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Kirstys Flashcards > BMP: TCA cycle and ETC > Flashcards

BMP: TCA cycle and ETC Flashcards

1
Q
  1. What are alternative names to the TCA cycle?
  2. Where does this process occur?
  3. What is utilised and where does this come from
A
  1. Krebs or citric acid
  2. Mtocondria of eukaroytes and cytosol of prokaryotes
  3. Utilises acetyl coA - the immediate precurosr of acetyl coA from carbohydrate metabolism is pyruvate
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2
Q

How does pyruvate enter the mitocondria?

What happens to it?

A

Under aerobic conditions pyruvate enters via a specific H+ transporter and undergoes further oxidation to CO2 and H20

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3
Q
  1. What happens to acetyl coA
  2. What is the outcomes of the TCA?
A
  1. IT is completely oxidised
  2. At the end of the cycle, 2 Carbons from the 6 carbons of citrate leave as CO2 to ultimately yield the 4 carbon oxaloacetate, which is used again in the first step of the next cycle
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4
Q

What does every molecule of acetyl coA produce?

A
  • 3 NADH
  • 1 FADH2 (flavin adenine dinucleotide)
  • 1GTP (ATP equivalent)
  • Co2

But remeber 1 glucose = 2 pyruvaye = 2 acetyl coenzyme A (therefore this will be doubled)

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5
Q

What molecules are required for TCA?

A
  • Acetyl (in the form of acetyl coA)
  • Citrate
    • consumed and then regenerated
  • Coenzymes
    • FAD and NAP+
  • GDP
  • H2O
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6
Q

What are products of TCA?

A
  • GTP (ATP equivalent)
  • CO2 (waste product)
  • CoA
  • Reduced coenzymes
    • later undergo oxidative phosphorylation (ETC)
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7
Q

Before the TCA cycle can begin, pyruvate must be converted to the intermediate acetyl coA for TCA.

  1. How does this happen?
A
  • Pyruvate under goes oxidative metabolism to acetyl coA via oxidative decarboxylation
  • This is catalysed by pyruvate dehydrogenase complex (PDC)

(NAD+ is also converted to NADH)

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8
Q

What regulates the activity of PDC?

A
  • PDC kinase (conversion to inactive form)
  • PDC phosphatase (conversion to active form)
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9
Q

What is the first step of TCA cycle?

A
  • Condensation
  • Transfer of a 2-carbon acetyl group from acetyl CoA to the 4-carbon oxaloacetate to form a 6-carbon compound (citrate)
  • This is catalysed by Citrate synthase
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10
Q

What is the 2nd step?

A
  • Isomerisation
  • The citrate is dehydrated to cis-aconitase via the enzyme aconitase
  • It is then rehydrated by the same enzyme to form isocitrate
  • This isomerisim is reversible
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11
Q

What is the 3rd step?

A

Isocitrate dehydrogenase catalayses the oxidation of isocitrate to oxalosuccinate. NADH is also produced

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12
Q

What is the 4th step?

A
  • Decarboxylation
  • Decarboxylation of oxalosuccinate to a-ketoglutartate (5C) by oxalosuccinate decarboxylase
  • This is the rate limiting step and is irreversible
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13
Q

What is the 5th step?

A
  • Oxidative decarboxylation
  • Oxadative decarboxylation of a-ketoglutartate by a-ketoglutartate to succinyl-coA (4C) and one molecule of NADH.
  • This step is irreversible
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14
Q

What is step 6?

A
  • Hydrolysis/ GTP synthase
  • Hydrolysis of succiny-CoA to succinate via succinyl-CoA synthase and producing one moleculr of GTP
  • –GTP generation driven by hydrolysis of high energy thioester bond
  • •Condensation of GDP + Pi
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15
Q

What happens in stage 7?

A

Oxidation of Succinate by succinic dehydrogenase to fumarate and one molecule of FADH2

FAD —> FADH2 genertes equivalent of 2ATP

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16
Q

What happens in stage 8?

A
  • Hydration
  • Hydration of fumarate to malate by fumarase
17
Q

What happens in stage 9?

A

Oxidation of malate by malate dehydrogenase to oxaloaxetate and one molecule of NADH

18
Q

Describe sources of energy from TCA

A
  • •TCA cycle produces
    • Reduced co-enzymes (NADH or FADH2) generated by action of four dehydrogenase enzymes
    • GTP produced by one thiokinase enzyme
      • Used to produce ATP (GTP + ADP → GDP + ATP)
  • Energy produced per molecule pyruvate
    • 3 NADH
    • 1 FADH2
    • 1 GTP
19
Q

What is the net reaction for TCA cycle?

What is the energy yield per cycle?

A
20
Q

What is the ATP count so far?

A
  • •Per molecule of glucose
  • –2 ATP from glycolysis
  • –2 ATP from TCA cycle
  • •Life requires far more than 4 ATP!!!
21
Q

What is the electron transport chain?

A

Couples electron transfer between an electon donor (NADH) and an electron acceptor (O2) with the transfer of a H+ (Proton)

Series of molecules build into the inner mitocondrial membrane

22
Q

How much energy is produced?

A

34 ATP from 1 glucose

23
Q

What coditions are required?

A

aerobic - O2

24
Q

What is the purpose of ETC?

A

To create an protein gradient between the inside and outside of the innermitocondiral membrane which ATP synthase uses to create ATP

25
Q

What is the process by which the mitocondria produces ATP?

A

Oxidative phosphorylation

“The generation of ATP from ADP through the oxidation of metabolic products (food) to CO2”

26
Q

What happens to energy during biological oxidation

A

Not just released - transducted to a more useful form - ATP

27
Q

What does protein complex 1 do?

A

Protons from NADH associate with proton complex I. Complex I (NADH dehydrogenase) removes 2 electrons from NADH and transferred to the lipid soluble carrier protein ubiquinone. Complex I translocates 4 protons across the innermembrane producing a proton gradient.

Complex 1 is a major site of premature electron leakage to O2 occurs

28
Q

What happens in complex II?

A

Electrons carried as FADH2 are passed to complex II. Complex II (succinate dehydrogenase) is a parellel electron transport pw to complex 1, but unlike complex 1 doesnt transport protons into the intermembrane space. This means it contributes less energy overall to the ETC process

29
Q

What does complex III do?

A

Hydrogen ions are transolcated into the intermembrane space by interaction with complex III (cytochrome bc1 complex) and, simulataneouly, an electron is passed to complex III

30
Q

What happens in complex IV?

A

In complex IV (Cytochrome c ocidase) four electrons are removed from 4 molecules of cytochrome c and transferred to molecular oxygen to produce 2 molecules of water

31
Q

What is the final electron acceptor?

A

Oxygen

32
Q

What inhibits complex IV?

A

Potassium cyanide

33
Q

How is ATP finally produced?

A

The proton gradient created from transferring protons across the IMM to the intermembrane space increases membrane potential and drives ATP synthase (therefore ATP production) as the built up H+ rushes back into the matrix

34
Q

What is the complete equation for cellular resperation?

A

6C6H12O6 + 6O2 —> 6H2O + 6CO2 + ~38 ATP

35
Q

Why migth actual ATP be less?

A

Premature leakage of e-s to O2

36
Q
A

Kirstys Flashcards (116 decks)

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