T2 L4: Mitochondrial respiratory chain

Question 1

Which mitochondrial membrane is impermeable to small molecules and ions?

Answer 1

The inner membrane. So it determines what goes in and out

Question 2

On which mitochondrial membrane is the e- transfer chain located?

Answer 2

The inner membrane

Question 3

What 2 soluble proteins link the reactions between the 4 complexes of the e- transport chain?

Answer 3

Ubiquinone (co-enzyme Q/10) and Cytochrome C

Question 4

Describe the structure of ubiquinone

Answer 4

A lipid soluble benzoquinone with a long isoprenoid tail

Question 5

Which enzyme is linked to complex I of the e- transport chain?

Answer 5

NADH dehydrogenase

Question 6

Which enzyme is linked to complex II of the e- transport chain?

Answer 6

Succinate dehydrogenase

Question 7

Which enzyme is linked to complex III of the e- transport chain?

Answer 7

Ubiquinone (cytochrome c oxidoreductase)

Question 8

Which enzyme is linked to complex IV of the e- transport chain?

Answer 8

Cytochrome oxidase

Question 9

Which complexes does cytochrome c move between?

Answer 9

Between complex III and IV

Question 10

In the e- transport chain, what is the energy from FAD and NAD used to do?

Answer 10

Pump H+ into the intramembrane space of mitochondria

Question 11

Describe what happens in complex I of the e- transfer chain

Answer 11

1. e- are passed to FMN to produce FMNH2
2. transfer to a series of iron-sulphur clusters which accept e-
3. Then transfer to ubiquinone

Question 12

In which complex of the e- transport chain is the overall reaction NADH + H+ + Q = NAD+ + QH2?

Answer 12

Complex I

Question 13

Describe what happens in complex II of the e-transport chain

Answer 13

1. FAD within complex II is reduced to FADH2 by e- gained from the conversion of succinate to fumarate in the TCA cycle
2. Complex II then passes e- to ubiquinone

Question 14

What is QH2?

Answer 14

Reduced ubiquinone

Question 15

Describe what happens in complex III of the e- transport chain

Answer 15

It’s a proton pump

Question 16

Describe what happens in complex IV of the e- transport chain

Answer 16

It the final proton pump which carries e- from cytochrome C to O2 to produce water e

Question 17

What is the final e- acceptor in the e- transport chain?

Answer 17

O2 to produce water

Question 18

What is the equation for ATP formation including the charges?

Answer 18

ADP3- + Pi2- + H+ = ATP4- + H2O

Question 19

What is Adenine nucleotide translocase and what is its function?

Answer 19

An integral protein of the inner mitochondrial membrane that transports ADP3- from the intramitochondrial membrane space into the matrix in exchange for ATP4-

Question 20

Why is the electrochemical gradient favoured by Adenine nucleotide translocase?

Answer 20

The H+ has created a very positive intramembrane space so exchange of ADP3- for ATP4- is favoured because of the charges on those molecules. This makes it a passive process

Question 21

What is an antiporter?

Answer 21

Something that transports 2 molecules in different directions

Question 22

Name an inhibitor of adenine nucleotide translocase

Answer 22

Atractyloside, a glycoside isolated from a thistle

Question 23

What is the function of phosphate translocase?

Answer 23

It transports both phosphate and hydrogen ions into the matrix

Question 24

What is a symporter?

Answer 24

Something that transports 2 molecules in the same direction

Question 25

Why is the function of phosphate translocase favoured by the electrochemical gradient?

Answer 25

H+ travel down the electrochemical gradient and bring the H2PO4- along with it

Question 26

Give an example of a F-type ATPase

Answer 26

ATP synthase

Question 27

What are the 2 functional domains of ATP synthase?

Answer 27

1. Fo, an oligomycin-sensitive proton channel embedded in the mitochondrial membrane 2. F1, an ATP synthase

Question 28

What 3 proteins work together in the mitochondrial membrane to bring in the raw materials into the matrix of mitochondria so ATP can be produced?

Answer 28

ATP synthase, phosphate translocase, and Adenine nucleotide translocase

Question 29

Describe the structure of ATP synthase

Answer 29

Fo is formed of 3 subunits - a,b, and c | F1 if formed of 5 subunits - 3 alpha, 3 beta, 1 gamma, 1 delta, and 1 epsilon

Question 30

Which subunits of ATP synthase have catalytic sites for ATP synthesis?

Answer 30

The 3 beta subunits

Question 31

How are the subunits of ATP synthase arranged?

Answer 31

Alpha and Beta subunits alternate on top like an orange. Gamma forms the stalk and epsilon forms the base of the stalk. Delta subunit interacts with the 2 'b' subunits of Fo

Question 32

Describe the theory of rotational catalysis of the ATP synthase

Answer 32

A beta subunit starts in conformation for binding ADP and pi and then changes conformation so the active site now binds the ATP tightly. Then the structure changes again to give the active site a lower affinity for ATP so ATP is released

Question 33

What process drives the theory of rotational catalysis?

Answer 33

The re-entering of H+ through ATP synthase

Question 34

How much ATP is produced from the oxidation of glucose?

Answer 34

30 or 32

Question 35

What effect do uncoupling regents have on the body and how do they work?

Answer 35

Normally e- flow and phosphorylation are tightly coupled but uncouplers dissipate the pH gradient by transporting H+ back into the matrix of mitochondria by bypassing the ATP synthase.

Question 36

What is UCP1?

Answer 36

Uncoupling protein 1 and thermogenin

Question 37

Where is UCP found and how does it work?

Answer 37

It's found in brown adipose tissue and has specific H+ channels through which [H+] can dissipate. The energy is released as heat instead

Question 38

What is brown adipose tissue (BAT) specialised for?

Answer 38

Heat generation

Question 39

What 2 features of brown adipose tissue make is specialised?

Answer 39

High numbers of mitochondria which contain UCP1

Question 40

At what age is brown adipose tissue most important?

Answer 40

In new-borns because they are susceptible to hypothermia

Question 41

What is DNP and how does it work?

Answer 41

An exogenous uncoupler that collects protons from the IMS and moves through the membrane with it, depositing it in the matrix

Question 42

Which uncoupler can be used for weight-loss?

Answer 42

DNP

Question 43

How does toxicity from DNP arise?

Answer 43

Toxicity through liver damage, reparatory acidosis and hyperthermia