Fructose, Glactose, Pentose Phosphate Pathways

Question 1

Where does fructose come from in the diet?

Answer 1

Honey and high fructose corn syrup. Also, fruit contains sucrose, which can be broken down by sucrase/isolmaltase to form fructose and glucose.

Question 2

What does the polyol pathway do?

Answer 2

• Generates fructose from glucose. Occurs normally in seminal vesicles, providing fuel for sperm.
• In uncontrolled diabetes, can lead to cataracts in eyes

Question 3

What are the two main purposes of the pentose phosphate pathway?

Answer 3

• Generation of NADPH: reducing power of NADPH is used for FA synthesis, cholesterol synthesis, nucleotide synthesis, oxidation of toxins by CYP, generation of reduced glutathione (major antioxidant of cell)
• Generation of 5 carbon sugars used primarily for synthesizing nucleotides.

Question 4

Where is the pentose phosphate pathway very active?

Answer 4

• liver
• adipose
• lactating mammary gland
• adrenal cortex
• red blood cells

Question 5

What are the products of fructose metabolism and where do they enter glycolysis?

Answer 5

• Glyceraldehyde 3-phosphate (in liver generally moves on gluconeogenesis pathway)
• Dihydroxyacetone-phosphate

Enter glycolysis just after fructose 1,6-phosphate. Skip major glycolysis regulatory step PFK-1 (fructose 6-phosphate to fructose 1,6-phosphate)