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MIMS > Metabolism > Flashcards

Metabolism Flashcards

1
Q

why is hydrolysis of ATP so exothermic?

A
  1. Pi and ADP have more resonance stabilisaiton than ATP
  2. Electrostatic favourability. pH7 - ATP has 4 - charge which repel and weaken P-O-P bond.
  3. More water bind to ADP/Pi so more stabilisation due to hydration.
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2
Q

what is phosphoryation potential?

A

ΔG in cell after dephosphorylating a metabolite

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3
Q

What does phosphorylation potential tell you?

A

metabolites with higher potential will be able to phosphorylate lesser ones.

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4
Q

How does phosphoryation potential of ATP compare to other metabolites? Significance of this?

A

It is in the middle. This means it can phosphorylate lesser ones like glucose and higher molecules like phosphoenolpyruvate can phosphorylate ADP –> ATP

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5
Q

What metabolites have higher phosphorylation potential than ATP? what does this mean?

A
  • phosphoenolpyruvate
  • phosphocreatine

This means both these can phosphorylate ADP —> ATP

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6
Q

What technique can be used to measure ATP changes in cell?

A

P-31 NMR

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7
Q

Turnover rate of ATP during exercise in humans?

A

0.5kg/min

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8
Q

How does ATP help in coupling chemical reactions?

A

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.

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9
Q

Difference between NAD and NADP? significance?

A

NADP has phosphate group attached to it - recognition site for biosynthetic enzymes.

Allows cell to achieve 2 different redox potentials.

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10
Q

Different roles of NAD and NADP?

A

NADP - biosynthesis of other metabolites

NAD - ATP production

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11
Q

How is enzyme activity controlled?

A
  • change amount of enzymes(transcription gene)

- metabolic control of enzyme eg. end product inhibition

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12
Q

How is enzyme reaction rate regulated?

A
  • Allosteric modification - allosteridc effector bind - change affinity for substrate
  • Covalent modification - eg. phosphorylation —> conformation change —> de/active enzyme
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13
Q

Compare the 2 ways in which enzymes reaction rates are regulated

A
  • ALLOSTERIC - rapid response to stimulus - intercelular signalling
  • COVALENT - slower response - extracellular control eg hormones
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14
Q

How is glucose intake into cells regulated?

A

BRAIN, LIVER, RBC - insulin independant glucose transporters thus only dependant on [glucose]

MUSCLE, FAT - insulin dependent glucose transporters

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15
Q

Describe the different glucose transporters

A

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

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16
Q

Diseases related to dysregulation of glucose?

A
  • neurodegenerative
  • amplification of ischaemic damage
  • cancer proliferation
17
Q

Which reactions in glycolysis are alosteric modifications?

A
  1. glucose —> G6P (hexokinase/glucokinase)
  2. F6P —> F1,6,BP (phosphofructokinase-1)
  3. PEP –> Pyr (pyruvate kinase)
18
Q

What is important about the reactions involving allosteric modification in glycolysis?

A

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.

19
Q

What is the first stage in glycolysis?

A

LYSIS - going from glucose to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate

20
Q

What hapens in the second stage in glycolysis?

A

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+

21
Q

What happens in the third stage of glycolysis?

A

REARRANGEMENT - 3-phosphoglycerate —> 2-phosphoglycerate —> phosphoenolpyruvate —> pyruvate

22
Q

Where does the energy come from to phosporylate ADP to ATP in the final step of glycolysis?

A

from converting C=C bond to C=O(more enrgetically favourable)

23
Q

Phosphoenolpyruvate to pyruvate catalysed by?

A

pyruvate kinase, K+, Mg2+

24
Q

Describe the production of lactate?

A

pyruvate —> lactate

NADH —> NAD+(regenrated for glycolysis)

enzyme = lactate dehydrogenase

25
Q

Fate of lactate?

A

exported to liver or converted back to pyruvate for oxidation of pyruvate and NADH in mitochondria

26
Q

Which muscles use anaerobic respiration?

A

fast twitch / white

27
Q

How is oxygen debt repaid?

A

increase rate of Krebs cycle to oxidise lactate produced

28
Q

How long does muscle phosphocreatine last?

A

4 secs

29
Q

How much does anaerobic glycolysis increase during short bursts of activity?

A

more than 1000 fold

30
Q

Outline ATP production / consumption in 3 stages of glycolysis

A

LYSIS - 2 ATP consumed
OXIDATION - 2 ATP and 2NADH produced
REARRANGEMENT - 2 ATP produced

31
Q

How much lactate in blood normally?

A

1mM

32
Q

pKa of lactate?

A

~ 3.86

33
Q

What happens in hyperlactaemia / lactic acidosis? cause?

A

Lactate increases to 5mM or more and acid not fully dissociated so pH blood drops to ~ 7

Caused by tissue hypoxia or decreased clearance of lactate from blood to other organs.

MIMS (1 decks)

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