Biosynthetic pathways 1

• What are the general features of anabolic pathways?

  They build up complex molecules using energy
• What is gluconeogenesis?

  It is the formation of glucose from non-carbohydrate precursors
• How is gluconeogenesis regulated?

  By hormones like insulin and glucagon
• How does gluconeogenesis relate to the overall map of metabolism?

  It connects various metabolic pathways for glucose production
• What is catabolism?

  It is the breakdown of molecules
• What is the result of anabolic pathways?

  Proteins, RNA/DNA, lipids, and carbohydrates
• What happens when nutrients are plentiful?

  Stores are built up in the body
• What occurs during the fasting state?

  Stores are used to maintain function
• What happens to plasma glucose in the 'fed' state?

  It increases
• What is the role of insulin in the 'fed' state?

  It increases secretion by the pancreas
• What is the response of the liver in the 'fed' state?

  It makes glycogen, proteins, and triglycerides
• What happens to plasma glucose in the 'fasting' state?

  It decreases
• What is the control mechanism during the fasting state?

  Decreased insulin and increased glucagon secretion
• What is the liver's response during the fasting state?

  It performs glycogenolysis and gluconeogenesis
• What fuels does muscle use during fasting?

  Fatty acids and ketone bodies
• What are ketone bodies used for?

  They are transported for energy in other tissues
• How long do glycogen stores last?

  10-18 hours
• What happens when glycogen is depleted?

  Glucose is formed from non-carbohydrate precursors
• What are some non-carbohydrate precursors for gluconeogenesis?

  Lactate, glycerol, and amino acids
• Why can't some glycolysis steps be reversed in gluconeogenesis?

  Because they are irreversible reactions
• What is the role of pyruvate kinase?

  It converts PEP to pyruvate
• What is the energy requirement for gluconeogenesis?

  It is an energy-requiring pathway
• What are the substrates for gluconeogenesis?

  Lactate, glycerol, and amino acids
• What is the source of lactate for gluconeogenesis?

  Anaerobic glycolysis
• How is glycerol released during fasting?

  By hydrolysis of triacylglycerols
• Where is glycerol kinase expressed?

  Liver, kidney, intestine, and mammary gland
• What does glycerol phosphate convert to in gluconeogenesis?

  Dihydroxyacetone phosphate (DHAP)
• What activates pyruvate carboxylase?

  High levels of acetyl CoA
• What inhibits fructose-1,6-bisphosphatase?

  AMP and fructose-2,6-bisphosphate
• Where does glucose-6-phosphatase occur?

  In the endoplasmic reticulum (ER)
• What is the function of glucose-6-phosphatase?

  It releases phosphate to produce glucose
• Why must the phosphate group be removed from glucose-6-phosphate?

  To release glucose into the bloodstream
• What provides ATP and NADH for gluconeogenesis?

  Primarily fatty acid oxidation
• What are the entry points of gluconeogenesis substrates?

  Glycerol, amino acids, and lactate
• What is the role of oxaloacetate in gluconeogenesis?

  It is a substrate for glucose production
• What are the substrates for gluconeogenesis?

  Amino acids
• How are amino acids used in gluconeogenesis?

  Converted to TCA cycle intermediates
• What is the role of oxaloacetate in gluconeogenesis?

  It is a precursor of phosphoenolpyruvate (PEP)
• What enzymes bypass irreversible reactions in gluconeogenesis?

  Specific enzymes like pyruvate carboxylase
• What is the function of pyruvate carboxylase?

  It converts pyruvate to oxaloacetate