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Principles 2018 > Biochemistry Part 7 > Flashcards

Biochemistry Part 7 Flashcards

1
Q

What is produced from one glucose molecule through glycolysis, PDC, TCA cycle…?

A

10 NADH + 10 H+

2 FADH2

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2
Q

What is the essence of oxidative phosphorylation?

A

Electrons from NADH and FADH2 are used to reduce O2 to H2O

Their energy is used to pump protons from the mitochondrial matrix to the inter membrane space
- pH decreases in inter membrane space, increases in the matrix

Protons flow back across the membrane, following their concentration gradient

Energy of proton flow is used to phosphorylate ADP to ATP

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3
Q

How does NADH from the cytoplasm get in?

A

The glycerol-3-phosphate and malate-aspartate shuttles overcome this problem

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4
Q

Describe the malate-aspartate shuttle?

A
  1. NADH from glycolysis is used to generate malate from oxaloacetate in cytosol
  2. Malate transporters transfer malate to mitochondrial matrix
  3. Malate conversion to oxaloacetate in TCA cycle generates NADH in addition to malate that arises from fumarate
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5
Q

What is the electron transfer potential of NADH converted into in oxidative phosphorylation?

A

The phosphoryl transfer potential of ATP

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6
Q

How can phosphorylation transfer potential be measured?

A

The free energy change, delta G for the hydrolysis of ATP

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7
Q

How can the electron transfer potential measured?

A

The redox potential (or reduction potential) of a compound

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8
Q

What is the redox potential?

A

The measure of how readily a substance will donate an electron in comparison to H2

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9
Q

What does a negative Eo mean?

A

The reduced form of X has a lower affinity for electrons that H2

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10
Q

What is the standard free energy proportional to?

A

The change in standard redox potential and the number of electrons transferred

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11
Q

What are the two stages of oxidative phosphorylation?

A

Electron transport

ATP synthesis

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12
Q

Describe electron transport

A

Electrons flow from NADH and FADH2 to O2

Respiratory chain

Energy is used to pump H+ out of the mitochondrial matrix

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13
Q

Describe ATP synthesis

A

Electrochemical gradient of H+ across mitochondrial inner membrane

Energy stored in this gradient can be used to synthesis ATP

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14
Q

How many complexes are involved in electron transport in the respiratory chain?

A

Four multisubunit complexes

Located in inner mitochondrial matric

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15
Q

What is complex I and what happens here in the respiratory chain?

A

NADH-Q oxidoreductase

Electrons from NADH enter

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16
Q

What is complex II and what happens here in the respiratory chain?

A

Succinate-Q reductase

Electrons from FADH2 enter here

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17
Q

What is complex III in the respiratory chain?

A

Q-cytochrome C oxidoreductase

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18
Q

What is complex IV in the respiratory chain?

A

Cytochrome C oxidase

19
Q

What are cytochromes?

A

Proteins which contain a haem group as a functional cofactor

20
Q

What does the haem group do?

A

Contains an Fe(II) ion which can take up and release electrons

21
Q

What is transfer of electrons through the respiratory chain coupled to?

A

Transport of H+ from the mitochondrial matrix to the inter membrane space

22
Q

Which three respiratory chain complexes pump H_?

A

I, III, IV

23
Q

What forms the electrochemical gradient in the inter membrane space and matrix?

A

More protons in the inter membrane space than in the matrix

24
Q

How is the flow of protons regulated across the membrane?

A

Respiratory chain pumps protons into inter membrane space

Protons flow back though ATP synthase

Two separate proton pump systems

25
Q

What is the other name for ATP synthase?

A

Mitochondrial ATPase

F1F0ATPase

26
Q

Describe the F1 unit of ATP synthase?

A

Protrudes into the mitochondrial matrix

27
Q

Describe the F0 unit of ATP synthase?

A

Hydrophobic complex in the inner membrane, contains the proton channel

28
Q

What forms the stator?

A

a, b, alpha, beta, sigma subunits

29
Q

What forms the rotor?

A

c, gamma and epsilon subunits

30
Q

What turns the rotor?

A

Flow of protons

31
Q

What leads to ATP synthesis?

A

Conformational change

32
Q

What can oxidative phosphorylation by inhibited by?

A

Cyanide, azide and CO

  • Inhibit transfer of electrons to O2
  • no proton gradient can be formed
  • no ATP can be synthesised
33
Q

Describe non-shivering thermogenesis?

A

Maintains body temperature in hibernating animals and newborn, and cold adapted animals by short circuiting the mitochondrial battery

34
Q

What is the uncoupling protein and where is it found?

A

UCP= thermogenic

Brown adipose tissue

35
Q

What does UCP-1 require for activation?

A

Free fatty acids

36
Q

What is DNP?

A

Artificial uncouples which acts as a protonophore in the inner membrane
- used as antiboesity drug

37
Q

Where is UCP-3 expressed?

A

Skeletal muscle

38
Q

What is uCP-3 involved in?

A

Skeletal muscle thermogenesis and limiting free radical production

39
Q

What is the pharmacological target of UCP-3?

A

MDMA, ecstasy

40
Q

How does MDMA cause death?

A

Sustained hyperthermia followed by skeletal muscle breakdown (rhabdomyolysis)

41
Q

What is the P/O ratio?

A

Measurement of the coupling of ATP synthesis to electron transport

42
Q

What does the number of molecules of inorganic phosphate incorporate into ATP per atom of oxygen used depend upon?

A

The substrate which is oxidised

43
Q

How many ATP does one glucose molecule yield?

A

30 to 32

ATP yield from the complete oxidation of one glucose molecule

Depends on precise values for the P/O ratio

Depends on which shuttle is used for transporting cytoplasmic NADH into the mitochondrial matrix

Principles 2018 (34 decks)

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