Feeding Glycolysis

Question 1

High fructose usually means..?

Answer 1

high glycerol-3P, high precursors for fatty acid synthesis

Question 2

What do sucrase and lactase do?

Answer 2

Sucrase breaks down sucrose to fructose and glucose
Lactase breaks down lactose to glucose and galactose

Question 3

What are other sources of glucose?

Answer 3

dietary glycogen and starch processed by amylase

Question 4

Glucose is converted to G6P in step 2 of glycolysis. What other carbohydrate can be synthesized to G6P?

Answer 4

Galactose

Question 5

How is galactose converted to a product to undergo glycolysis?

Answer 5

Galactose can be converted to Gal-1-phosphate and UDP-glucose via galactokinase. Gal-1-phosphate is converted to G1P and UDP-galactose via transferase. Finally, G1P is isomerized to G6P via phosphoglucomutase which proceeds to the next steps.

Question 6

In the normal glycolysis, G6P is the substrate to F6P. Can F6P be synthesized by other carbohydrate/s? How?

Answer 6

Mannose is converted to mannose-6-phosphate (M6P) via hexokinase and then phosphomannose isomerase converts M6P to F6P.

Subsequently, fructose can supply F6P by catalyzing fructose in the muscles with hexokinase yielding F6P

Question 7

In normal glycolysis, G3P is a product of cleavage of FBP, however what is/are an/other way to synthesize G3P

Answer 7

Fructose in the liver is converted to F1P via fructokinase (more abundant than hexokinase in liver). F1P yields DHAP and glyceraldehyde which can then be used to process G3P.

However, glyceraldehyde can form glycerol-3-phosphate (glycerol-3P) instead. Glycerol-3P can undergo lipid synthesis or it can be used to yield DHAP.