Metabolism Flashcards
(33 cards)
why is hydrolysis of ATP so exothermic?
- Pi and ADP have more resonance stabilisaiton than ATP
- Electrostatic favourability. pH7 - ATP has 4 - charge which repel and weaken P-O-P bond.
- More water bind to ADP/Pi so more stabilisation due to hydration.
what is phosphoryation potential?
ΔG in cell after dephosphorylating a metabolite
What does phosphorylation potential tell you?
metabolites with higher potential will be able to phosphorylate lesser ones.
How does phosphoryation potential of ATP compare to other metabolites? Significance of this?
It is in the middle. This means it can phosphorylate lesser ones like glucose and higher molecules like phosphoenolpyruvate can phosphorylate ADP –> ATP
What metabolites have higher phosphorylation potential than ATP? what does this mean?
- phosphoenolpyruvate
- phosphocreatine
This means both these can phosphorylate ADP —> ATP
What technique can be used to measure ATP changes in cell?
P-31 NMR
Turnover rate of ATP during exercise in humans?
0.5kg/min
How does ATP help in coupling chemical reactions?
ATP hydrolysis coupled with reactions so that overal ΔG is negative and favourable compared to the reaction by itself which is positive.
It increases equilibrium constant many 10 fold so favours products.
Difference between NAD and NADP? significance?
NADP has phosphate group attached to it - recognition site for biosynthetic enzymes.
Allows cell to achieve 2 different redox potentials.
Different roles of NAD and NADP?
NADP - biosynthesis of other metabolites
NAD - ATP production
How is enzyme activity controlled?
- change amount of enzymes(transcription gene)
- metabolic control of enzyme eg. end product inhibition
How is enzyme reaction rate regulated?
- Allosteric modification - allosteridc effector bind - change affinity for substrate
- Covalent modification - eg. phosphorylation —> conformation change —> de/active enzyme
Compare the 2 ways in which enzymes reaction rates are regulated
- ALLOSTERIC - rapid response to stimulus - intercelular signalling
- COVALENT - slower response - extracellular control eg hormones
How is glucose intake into cells regulated?
BRAIN, LIVER, RBC - insulin independant glucose transporters thus only dependant on [glucose]
MUSCLE, FAT - insulin dependent glucose transporters
Describe the different glucose transporters
GLUT1/2/3 - insulin independent - always embedded in membrane(brain, RBC, liver)
GLUT4 - insulin dependent - traped in intracellular vesices but insuin recruits it to cell membrane
Diseases related to dysregulation of glucose?
- neurodegenerative
- amplification of ischaemic damage
- cancer proliferation
Which reactions in glycolysis are alosteric modifications?
- glucose —> G6P (hexokinase/glucokinase)
- F6P —> F1,6,BP (phosphofructokinase-1)
- PEP –> Pyr (pyruvate kinase)
What is important about the reactions involving allosteric modification in glycolysis?
They are irreversible whereas the other stages aren’t.
This is because the ΔG is too large. In each of these stages, ATP is either hydroysed or produced from ADP.
What is the first stage in glycolysis?
LYSIS - going from glucose to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate
What hapens in the second stage in glycolysis?
OXIDATION - converting the aldehyde group of G3P to a carboxylic acid(more energetically favourable)
ADP —> ATP
oxygen for oxidation comes from water
oxidising agent = NAD+
What happens in the third stage of glycolysis?
REARRANGEMENT - 3-phosphoglycerate —> 2-phosphoglycerate —> phosphoenolpyruvate —> pyruvate
Where does the energy come from to phosporylate ADP to ATP in the final step of glycolysis?
from converting C=C bond to C=O(more enrgetically favourable)
Phosphoenolpyruvate to pyruvate catalysed by?
pyruvate kinase, K+, Mg2+
Describe the production of lactate?
pyruvate —> lactate
NADH —> NAD+(regenrated for glycolysis)
enzyme = lactate dehydrogenase
