • Transmethylation in the liver.
• A small percentage of creatine and creatine phosphate is converted to creatinine, and excreted in the urine daily
• Serum creatinine levels are 0.6-1.2 mg/dL

Creatine Metabolism

• During rest, creatine is phosphorylated by creatine phosphokinase (CPK) using ATP, creating stored energy in the form of creatine phosphate (CP)
• During muscle exercise, creatine phosphate is dephosphorylated, regenerating ATP for energy production, catalyzed by creatine-ATP transphosphorylase.

Creatinine Clinical Significance

• Creatinine clearance rate from blood to urine is a measure of kidney function (Creatinine clearance test)
• High blood creatinine and urea levels indicate potential renal impairment like renal failure.

This quiz covers key concepts related to amino acids, particularly glycine and glutathione. Test your knowledge on their functions, synthesis, and roles in detoxification and muscular exercise. Perfect for students studying biochemistry or health sciences.