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 - OxaloacetateOxaloacetate - PEPPyruvate 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, PEPNo 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
How is galactose converted to glucose 1-phosphate?
Through use of sugar-nucleotide derivative UDP-galactose
What is the function of the pentose phosphate pathway?
Produces NADPH for all organisms, produces pentose sugars, metabolises the small amount of pentoses in the diet (usually come from digestion of nucleotides)
What is the oxidative irreversible part of the pentose phosphate pathway?
Generates NADPHConverts G-6-P to pentose phosphateRequired when lots of NADPH is needed
What is the reversible non-oxidative part?
Interconverts G-6-P and pentose phosphate to produce lots of different 3,4,5,6,7 carbon sugarsWhen lots of nucleotides are required
What is the function of NADPH?
Links anabolic and catabolic pathways
What type of reaction is NAD+ involved in?
Metabolism of dietary sugars in the redox reactions of glycolysis and the citric acid cycle
What type of reactions is NADP+ involved in?
Anabolism to convert simple precursors into things like fatty acidsAlso acts as an antioxidant
What stops NADP+ being used in metabolism?
Enzyme specificity
What is the effect of being drunk on gluconeogenesis?
Reduced gluconeogenesis
How can being drunk be linked to lacticacidaemia?
Reduced level of NAD+Less lactate converted into pyruvate
How can being drunk be linked to hypoglycemia?
Decreased blood glucose concentration since gluconeogenesis is inhibited
