Carbohydrates 2 Flashcards
What is glycolysis?
The process of glucose converting into 2 pyruvate molecules
What happens to glucose when it enters a cell?
It is phosphorylated by kinase using ATP
Where is glucokinase found and when is it active?
Liver and pancreas. In the prescience of insulin only
Can G6P be converted back into glucose?
In glycolysis, the reaction is irreversible. It IS possible but requires a lot of energy
What happens after G6P is created?
It is converted to F6P (fructose 6 phosphate)
What happens once G6P has been converted to F6P? Can this next step be reversed?
F6P is phosphorylated again to form Fructose 1-6 bis phosphate. This step is not reversible.
What is the rate limiting step of glycolysis and why?
Rate of conversion of F6P to F1-6BP. It’s the slowest step.
When do our bodies produce the enzymes required to undergo glycolysis?
When we need energy
What are the net products of glycolysis?
2 Pyruvate, 2 ATP and 2 NADH molecules
What are the three irreversible reactions in glycolysis?
Glucose to G6P (phosphorylation), F6P to fructose 1-6 bisphosphate (phosphorylation), and PEP (phosphoenolpyruate) to Pyruvte (dephosphorylation)
What are three products that pyruvate can produce?
Ethanol, Lactate, Acetyl CoA then co2
How is ethanol formed from pyruvate?
Converted to acetaldehyde, then to ethanol, using H+ from NADH
How is lactate produced from pyruvate?
Lactate dehydrogenase catalysed reaction, using H+ from NADH
What is the fate of blood lactate?
It’s released into the blood and taken to the liver where gluconeogenesis occurs. Eventually converted back into glucose
What is the function of pyruvate dehydrogenase?
Converts pyruvate into Acetyl CoA. Removed H+ from pyruvate, generating NADH, hence dehydrogenase
Where does the conversion of pyruvate to acetyl coA occur?
Mitochondria
Why are there 3 irreversable steps in glycolysis?
The delta G values of those reactions are too low, so it would take too much energy to reverse
What is the function of gluconeogenesis and where does it occur?
To convert pyruvate back into glucose, to be released in the blood. Occurs in the liver
What is the 1st step in process of gluconeogenesis?
Pyruvate is converted to oxaloacetate, then PEP. Occurs partly in mitochondria
What is the second step of gluconeogenesis and the product?
Fructose 1-6 bisphosphate is converted into fructose 6 phosphate. Phosphate is released as a free ion and not converted back to ATP as it requires too much energy
What is the third step of gluconeogenesis and its product?
G6P to Glucose. Produces phosphate, released as a free ion
What is the fate of absorbed galactose?
It is converted into G6P in the liver
What is the fate of absorbed fructose?
It’s converted into other molecules later on in the glycolysis cycle
What is the effect of drinking alcohol on gluconeogenesis?
It converts NAD+ to NADH, inhibiting gluconeogenesis. Too much alcohol can kill, as glucose cannot be made.
What is the cori cycle?
Muscles producing lactate through substrate-level phosphorylation which can then be converted to glucose through gluconeogenesis. Allows muscle to continue contracting
What are bypass reactions and where are the found?
Found in gluconeogenesis to make the process energetically feasible
Is glycogen osmotically active?
No - its osmotically inactive because it can’t leave the cell membrane and doesn’t affect osmolarity. This is a benefit of storing glucose as glycogen
