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POM (Principles of Medicine) > Cell Integrity > Flashcards

Cell Integrity Flashcards

1
Q

Where does oxidative phosphorylation occur?

A

MItochondria

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2
Q

Where is the bulk of ATP generated within the mitochondria?

A

Electron transport chain in the inner membrane

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3
Q

What are cristae?

A

Folds that project inwards

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4
Q

What is the role of cristae?

A

Increase the surface upon which oxidative phosphorylation can take place

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5
Q

What happens to NADH and FADH2 in the mitochondria?

A

They are reoxidised by molecular oxygen

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6
Q

What is the equation for the oxidation of NADH?

A

NADH + H+ + 1/2 O2 —> NAD+ & H2O

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7
Q

What is the equation for the oxidation of FADH2?

A

FADH2 + H+ + 1/2 O2 —> FAD &H2O

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8
Q

What membrane proteins are present in the ETC?

A 
Complex I (NADH dehydrogenase)
Complex II (succinate dehydrogenase)
Complex III ( Q- cytochrome C oxioreductose)
Complex IV (cytochrome C oxidase)
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9
Q

What are the mobile carriers present in the ETC?

A 
Coenzyme Q (ubiquinone)
Cytochrome C
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10
Q

What is the process of the electron transport chain?

A

Complexes I, II & IV accept e- and a proton (H+) from the aqueous solution.

As the e- pass through each of these complexes, a proton is pumped into the inter membrane space

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11
Q

What is succinate dehydrogenase?

A
  • An enzyme of the TCA cycle
  • sits in the inner mitochondrial membrane
  • uses FAD as a cofactor
  • can communicate directly with coenzyme Q
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12
Q

What happens when complex I is successfully bypassed?

A

Fewer H+ are pumped to the inter membrane space when FADH2 is reoxidised compared to NADH

FEWER ATP MOLECULES ARE GENERATED FROM THE REOXIDATION OF FADH2

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13
Q

What is the definition of a REDOX reaction?

A

Electron transfer reactions involving a reduced substrate (which donates e- & is oxidised) and an oxidised substrate (which accepts e- and becomes reduced)

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14
Q

What is the definition of a REDOX couple?

A

The substrate can exist in both oxidised & reduced forms

NAD+ & NADH
FAD & FADH2
Fe3+ & Fe 2+
1/2 O2 & H2O

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15
Q

What is the definition of a REDOX potential?

A

The ability of a REDOX couple to accept/donate e-

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16
Q

How can the standard redox potentials (Eo) be measured?

A

Using a hydrogen electrode as a reference experimentally

17
Q

(-)ve Eo

A

The redox couple has a tendency to donate e- and has more reducing power than H

NAD+/ NADH Eo= -0.32V

18
Q

(+)ve Eo

A

The redox couple has a tendency to accept e- and therefore has more oxidant power than H

Fe3+/ Fe2+ Eo= + 0.82 V

19
Q

What happens as the e- progress along the ETC?

A

They lose energy

The transfer of e- from one complex to another is energetically favourable

20
Q

What is ATP synthase?

A

A multi Eric enzyme consisting of a membrane bound part Fo and F1 part which projects into the matrix space

Rotation of the enzyme drives transition states with alternating affinities for ATP & ADP

21
Q

How does ATP synthase work?

A

Conformational E flows from the catalytic subunit into the bound ADP and Pi to promote the formation of ATP
CHEMICAL Energy

22
Q

What the direction of proton flow through ATP synthase determine?

A

Determines ATP synthesis Vs ATP hydrolysis

ATP synthesis: H+ into the matrix
ATP hydrolysis: H+ out of the matrix into inter membrane space

23
Q

What is the oxygen electrode?

A

A device that measures O2 conc in a solution within a small chamber

24
Q

What are the steps taken for an Oxygen Electrode?

A
  1. A small voltage of 0.6V is applied between the anode(+) and the cathode(-)
  2. O2 diffuses through the Teflon membrane & is reduced to H2O at the Pt cathode
    O2 + 4H+ 4e- —> 2H2O
  3. The circuit is completed at the Ag anode which is slowly oxidised to AgCl by the KCl electrolyte
    4Ag+ + 4Cl- —> AgCl + 4 e-
  4. Current is proportional to the O2 conc
25
Q

What are the the steps in the practical to dissect various components of the ETC using an O2 electrode?

A
  1. Prepare a suspension of mitochondria and place them in the chamber
  2. Monitor O2 consumption of the suspension for a set period of time
    * can be used to determine the effects of various substrates and inhibitors on the ETC
26
Q

What is the lifespan of an ATP molecule?

A

1-5 mins

27
Q

What is the common cause of a failure of Oxidative phosphorylation?

A

Lack of O2

HYPOXIA

28
Q

What is respiratory control?

A

Uptake of O2 by mitochondria is controlled by the components of ATP production: ATP & Pi

Allows the body to adapt O2 consumption to actual E requirements

29
Q

What are metabolic poisons?

A

Molecules that interfere with either the flow of e- along the ETC or the flow of H+ through ATP synthase

30
Q

What is malonate?

A
  • closely resembles succinate

- acts as a competitive inhibitor of succinate dehydrogenase

31
Q

How does malonate affect ETC?

A

It slows down the flow of e- from succinate to ubiquinone by inhibiting the oxidation of succinate to fumarate

32
Q

How do cyanide (CN-) and azide (N3-) affect the ETC?

A

Bind with high affinity to the ferric form of the haem group in the cytochrome oxidase complex blocking the final step of ETC

33
Q

What is rotenone?

A

-metabolic poison

Isoflavone found in the roots and seeds of some plants

34
Q

How does rotenone affect the ETC?

A

It inhibits the transfer of e- from complex I to ubiquinone

35
Q

What is Dinitrophenol (DTP)?

A
  • metabolic poison

- a proton ionophore

36
Q

How does Dinitrophenol affect the ETC?

A

Shuttles protons across the inner mitochondrial membrane

37
Q

What is oligomycin?

A
  • metabolic poison

- antibiotic produced by streptomyces

38
Q

How does oligomycin affect the ETC?

A

It inhibits oxidative phosphorylation by binding to the ‘stalk’ of ATP synthase & blocking the flow of protons through the enzyme

POM (Principles of Medicine) (17 decks)

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