lecture 28 - glucose as a fuel molecule Flashcards
glucose is oxidised where
glycolysis in the cytoplasm
what is glucose essential for
fuel for red blood cells
- as they do not have mitochondria - dont have other pathways
why is glucose the preferred fuel for the brain
high energy requirement
- glucose easily crosses the blood brain barrier
- a high fatty acid metabolism is dangerous
why is glucose the favoured fuel in the eye
because blood vessels (brining oxygen) and mitochondria would refract light in the optical path to retina
= uses glycolysis
why do white muscles tend to use glucose as fuel but red uses fats
white muscle = short term muscle, used in sprinting etc
works under anaerobic conditions = oxygen low so uses glycolysis
what is glycolysis
the splitting of glucose
- conversion of one molecule of glucose (6 carbon) to two molecules of pyruvate (3 carbon)
how is energy conserved in glycolysis
ATP and NADH
what is the energy investment phase of glycolysis
activation of glucose = getting the molecule in a form so energy can be captured
requires energy input (2 ATP)
- splitting (6C to 3C) the molecule occurs at the end of the investment phase
what is the energy pay off phase of glycolsys
- making ATP profit
after conversion, both 3C molecules processed the in the same way
how many ATP are produced in the energy pay off phase of glycolysis
4 ATP
how many NADH are produced in the energy pay off phase of glycolysis
2 NADH
what is the net profit of ATP in glycolysis
2 ATP
what does the reaction from glucose to glucose-6-phosphate involve in glycolysis
couples two reactions to make the reaction spontaneous
what happens in the reaction from glucose-6-phosphate to fructose-6-phosphate
rearrangement
happens in the reaction from fructose-6-phosphate to fructose-1,6-biphosphate in glycolysis
2nd activation of glucose; ATP hydrolysis
what is substrate phosphorylation
the direct use of energy from a substate molecule to drive the synthesis of ATP (or equivalent)
does the addition of a phosphate require ATP
no
what does cleaving a phosphate do in terms of energy
releases energy
what is the overall reaction of glycolysis
glucose + 2NAD+ + 2ADP + 2Pi > 2 pyruvate + 2NADH + 2H+
what is aerobic oxidation
oxygen available = occurs in the mitochondrial matrix
- oxidative decarboxylation
what is the oxidative decarboxylation reaction that occurs in aerobic oxidation
CO2 released (3C to 2C)
pyruvate is oxidised energy captured in NADH and used to add Coenzyme A to two carbon chain
what is anaerobic glycolysis
low oxygen
- red blood cells, muscles in anaerobic conditions
what happens in anaerobic glycolysis
lactate dehydrogenase oxidises NADH to NAD+ to convert pyruvate to lactate
- energy captured in NADH is lost
- lactate causes muscle fatigue
why does the lactate dehydrogenase reaction occur and what occurs in aerobic oxidation
- low concentration of co enzymes in cells
- during aerobic oxidation coenzymes are oxidised (regenerated) in oxidative phosphorylation
how does lactate formation allow for the regeneration of NAD+
- lactate dehydrogenase oxidises NAD - so that glycolysis can continue
