a) Fructose in the liver can be phosphorylated only by fructokinase to fructose 1-phosphate ie., a phosphate group attached to the 1st carbon of 5 carbons in fructose. This phosphate in 1st position, cannot take place in substrate phosphorylation to yield ATP. even though fructolysis can yield, after some of the steps , in which Fructose 1-phoaphate is converted to glyceraldehyde-3 phosphate but only within the liver. b) GLUT5 is a fructose passive transporter, found in the epithelial cells of intestine, which transports fructose from a higher concentration to a lower concentration area across the plasma membrane without the need of energy(ATP) c) The major product of fructolysis has 16 carbons in it, which is similar to palmitate. d) hexokinase can phosphorylate only 6 carbon sugars. fructose is a 5 carbon sugar. hexokinase adds a phosphate group to the 6th carbon of the sugar, while fructokinase phosphorylates the 1st carbon. Even though we make human epithelial cells to express GLUT5, the fructose in blood vessels(say) will be absorbed and stored as fat, when the hexokinase miraculously phosphorylates them. e)From our diet before which lacked Fructose and was rich in glycogen and starch, all we got was energy in the form of ATP and good metabolism which utilizes those ATPs. But now, the diet has been changed being rich in fructose which resulted in obesity. Only, the liver can metabolise fructose, because it has fructose transporters in it, and that the first decision it takes, when it encounters fructose is to convert them into glycogen. but when fructose incoming exceeds, all the excess fructose will be converted to fat and triglycerides which can now be transported outside of the liver to be stored for long term, hence making us obese. Solution a) Fructose in the liver can be phosphorylated only by fructokinase to fructose 1-phosphate ie., a phosphate group attached to the 1st carbon of 5 carbons in fructose. This phosphate in 1st position, cannot take place in substrate phosphorylation to yield ATP. even though fructolysis can yield, after some of the steps , in which Fructose 1-phoaphate is converted to glyceraldehyde-3 phosphate but only within the liver. b) GLUT5 is a fructose passive transporter, found in the epithelial cells of intestine, which transports fructose from a higher concentration to a lower concentration area across the plasma membrane without the need of energy(ATP) c) The major product of fructolysis has 16 carbons in it, which is similar to palmitate. d) hexokinase can phosphorylate only 6 carbon sugars. fructose is a 5 carbon sugar. hexokinase adds a phosphate group to the 6th carbon of the sugar, while fructokinase phosphorylates the 1st carbon. Even though we make human epithelial cells to express GLUT5, the fructose in blood vessels(say) will be absorbed and stored as fat, when the hexokinase miraculously phosphorylates them. e)From our diet before which lacked Fructose and was rich in glycogen and starch, all w.

1. a) Fructose in the liver can be phosphorylated only by fructokinase to fructose 1-phosphate ie., a
phosphate group attached to the 1st carbon of 5 carbons in fructose. This phosphate in 1st
position, cannot take place in substrate phosphorylation to yield ATP. even though fructolysis
can yield, after some of the steps , in which Fructose 1-phoaphate is converted to
glyceraldehyde-3 phosphate but only within the liver.
b) GLUT5 is a fructose passive transporter, found in the epithelial cells of intestine, which
transports fructose from a higher concentration to a lower concentration area across the plasma
membrane without the need of energy(ATP)
c) The major product of fructolysis has 16 carbons in it, which is similar to palmitate.
d) hexokinase can phosphorylate only 6 carbon sugars. fructose is a 5 carbon sugar. hexokinase
adds a phosphate group to the 6th carbon of the sugar, while fructokinase phosphorylates the 1st
carbon. Even though we make human epithelial cells to express GLUT5, the fructose in blood
vessels(say) will be absorbed and stored as fat, when the hexokinase miraculously
phosphorylates them.
e)From our diet before which lacked Fructose and was rich in glycogen and starch, all we got
was energy in the form of ATP and good metabolism which utilizes those ATPs. But now, the
diet has been changed being rich in fructose which resulted in obesity. Only, the liver can
metabolise fructose, because it has fructose transporters in it, and that the first decision it takes,
when it encounters fructose is to convert them into glycogen. but when fructose incoming
exceeds, all the excess fructose will be converted to fat and triglycerides which can now be
transported outside of the liver to be stored for long term, hence making us obese.
Solution
a) Fructose in the liver can be phosphorylated only by fructokinase to fructose 1-phosphate ie., a
phosphate group attached to the 1st carbon of 5 carbons in fructose. This phosphate in 1st
position, cannot take place in substrate phosphorylation to yield ATP. even though fructolysis
can yield, after some of the steps , in which Fructose 1-phoaphate is converted to
glyceraldehyde-3 phosphate but only within the liver.
b) GLUT5 is a fructose passive transporter, found in the epithelial cells of intestine, which
transports fructose from a higher concentration to a lower concentration area across the plasma
membrane without the need of energy(ATP)
c) The major product of fructolysis has 16 carbons in it, which is similar to palmitate.
d) hexokinase can phosphorylate only 6 carbon sugars. fructose is a 5 carbon sugar. hexokinase
adds a phosphate group to the 6th carbon of the sugar, while fructokinase phosphorylates the 1st

2. carbon. Even though we make human epithelial cells to express GLUT5, the fructose in blood
vessels(say) will be absorbed and stored as fat, when the hexokinase miraculously
phosphorylates them.
e)From our diet before which lacked Fructose and was rich in glycogen and starch, all we got
was energy in the form of ATP and good metabolism which utilizes those ATPs. But now, the
diet has been changed being rich in fructose which resulted in obesity. Only, the liver can
metabolise fructose, because it has fructose transporters in it, and that the first decision it takes,
when it encounters fructose is to convert them into glycogen. but when fructose incoming
exceeds, all the excess fructose will be converted to fat and triglycerides which can now be
transported outside of the liver to be stored for long term, hence making us obese.