Lecture 03

• What are the two main endogenous energy stores?

  Carbohydrates and lipids
• What is the primary form of carbohydrate storage in the body?

  Glycogen
• What is the structure of glycogen?

  It is a branched polymer of glucose
• How is glycogen made easily accessible as an energy store?

  Through 1,4 and 1,6 linkages
• What is the role of glycogen in the liver?

  To supply glucose to the brain and tissues
• What is the role of glycogen in muscles?

  For energy needs during exercise
• How long can glycogen supply energy?

  Up to 24 hours
• What are the three stages of glycogen synthesis?

  1. Activation
  2. Polymerisation
  3. Formation of branched molecule
• What is the first step in glycogen activation?

  Conversion to glucose-1-phosphate

  
• Which enzyme is responsible for the conversion to glucose-1-phosphate?

  Phosphoglucomutase
• What drives the formation of UDP-glucose?

  Hydrolysis of PPi

  
• What enzyme is used to form UDP-glucose?

  UDP-glucose pyrophosphorylase
• What is needed for the polymerisation of glycogen?

  A primer of small polysaccharide unit
• What enzyme is responsible for glycogen polymerisation?

  Glycogen synthase
• What does the branching enzyme do during glycogen synthesis?

  Transfers a block of residues to form a branch

  
• What are the steps involved in glycogen mobilisation?

  1. Phosphorolysis
  2. Debranching
  3. Further phosphorolysis
• What is the final product of glycogen mobilisation?

  Glucose 6-phosphate
• How is glucose 6-phosphate used in the body?

  In glycolysis and pentose phosphate pathway
• What happens to glucose 6-phosphate in the liver?

  It is dephosphorylated and released into blood
• Which enzyme is used in the phosphorolysis of glycogen?

  Glycogen phosphorylase
• What are the two functions of the bifunctional enzyme in debranching?

  Transferase and α-1,6-glucosidase
• What are glycogen storage diseases caused by?

  • Defective enzymes
  • 13 well-documented types
• What is Type I glycogen storage disease known as?

  Von Gierke’s disease
• What defect is associated with Von Gierke’s disease?

  Defect in phosphatase for glucose-6-phosphate
• What is Type V glycogen storage disease known as?

  McArdle disease
• What defect is associated with McArdle disease?

  Defect in muscle phosphorylase
• What are triglycerides composed of?

  Three fatty acids and glycerol
• What is another name for triglycerides?

  Triacylglycerols
• Where are triglycerides primarily stored?

  In adipose tissue
• Where are triglycerides mainly synthesised?

  In the liver
• What initiates triglyceride synthesis?

  On the endoplasmic reticulum or mitochondrial membrane
• What is the starting point for triglyceride synthesis?

  Glycerol-3-phosphate

  
• From where is glycerol-3-phosphate mainly derived?

  From dihydroxyacetone phosphate (DHAP)
• What is the first step in the formation of phosphatidate?

  Transfer of 2 fatty acids from fatty acyl CoA
• What enzyme is used to form phosphatidate?

  Glycerol phosphate acyl transferase
• What is the product of the first step in triglyceride formation?

  Diacylglycerol-3-phosphate
• What are the two reactions involved in the formation of triglyceride?

  Removal of phosphate and addition of third fatty acid
• What is the intermediate in triglyceride formation?

  Diacylglycerol (DAG)

  
• What enzyme complexes are involved in triglyceride formation?

  Specific phosphatase and diglyceride acyltransferase
• What are the steps involved in fat mobilisation for energy?

  1. Mobilisation by degradation to fatty acids and glycerol
  2. Fatty acids activated and transported into mitochondria
  3. Undergo β-oxidation