Bioenergetics 3

Question 1

For NADH dehydrogenase, how many protons are pumped outside during the transfer of 2 electrons?

Answer 1

4 protons/2 electrons.

4 charges per 2 electrons. 4q/2e

Question 2

What is the redox free energy of the first electron transfer in the cyt bc1 complex used for?

Answer 2

Redox free energy of electron transfer is used for hinge mechanism: confirmational change of the riske iron sulfur protein.

Question 3

How many charge seperations per protons does the bc-1 complex give?

Answer 3

the proton stays outside and the accompanying second electron stays inside: one charge per one electron (1q/1e).

Question 4

How many charge seperations does the bc-1 give in total?

Answer 4

It keeps going until 8H+ is outside and 4q/4e is reached.

Question 5

What is the charge seperations in aa3-type oxidase?

Answer 5

. 8q/4e. Pumps out 4 H+ and also negative charge of 4H+ comes to relative half of the enzyme

Question 5

What is the charge seperations in aa3-type oxidase?

Answer 5

. 8q/4e. Pumps out 4 H+ and also negative charge of 4H+ comes to relative half of the enzyme

Question 6

Endresult of charge seperations for 2 NADH molecules?

Answer 6

20q/4e

Question 7

What does succinate dehydrogenase do?

Answer 7

-> It oxidizes succinate to fumerate in the TCA cycle, 2 electrons from this oxidation step -> FAD cofactor -> to quinone. Becomes quinole that can go to Ba3 type quinol oxidase or bc1-complex. IN BACTERIA

Question 8

Is succinate dehydrogenase electrogenic?

Answer 8

This enzyme is not electrogenic -> energy transduced into heat.

Question 9

If two succinate molecules are being oxidized, how many charge seperations do you get?

Answer 9

12q/4e.

Succinate dehydrogenase functions as a NADH dehydrogenase but is not electrogenic. 4q/4e + 8q/4e = 12q/4e

Question 10

vElectron flow from NADH to oxygen via the ba3-type quinol oxidase: how many charge separations?

Answer 10

NADH dehydr = 8q/4e + ba3-type = 8q/4e = 16q/4e

Question 11

What bacterial enzymes are expressed under low oxygen circumstances?

Answer 11

nitrate (NO3-) reductase (=NAR) or periplasmic nitrite reductase (NAP?), nitrite (NO2-) reductase, nitric oxide (NO) reductase and nitrice oxide (N2O) reductase

Question 12

Nitrite reductase: characteristics?

Answer 12

stoichiometry = same as bc-1 complex. 1q/1e
Electrogenic
Dimer
cytoplasmic transmembrane + connecting subunit
electron donor = quinol

Question 13

If you take 2 electrons and you have NADH dehydr and nitrite reductase, how many charge seperations?

Answer 13

> If you take 2 electrons (1 NADH molecule): NADH dehydr. = 8q/4e = 4q/2e. Nitrite reductase = 1q/1e = 2q/2e. 4 + 2 = 6q/2e.

Question 14

Nitrite reductase NarGHI

Answer 14

no charge seperations: 0q.
Looks like ufo
electron accepting site (heme c)
catalytic site (heme d1)
> products: 2 nitric oxide molecules + 2 H2O molecules

Question 15

NADH dehydr, cut bc 1 complex and nitric reductase: how many charge sep per 2 electrons?

Answer 15

4 + 2 = 6

Question 16

3) Nitric oxide reductase

Answer 16

Oxidases all have proton pumps, NO reductase not. It has no redox energetics. 0q
NON-electrogenic.
Then, electrons move much faster as NO is a very dangerous molecule (stress). It can bind everywhere oxygen can bind. Can also block the reaction center of an oxidase. Reduce NO as fast as possible.
electron donor = cytochrome
Another property of NO reductase = it can be protective for some bacteria species.

Question 17

NADH + cyt bc1 + NO reductase: how many charge sep?

Answer 17

NADH dehydr = 8q/4e = 4q/2e.
Cyt bc-1 = 2q/2e = 6q/2e.
No PMF with NO reductase.

Question 18

4) NOS: Nitrous oxide reductase

Answer 18

Catalyzes reduction of nitrous oxide into N2
Electron transfer in monomer is not possible: too much ämströng of zo. Between monomers is possible. Neither of monomers can work independently. Electron transfer in monomer is not possible: too much ärmstron of zo. Between monomers is possible. Neither of monomers can work independently.
No charge sep

Question 19

NADH dehydr + cyt bc1 + nitrous oxide reductase = how many charge sep?

Answer 19

: still 6

Question 20

How many ATP = dentrification and how many is aerobic?

Answer 20

30q/10e vs 50q/10e

dentric = 40% less effective

Question 21

Also: there was still the periplasmic bound nitrate reductase.

Answer 21

Not electrogenic. Not efficient but higher rate. charge sep with nadh dehydr = 4q/2e

Question 22

Efficiency of free energy transduction during respiration depends on

Answer 22

1. gibbs free energy

2. types of enzymes: elecrogenic enzymes or not (rate of resp)