Carbohydrates 4 Flashcards
Which cells rely on glucose as their main source of energy?
Brain cells, RBC’s, nervous system, testis, embryonic tissue
How many out of the 10 glycolysis reactions are irreversible?
3
What are the 4 reactions called that side step the three irreversible reactions of glycolysis
Bypass reactions, allow for the independant control of pathways and to stop them canceling each other out
Where do the first two bypass reactions occur?
Mitochondria
What are the first two bypass reactions?
Pyruvate - Oxaloacetate
Oxaloacetate - PEP
Pyruvate can be derived from lactate, Lactate +(NAD)+ (lactate dehydrogenase) = pyruvate + NADH
What is the pathway of molecules in the first bypass reactions if pyruvate has and hasn’t been derived from Lactate?
Lactate : Lactate, Pyruvate, Oxaloacetate, PEP
No Lactate: Pyruvate, Oxaloacetate, Malate, Oxaloacetate, PEP
What is the control point for gluconeogenesis?
The third bypass reaction for, it is irreversible under cell conditions
What enzyme catalyses the hydrolysis of f-1,6-bisP to Fructose-6-Phosphate?
Fructose 1,6-bisphosphatase
What is the fourth bypass reaction?
Dephosphorylation of G-6-P to glucose, the final stage in gluconeogenesis. Glucose 6-phosphatase is the catalyst
Why is G-6-P normally the end point for gluconeogenesis?
Allows the cells to ‘trap’ the glucose
Where does the final step of gluconeogeneogenesis to make free glucose take place?
Lumen of the ER
Where is most fructose metabolised?
Liver
How many ATP are used for each molecule of Frutose converted into Glyceraldehyde -3- phosphate?
1 or 2§
What is the first molecule of ATP used for?
Converts fructose to fructose - 1 - Phosphate (using fructokinase enzyme)
What is the reaction pathway for fructose-1-phosphate?
Reacts with fructose-1-phosphate aldolase froming glyceraldehyde and dihydroxyacetone phosphate. Glyceraldehyde reacts with triose kinase and another molecule of ATP to form Glyceraldehyde 3-Phosphate
