Bioenergetics 3: Glycolysis Flashcards
How can the pathway of process of glycolysis be regulated
Only certain bonds are oxidised.
Phosphofructokinase (PFK) catalysing step 3 is most important regulator
Inhibited by High ATP, citrate and acidification (signals of plentiful energy source don’t need to break down glucose)
Activated by AMP, ADP and fructose-2,6-biphosphate.
What are the three main reaction types involved in glycolysis
- Rearrangement/preparation involving making isomers
- Condensation / splitting
- Oxidation reduction
What bonds in glucose oxidised
C-C bonds aren’t oxidised directly so they need to be rearranged to C-H or C-OH for oxidation
What enzymes do redox reactions use
Dehydrogenases (they remove H+ + e
How is cellular respiration different to combustion
Instead of explosive release of energy all at once, metabolism releases energy through steps that are controlled and used to synthesis ATP which captures energy.
How is glucose trapped in cells (glucose can leave too)
After going through cells facilitated transport GLUT, Hexokinase or Glucokinase adds a phosphate which is negatively charged. This means it can’t go through the glucose transporters again
What is the difference between Hexokinase and Glucokinase
Hexokinase in all tissues, Glucokinase in liver, kidneys, pancreatic b cells. Hexokinase works at low concentrations for anything that comes through (low Km=high affinity )
Glucokinase responds to high glucose and is super fast to clear it out of your blood (high Km= low affinity)
What does phosphoglucoisomerase do (what reaction) (2)
It rearranges glucose-6-phosphate into fructose-6-phosphate
isomerism reaction
What does phosphofructokinase do (what reaction). Is this commitment step (3)
it adds a phosphate to fructose-6-phosphate to fructose-1,6-biphosphate. this requires investment of ATP to provide the phosphate so yes commitment.
What does Aldolase do (4), (5)
It splits fructose-1,6-biphosphate into 2 products which are not symmetrical so the dihydroxyacetone phosphate is converted into the one we want glyceraldehyde-3-phosphate one by another enzyme 5. Triose phosphate isomerase
What is step 6 doing (glyceraldehyde-3-phosphate dehydrogenase)
Its adding a phosphate from cytosol to the two now symmetric products from the last reaction. This kicks out an H from both of them which makes 2 NADH
What is step 7 doing (phosphoglycerokinase)
This is the only reversible kinase. It takes 1 Pi from each of the 2 1,3-biphosphoglycerate to make 2 ATP
What does phosphoglyceromutase (step 8) and Enolase (step 9) do
- It shuffles the phosphate around to make it less stable.
9. Removes a water makes it even more stable
what does step 10 do pyruvate kinase
It removes the last phosphate to make the 2 ATP and PYRUVATE -
What enzymes making ATP from making substrate level phosphorylation
the enzymes phosphoglycerate kinase and Pyruvate kinase catalyse the addition of Pi from the sugar directly to ADP
What is the most important regulator of glucose
PFK is inhibited by high ATP, Citrate from CAC, and acidification (pyruvate is acidic)
PFK is activated by AMP
What is the advantage of glycolysis going through an aerobic pathway vs an anaerobic pathway
Much more ATP produced through aerobic but Anaerobic is less efficient (less ATP) but much faster.
what are the limiting factors of glycolysis (anaerobic)
If it is overused it uses a lot of NAD+ ->NADH and there is no pathway to oxidise it back so the redox state of the cell changes.
Also Pyruvate is acidic in cells
What is the energy investment and payoff in glycolysis
2ATP are invested at steps 1 and 3 and 4ATP are made by substrate level phosphorylation at steps 7 and 10. It also produces 2 NADH at step 6 and 2 pyruvate.
How does glycolysis happen in anaerobic conditions (strenuous exercise where ATP demands can exceed the capacity of mitochondria to re oxidise NADH)
Pyruvate produced by glycolysis in muscle is reduced to lactate using the H from NADH by lactate dehydrogenase in the cytosol. This regenerates the 2NAD+ required for glycolysis.
Lactate is then transported to the liver where it can be converted back to glucose by gluconeogenesis.
