Question

Imagine that you are studying the metabolism of a baby who is feeding on breast milk. You are going to compare the catabolism of two molecules of galactose from lactose in milk with the catabolism of two molecules of leucine from casein in milk. 

Answer 1

CATABOLISM OF GALACTOSE FROM LACTOSE

                                     The main sources of galactose in human deit are milk and milk products, incase of infants source of galactose is from breast milk which they feed on. The disaccharide lactose from these sources is hydrolyzed in intestine to it's constituent monosaccharides , glucose and galactose.

                                     Galactose is metabolized primarily in the liver in a sequence of three reactions that yield one molecule of glucose 1-phosphate per molecule of galactose. First, it is phosphorylated to give galactose 1-phoshphate . Then galactose 1-phosphate and UDP-Glucose react to form UDP-galactose and glucose 1-phosphate and UDP-galactose undergoes epimerization to form UDP-glucose . In a reaction shared with another pathways , glucose 1-phosphate can be converted into glucose 6-phosphate.

Breakdown of casein in infants (catabolism ) is done with the help of a proteolytic enzyme found in gastric juice of infants ,rennin , helps in breakdown of mammalian milk protiens like casein into its amino acids containing leucine and other amino acids.